TROPHIC STRUCTURE OF MIDWATER FISHES OVER COLD SEEPS IN THE... CENTRAL GULF OF MEXICO Jennifer P. McClain-Counts

TROPHIC STRUCTURE OF MIDWATER FISHES OVER COLD SEEPS IN THE NORTH

CENTRAL GULF OF MEXICO

Jennifer P. McClain-Counts

A Thesis Submitted to the

University of North Carolina Wilmington in Partial Fulfillment of the Requirements for the Degree of

Master of Science

Center for Marine Science

Steve W. Ross

Chair

University of North Carolina Wilmington

2010

Approved by

Advisory Committee

Lawrence B. Cahoon

Joan W. Willey

Accepted by

DN: cn=Robert D. Roer, o=UNCW, ou=Dean of the Graduate School &

Research, email=roer@uncw.edu, c=US

Date: 2011.04.04 09:05:15 -04'00'

Dean, Graduate School

TABLE OF CONTENTS

ABSTRACT....................................................................................................................... iv

ACKNOWLEDGMENTS ................................................................................................. vi

DEDICATION.................................................................................................................. vii

LIST OF TABLES........................................................................................................... viii

LIST OF FIGURES ........................................................................................................... xi

INTRODUCTION ...............................................................................................................1

METHODS ..........................................................................................................................4

Study Area ................................................................................................................4

Sample Collection ....................................................................................................5

Dietary Analyses ......................................................................................................6

Gut Content Analyses ...................................................................................6

Stable Isotope Analyses ................................................................................7

IsoSource Mixing Model ............................................................................10

Trophic Position Analyses......................................................................................10

Statistical Analyses.................................................................................................11

RESULTS ..........................................................................................................................13

Catch Data ..............................................................................................................13

Gut Content Analyses.............................................................................................13

Diet composition .........................................................................................13

Factors influencing diet composition..........................................................17

Stable Isotope Analyses..........................................................................................19

Trophic Position Calculations ................................................................................23 ii

DISCUSSION ....................................................................................................................24

Diet composition ....................................................................................................24

Spatial and Temporal influences on diet ................................................................30

Additional insight with SIA....................................................................................32

Site differences............................................................................................32

Diet variations .............................................................................................33

Methodology...........................................................................................................34

Interesting Note ......................................................................................................35

CONCLUSIONS................................................................................................................36

LITERATURE CITED ......................................................................................................37 iii

ABSTRACT

Midwater fishes are an important component of pelagic food webs and provide insight into energy utilization and movement through the water column. In this study, the diets of midwater fishes collected over cold seep habitats were examined to determine general feeding patterns and whether size, depth, time of day or location affected diet composition within fish species. The base of the midwater food web was also examined to determine whether chemosynthetic energy in benthic cold seeps was incorporated into the midwater fish community. Discrete depth Tucker trawling was conducted in August 2007 over three cold seep habitats (> 1000 m) in the northcentral Gulf of Mexico. Surface sampling was also conducted to provide a prey base

(zooplankton and POM) for stable isotope analyses (SIA). Gut content analysis (GCA) and SIA

( δ 13 C and δ 15 N) in conjunction with IsoSource software were utilized for diet reconstruction and to determine trophic positions. SIA also aided efforts to determine chemosynthetic influences on the midwater food web. GCA was performed on 31 species in the five most abundant families

(Gonostomatidae, Myctophidae, Phosichthyidae, Sternoptychidae and Stomiidae), with midwater fishes classified into one of three guilds: piscivore, large crustacean consumer, or zooplanktivore. SIA was performed on 6 fish families (Gonostomatidae, Myctophidae,

Phosichthyidae, Sternoptychidae, Stomiidae, and Melamphaidae), 13 invertebrate categories, and

3 primary producers (POM,

Sargassum

spp. and detritus), and classified all fishes as zooplanktivores. Using IsoSource, more precise contributions of individual prey taxon were documented, which did not always support results from GCA. Size, depth, time of day and location did not affect diet composition within a species; however migration trends suggested competition may be reduced by feeding over a range of depths and over a 24 hour period.

Significant differences in trophic position calculations between GCA and SIA highlighted the iv

importance of using multiple techniques to describe trophic structure, as each method characterized the diets differently. v

ACKNOWLEDGMENTS

This project was largely funded by the Department of the Interior U.S. Geological Survey under Cooperative Agreement No. 05HQAG0009, sub agreement 05099HS004. I thank the crew of the R/V Cape Hatteras and all scientific personal for assisting with fishing operations and sample processing. S. Artabane, A. Quattrini, and A. Roa-Varon assisted with fish identifications and C. Ames assisted with invertebrate identifications. Guidance and support during stable isotope analyses were provided by Drs. A. Demopoulos and C. Tobias, and K.

Duernberger. I would also like to thank S. Artabane, T. Casazza and A. Roa-Varón for their assistance in dissecting and processing fish stomachs. Special thanks to my committee, Drs. S.

Ross, L. Cahoon, and J. Willey, for their guidance and support during the duration of this project.

I would additionally like to thank my advisor, Dr. S. Ross, for setting me up with this project and

Dr. L. Cahoon for his assistance with statistics. Finally, thanks to S. Ross, T. Casazza, A.

Demopoulos, A. Quattrini, L. Truxal and M. Carlson for their suggestions and edits provided throughout the writing process of this thesis. vi

DEDICATION

I would like to dedicate this thesis to my parents, who encouraged my early passion in marine science and gave me the confidence to follow my dreams and overcome any obstacles.

Your constant love and support was unwavering and because of that, I can present this Masters project. vii

LIST OF TABLES

Table Page

1. Surface and midwater stations sampled over three cold seep sites

(AT340, GC852, and AC601) (see Fig.1) in the Gulf of Mexico

(9-25 August 2007)................................................................................................48

2. The total number of all midwater fishes, invertebrates and autotrophs examined in dietary analyses from the North-central

Gulf of Mexico ......................................................................................................55

3. Results of ANOSIM comparing effects of size, time of day, depth and location on the general prey categories consumed for each fish species.............................................................................................................58

4. Percent volume and frequency of prey items consumed by

Chauliodus sloani collected from three sites in the Gulf of Mexico

(AC601, GC852, AT340) separated by time of day..............................................59


Gonostoma elongatum collected from three sites in the Gulf of

Mexico (AC601, GC852, AT340) separated by time of day ................................60


Stomiidae collected from three sites in the Gulf of Mexico



Cyclothone alba collected from three sites in the Gulf of Mexico



Cyclothone braueri collected from three sites in the Gulf of



Cyclothone pseudopallida collected from three sites in the Gulf of



Hygophum benoiti collected from three sites in the Gulf of Mexico (AC601, GC852, AT340) separated by time of day ............................68 viii


Valenciennellus tripunctulatus collected from three sites in the

Gulf of Mexico (AC601, GC852, AT340) separated by time of day....................69


Diaphus mollis collected from three sites in the Gulf of Mexico



Cyclothone pallida collected from three sites in the Gulf of Mexico



Vinciguerria poweria collected from three sites in the Gulf of



Myctophum affine

collected from three sites in the Gulf of



Argyropelecus aculeatus collected from three sites in the Gulf of



Argyropelecus hemigymnus collected from three sites in the Gulf of Mexico (AC601, GC852, AT340) separated by time of day ............................81


Pollichthys mauli collected from three sites in the Gulf of



Benthosema suborbitale collected from three sites in the Gulf of Mexico



Lampanyctus alatus collected from three sites in the Gulf of



Lepidophanes guentheri collected from three sites in the Gulf of Mexico

(AC601, GC852, AT340) separated by time of day..............................................88 ix


Notolychnus valdiviae collected from three sites in the Gulf of



Ceratoscopelus warmingii collected from three sites in the Gulf of Mexico (AC601, GC852, AT340) separated by time of day ............................92

24. Mean (± 1 SE) δ 13 C and δ 15 N values for midwater fishes, invertebrates and carbon sources collected from each site (AC601, AT340, GC852) ...............95

25. Percent of prey contributions for each midwater fish species using

IsoSource ...............................................................................................................98

26. Mean trophic position (TP), one standard deviation (SD), range

(minimum – maximum) and number of fish (n) for each midwater fish species collected in the North-central Gulf of Mexico, using data from stable isotope and gut content analyses ......................................................100 x

LIST OF FIGURES

Figure Page

1. Sampling areas in the North-central Gulf of Mexico for midwater fauna, 9-25 August 2007. The three cold seep sites (AT340, GC852,

AC601) were located on the continental slope at depths > 1000 m.

Each dot represents one station ...........................................................................101

2. Multidimensional scaling (MDS) plot documenting the differences among the gut contents of midwater fishes. Data were based on the

Bray-Curtis similarity matrix calculated from standardized, square root transformed, mean volumes of prey (12 general categories) .......................102

3. Relationships among stomach fullness, mean depth of capture and time for midwater fishes. Data were compiled from all sites and excluded specimens lacking depth data...............................................................103

4.

Plot of the average δ 15 N values against the average δ 13 C values

(± 1 standard error) for midwater fishes, invertebrates and primary producers collected in the Gulf of Mexico ..........................................................111 xi

INTRODUCTION

Midwater fishes constitute an important component of the pelagic food web due to their high abundances, migratory behavior, and global distribution (Gjøsaeter and Kawaguchi 1980;

Cornejo and Koppelmann 2006). Many of these unique fishes inhabit the mesopelagic zone (200 to 1000 m), and although they are consumed by a variety of marine fauna, such as benthic grenadiers (Laptikhovsky 2005), pelagic tuna (Potier et. al. 2007), and penguins (Adams et al.

2004), midwater fishes are also fierce predators. In the eastern Gulf of Mexico, midwater fishes consume 5-10% of the daily zooplankton production in the epipelagic zone (< 200 m) (Hopkins et al. 1996). The ability of midwater fishes to impact both surface and bottom communities results from diel vertical migrations (DVMs), a unique behavior exhibited by many midwater fish species. Species that undergo DVMs migrate from the mesopelagic zone to the epipelagic zone at night, primarily at sunset, and return to the mesopelagic zone at sunrise. Through DVMs, midwater fishes, particularly myctophids (Kinzer 1977; Hidaka et al. 2001; Cornejo and

Koppelmann 2006), contribute significantly to the vertical transport of organic matter from the epipelagic zone to the mesopelagic zone (Ashjian et al. 2002; Brodeur and Yamamura 2005), thus impacting the trophic structure of the water column. By tracking these trophic relationships, a more thorough understanding of pelagic energy and material flow through the water column can be established.

Previous dietary studies on midwater fishes (Hopkins and Baird 1985a,b; Lancraft et al.

1988; Hopkins et al. 1996; Butler et al. 2001; Pusch et al. 2004) utilized gut content analyses

(GCA) to determine trophic relationships. Generally, midwater fishes were divided into three major feeding guilds: zooplanktivores, which consume planktonic organisms such as amphipods, copepods and euphausiids; micronektonivores, which consume fishes and cephalopods; and

1

generalists, which consume a variety of unrelated taxa (Gartner et al. 1997). Unfortunately, as

GCA only represent short-term diet (< 24 hours) (Hadwen et al 2007), placement into these feeding guilds could vary and may be inaccurate. Guild placement can be affected by dietary shifts resulting from changes in prey abundance (Kawaguchi and Mauchline 1982), seasonality

(Kawaguchi and Mauchline 1982) and ontogeny (Kawaguchi and Mauchline 1982; Young and

Blaber 1986; Hopkins et al. 1996; Beamish et al. 1999; Williams et al. 2001; Butler et al. 2001).

Additionally, accurate guild placement is not possible for specimens with empty stomachs, common in midwater fishes (Gartner et al. 1997). The trophic relationships relating midwater fishes to their carbon sources are also limited with GCA, which may not always allow the determination of which autotrophs contributed to a food web (Thomas and Cahoon 1993).

Therefore, despite providing detailed dietary data, GCA only documents a portion of the trophic structure.

Issues related to GCA (noted above) may be addressed using stable isotope analyses (SIA).

Although SIA cannot provide detailed prey data (e.g., species level prey identifications), SIA provides general information on the cumulative feeding habits of an organism (Fry 2006).

Trophic positions within a food web (Fry 1988; Van Dover 2000; Hobson 2002; Behringer and

Butler 2006; Fry 2006; Paradis et al. 2008) can be estimated from SIA due to the isotopic ratio of nitrogen ( 15 N/ 14 N or δ 15 N), increasing an average of 3.4‰ per trophic level (Minagawa and

Wada 1984; Post 2002). In contrast to nitrogen, the isotopic ratio of carbon ( 13 C/ 12 C or δ 13 C), has little fractionation between trophic levels, with an increase ≤ 1‰ per trophic level (Post 2002;

Lajtha and Michener 1994; Minagawa and Wada 1984). Despite this low fractionation, carbon is useful for determining carbon sources as distinct ranges are documented for different autotrophs:

-22 to -16‰ for marine phytoplankton (Post 2002; Fry 2006), -18 to -15‰ for

Sargassum

spp.

2

(Rooker et al. 2006), -16 to -5‰ for turtlegrass (Hemminga and Mateo 1994), and -75 to -28‰ for chemosynthetic material (Kennicutt et al. 1992). Unfortunately, despite the added benefit of combining SIA and GCA in dietary analyses, few studies (e.g. Vander Zanden et al. 1997;

Hadwen et al. 2007; Drazen et al. 2008; Rybczynski et al. 2008) have done so.

In the Gulf of Mexico (GOM), trophic structure may be affected by the complex bottom topography and hydrography. The dominant current, the Loop Current, flows from the Caribbean

Sea through the Yucatan Channel, around the east-central portion of the GOM and flows out near southern Florida (Hyun and Hogan 2008; Sturges et al. 2005). The oscillation of this current often results in warm- and cold-core rings breaking off, which affect circulation (Schmitz et al.

2005), primary productivity and food web dynamics (Waite et al. 2007). Additionally, the

Mississippi River flows into the northern portion of the basin providing large amounts of freshwater, sediments and nutrients, affecting both the water physics and chemistry and faunal communities (Baguley et al. 2006; Jarosz and Murray 2005). The presence of benthic features, like cold seeps or corals, can also affect trophic complexity, particularly as chemosynthetic communities can be associated with cold seeps. Higher abundances of non-seep, benthic fauna were occasionally observed in the vicinity of seeps (Levin 2005) and may consume chemosynthetic material (MacAvoy et al. 2002; 2008). However, whether midwater fishes are impacted by chemosynthetic energy pathways either in the water column above the seep areas or by interactions with the associated benthic communities has not been examined.

Food web studies provide an effective means of tracking energy flow through an ecosystem.

The purpose of this study was to examine the trophic structure of midwater fishes over cold seep areas (> 1000 m) in the north-central GOM. The presence of changing hydrography and prey resources at the sites may affect trophic structure. This study used both GCA and SIA to

3

thoroughly document the trophic relationships of midwater fishes. The objectives were to: 1) determine basic feeding patterns of the dominant midwater fish species collected, 2) document feeding changes, if any, that occurred among species due to differences in size, time of day, depth or location, 3) examine the relationship, if any, between feeding and DVM patterns in the midwater fishes, 4) document the differences in short term (GCA) and long term (SIA) feeding, and 5) examine the base of the midwater food web to determine whether the midwater community utilized chemosynthetic energy sources from cold seeps.

METHODS

Study Area

Three cold seep sites in the GOM were selected for sampling based on data collected by TDI-

Brooks International, Inc: Atwater Valley Block 340 (AT340), Green Canyon Block 852

(GC852), and Alaminos Canyon Block 601 (AC601). These three sites are located on the middle to lower continental slope in the north-central GOM, and each contained benthic chemosynthetic communities (Fig. 1). Detailed bottom topography was documented for each site from previous seismic profiles and surveys from a submersible and a remotely operated vehicle (Roberts et al.

2007). AT340 (2216 m) contained multiple mounds located on a topographic high. Submersible surveys of the area documented extensive carbonate substrata, large mussel beds, clumps of tubeworms and a few soft corals. GC852 (1450 m) was characterized by an elongated ridge approximately 2 km long running north to south, with vast amounts of carbonate substrata and numerous corals on the crest. Tubeworms and mussel beds were also documented at this site.

Additionally, oil slicks were present on the surface and bubble streams were reported on the bottom, which may be potential mechanisms for transporting benthic material to the surface.

AC601 (2340 m) differed from the other two sites, having low topography and a large brine pool.

4

Some carbonate substrata and a few isolated aggregations of tubeworms were present, none of which were near the brine pool. High methane concentrations in the water column were also recorded in the water column over this site (Roberts et al. 2007).

Sample Collection

Intense sampling of the upper 1000 m of the water column was conducted during 24 hour operations at all three sites from 9-25 August 2007; however, due to inclement weather, only minimal night sampling was conducted at AC601. A total of 173 stations (45 day, 108 night, and

20 twilight) were sampled (Table 1). Multiple gear types were utilized to adequately sample the fauna, including a Tucker trawl, Neuston net, and plankton nets, though discrete-depth Tucker trawling was emphasized. Midwater fauna were collected using a Tucker trawl (2 x 2 m, 1.59 mm mesh, 505 μ m cod end.) with a plankton net (0.5 m diameter, 335 μ m mesh) attached inside the Tucker trawl mouth to simultaneously sample the smaller components of the midwater fauna.

Trawls were equipped with a Sea-Bird SBE39 temperature-depth recorder (TDR) attached to the upper frame bar to record time, depth, and temperature during deployment. The Tucker trawl was deployed open, and it was assumed no significant fishing occurred during deployment due to the rapid lowering, steep wire angle, and minimal forward movement of the vessel (Gartner et al., 2008; Ross et al. 2010). Upon reaching the designated depth, the trawl fished for approximately 30 min at a 2 knot (3.7 km/hr) ground speed and was triggered closed using a double trip mechanism. Actual time and depth fished for each trawl was determined post-tow using data from the TDR. TDR data were used throughout the cruise to adjust fishing strategies to achieve desired sampling depths. The mean depth for each Tucker trawl tow was calculated by averaging all depths recorded by the TDR from the start to the end of each tow. Tucker trawling

5

intensely sampled the upper 1000 m of the water column over the 24 hour time period at GC852 and AT340.

Zooplankton samples were collected from a 1.1 x 2.4-m Neuston net (6.4-mm mesh body and

3.2-mm tail bag) or plankton nets (0.5 m diameter, 335 μ m and 1.0 m diameter, 505 μ m mesh) deployed at the surface and towed for 15-30 minutes (Table 8.1). Particulate organic material

(POM) was collected by filtering seawater through a 125μ m precombusted glass filter, and it was assumed that the majority of POM was phytoplankton derived (Kling et al., 1992). POM and zooplankton samples provided a food web base for SIA.

Fishes collected were preserved in 10% seawater-formalin solution and later transferred to

50% isopropyl for storage until dietary analyses. Invertebrates were preserved in 70% ethanol, with the exception of jelly and salp specimens that were preserved in 10% seawater-formalin solution. All specimens were sorted, identified to the lowest possible taxa and measured to the nearest millimeter standard length (SL) (fishes) or total length (TL) (invertebrates). The life history stage of fishes was also documented based on the presence or absence of gonads. Fish specimens were classified as juvenile when either no gonads or immature gonads were present.

Dietary Analyses

Gut Content Analysis (GCA)

GCA was conducted for the five most abundant midwater families (31 species) using methods outlined in Ross and Moser (1995). All abundant species collected (> 30 individuals, with the exception of stomiids) were analyzed. In order to increase sample size for Stomiidae, all stomiids, with the exception of

C. sloani

, were grouped together and were collectively referred to as Stomiidae. Highly abundant fish species,

Cyclothone alba

(n = 614)

, C. braueri

(n = 669)

, C. pallida

(n = 885)

, C. pseudopallida

(n = 744)

, Valenciennellus tripunctulatus

(n = 248)

, and

6

Notolychnus valdiviae (n = 1139), were randomly subsampled, with selected specimens spanning the collected size range of the species, encompassing all depths sampled, and including day, night and twilight samples. Selected fishes were dissected and the stomachs were removed.

Stomach fullness was estimated as 0%, 5%, 25%, 50%, 75% or 100%. Empty stomachs were documented, though not included in most analyses, for day, night and twilight samples at all sites. Stomach contents were placed on a Petri dish and identified to the lowest possible taxon.

Similar prey items were then piled together on a grid of 1 mm squares and flattened to a uniform height, which was measured. This height multiplied by the number of squares occupied by the food item yielded volume in mm 3 . The frequency of occurrence for a prey item equaled the number of times a prey item occurred in the fish species examined divided by the total number of stomachs analyzed.

The relationship between DVMs and stomach fullness was examined by plotting stomach fullness against time of day and mean sampling depth. Time of day was divided into three categories: day (0730 to 1830 hr CDT), night (2030 to 0530 hr CDT), and twilight (0530 to 0730 hr CDT, one hour on either side of average sunrise, and 1830 to 2030 hr CDT, one hour on either side of average sunset) and mean sampling depths were calculated based on Ross et al. (2010).

TT tows where no mean sampling depth was calculated were excluded.

Stable Isotope Analysis (SIA)

Prior to specimen preservation in formalin or ethanol, samples of white muscle tissue were dissected from fishes and invertebrates and frozen. For consistency, tissue was removed from similar body regions based on the type of specimen (i.e., muscle tissue removed from the dorsal region of fishes, the caudal region of shrimps, the legs of crabs and the mantle of mollusks).

When specimens were too small to extract a tissue sample, the whole body was used. Minimal contamination from other tissue types occurred as the head, scales, photophores, and entrails

7

were removed from specimens taken whole. For these specimens, species identification was made either prior to tissue collection, or a replicate specimen was vouchered for future identification. All collected isotope samples were dried and crushed into a powder. The majority of samples were dried to a constant weight in an oven at 50-60 ˚ C. Additional samples were frozen at -80 ˚ C for ≥ 24 hours and freeze dried in a VirTis Benchtop 3.3 Vac-Freeze. I assumed there were no significant differences in isotopic ratios as a result of different drying techniques

(Bosley and Wainright 1999).

Tissue samples were analyzed for carbon and nitrogen isotope ratios. For each sample, 400-

600 μ g were placed into a tin capsule and combusted in an Elemental Combustion System Model

4010 coupled to a Delta V Plus Isotope Ratio Mass Spectrometer (IRMS) via Conflo II interface at the University of North Carolina Wilmington (UNCW). POM (provided by A. Demopoulos,

USGS), 49 fishes and 24 invertebrates were analyzed by IRMS at Washington State University using a Costech (Valencia, USA) elemental analyzer interfaced to a GV instruments

(Manchester, UK) Isoprime IRMS. Precision of the IRMS at UNCW was verified by repeated analysis of standards USGS 40 and USGS 41, which were incorporated into each sample run.

Raw delta values were corrected for linearity and normalized to known reference materials

USGS 40 and USGS 41. A similar procedure was utilized at Washington State University using egg albumin powder calibrated against National Institute of Standards reference materials.

Reproducibility was monitored using several organic reference standards (Fry 2007). Isotope ratios were expressed in the standard delta ( δ ) notation as parts per thousand (‰) according to the following equation:

δ

X =

(R sample

R standard

)

R standard

* 1000 (1)

8

where X is 13 C or 15 N and R is the corresponding ratio 13 C/ 12 C or 15 N/ 14 N. The global standards for δ 13 C and δ 15 N are Vienna PeeDee Belemnite and atmospheric nitrogen (air). A minimum of 5 samples were analyzed per fish species. Similar to GCA, the sample size of Stomiidae was increased by combining all species, with the exception of C. sloani . Similarly, 3 melamphid species (

Melamphaes simus, M. typhlops, and

Scopelogadus mizolepis

) were grouped together to increase sample size for analyses and were referred to as Melamphaidae. Diaphus spp. included

D. mollis and

D. lucidus

and

Sternoptyx

spp. included

S. diaphana and

S. pseudobscura

.

Data were examined after SIA to determine whether inorganic carbon or lipids may have significantly impacted the isotope results. According to Post et al. (2007) samples with C:N > 4 are likely affected by the presence of lipids, and inorganic carbon may be present when C:N >

3.5 or δ 13 C is highly enriched. Our results (all C:N < 4) indicated that neither lipids nor inorganic carbon significantly impacted the isotope ratios of fishes; therefore, no lipid extraction or acidification methods were utilized for fish isotope samples. In contrast, some invertebrates had high C:N values that suggested the presence of inorganic carbon in the samples. As a result, an acidification process was conducted on a subset of invertebrate samples, which included amphipods, copepods, euphausiids, jellyfish, pterapods, salps, and zooplankton, to remove any inorganic carbon. To acidify samples, 1.0 N hydrochloric acid was added one drop at a time to dried, crushed tissue samples until bubbling no longer occurred. Acidified samples were air dried for 8 hours before being re-dried in an oven at 50-60 ˚ C for 24 hours. These samples were then processed by the same method utilized for nonacidifed samples (see above). As acidification can affect N values, acidified samples were reported with δ 15 N reflecting the ratio from the untreated sample and δ 13 C reflecting the acidified sample (Jacob et al. 2005; Pinnegar and Polunin 1999).

9

Isotope Mixing Models

Isotope data were analyzed using IsoSource 3.5. IsoSource is a multisource mixing model program that calculates all possible solutions for the contribution of each prey source to a consumer’s diet based on the isotopic signatures of the prey and predator (Phillips and Gregg

2003; Benstead et al. 2006). For this study, the average carbon and nitrogen values for each prey item and fish were entered into the mixing model to determine all feasible contributions. Prior to analysis, nitrogen values for consumers were corrected for trophic fractionation, set at 2‰, based on the trophic shift documented in my isotope data. It was assumed no trophic fractionation occurred in carbon (Demopoulos et al. 2007; France and Peters 1997). Tolerance was set at 0.2% with source increments set at 0.2%. Reported ranges represented the 1-99th percentile because the resulting ranges (minimum to maximum) are sensitive to small numbers of observations at the ends of the distribution and the 1-99th percentile range may be more robust to outliers

(Philips and Gregg 2003).

Trophic position analysis

Data collected during GCA and SIA were used to calculate the trophic position of each individual fish based on the following two equations from Vander Zanden et al. (1997)

TP

GC

=

∑

[

(

V i

)(

TP i

)

]

+ 1 (2) where TP

GC

is the trophic position of the fish based on gut content analysis, V i is the percent volume of a n th prey item and TP i is the trophic position of n th prey item based on data from

Rybczynski et al. (2008) and

TP

SIA

=

( δ 15

N fish

− δ 15

N

1 ° consumer

)

( f

)

+ 2 (3)

10

where TP

SIA

is the trophic position of the fish based on stable isotope analysis and f is the trophic fraction for one trophic level.

Statistical Analyses

Multivariate analyses were conducted on gut contents of each fish species to examine diet differences based on four factors: size, time of day, depth and location. All analyses utilized the software PRIMER-E version 6.1 (Clarke and Warwick 2001; Clarke and Gorley 2006). Factors were divided into groups as follows: SL was divided into size classes based on 5 mm increments

(10-14 mm, 15-19 mm, 20-24 mm, 25-29 mm, 30-34 mm, 35-39 mm, 40-44 mm, 45-49 mm, 50-

54 mm, 55-59 mm, 60-64 mm, 65-69 mm, 70-74 mm, 75-79 mm, 80-84 mm, 85-89 mm, 90-94 mm, 95-99 mm, 100-104 mm, 105-109 mm, 110-114 mm, ≥ 115 mm); time of day was divided into three categories, day (0730 to 1830 hr CDT), night (2030 to 0530 hr CDT), and twilight

(0530 to 0730 and 1830 to 2030 hr CTD); depth (based on mean sample depth) was divided into ranges based on 50 m increments (surface-49 m, 50-99 m, 100-149 m, 150-199 m, 200-249 m,

250-299 m, 300-349 m, 350-399 m, 400-449 m, 450-499 m, 500-549 m, 550-599 m, 600-649 m,

650-699 m, 700-749 m, 850-899 m, 900-949 m, 950-999 m, 1000-1049 m, 1050-1099 m, 1100-

1149 m, 1150-1199 m); and location was divided into the three sites (AT340, GC852, AC601).

Organic material and animal parts (e.g., amphipod parts, copepod parts, decapod parts) were excluded prior to analyses as these food items were ambiguous and may be pieces of prey items identified to lower taxa. For each fish species, the prey item volumetric data were standardized for each individual fish by dividing the volume of each prey item by the total volume of the stomach in order to account for stomach fullness variability. Standardized volumes were then square root transformed to down weight the contributions of abundant prey items. Next, similarities among fish species were calculated using a Bray-Curtis similarity coefficient based

11

on each factor. The resulting similarity matrix was then subjected to a one way analysis of similarities (ANOSIM) to determine if diets were significantly different for each factor, with

R>0.40 and p<0.05 used as the criteria for statistical significance. When significant differences were found using ANOSIM, a similarity percentages routine (SIMPER) was utilized to determine which prey items contributed to the dissimilarities. This process was repeated for each fish species.

A similar multivariate procedure was implemented for diet comparisons among all 31 fish species, disregarding the factors size, time of day, depth and location. After constructing a Bray-

Curtis similarity matrix, results were subjected to hierarchical clustering with group average linkage and non-metric multidimensional scaling (MDS). With a large sample size (n = 1327), a

MDS plot can become cluttered with substantial “noise” in individual samples; therefore, data were averaged by PRIMER based on species prior to standardization (see above for standardization process) (Clarke and Gorley 2006). Additionally, to determine general feeding guilds, all fish species were analyzed using general prey categories (Amphipoda, Annelida,

Chaetognatha, Cnidaria, Copepoda, Crustacea, Decapoda, Euphausiacea, Fish, Mollusca,

Ostracoda, Salpida, and Other). For this analysis, identifiable animal parts were included in the general categories (i.e., copepod parts were included in Copepoda), but organic material and unidentifiable animal parts (e.g., crustacean parts, animal parts) were excluded. Clusters were defined at the 30% and 60% similarity levels.

Statistical analyses were conducted on isotope ratios and trophic-level calculations using

SigmaStat 3.4. Data were analyzed for normality and homogeneity of variance using

Kolmogorov-Smirnov and Levene Median tests. One-way analysis of variance (ANOVA) was used to determine significant differences in isotopic values for primary producers, invertebrates

12

and fishes, with the exception of Phosichthyidae, where a t-test was used to determine differences between

P. mauli

and

V. poweriae

. A post-hoc Tukey test was used to determine specific differences among groups. Data that failed normality or equal variance tests were analyzed with ANOVA on the Ranks and the post-hoc Dunn’s test. Species comparisons between sites AT340 and GC852 were analyzed using a two-way ANOVA and post-hoc Holm-

Sidak test. An ANOVA on the Ranks, followed by Dunn’s test, was used to determine significant differences in the trophic position based on GCA or SIA. Trophic positions calculated from GCA were compared to trophic positions calculated from SIA using a t-test; however, data that failed normality were analyzed using a Mann-Whitney rank sum test. Species with low sample sizes (n

< 5) were not analyzed statistically. Regressions of δ 15 N against fish SL were conducted to determine whether ontogenetic shifts in diet occurred. Statistical significance was determined when p < 0.05. Isotope data were reported with the mean ± 1 standard error.

RESULTS

Catch data

Tucker trawling consisted of 123 tows (33 day and 90 night) from three sites (AT340,

GC852, and AC601); however, minimal sampling (n = 5, night only) was conducted at AC601.

The mean depth ranges sampled were: 63 to 1503 m for AT340, 21 to 1067 m for GC852, and 45 to 584 m for AC601. A total of 8,716 fishes (30 families) were collected, but 97.7% of these fishes were from five midwater fish families: Gonostomatidae (58.8%), Myctophidae (27.4%),

Phosichthyidae (5.8%), Sternoptychidae (4.4%) and Stomiidae (1.3%).

Gut Content Analyses (GCA)

Diet composition

GCA were conducted on 31 species from the five most abundant midwater fish families

13

(Table 2). Gut contents were analyzed from 2,989 fishes, of which 1,658 (55%) stomachs were empty. A total of 125 prey items (45 species, 37 families) were identified in the stomachs of all midwater fishes, and items were grouped into 13 general prey taxa: Amphipoda, Annelida,

Chaetognatha, Cnidaria, Copepoda, Crustacea, Decapoda, Euphausiacea, Fish, Mollusca,

Ostracoda, Salpida, and Other. Copepods were the dominant prey, identified in 79% of stomachs and were consumed by all species except C. sloani . The MDS ordination plot of mean prey volumes for the 31 midwater fish species defined three general feeding guilds at a 30% similarity level (Fig. 2): piscivores, large crustacean consumers, and zooplanktivores. At a 60% similarity, the piscivore guild remained unchanged, but the large crustacean consumer guild was subdivided into two subguilds, decapod-euphausiid consumer and decapod-piscivore, and the zooplanktivore guild was subdivided into three subguilds, copepod consumer, mixed zooplanktivore, and a generalist consumer (Fig. 2).

The piscivore guild contained only one species,

C. sloani

(Fig. 2)

.

Empty stomachs occurred in over 80% of all stomachs analyzed (Table 4). Within stomachs that contained food, six prey items (3 prey categories) were identified. Myctophidae and

Bregmaceros spp. were the most important prey items in overall percent volume and frequency, and no identifiable invertebrates were documented (Table 4).

Large crustacean consumers consisted of

G. elongatum

and Stomiidae (Fig. 2). Decapods were the dominant prey item, comprising over 70% of the identifiable prey volume of this guild.

At 60% similarity, this guild was divided into two subguilds: decapod-euphausiid consumer and decapod-piscivore consumer. The decapod-euphausiid consumer subguild contained one species,

G. elongatum.

Empty stomachs, all from night collections, occurred in 24% of analyzed

G. elongatum

(Table 5). This species had 29 prey items (9 prey categories) identified (Table 5), and

14

while decapods and euphausiids were important prey volumetrically, copepods, particularly calanoid, were consumed more frequently (Table 5). The decapod-piscivore consumer subguild was comprised of Stomiidae. Empty stomachs occurred more frequently in this subguild and were documented in 69% of all stomiids (Table 6). The diet of Stomiidae was less variable than

G. elongatum

and was characterized by 11 prey items (4 prey categories) identified in the stomachs. Decapods and myctophids were the most important prey in overall percent volume and frequency for Stomiidae (Table 6).

All other midwater fishes were classified as zooplanktivores, which was divided into three subguilds. The copepod consumer subguild contained C. alba, C. braueri, C. pseudopallida, V. tripunctulatus, D. mollis,

and

H. benoiti

. Copepods comprised over 90% of the diet (Fig. 2). A high percentage (> 68%) of empty stomachs occurred in C. alba (Table 7) , C. braueri (Table 8),

C. pseudopallida

(Table 9), and

H. benoiti

(Table 12), while fewer empty stomachs were documented in

V. tripunctulatus

(17%, Table 10) and

D. mollis

(9%, Table 11)

.

Although

Copepoda was the major prey category consumed in terms of volume and frequency, stomachs contained a diversity of prey (Tables 7-12), ranging from 13 prey items for

H. benoiti

(Table 10) to 36 prey items for

V. tripunctulatus

(Table 11).

Pleuromamma spp. was the dominant copepod in terms of volume and frequency consumed by

C. alba

(Table 7)

, V. tripunctulatus

(Table 11)

, and

D. mollis

(Table 12)

,

whereas

Aegisthus mucronatus

was more important in the diets of

C. braueri (Table 8). Valdiviella minor was volumetrically more important in the diet of C. pseudopallida

, but

Lubbockia spp. occurred more frequently (Table 9). Calanoid copepods were volumetrically important in the diets of

H. benoiti

, but cyclopoid copepods occurred more frequently (Table 10).

15

The mixed zooplanktivores subguild was defined by a general crustacean diet, with species consuming a variety of zooplankton. This subguild contained

C. pallida, A. aculeatus, A. hemigymnus, P. mauli, V. poweriae, B. suborbitale, L. alatus, L. guentheri, M. affine,

and

N. valdiviae (Figure 2). The presence of empty stomachs was variable in this subguild, ranging from

21% of specimens containing empty stomachs (

L. alatus

) to 94% of specimens containing empty stomachs ( C. pallida ). Examination of gut contents revealed the overall diet diversity for mixed zooplanktivores was greater than copepod consumers, ranging from 10 prey items for

C. pallida

(Table 13) to 42 prey items for

V. poweriae

(Table 14)

.

Amphipoda was more important volumetrically in the diet of C. pallida (Table 13) and M. affine (Table 15), while Conchoecinae

(Ostracoda) was more important for

A. aculeatus

(Table 16) and

A. hemigymnus

(Table 17)

.

Ostracods, particularly Conchoecinae, also occurred frequently in the stomachs of C. pallida

(Table 13)

, A. aculeatus

(Table 16)

,

and

P. mauli

(Table 18)

, while calanoid copepods

(particularly

Pleuromamma spp.) occurred more frequently in the stomachs of

M. affine

(Table

15) , A. hemigymnus (Table 17) , B. suborbitale (Table 19) , L. alatus (Table 20) , L. guentheri

(Table 21) and

N. valdiviae

(Table 22). Similar to copepod consumers,

Pleuromamma spp. and other calanoid copepods were important prey items for

P. mauli

(Table 18)

, B. suborbitale

(Table 19)

, L. alatus

(Table 20)

, L. guentheri

(Table 21) and

N. valdiviae

(Table 22); however decapods, euphausiids and ostracods also influenced their diets volumetrically.

Vinciguerria poweriae exhibited a more unique diet compared to other mixed zooplanktivores, with myctophids and Candaciidae (Copepoda) dominating the diet volumetrically, but Conchoecinae and calanoid copepods occurring more frequently (Table 14).

The generalist subguild contained only

C. warmingii.

This fish had the most variable diet of any zooplanktivore, with more non-crustacean prey consumed than any other zooplanktivore.

16

Empty stomachs occurred in 18% of C. warmingii , while stomach contents revealed a total of 39 prey items (13 categories, Table 23). Crustaceans comprised roughly 60% of the identifiable diet and non-crustacean prey comprised about 40% (Table 23). Fish, molluscs, and copepods were more important in overall percent volume of the diet, though copepods occurred more frequently than any other prey item (Table 23).

Factors influencing diet composition

Variations in diet composition due to size differences were investigated using GCA. The size range was reported for each fish species (Table 2). No significant differences in diet composition were documented based on size within species (Table 3), although the majority (79%) of fishes analyzed were juveniles.

Gut contents were analyzed to determine whether time affected diet composition.

Statistically, similar prey was consumed by midwater fish species regardless of the time of day

(Table 3); however, some general trends were documented in regards to the prevalence of empty stomachs. Empty stomachs occurred more frequently during the day (0730-1830) in C. sloani

(Tables 4)

, C. pallida

(Tables 13)

, V. poweriae

(Tables 14),

M. affine

(Tables 15),

P. mauli

(Tables 18)

, B. suborbitale

(Tables 19)

, L. alatus

(Tables 20)

, and

C. warmingii

(Tables 23), while empty stomachs occurred more frequently in the day and twilight (0730-2030) in

C. alba

(Tables 7)

, C. braueri

(Tables 8),

C. pseudopallida

(Tables 9),

H. benoiti

(Tables 10)

, V. tripunctulatus (Tables 11), and D. mollis (Table 12). For G. elongatum (Tables 5), Stomiidae

(Tables 6),

A. aculeatus

(Tables 16)

, A. hemigymnus

(Tables 17) and

L. guentheri

(Tables 21), empty stomachs were documented more frequently in specimens collected at night (2030-0530), and more specimens of

N. valdiviae

with empty stomachs were collected at twilight (0530-0730 and 1830-2030, Table 22).

17

Diet composition was examined on horizontal and vertical spatial scales in addition to temporal scales. Comparisons among sites yielded no significant differences in diet composition

(Table 3). There was also no significant difference in diet composition based on depth, with the exception of A. hemigymnus (ANOSIM, R = 0.546, p = 0.019). SIMPER analysis documented an average dissimilarity of 59.3% for

A. hemigymnus

collected between 400-449 m compared to

450-499 m. Ostracoda (32.8%), Copepoda (32.1%) and Euphausiacea (29.2%) contributed to the diet dissimilarity between these depths, with less diet variability (copepods only) documented in the stomachs of specimens collected between 400-449 m.

Despite the lack of significant differences temporally and spatially, migration patterns were examined to document general trends in feeding. No DVMs were documented for

C. alba

or

C. braueri (Figure 3A-B), with more full stomachs documented at night (2030-0530) in the mid mesopelagic range (350 – 700 m). DVMs were slightly evident for

C. pallida

,

C. pseudopallida

,

A. hemigymnus

, and

V. tripunctulatus

(Figure 3C-F), with more full stomachs documented during the day (0730-1830) in the lower mesopelagic (700 – 1100 m) for C. pallida (Figure 3C), more full stomachs documented at night (2030-0530) in the mid mesopelagic range (350 – 700 m) for

A. hemigymnus

(Figure 3E) and

V. tripunctulatus

(Figure 3F), and

C. pseudopallida consuming prey during a 24 hour period (Figure 3D). For species that underwent DVMs,

G. elongatum, A. aculeatus, P. mauli, V. poweriae, B. suborbitale, C. warmingii, D. mollis, H. benoiti, L. alatus, L. guentheri, and N. valdiviae (Fig. 3G-Q), fuller stomachs occurred more frequently at night in the epipelagic/upper mesopelagic (surface to 350 m).

Myctophum affine deviated from this pattern in migrating midwater fishes, with fuller stomachs occurring more frequently at night in the mid mesopelagic (Fig. 3R). Stomiids were another exception, with

C. sloani

having more full stomachs at night in the mid mesopelagic (350 – 700 m, Fig. 3S) and

18

Stomiidae having more full stomachs during the day in the lower mesopelagic (700 – 1100 m,

Fig. 3T).

Stable isotope analyses (SIA)

SIA were conducted on 337 samples, collected from the Neuston net (n = 1), plankton nets (n

= 41), TT (n = 274), and filtered seawater (n= 21). These samples represented 30 fish species (6 families), 10 general invertebrate taxa (Amphipoda, Cephalopoda, Chaetognatha, Cnidaria,

Copeopda, Decapoda, Euphausicea, Gastropoda, Salpida, Zooplankton) and three potential carbon sources (detritus,

Sargassum

spp., and POM, Table 2).

Spatial variations in δ 13 C and δ 15 N were examined for fishes, invertebrates and carbon sources (Table 24). No statistical comparisons were conducted on detritus (only collected at

AT340), or Sargassum spp. (n < 5 at AC601 and AT340). POM sampling revealed no significant difference in δ 13 C among sites; however, samples collected at GCA852 were depleted in 15 N compared to AT340 (post-hoc Tukey test, p = 0.003). Small sample sizes of invertebrates at each site also prevented statistical spatial comparisons on all invertebrate categories except

Copepoda, Decapoda and Euphausiacea (Table 24). There were no significant differences in 13 C or 15 N for Copepoda between sites GC852 and AT340. Neither Decapoda nor Euphausiacea had any significant differences in 13 C between GC852 and AT340; however, both were significantly enriched in 15 N at GC852 compared to AT340 (post-hoc Tukey test, p < 0.001). Spatial comparisons among fishes collected GC852 and AT340 were also limited by small sample sizes and only conducted on

G. elongatum, A. aculeatus, V. poweriae,

and

L. alatus

. There were no significant differences in δ 13 C within any fish species collected at GC852 or AT340

.

Nitrogen was significantly enriched in

G. elongatum and

L. alatus

collected at GC852 compared to specimens collected at AT340 (Holm-Sidak, unadjusted p < 0.001, unadjusted p = 0.008), while

19

A. aculeatus was depleted in 15 N at GC852 compared to AT340 (Holm-Sidak, unadjusted p =

0.049) and

V. poweriae

had no significant differences in δ 15 N between GC852 and AT340.

Valenciennellus tripunctulatus

, the only fish species statistically analyzed at all three sites, was significantly enriched in 13 C at AT340 compared to V. tripunctulatus collected at GC852 and

AC601 (Tukey, p = 0.018); however, there were no significant differences in δ 15 N among sites.

Data were also compared across sites to evaluate non-spatial species differences in isotopes.

There was a clear distinction in δ 13 C for each of the three carbon sources. Detritus was significantly enriched in 13 C compared to POM (Tukey, p < 0.001) and

Sargassum spp. (Tukey, p < 0.001), while Sargassum spp. was significantly enriched in 13 C compared to POM (Tukey, p

= 0.031). There were no significant differences in δ 15 N between detritus and

Sargassum spp. or detritus and POM; however, Sargassum spp. was significantly depleted in 15 N compared to POM

(Dunn’s, p < 0.05).

Examination of non-spatial differences in isotopes among invertebrate taxa was also conducted; however, most specimens were grouped into general taxa categories due to small sample sizes. Both δ 15 N and δ 13 C were similar among invertebrates with the following exceptions. Salpida was depleted in 15 N compared to all other invertebrates, although this difference was only significant compared to Chaetognatha,

Gennadas valens, Acanthephyra purpurea, and Copepoda (all comparisons, Dunn’s, p < 0.05). Also,

Acanthephyra purpurea

and

Systellaspis debilis were both significantly enriched in 13 C compared to Chaetognatha,

Copepoda, and Zooplankton (all comparisons, Dunn’s, p < 0.05). Comparisons among three decapod species,

Gennadas valens, Acanthephyra purpurea

, and

Systellaspis debilis,

revealed that

G. valens

was significantly depleted in 13 C compared to

A. purpurea

(Tukey, p = 0.02), and

20

S. debilis (Tukey, p = 0.02), and A. purpurea were significantly enriched in 15 N compared to S. debilis

(Dunn’s, p < 0.05).

Similarly, non-spatial differences in δ 13 C and δ 15 N were examined among midwater fish families and species. No significant differences in δ 13 C existed among the 6 fish families; however, Sternoptychidae was significantly enriched in 15 N compared to Phosichthyidae and

Myctophidae (Dunn’s, p < 0.05). Additional differences were documented among individual species within each family as follows. In Gonostomatidae, there were no significant differences in δ 13 C; however,

C. pallida

was significantly enriched in 15 N compared to

C. alba

and

C. pseudopallida (Dunn’s, p < 0.05). In Sternoptychidae, A. aculeatus and A. hemigymnus were enriched in 13 C compared to

Sternoptyx spp. and

V. tripunctulatus

(all comparisons, Tukey, p <

0.05), while V. tripunctulatus was significantly enriched in 15 N compared to A. hemigymnus

(Dunn’s, p < 0.05). Between phosichthyid species,

V. poweriae was significantly enriched in 15 N, but depleted in 13 C compared to

P. mauli

(t-test, p < 0.001). All stomiid species exhibited similar isotopic signatures, with no significant differences in δ 15 N or δ 13 C. Among myctophid species,

M. affine

was significantly depleted in 13 C compared to all other myctophids (Tukey, p < 0.05) and was also depleted in 15 N, though differences were only significant when compared to

Diaphus

spp.,

D. problematicus, and

L. alatus

(all comparisons, Dunn’s, p < 0.05).

Diaphus spp. was significantly enriched in 15 N compared to

C. warmingii

(Dunn’s, p < 0.05) and

D. problematicus was enriched in 13 C compared to L. alatus (Tukey, p < 0.05).

SIA also indicated trophic relationships within the mesopelagic food web. Enrichment in 15 N was evident with increasing trophic levels, with a trophic fractionation of roughly 2‰, while trophic fractionation in δ 13 C was less apparent (Fig. 4). No distinct chemosynthetic signature

( δ 13 C ranging from -75 to -28‰) was detected in any flora or fauna, with the δ 13 C values for all

21

fishes reported within the range of photosynthetic-based material. The first trophic level, representing the base of the mesopelagic food web, was comprised of POM (Fig. 4). The second trophic level, identified after applying a 2‰ trophic fractionation to POM, contained mostly zooplankton, such as Copepoda, Euphausiacea, and Amphipoda (Fig. 4). The third trophic level, designated by a second 2‰ trophic enrichment, encompassed the majority of mesopelagic fishes

(Fig. 4), with one exception ( M. affine ) , which was depleted in both 15 N and 13 C, relegating it to the second trophic level.

IsoSource was used to calculate the potential contribution of each prey category to the midwater fishes (Table 25). Crustaceans were the dominant prey and were reported in the diets of all midwater fishes. Zooplankton was an important prey item for

C. alba, Sternoptyx

spp.,

V. tripunctulatus, C. sloani, and Melamphaidae, with potential contributions ranging from 18-98% of their diets. For

A. aculeatus, A. hemigymnus, P. mauli,

Stomiidae

, D. problematicus,

and

L. guentheri,

Decapoda was an important prey item, with potential contributions ranging from 2-

84%. Non-crustacean prey items, such as Pterapoda, had contributions ranging from 2-54% of the diets of

C. alba, Sternoptyx

spp.,

V. poweriae, P. mauli, and

C. warmingii

, while Salpida had contributions ranging from 8-66% of the diet for

P. mauli

. In some cases, such as

C. pallida, C. pseudopallida, G. elongatum, B. suborbitale and

L. alatus

, it was not possible to determine prey contributions to the diets with confidence. The lack of confidence in determining prey contributions stemmed from all prey sources having a minimal contribution of zero to the diets , with these fishes not confined within the isotopic signatures of the prey items analyzed in

IsoSource.

Myctophum affine

deviated from all other midwater fishes, with no solutions generated for diet contribution based on the zooplankton and POM analyzed due to the depleted

13 C reported; however, solutions were generated when the average isotopic signature of

22

chemosynthetic material (based on published literature) was included in the IsoSource analysis.

Minimal contributions of chemosynthetic material ranged from 22-30% of the diet for

M. affine

; however, this did not necessarily indicate consumption of chemosynthetic material because values were based on averages and the isotopic signature of M. affine was within the range of photosynthetic material.

Ontogenetic shifts were investigated for Cyclothone alba, C. pallida, C. pseudopallida, G. elongatum, A. aculeatus

,

A. hemigymnus

,

Sternoptyx spp.,

V. tripunctulatus

,

P. mauli

,

V. poweriae, C. sloani

, Stomiidae,

B. suborbitale

,

C. warmingii

,

Diaphus spp.,

D. problematicus

,

L. alatus , L. guentheri , M. affine, and Melamphaidae (Fig 5A-T) by examining the relationships between δ 15 N and SL. Positive relationships between δ 15 N and SL were identified in nineteen of the twenty species analyzed; however, significant relationships were identified in C. pseudopallida

(R 2 = 0.736, p = 0.002)

, G. elongatum

(R 2 = 0.618, p = 0.002)

, V. poweriae

(R 2 =

0.614, p < 0.001)

, C. sloani

(R 2 = 0.852, p = 0.009)

, D. problematicus

(R 2 = 0.738, p = 0.013)

,

Diaphus spp. (R 2 = 0.838, p = 0.029) and Melamphaidae (R 2 = 0.687, p = 0.003). One significant negative relationship was also identified in

M. affine

(Fig. 3S)

,

with lower δ 15 N documented in larger individuals (R 2 = 0.408, p = 0.047).

Trophic position calculations

Trophic position calculations for the midwater fishes varied by the type of analysis (GCA versus SIA). Using data from GCA, the calculated trophic positions among fish species ranged from 2.90 (

C. warmingii

) to 4.00 (Stomiidae, Table 26). Significant differences among these trophic positions only occurred between

C. sloani and

C. braueri

(Dunn’s, p < 0.05) and

Stomiidae and

C. braueri

(Dunn’s, p < 0.05), with the stomiids occupying a higher trophic position. For isotope data, the calculated trophic positions of midwater fishes had a broader range

23

than those derived from GCA. Trophic positions from SIA ranged from 1.19 ( M. affine ) to 3.96

(

C. pallida

), and more significant differences in trophic positions were documented among fish species. The myctophid

M. affine

occupied a significantly lower trophic position than

C. pallida,

A. aculeatus, Sternoptyx spp.

, V. tripunctulatus, Diaphus spp., and Melamphaidae, while C. warmingii

occupied a significantly lower trophic position than

C. pallida, V. tripunctulatus

and

Diaphus spp. (All comparisons, Dunn’s, p < 0.05). Also, P. mauli occupied a significantly lower trophic position than

C. pallida

(Dunn’s, p < 0.05)

, A. aculeatus

(Dunn’s, p < 0.05)

, V. tripunctulatus

(Dunn’s, p < 0.05)

, and

Diaphus spp. (Dunn’s, p < 0.05), while

V. tripunctulatus occupied a significantly higher trophic position than B. suborbitale (Dunn’s, p < 0.05) and L. guentheri

(Dunn’s, p < 0.05)

.

Trophic positions of midwater fishes calculated from SIA data were significantly lower than trophic positions calculated from gut content data for C. alba

(Mann-Whitney, p < 0.001)

, C. pseudopallida

(p < 0.001)

, P. mauli

(p < 0.001)

, V. poweriae

(p

= 0.025)

, C. sloani

(p < 0.001)

,

Stomiidae (p = 0.022)

, B. suborbitale

(p < 0.001)

, C. warmingii

(t-test, p < 0.001), L. guentheri (Mann-Whitney, p < 0.001) , and M. affine (Mann-Whitney, p <

0.001)

.

In contrast,

C. pallida

(Mann-Whitney, p = 0.022) and

V. tripunctulatus,

(p < 0.001) occupied significantly higher trophic positions according to data from SIA than GCA. There were no significant differences between trophic positions calculated from GCA and SIA for

G. elongatum, A. aculeatus, A. hemigymnus, Diaphus spp. and

L. alatus

.

DISCUSSION

Diet Composition

Zooplankton was the dominant prey for midwater fishes. Based on SIA, all species, with the exception of

M. affine,

were one trophic level above zooplankton. Additionally, copepods, particularly

Pleuromamma

spp., were prevalent in the stomachs of all midwater fishes except

C.

24

sloani . This prevalence of zooplankton in the diets of midwater fishes, which was support with

SIA, suggested midwater fishes may be competing for zooplankton prey; however, a more detailed examination of diet composition using GCA revealed three feeding guilds within midwater fishes, similar to results from Gartner et al. (1997).

Chauliodus sloani

occupied a different guild than all other midwater fishes, with only fishes documented in the stomachs. Physical adaptations, such as large curved teeth, an expansive oral cavity and a lack of ossification in the anterior vertebrate, which allow the skull to move upward and back (Borodulina 1972), make it easier for

C. sloani

to capture larger prey like myctophids and Bregmaceros spp. The high number of empty stomachs in C. sloani may indicate that foraging was not always successful in the epipelagic zone (Sutton and Hopkins 1996; present study). Sutton (2005) suggested zooplankton may be consumed by C. sloani to sustain energetic needs between successful feeding on larger prey and crustaceans were previously documented in the stomachs of

C. sloani

in the eastern GOM (Hopkins et al. 1996; Sutton and Hopkins 1996),

Arabian Sea (Butler et al. 2001) and off Hawaii (Clarke 1982). IsoSource also supported this concept of zooplankton consumption, with 48-90% of the diet of

C. sloani

comprised of zooplankton

.

This relationship between foraging success and zooplankton consumption may also explain ontogenetic diet shifts documented in

C. sloani using SIA. Roe and Badcock (1984) reported that crustaceans, particularly euphausiids, were consumed more by smaller (< 120 mm) specimens of C. sloani (Roe and Badcock 1984), which were likely less efficient at capturing fishes. Overall, the incorporation of zooplankton suggested that despite occupying the piscivore guild,

C. sloani

may feed more similar to other midwater fishes than previously thought.

Similar to

C. sloani

, Stomiidae occupied a different guild than the majority of midwater fishes. Fishes, particularly myctophids, were consumed by Stomiidae, revealing some trophic

25

similarity to C. sloani ; however, Stomiidae was classified as a large crustacean consumer due to the dominance of decapods in the diet. Placement in this guild was further supported by

IsoSource, with decapods comprising 2-58% of the diets. Previous literature documented decapods, euphausiids and copepods in the stomachs of stomiid species, such as Astronesthes,

Photostomias and

Malacosteus

; however, other stomiids, such as

Idiacanthus

and

Stomias consumed fishes, (Clarke 1982; Hopkins et al. 1996; Sutton and Hopkins 1996; Sutton 2005; present study). Differences in diet composition among stomiid species suggested that guild classification for Stomiidae was not robust because guild placement for Stomiidae was dependent on the species grouped together for analyses; therefore, if more piscivorous stomiids were analyzed in this study, Stomiidae would occupy a niche more similar to

C. sloani

than

G. elongatum . Even though guild placement was variable, the overall trophic position of Stomiidae remained unchanged because large crustaceans, such as the decapod

G. valens,

consumed zooplankton (Hopkins et al. 1994), similar to myctophids, such as

D. mollis

; therefore, regardless of whether Stomiidae consumed fishes or large crustaceans, Stomiidae remained a tertiary consumer.

Gonostoma elongatum

was classified in the same guild as Stomiidae, with decapods documented as the dominant prey. In addition to consuming large crustaceans,

G. elongatum frequently incorporated smaller zooplankton, such as the copepod

Pleuromamma

spp., into its diet. This was similar to previous findings in the eastern GOM (Lancraft et al. 1988; Hopkins et al. 1996) and was supported by SIA. Clarke (1982) suggested

G. elongatum

was a zooplanktivore but it consumed large crustaceans because it reached larger sizes than other zooplanktivores. This, along with the previously mentioned studies, suggested diets shifted with ontogeny; however, GCA reported

G. elongatum consumed similar prey regardless of size. It

26

was possible that larger G. elongatum consumed similar, but trophically higher prey specimens.

Ontogenetic diet changes were documented in prey like euphausiids (Gurney et al. 2001), and could reveal ontogenetic diet shifts in

G. elongatum

with isotope data, which was documented in this study. These diet changes can alter the trophic position of G. elongatum , with larger specimens that consumed predatory prey, such as chaetognaths and

Gennada valens

, reported as trophically similar to piscivorous stomiiids, while smaller specimens were trophically similar to zooplanktivores. As a result,

G. elongatum may occupy two different trophic guilds despite consuming similar taxa.

The majority of midwater fishes were classified in the zooplanktivore guild. Isotope data also indicated a zooplanktivorous diet for midwater fishes, as fish species occupied roughly one trophic level above zooplankton.

Overall, Pleuromamma spp. was the dominant prey consumed by the majority of midwater fishes (Hopkins and Baird, 1981; Hopkins et al., 1996; Sutton et al.,

1998; present study), and the prevalence of

Pleuromamma

spp. in stomachs was attributed to its wide distribution in the upper 1000 m (Deevey and Brooks 1977). Despite the prevalence of

Pleuromamma

spp. in midwater fishes stomachs, the inclusion of other zooplankton species subdivided the zooplanktivore guild into copepod consumers, mixed zooplanktivores and generalists, which may reduce competitive pressures on prey among the zooplanktivores.

Copepods were the dominant prey for

C. alba, C. braueri, C. pseudopallida, V. tripunctulatus, D. mollis and H. benoiti , supporting previous reports (Hopkins and Baird 1981;

Hopkins et al. 1996). Although over 90% of the diet contained copepods, examination of the composition and vertical distribution of the copepod prey (Pearcy et al. 1979), suggested competitive pressure on copepods was not high as species were not consuming the same copepod species. The deepwater copepod


, documented 500 to 1500 m (Deevy and

27

Brooks 1977; Razouls et al. 2005-2010) was only reported in the stomachs of C. braueri, C. pseudopallida

and

V. tripunctulatus, suggesting these species fed at a deeper depths and indicating vertical space as a factor contributing to diet composition. Interestingly, shallower water copepod species, such as Lubbockia aculeata (0-500 m, Deevey and Brooks 1977) and

Corycaeus spp. (0-300 m, Roehr and Moore 1965), were also present in the stomachs of

C. braueri, C. pseudopallida and V. tripunctulatus . This indicated DVMs, which although not reported in

C. braueri

. (Badcock and Merrett 1977; Miya and Nemoto 1987; present study) was documented in

C. pseudopallida

and

V. tripunctulatus

(Ross et al. 2010; present study). Even though depth appeared to have some influence in prey selection, according to GCA, depth did not significantly affect prey preferences, with species generally consuming the same prey at all depths. Size could have influenced this depth related diet composition, as larger individuals of a fish species often occupied deeper depths (Hopkins and Sutton 1998) and therefore consumed deepwater copepods, while smaller midwater fishes that occupied shallower depths consumed shallow water copepod species. Unfortunately, gut content data did not support diet variation by growth, and isotope data only identified ontogenetic diet shifts in

C. pseudopallida and

Diaphus spp. Therefore, other parameters must be investigated to determine what other factors influence prey selection within copepod consumers.

Differentiation in the diets of copepod consumers can also reduce competition for copepod prey. Cyclothone alba occupied the mid mesopelagic, similar to other Cyclothone spp., but C. alba

consumed decapods, in addition to copepods, thus utilizing different prey resources.

Similarly,

H. benoiti, D. mollis,

and

V. tripunctulatus

occupied overlapping vertical depths, but only the myctophids incorporated decapods into their diets. Additionally,

D. mollis

consumed a variety of non-crustacean prey, such as fish, chaetognaths and mollusks, which separated it from

28

H. benoiti . These variations may reduce competition for copepods within the copepod consumer subguild, particularly as similar vertical space was occupied.

The majority of zooplanktivorous midwater fishes were classified as mixed zooplanktivores, which was supported by isotope data. Calanoid copepods, particularly Pleuromamma , were an important diet component for

C. pallida

,

A. aculeatus, A. hemigymnus, P. mauli, V. poweriae, B. suborbitale, L. alatus, L. guentheri, and N. valdiviae, but ostracods, euphausiids, and amphipods were also incorporated (Hopkins and Baird 1981; Hopkins and Baird 1985a; Hopkins et al. 1996;

Sutton et al. 1998; present study), which may reduce competition for Copepoda by consuming different compositions of zooplankton. Argyropelecus spp. ate a mixture of copepods, ostracods, amphipods and euphausiids, which agreed with previous studies (Hopkins and Baird 1981;

Hopkins and Baird 1985a; Sutton et al. 1998); however, A. aculeatus also targeted noncrustacean prey, particularly mollusks, while

A. hemigymnus

targeted only ostracods and copepods (Hopkins and Baird 1985a; Kawaguchi and Mauchline 1987; present study). For

C. pallida and M. affine, amphipods were selectively consumed; however, previous studies only supported this selectivity for

M. affine

(Hopkins and Gartner 1992), as

C. pallida

was previously known to target ostracods (Burghart et al. 2010).

Lampanyctus alatus and

L. guentheri

targeted halocyprid ostracods, though euphausiids were considered a dominate prey item in previous studies (Hopkins and Baird 1985b; Hopkins et al. 1996). The importance of euphausiids in the diets of L. alatus and L. guentheri increased with size (Hopkins and Baird 1985b; Hopkins and

Gartner 1992), and the differences in diet composition among these studies were attributed to the majority (84%) of specimens in this study being juveniles (< 30 mm). The prevalence of juveniles also explained the lack of ontogenetic diet shifts in GCA. Other species, such as

V. poweriae, B. suborbitale, and

D. mollis,

occasionally incorporated fishes into their diets, which

29

reduced competition for copepods, amphipods, ostracods and euphausiids as prey. This also explained the enriched δ 15 N documented in

V. poweriae

compared to

P. mauli

, which did not consumed any fishes. Gelatinous prey, such as salps and mollusks, also played a role in the diets of mixed zooplanktivores, though these prey were often underestimated since they were digested more quickly than crustaceans (Gartner et al. 1997).

Ceratoscopelus warmingii also had a mixed zooplankton diet, with almost 40 different prey items identified in its stomach; however,

C. warmingii

was classified into its own subguild because almost 40% of the diet contained non-crustacean prey, which was supported by

IsoSource. This high diet diversity in C. warmingii was previously documented in Hopkins and

Baird (1975) and Hopkins et al. (1996), with Robinson (1984) also noting

C. warmingii

as an occasional herbivore. By establishing a generalist feeding strategy, C. warmingii can occupy a unique niche, despite being restricted by a narrow spatial and temporal feeding pattern as documented in the majority of zooplanktivores (Robinson 1984).

Spatial and Temporal influences on diet

Resource partitioning in the midwater community was previously reported by Hopkins and

Sutton (1998) using parameters such as depth, time and size. Although size, depth, location and time of day did not affect prey preferences for individual species, it was evident these parameters influenced the trophic structure of the midwater community (Hopkins and Sutton 1998).

In the piscivore guild, competition for fish prey may be reduced through the utilization of vertical space even though all specimens of

C. sloani

occupied the same feeding guild.

Chauliodus sloani

occupied the mid mesopelagic, which contained fewer midwater fish species than the upper mesopelagic for

C. sloani to compete with for fish prey. Additionally, asynchronous migrations previously documented in

C. sloani

suggested only the hungry portion

30

of stomiids migrate to the epipelagic (Sutton and Hopkins et al. 1996). This migration pattern was also apparent in this study and utilization of vertical space in this manner allowed

C. sloani to effectively partition resources, even with

C. sloani

occupying the same guild and habitat as other midwater fish species.

Competition among large crustacean consumers for decapods was also influenced by vertical space. In general, Stomiidae occupied the lower mesopelagic zone during the day, while G. elongatum

occupied the mid mesopelagic. This spatial variation suggested these species may not be competing for large crustaceans, as

G. elongatum

and Stomiidae may consume prey at different depths. Additionally, these crustacean prey were also vertically distributed (Hopkins and Sutton 1998) and therefore may be consumed at different depths. Utilization of vertical space for migrations was also used differently with this guild, with Stomiidae undergoing asynchronous migrations (Sutton and Hopkins et al. 1996; Kenaley 2008; present study), thereby reducing predation pressures on large crustaceans since all stomiids did not migrate to the epipelagic at night, while G. elongatum underwent DVMs, with the majority of specimens migrating to the upper mesopelagic/epipelagic to feed (Lancraft et al. 1988; present study). This was similar to the migration pattern documented in zooplanktivores, like myctophids (Hopkins and Gartner 1992), suggesting

G. elongatum

may be more similar to zooplanktivores than to

Stomiidae.

Despite the lack of DVMs in C. alba and C. braueri, utilization of vertical space may influence other copepod consumers, like

D. mollis and

H. benoiti.

These myctophids migrated to the surface at night, feeding at shallower depths than the other copepod consumers. Additionally, the DVMs undertaken by these fishes followed the migration of copepod prey, such as

Pleuromamma

spp. (Pusch et al. 2004), which enabled these myctophid species to feed on dense

31

prey populations in the epipelagic. This use of vertical space ensured D. mollis and H. benoiti did not have to compete with other copepod consumers for their copepod prey sources.

Examination of time, though not significant within any species emphasized a general trend for feeding at night. Despite the apparent preference for feeding at night, all species, except M. affine

, occasionally consumed prey during the day. Feeding spread across a 24 hour period was previously documented in myctophids and sternoptychids (Merrett and Roe 1974; Clarke 1978;

Pusch et al. 2001) and can enhance resource partitioning (Hopkins and Sutton 1998) as species have less restrictions.

Additional insights with SIA

Site differences

Spatial variation due to the complex bottom topography and hydrography in the GOM was hypothesized to affect diet composition in midwater fishes, particularly as diet variations were previously attributed to locality in myctophids (Pakhomov et al. 1996; Pusch et al. 2004).

However, GCA documented similar feeding among sites, which was also supported by previous findings in the eastern GOM (Hopkins et al. 1996). In contrast, spatial variations were documented with SIA and indicated potential changes in the prey species consumed. Carbon values for phytoplankton were similar among sites; however,

V. tripunctulatus

was enriched δ 13 C at AT340. Warm core rings, such as the one present during sampling at AT340 (Ross et al.

2010), can change zooplankton biomass by increasing diatom productivity and thereby alter isotopic composition in POM and zooplankton (Waite et al. 2007). Since enriched values reflected the assimilated prey consumed by

V. tripunctulatus

at an earlier time than it was possible that POM and invertebrate samples would also reflect enriched δ 13 C if collected after the ring moved out of the sampling area. This concept was also true for invertebrates. Although

32

δ 13 C was similar, both decapods and euphausiids were enriched in δ 15 N at GC852 compared to

AT340, which suggested these species may have consumed trophically higher organisms or that the zooplankton biomass present during sampling was different from the zooplankton present before the warm-core ring. Unfortunately as sampling was only conducted during the presence of the warm core ring, it was not possible to confirm this notion.

In contrast, G. elongatum, A. aculeatus, and L. alatus were enriched in δ 15 N at GC852 compared to AT340

.

Generally, an increase δ 15 N suggested an increase in trophic level (Fry

1988); however, the overall trophic structure was similar at both sites, with specimens documented as zooplanktivores, which was confirmed with GCA. Ontogenetic diet shifts could also explain this difference, but an ontogenetic diet shift was only documented in

G. elongatum.

The location of the study sites may also influence isotope values of these fishes. The Mississippi

River affected isotope values in the northwestern GOM, with riverine sources causing enriched

δ 15 N in king mackerel (Roelke and Cifuentes 1997). If the Mississippi River did cause this spatial difference, its effects would be apparent in more taxa; however, this was not the case.

Therefore, diet composition may was the most likely cause for enriched 15 N in

G. elongatum, A. aculeatus, and

L. alatus

. Soft bodied prey, such as chaetognaths and mollusks, may be consumed more at GC852, but, as previously stated, were underestimated in GCA due to faster digestive rates of soft bodied prey.

Diet variations

SIA implied

M. affine

utilized a generalist feeding strategy similar to

C. warmingii

.

Myctophum affine

was previously reported to primarily consume crustaceans (Hopkins and

Sutton 1998), placing it on the third trophic level; however, the low δ 15 N values suggested

M. affine occupied the second trophic level. Low δ 15 N values in

M. affine may result from

M. affine

33

ingesting Trichodesium , a cyanobacterium with global distribution that can undergo extensive blooms and supply new nitrogen to areas in which it is found (Holl et al. 2007). Previous literature reported

Trichodesmium

depleting δ 15 N values of POM (Montoya et al. 2002), a signal that may be passed up the food chain. It was also possible that M. affine was herbivorous, although GCA revealed only minimal amounts of phytoplankton in the stomach. Additionally,

M. affine may consume δ 15 N depleted prey items, such as salps, which would place M. affine in a niche more closely related to

C. warmingii

.

Methodology

Trophic position calculations provided a characterization of the trophic structure of midwater fishes by using GCA and SIA (Vander Zanden et al. 1997; Woodward and Hildrew 2002;

Rybcynski et al. 2008) and enabled a quantitative comparison between GCA and SIA. Of the 17 midwater fish species compared, differences between methods were significant in 12 species, highlighting the importance of incorporating multiple techniques to discern trophic relationships among midwater fishes (Vander Zanden et al. 1997; Woodward and Hildrew 2002; Rybcynski et al. 2008). In most cases, SIA designated fish species at a trophically lower position than GCA. It was possible that nitrogen-depleted gelatinous prey, which are quickly digested and often unidentifiable (Gartner et al. 1997), were consumed more frequently than previously documented and play a more significant role in the diets of midwater fishes. Also, if midwater fishes consumed trophically higher prey items, like fish, on occasion then GCA-based trophic positions would be greater than SIA-based because rare prey are masked by the continuous presence of trophically low prey items, like copepods, but its presence in the gut would increase the GCAbased trophic position.

34

Utilization of both methods allowed inferences to be made when limitations occur in one method, such as limited data from empty stomachs or documenting only generalized prey categories in the diets. For example, all

Cyclothone spp. were zooplanktivores, however,

C. pallida was enriched in 15 N compared to other Cyclothone spp. GCA revealed that C. pallida consumed mixed zooplankton as opposed to targeting copepods, as documented in

C. alba, C. braueri and C. pseudopallida . This difference in prey composition were also evident for sternoptychids, with the mixed zooplanktivore

A. hemigymnus

having enriched 15 N compared to the copepod consumer

V. tripunctulatus

. Although these differences were documented using

SIA, SIA only provides a general overview of the diet and GCA was needed to identify the subtle difference in diets for species within the trophic guild (Rybczynski et al. 2008). Another advantage of utilizing SIA was the ability to determine diet information if few specimens are collected or if GCA provided little data.

Sternoptyx

spp. and Melamphaidae were analyzed using

SIA and were placed in the zooplanktivore guild despite low sample sizes and examination of previous literature (Hopkins and Baird 1985a; Hopkins et al. 1996) supported these results.

Interesting Note

SIA indicated that chemosynthetic energy did not significantly influence the midwater community. This does not however prove that chemosynthetic energy had no influence, but rather the extent of influence was below a measurable degree using the above methods.

Additionally, one G. elongatum , captured in the benthic otter trawl, was significantly depleted

13 C (-25‰) indicating the assimilation of chemosynthetic material. This specimen, though collected in the benthic otter trawl, may undergo DVM and interact with other species in the water column. It was also possible that midwater fishes were aggregating on the bottom and exploiting food resources, as previously documented in the southeastern US (Gartner et al. 2008)

35

and documented in benthic fauna near seeps (MacAvoy 2002). Unfortunately, midwater sampling conducted in this study did not extend to the bottom and therefore would have avoided capture.

CONCLUSIONS

1) The basic trophic structure of midwater fishes in the north-central GOM was classified in to three guilds: piscivore, large crustacean consumer and zooplanktivore; however zooplankton was a common prey source and documented in the stomachs of all species except

C. sloani.

2) Although size, depth, time and location did not significant affect diet composition, size and depth may influence prey selection, as the majority of specimens analyzed were juveniles and different species occupied different depth ranges.

3) DVMs were apparent in many species, with species following prey to the epipelagic at night; however, feeding was not limited to the epipelagic or to night, which may help reduce competitive pressure for zooplankton.

4) GCA and SIA complemented each other and differences between methods highlighted the importance of utilizing both to discern trophic structure accurately because SIA documented only general feeding patterns, while GCA provided details on the prey that assist with determining feeding guilds in the midwater fish community.

5) Utilization of chemosynthetic energy sources was not documented in the midwater fish community, though this did not prove chemosynthetic cold seep community had no influence on midwater fishes, as influences may be minor and undetected by the methods utilized in this study.

36

LITERATURE CITED

Adams, N.J., Moloney, C. and R. Navarro. 2004. Estimated food consumption by penguins at the

Prince Edward Islands. Antarctic Science 5: 245-252.

Ashjian, C., Smith, S., Flagg, C., and N. Idrisi. 2002. Distribution, annual cycle, and vertical migration of acoustically derived biomass in the Arabian Sea during 1994-1995. Deep-Sea

Research 49: 2377-2402.

Badcock, J., and N.R. Merrett, 1977. On the distribution of midwater fishes in the eastern North

Atlantic. In: Andersen, N.R., Zahuranec, B.J. (Eds.). Oceanic sound scattering prediction.

Plenum Press, N.Y., pp. 249-282.

Baguley, J.G., Montagna, P.A., Hyde, L.J., Kalke, R.D. and G.T. Rowe. 2006. Metazoan meiofauna abundances in relation to environmental variables in the northern Gulf of

Mexico deep sea. Deep-Sea Research I 53: 1344-1362.

Beamish, R.J., Leask, K.D., Ivanov, O.A., Balanov, A.A., Orlov, A.M. and B. Sinclair. 1999.

The ecology, distribution, and abundance of midwater fishes of the Subartic Pacific gyres.

Progress in Oceanography 43: 399-442.

Behringer, D.C. and M.J. Butler, IV. 2006. Stable isotope analysis of production and trophic relationships in a tropical marine hard-bottom community. Oecologia 148: 334-341.

Benstead, J.P., March, J.G., Fry, B., Ewel, K., and C.M. Pringle. 2006. Testing IsoSource: stable isotope analysis of a tropical fishery with diverse organic matter sources. Ecology 87: 326-

333.

Borodulina, O.D. 1972. The feeding of mesopelagic predatory fish in the open ocean. Journal of

Ichthyology 12: 692-703.

37

Bosley, K.L. and S.C. Wainright. 1999. Effects of preservatives and acidification on the stable isotope ratios ( 15 N: 14 N, 13 C: 12 C) of two marine animals. Canadian Journal of Fisheries and

Aquatic Sciences 56: 2181-2185.

Brodeur, R., and O. Yamamura. 2005. Micronekton of North Pacific. PICES report N ˚ 30, pp 11.

Burghart, S.E., Hopkins, T.L., and J.T. Torres. 2010. Partitioning of food resources in bathypelagic micronekton in the eastern Gulf of Mexico. Marine Ecology Progress Series

399: 131-140.

Butler, M., Bollens, S.M., Burkhalter, B., Madin, L.P. and E. Horgan. 2001. Mesopelagic fishes of the Arabian Sea: distribution, abundance and diet of Chauliodus pammelas, Chauliodus sloani, Stomias affinis,

and

Stomias nebulosus

. Deep-Sea Research II 48: 1369-1383.

Clarke, K.R., Warwick, R.M., 2001. Change in marine communities: an approach to statistical analysis and interpretation, 2 nd edition. PRIMER-E, Plymouth. 172 pp.

Clarke, K.R., Gorley, R.N., 2006. PRIMER v6: User manual/tutorial. PRIMER-E, Plymouth.

186 pp.

Clarke, T.A. 1982. Feeding habits of stomiatoid fishes from Hawaiian waters. Fishery Bulletin

80: 287-304.

Cornejo, R. and Koppelmann R. 2006. Distribution patterns of mesopelagic fishes with special reference to

Vinciguerria lucetia

Garman 1899 (Phosichthyidae: Pisces) in the Humbolt

Current Region off Peru. Marine Biology 149: 1519-1537.

Deevey, G.B. and A.L. Brooks. 1977. Copepods of the Sargasso Sea off Bermuda: species composition, and vertical and seasonal distribution between the surface and 200 m.

Bulletin of Marine Science 27: 256-291.

38

Demopoulos, A.W.J., Fry, B., and C.R. Smith. 2007. Food web structure in exotic and native mangroves: a Hawaii-Puerto Rico comparison. Oecologia 153: 675-686.

Drazen, J.C., Popp, B.N., Choy, C.A., Clemente, T., DeForest L.G., and K.L. Smith. 2008.

Bypassing the abyssal benthic food web: macrourid diet in the eastern North Pacific inferred from stomach contents and stable isotopes analyses. Limnology and

Oceanography 53: 2644-2654.

France, R.L. and R.H. Peters. 1997. Ecosystem differences in the trophic enrichment of δ 13 C in aquatic food webs. Canadian Journal of Fisheries and Aquatic Sciences 54: 1255-1258.

Fry, B. 1988. Food web structure on Georges Bank from stable C, N, and S isotopic compositions. Limnology and Oceanography 33: 1182-1190.

Fry, B. 2006. Stable Isotope Ecology. Springer, New York.

Fry, B. 2007. Couple N, C, S stable isotope measurements using a dual-column gas chromatography system. Rapid Communications in Mass Spectrometry 21: 750-756.

Gartner, Jr., J.V., Crabtree, R.E. and K.J. Sulak. 1997. Feeding at Depth. pp115-194. In: D.J.

Randall and A.P. Farrell (Eds) Deep Sea Fishes. Academic Press, New York.

Gartner, Jr. J.V., Sulak, K.J., Ross, S.W. and A.M. Necaise. 2008. Persistent near-bottom aggregations of mesopelagic animals along the North Carolina and Virginia continental slopes. Marine Biology 153: 825-841.

Gjøsaeter, J. and K. Kawaguchi. 1980. A review of the world resources of mesopelagic fish.

FAO Fisheries Technical Paper 193: 151 pp.

Gurney, L.J., Froneman, P.W., Pakhomoc, E.A., and C.D. McQuaid. 2001. Trophic positions of three euphausiid species from the Prince Edward Islands (Southern Ocean): implications for the pelagic food web structure. Marine Ecology Progress Series 217: 167-174.

39

Hadwen, W.L., Russel, G.L., and A.H. Arthington. 2007. Gut content- and stable isotope-derived diets of four commercially and recreationally important fish species in two intermittently open estuaries. Marine and Freshwater Research 58: 363-375.

Hemminga, M.A. and M.A. Mateo. 1996. Stable carbon isotope in seagrasses: variability in ratios and use in ecological studies. Marine Ecology Progress Series 140: 285-298.

Hidaka, K., Kawaguchi, K., Murakiami, M. and M. Takahashi. 2001. Downward transport of organic carbon by diel migratory micronekton in the western equatorial Pacific: its quantitative and qualitative importance. Deep-Sea Research I 48: 1923-1939.

Hobson, K.A., Fisk, A., Karnovsky, N., Holst, M. Gagnon, J.M. and M. Fortier. 2002. A stable isotope ( δ 13 C, δ 15 N) model for the North Water food web: implications for evaluating trophodynamics and the flow of energy and contaminants. Deep-Sea Research II 49: 5131-

5150.

Holl, C.M., Villareal, T.A., Payne, C.D., Clayton, T.D., Hart, C. and J.P. Montoya. 2007.

Trichodesmium in the western Gulf of Mexico: 15 N

2

-fixation and natural abundance stable isotope evidence. Limnology and Oceanography 52: 2249-2259.

Hopkins, T.L. and R.C. Baird. 1975. Net feeding in mesopelagic fishes. Fishery Bulletin US 73:

908-914.

Hopkins, T.L. and R.C. Baird. 1981. Trophodynamics of the fish


.

I. Vertical distribution, diet and feeding chronology. Marine Ecology Progress Series 5: 1-

10.

Hopkins, T.L. and R.C. Baird. 1985a. Feeding ecology of four hatchetfishes (Sternoptychidae) in the eastern Gulf of Mexico. Bulletin of Marine Science 36: 260-277.

40

Hopkins, T.L. and R.C. Baird. 1985b. Aspects of the trophic ecology of the mesopelagic fish

Lampanyctus alatus

(Family Myctophidae) in the eastern Gulf of Mexico. Biological


Hopkins, T.L., Flock, M.E., Gartner, Jr., J.V. and J.J. Torres. 1994. Structure and trophic ecology of a low latitude midwater decapod and mysid assemblage. Marine Ecology Progress

Series 109: 143-156.

Hopkins, T.L. and Gartner, Jr., J.V. 1992. Resource portioning and predation impact of a low latitude myctophid community. Marine Biology 114: 185-197.

Hopkins, T.L. and T.T. Sutton. 1998. Midwater fishes and shrimps as competitors and resources partitioning in low latitude oligotrophic ecosystems. Marine Ecology Progress Series 164:

37-45.

Hopkins, T.L., Sutton, T.T., and T.M. Lancraft. 1996. The trophic structure and predation impact of a low latitude midwater fish assemblage. Progress in Oceanography. 38: 205-239.

Hyun, K.H. and P.J. Hogan. 2008. Topographic effects on the path and evolution of Loop

Current eddies. Journal of Geophysical Research 113, doi: 10.1029/2007JC004155.

Jacob, U., Mintenbeck, K., Brey, T., Knust, R., and K. Beyer. 2005. Stable isotope food web studies: a case for standardized sample treatment. Marine Ecology Progress Series 287:

251-253.

Jarosz, E. and S.P. Murray. 2005. Velocity and transport characteristics of the Louisiana-Texas coastal current. pp. 143-156. In: W.S. Sturges and A. Lugo-Fenandez (Eds.) Circulation in the Gulf of Mexico: Observations and Models. AGU Geophysical Monograph Series.

Washington, DC.

41

Kawaguchi, K. and J. Mauchline. 1982. Biology of myctophid fishes (Family Myctophidae) in the Rockall Trough, Northeastern Atlantic Ocean. Biological Oceanography 1: 337-373.

Kehayias, G., Lykakis, J. and N. Fragopoulu. 1996. The diets of the chaetognaths

Sagitta enflata,

S. erratodentata atlantica and S. bipunctata at difference seasons in Eastern Mediterranean coastal waters. ICES Journal of Marine Science 53: 837-846.

Kenaley, C.P. 2008. Diel vertical migrations of the loosejaw dragonfishes (Stomiiformes:

Stomiidae: Malacosteinae): a new analysis for rare pelagic taxa. Journal of Fish Biology

73: 888-901.

Kennicutt II, M.C., Burke, R.A., MacDonald, I.R., Brooks, J.M., Denoux, G.J. and S.A. Macko.

1992. Stable isotope partitioning in seep and vent organisms: chemical and ecological significance. Chemical Geology 101: 293-310.

Kharlamenko, V.I., Kiyashko, S.I., Imbs, A.B. and D.I. Vyshkvartev. 2001. Identification of food sources of invertebrates from the seagrass

Zostera marina

community using carbon and sulfur stable isotope ratio and fatty acid analyses. Marine Ecology Progress Series 220:

103-117.

Kinzer, J. 1977. Observations on feeding habits of mesopelagic fish

Benthosema glaciale

(Myctophidae) off NW Africa. pp. 381-392. In: Anderson, N.R., Zahuranec, B.J. (Eds.),

Oceanic Sound Scattering Prediction. Plenum Press, New York.

Kling, G.W., Fry, B. and J. O’Brien. 1992. Stable isotopes and planktonic trophic structure in

Arctic lakes. Ecology 73: 561-566.

Lajtha, K. and R.H. Michener. (Eds.) 1994. Stable isotopes in ecology and environmental science. Blackwell Scientific Publications. Boston, MA.

42

Lancraft, T.M., Hopkins, T.L. and J.J. Torres. 1988. Aspects of the ecology of the mesopelagic fish


(Gonostomatidae, Stomiiformes) in the eastern Gulf of Mexico.

Marine Ecology Progress Series 49: 27-40.

Laptikhovsky, V.V. 2005. A trophic ecology of two grenadier species (Macrouridae, Pisces) in deep waters of the Southwest Atlantic. Deep-Sea Research I 52: 1502-1514.

Levin, L.A. 2005. Ecology of cold seep sediments: Interactions of fauna with flow, chemistry and microbes. Oceanography and Marine Biology: An Annual Review 43: 1-46.

MacAvoy, S.E., Carney, R.S., Fisher, C.R. and S.A. Macko. 2002. Use of chemosynthetic biomass by large, mobile, benthic predators in the Gulf of Mexico. Marine Ecology

Progress Series 225: 65-78.

MacAvoy, S.E., Morgan, E., Carney, R.S. and S.A. Macko. 2008. Chemoautotrophic production incorporated by heterotrophs in Gulf of Mexico hydrocarbon seeps: an examination of mobile benthic predators and seep residents. Journal of Shellfish Research 27: 153-161.

Merrett, N.R. and H.S.J. Roe. 1974. Patterns and selectivity in the feeding of certain mesopelagic fishes. Marine Biology 28: 115-126.

Minagawa, M. and E. Wada. 1984. Stepwise enrichment of 15 N along food chains: further evidence and the relation between δ 15 N and animal age. Geochimica et Cosmochimica

Acta 48: 1135-1140.

Miya, M. and T. Nemoto. 1987. Some aspects of the biology of the micronektonic fish

Cyclothone pallida and

Cyclothone acclinidens

(Pisces: Gonostomatidae) in Sagami Bay, central Japan. Journal of the Oceanographical Society of Japan 42: 473-480.

43

Montoya, J.P., E.J. Carpenter, and D.G. Capone. 2002. Nitrogen-fixation and nitrogen isotope abundances in zooplankton of the oligotrophic North Atlantic. Limnology and


Pakhomov, E.A., Perissinotto, R., and C.D. McQuaid. 1996. Prey composition and daily rations of myctophid fishes in the Southern Ocean. Marine Ecology Progress Series 134: 1-14.

Paradis, Y., Bertolo, A. and P. Magnan. 2008. What do the empty stomachs of northern pike

(

Esox lucius

) reveal? Insights from the carbon ( δ 13 C) and nitrogen ( δ 15 N) stable isotopes.

Environmental Biology of Fish 83: 441-448.

Pearcy, W.G., Lorz, H.V. and W.T. Peterson. 1979. Comparison of the feeding habits of migratory and non-migratory

Stenobrachius leucopsarus

(Myctophidae). Marine Biology

51: 1-8.

Phillips, D.L. and J.W. Gregg. 2003. Source partitioning using stable isotopes: coping with too many sources. Oecologia 136: 261-269.

Pinnegar, J.K. and N.V.C. Polunin. 1999. Differential fractionation of δ 13 C and δ 15 N among fish tissues: implications for the study of trophic interactions. Functional Ecology 13: 225-231.

Post, D.M. 2002. Using stable isotopes to estimate trophic position: Models, methods and assumptions. Ecology 73: 703-718.

Potier, M., Marsac, F., Cherel, Y., Lucas, V., Sabatié, R., Maury, O. and F. Ménard. 2007.

Forage fauna in the diet of three large pelagic fishes (lancetfish, swordfish and yellowfin tune) in the western equatorial Indian Ocean. Fisheries Research 83: 60-72.

Pusch, C., Hulley, P.A., and K.H. Kock. 2004. Community structure and feeding ecology of mesopelagic fishes in the slope waters of King George Island (South Shetlands Islands,

Antarctica). Deep-Sea Research 51: 1685-1708.

44

Razouls, C., de Bovee, F., Kouwenberg, J., and N. et Desreumaux. 2005-2010. Diversity and geographical distributions of marine planktonic copepods. http://copepodes.obsbanyuls.fr/en.

Robinson, B.H. 1984. Herbivory by the myctophid fish Ceratoscopelus warmingii . Marine

Biology 84: 119-123.

Roberts, H.H., Fisher, C.R., Brooks, J.M., Bernard, B., Carney, R.S., Cordes, E., Shedd, W.,

Hunt, Jr., J., Joye, S., MacDonald, I.R., and C. Morrison. 2007b. Exploration of the deep

Gulf of Mexico slope using DSV Alvin: site selection and geologic character. Gulf Coast

Association of Geologists Society Transactions 57: 647-659.

Roe, H.S.J. and J. Badcock. 1984. The diel migrations and distributions within a mesopelagic community in the northeast Atlantic. 5. Vertical migrations and feeding of fish. Progress in


Roehr, M.G. and H.B. Moore. 1965. The vertical distribution of some common copepods in the straits of Florida. Bulletin of Marine Science 15: 565-570.

Roelke, L.A. and L.A. Cifuentes. 1997. Use of stable isotopes to assess groups of king mackerel,

Scomberomorus cavalla

, in the Gulf of Mexico and southeastern Florida. Fishery Bulletin

95: 540-551.

Rooker, J. R., Turner, J.P. and S.A. Holt. 2006. Trophic ecology of

Sargassum

-associated fishes in the Gulf of Mexico determine from stable isotopes and fatty acids. Marine Ecology

Progress Series 313: 249-259.

Ross, S.W. and M.L. Moser. 1995. Life history of juvenile gag,

Mycteroperca microlepis

, in

North Carolina estuaries. Bulletin of Marine Science 56: 222-237.

45

Ross, S.W., Quattrini, A.M., Roa-Varon, A.Y. and J.P. McClain. 2010. Species composition and distributions of mesopelagic fishes over the slope of the north-central Gulf of Mexico.

Deep-Sea Research II, doi: 10.1016/j.dsr2.2010.05.008.

Rybczynski, S.M., Walters, D.M., Fritz, K.M. and B.R. Johnson. 2008. Comparing trophic position of stream fishes using stable isotope and gut content analyses. Ecology of

Freshwater Fish 17: 199-206.

Schmitz, Jr., W.J., Biggs, D.C., Lugo-Fernandez, A., Oey, L.Y. and W. Sturges. 2005. A synopsis of the circulation in the Gulf of Mexico and on its continental margins. pp. 11-30.

In: W.S. Sturges and A. Lugo-Fenandez (Eds.) Circulation in the Gulf of Mexico:

Observations and Models. AGU Geophysical Monograph Series. Washington, DC.

Sturges, W., A. Lugo-Fernandez, and M.D. Shargel. 2005. Introduction. pp 1-10. In: W.S.

Sturges and A. Lugo-Fenandez (Eds.) Circulation in the Gulf of Mexico: Observations and

Models. AGU Geophysical Monograph Series. Washington, DC.

Sutton, T.T. 2005. Trophic ecology of the deep-sea fish Malacosteus niger (Pisces: Stomiidae): an enigmatic feeding ecology to facilitate a unique visual system. Deep-Sea Research I 52:

2065-2076.

Sutton, T.T. and T.L. Hopkins. 1996. Species composition, abundance, and vertical distribution of the stomiid (Pisces: Stomiiformes) fish assemblage of the Gulf of Mexico. Bulletin of

Marine Science 59: 530-542.

Sutton, T.T., Hopkins, T.L. and T.M. Lancraft. 1998. Trophic diversity of a mesopelagic fish community. In: Pierrot-Bults, A.C. and S. van der Spoel (Eds.), Pelagic Biogeography

ICoPB II. Proceedings of the Second International Conference. IOC Workshop Report No.

142. UNESCO, Paris, pp. 353-357.

46

Thomas, C.J. and L.B. Cahoon. 1993. Stable isotope analyses differentiate between trophic pathways supporting rocky-reef fishes. Marine Ecology Progress Series. 95: 19-24.

Vander Zanden, M.J., Cabana, G., and J.B. Rasmussen. 1997. Comparing trophic positions of freshwater fish calculated using stable nitrogen isotope rations ( δ 15 N) and literature diet data. Canadian Journal of Fisheries and Aquatic Sciences 54: 1142-1158.

Van Dover, C.L. 2000. The ecology of deep-sea hydrothermal vents. Princeton University Press:

Princeton, NJ.

Waite, A.M., Muhling, B.A., Holl, C.M., Beckley, L.E., Montoya, J.P., Strzelecki, J., Thompson,

P.A. and S. Pesant. 2007. Food web structure in two counter-rotating eddies based on δ 15 N and δ 13 C isotopic analyses. Deep-Sea Research II 54: 1055-1075

Williams, A., Koslow, J.A., Terauds, A. and K. Haskard. 2001. Feeding ecology of five fishes from the mid-slope micronekton community off southern Tasmania, Australia. Marine

Biology 139: 1177-1192.

Woodward, G. and A.G. Hildrew. 2002. Food web structure in riverine landscapes. Freshwater

Biology 47: 777-798.

Young, J.W. and S.J.M. Blaber. 1986. Feeding ecology of three species of midwater fishes associated with the continental slope of eastern Tasmania, Australia. Marine Biology 93:

147-156.

47

Table 1. Surface and midwater stations sampled over three cold seep sites (AT340, GC852, and AC601) (see Fig.1) in the Gulf of

Mexico (9-25 August 2007). TT = Tucker trawl including plankton net inside Tucker trawl, PN 1 = 0.5 m dia. plankton net, PN 2 = 1 m dia. plankton net, NN = Neuston net, 5 GB = 5 gallon bucket for POM samples, D = day (0730 to 1830 hr CDT), N = night (2030 to

0530 hr CDT), TW = twilight (0530 to 0730 and 1830 to 2030 hr CDT). * = maximum depths sampled for non discrete tows (TT did not close and fished to surface). Blanks in depth columns indicated TDR did not record any data.

Station Date Site Gear Time

Start

Latitude

Start

Longitude

End

Latitude

End

Longitude

Mean Depth

Sampled (m)

CH-2007-002 09-Aug-07 GC852 TT

CH-2007-003 09-Aug-07 GC852 TT

N

N

27° 07.200 91° 09.769 27° 06.278 91° 09.945

27° 07.263 91° 09.781 27° 06.404 91° 10.023

611

390

CH-2007-004 10-Aug-07 GC852 5 GB N

CH-2007-005 10-Aug-07 GC852 TT N

CH-2007-006 10-Aug-07 GC852 5 GB N

CH-2007-007 10-Aug-07 GC852 TT

CH-2007-008 10-Aug-07 GC852 TT

N

N

CH-2007-009 10-Aug-07 GC852 PN 1 N

CH-2007-017 10-Aug-07 GC852 TT N

CH-2007-018 10-Aug-07 GC852 TT N

27° 07.979

27° 07.547

27° 07.288

27° 06.354

91° 09.028

91° 09.694

91° 09.771

91° 09.929

27° 07.979

27° 06.552

27° 07.288

27° 07.386

91° 09.028

91° 09.927

91° 09.771

27° 07.318 91° 09.736 27° 08.244 91° 09.480

27° 06.984 91° 09.844 27° 06.034 91° 10.025

27° 07.042 91° 09.829 27° 06.048 91° 10.025

27° 07.407 91° 09.878 27° 06.436 91° 09.948

91° 09.858

0

323

0

296*

303

0

612

486*

CH-2007-019 10-Aug-07 GC852 TT

CH-2007-020 11-Aug-07 GC852 TT

CH-2007-021 11-Aug-07 GC852 TT

CH-2007-022 11-Aug-07 GC852 TT

CH-2007-023 11-Aug-07 GC852 TT

N

N

CH-2007-024 11-Aug-07 GC852 PN 1 N

CH-2007-028 11-Aug-07 GC852 PN 1 D

CH-2007-029 11-Aug-07 GC852 TT D

N

N

N

27° 07.823

27° 05.979

27° 07.074

91° 09.780

91° 09.940

91° 09.893

27° 06.975

27° 07.053

27° 06.278

91° 09.917

91° 09.864

91° 09.982

27° 06.550 91° 09.957 27° 07.604 91° 09.886

27° 07.715 91° 09.851 27° 06.680 91° 09.963

27° 08.093 91° 09.807 27° 07.078 91° 09.925

27° 07.769 91° 09.810 27° 08.269 91° 09.817

27° 10.481 91° 09.684 27° 09.381 91° 09.547

CH-2007-030 11-Aug-07 GC852 TT TW 27° 07.591 91° 09.272 27° 06.815 91° 09.939

CH-2007-031 11-Aug-07 GC852 TT N 27° 06.280 91° 10.229 27° 07.036 91° 09.676

CH-2007-032 11-Aug-07 GC852 TT

CH-2007-033 12-Aug-07 GC852 TT

N

N

27° 07.289

27° 06.204

91° 09.857

91° 10.505

27° 06.706

27° 07.071

91° 10.685

91° 09.742

410

197

249

345

712*

0

0

722

378

382*

492

248

48

CH-2007-034 12-Aug-07 GC852 5 GB N

CH-2007-035 12-Aug-07 GC852 TT

CH-2007-036 12-Aug-07 GC852 TT

CH-2007-037 12-Aug-07 GC852 TT

N

N

N

CH-2007-038

CH-2007-039

CH-2007-041

CH-2007-043

CH-2007-044

12-Aug-07 GC852

12-Aug-07 GC852

12-Aug-07 GC852

12-Aug-07 GC852

12-Aug-07 GC852

TT

PN 1

PN 1

NN

TT

N

N

D

D

D

Table 1 cont.

27° 06.928 91° 09.881 27° 06.928 91° 09.881

27° 07.282 91° 09.630 27° 06.444 91° 10.342

27° 06.467 91° 10.403 27° 07.270 91° 09.604

27° 07.284 91° 09.637 27° 06.455 91° 10.320

27° 06.779 91° 10.077 27° 08.391 91° 08.713

27° 08.036 91° 08.901 27° 08.138 91° 08.817

27° 02.139 91° 09.618 27° 01.057 91° 09.738

27° 10.116 91° 09.910 27° 10.824 91° 09.867

27° 12.181 91° 09.454 27° 10.146 91° 09.474

CH-2007-045 12-Aug-07 GC852 TT TW 27° 08.756 91° 09.574 27° 07.816 91° 09.565

CH-2007-046 12-Aug-07 GC852 TT N 27° 06.034 91° 09.704 27° 05.290 91° 09.704

CH-2007-047 12-Aug-07 GC852 TT N 27° 05.665 91° 09.647 27° 06.713 91° 09.744

CH-2007-048 12-Aug-07 GC852 TT

CH-2007-049 13-Aug-07 GC852 TT

N

N

CH-2007-050 13-Aug-07 GC852 TT N

CH-2007-051 13-Aug-07 GC852 5 GB N

CH-2007-052 13-Aug-07 GC852 PN 1 N

27° 07.203 91° 09.795 27° 06.338 91° 09.781

27° 06.454 91° 09.621 27° 07.493 91° 09.626

27° 07.626 91° 09.789 27° 06.726 91° 09.752

27° 07.516 91° 09.790 27° 07.516 91° 09.790

27° 07.274 91° 09.786 27° 06.794 91° 09.760

CH-2007-053 13-Aug-07 GC852 TT N 27° 06.415 91° 09.700 27° 05.454 91° 09.695

CH-2007-054 13-Aug-07 GC852 TT TW 27° 08.270 91° 09.827 27° 07.304 91° 09.805

CH-2007-063 13-Aug-07 GC852 TT TW 27° 07.349 91° 10.193 27° 06.229 91° 10.163

CH-2007-064 13-Aug-07 GC852 TT

CH-2007-065 13-Aug-07 GC852 TT

N

N

CH-2007-066 13-Aug-07 GC852 TT N

CH-2007-067 13-Aug-07 GC852 5 GB N

CH-2007-068 14-Aug-07 GC852 TT N

CH-2007-069 14-Aug-07 GC852 PN 1 N

CH-2007-070 14-Aug-07 GC852 TT N

CH-2007-071 14-Aug-07 GC852 TT N

27° 05.002 91° 10.098 27° 06.993 91° 10.152

27° 07.318 91° 10.205 27° 06.339 91° 10.338

27° 06.364 91° 10.472 27° 07.361 91° 10.404

27° 07.166 91° 10.418 27° 07.166 91° 10.418

27° 07.655 91° 10.406 27° 06.498 91° 10.396

27° 07.505 91° 10.418 27° 07.015 91° 10.406

27° 06.208 91° 10.393 27° 07.194 91° 10.422

27° 07.462 91° 10.356 27° 06.522 91° 10.354

49

484

239

406

195

154

642

0

657

0

498

208

551

325*

273

195

455

671

0

0

0

155

149

185

462

0

0

0

791

CH-2007-072 14-Aug-07 GC852 TT N

CH-2007-075 14-Aug-07 GC852 NN D

CH-2007-076 14-Aug-07 GC852 5 GB D

CH-2007-078 14-Aug-07 GC852 NN D

Table 1 cont.

27° 06.686 91° 10.480 27° 07.828 91° 10.481

27° 08.616 91° 10.180 27° 08.149 91° 10.169

27° 06.656 91° 10.079 27° 06.656 91° 10.079

27° 09.228 91° 11.366 27° 08.309 91° 09.667

CH-2007-079 14-Aug-07 GC852 5 GB D

CH-2007-080 14-Aug-07 GC852 TT D

CH-2007-081 14-Aug-07 GC852 5 GB D

CH-2007-082 14-Aug-07 GC852 TT D

27° 09.388

27° 10.379

27° 09.660

27° 07.841

91° 09.765

91° 09.659

91° 09.695

91° 09.948

27° 09.388

27° 09.372

27° 09.660

27° 06.897

91° 09.765

91° 09.736

91° 09.695

91° 09.925

CH-2007-083 14-Aug-07 GC852 TT TW 27° 05.076 91° 09.857 27° 04.136 91° 09.852

CH-2007-084 14-Aug-07 GC852 TT

CH-2007-085 14-Aug-07 GC852 TT

CH-2007-086 14-Aug-07 GC852 TT

N

N

N

27° 05.194 91° 09.691 27° 06.258 91° 09.810

27° 07.000 91° 09.830 27° 06.055 91° 09.802

27° 06.133 91° 09.832 27° 07.162 91° 09.915

CH-2007-087 15-Aug-07 GC852 TT

CH-2007-088 15-Aug-07 GC852 TT

N

N

27° 07.043 91° 09.791 27° 06.157 91° 09.875

27° 05.024 91° 09.692 27° 06.632 91° 09.703

CH-2007-089 15-Aug-07 GC852 TT N 27° 07.452 91° 09.710 27° 06.456 91° 09.731

CH-2007-090 15-Aug-07 GC852 TT TW 27° 06.872 91° 10.013 27° 07.949 91° 10.191

CH-2007-092 15-Aug-07 GC852 TT D 27° 08.468 91° 07.273 27° 07.702 91° 06.813

CH-2007-093 15-Aug-07 GC852 TT

CH-2007-094 15-Aug-07 GC852 TT

CH-2007-095 15-Aug-07 GC852 TT

D

D

D

27° 09.883 91° 09.198 27° 09.065 91° 08.610

27° 09.020 91° 09.419 27° 08.421 91° 08.831

27° 08.001 91° 09.940 27° 07.224 91° 09.176

CH-2007-096 15-Aug-07 GC852 TT D 27° 06.985 91° 10.006 27° 07.324 91° 09.216

CH-2007-097 15-Aug-07 GC852 TT TW 27° 06.474 91° 10.045 27° 06.090 91° 09.078

CH-2007-098 15-Aug-07 GC852 TT

CH-2007-099 15-Aug-07 GC852 TT

N

N

27° 05.122

27° 06.869

91° 10.161

91° 09.295

27° 04.635

27° 04.437

91° 09.361

91° 08.386

CH-2007-101 16-Aug-07 GC852 TT TW 27° 06.882 91° 09.207 27° 06.447 91° 08.140

CH-2007-103 16-Aug-07 GC852 TT

CH-2007-104 16-Aug-07 GC852 TT

CH-2007-105 16-Aug-07 GC852 TT

D

D

D

27° 07.981 91° 10.268 27° 07.663 91° 09.187

27° 06.933 91° 10.182 27° 06.401 91° 09.166

27° 06.146 91° 10.299 27° 05.025 91° 10.148

50

1035

586

569*

332

723

606

493

555

915

480

350

791

966

518

150

423

1004

368

0

0

0

0

899

0

201

763

CH-2007-106 16-Aug-07 GC852 TT D

Table 1 cont.

27° 05.257 91° 10.480 27° 06.145 91° 10.673

CH-2007-107 16-Aug-07 GC852 TT TW 27° 07.714 91° 10.575 27° 06.697 91° 10.493

CH-2007-108 16-Aug-07 GC852 TT TW 27° 05.657 91° 09.916 27° 04.715 91° 09.464

CH-2007-110 16-Aug-07 GC852 TT N 27° 05.265 91° 09.515 27° 06.212 91° 09.680

CH-2007-111 16-Aug-07 GC852 TT

CH-2007-112 16-Aug-07 GC852 TT

CH-2007-113 17-Aug-07 GC852 TT

CH-2007-114 17-Aug-07 GC852 TT

CH-2007-115 17-Aug-07 GC852 TT

N

N

N

N

N

27° 07.135

27° 06.082

27° 06.958

27° 05.795

27° 07.113

91° 09.955

91° 10.482

91° 10.845

91° 10.799

91° 10.611

27° 06.190

27° 06.929

27° 06.001

27° 06.978

27° 06.010

91° 10.241

91° 10.661

91° 10.946

91° 10.690

91° 10.542

CH-2007-116 17-Aug-07 GC852 TT

CH-2007-117 17-Aug-07 GC852 TT

CH-2007-118 17-Aug-07 AC601 TT

CH-2007-119 18-Aug-07 AC601 TT N

CH-2007-120 18-Aug-07 AC601 PN 1 N

CH-2007-121 18-Aug-07 AC601 5 GB N

CH-2007-122 18-Aug-07 AC601 TT N

CH-2007-123 18-Aug-07 AC601 5 GB N

N

N

N

27° 05.701

27° 06.340

26° 23.314

91° 10.320

91° 10.268

94° 30.559

27° 07.004

27° 05.345

26° 22.580

91° 10.227

91° 10.336

94° 31.020

26° 23.215 94° 30.841 26° 24.247 94° 30.814

26° 22.991 94° 30.838 26° 23.584 94° 30.851

26° 24.247 94° 30.814 26° 24.247 94° 30.814

26° 23.450 94° 30.771 26° 22.905 94° 30.832

26° 22.941 94° 30.823 26° 22.941 94° 30.823

CH-2007-124 18-Aug-07 AC601 TT N

CH-2007-125 18-Aug-07 AC601 5 GB N

CH-2007-126 18-Aug-07 AC601 TT N

26° 22.962 94° 30.903 26° 24.152 94° 31.038

26° 23.705 94° 30.996 26° 23.705 94° 30.996

26° 24.786 94° 31.143 26° 23.872 94° 31.135

CH-2007-129 18-Aug-07 AC601 5 GB D

CH-2007-133 18-Aug-07 AC601 5 GB D

26° 23.683 94° 30.923 26° 23.683 94° 30.923

26° 22.504 94° 31.365 26° 22.504 94° 31.365

CH-2007-136 20-Aug-07 AT340 TT TW 27° 38.175 88° 21.014 27° 38.083 88° 21.956

CH-2007-137 20-Aug-07 AT340 TT N 27° 38.258 88° 21.699 27° 38.066 88° 22.702

CH-2007-138 20-Aug-07 AT340 TT N 27° 38.876 88° 21.910 27° 38.752 88° 22.889

CH-2007-139 21-Aug-07 AT340 TT

CH-2007-140 21-Aug-07 AT340 TT

CH-2007-141 21-Aug-07 AT340 TT

N

N

N

27° 38.685 88° 22.052 27° 38.593 88° 23.286

27° 38.659 88° 22.195 27° 38.642 88° 23.122

27° 38.733 88° 22.647 27° 38.862 88° 23.578

51

318

0

45

0

0

331

264

217

124

425

586

21

540

253

171

0

0

584

0

1067

287

139

473

94

138

59

51

81

CH-2007-142 21-Aug-07 AT340 5 GB N

CH-2007-146 21-Aug-07 AT340 5 GB D

CH-2007-147 21-Aug-07 AT340 TT D

CH-2007-148 21-Aug-07 AT340 5 GB D

Table 1 cont.

27° 39.388 88° 24.022 27° 39.388 88° 24.022

27° 38.812 88° 21.766 27° 38.812 88° 21.766

27° 38.824 88° 21.738 27° 39.425 88° 22.230

27° 38.905 88° 21.766 27° 38.905 88° 21.766

CH-2007-149 21-Aug-07 AT340 TT TW 27° 38.443 88° 21.670 27° 38.997 88° 22.314

CH-2007-150 21-Aug-07 AT340 5 GB N 27° 38.770 88° 21.118 27° 38.770 88° 21.118

CH-2007-151 21-Aug-07 AT340 TT N 27° 38.083 88° 21.521 27° 38.751 88° 21.994

CH-2007-152 22-Aug-07 AT340 TT TW 27° 38.319 88° 21.485 27° 38.875 88° 22.066

CH-2007-154 22-Aug-07 AT340 TT D 27° 37.987 88° 21.708 27° 38.762 88° 22.018

CH-2007-155 22-Aug-07 AT340 PN 1 D

CH-2007-156 22-Aug-07 AT340 TT D

CH-2007-157 22-Aug-07 AT340 TT D

27° 37.933 88° 21.129 27° 37.921 88° 21.422

27° 38.326 88° 21.637 27° 38.811 88° 21.935

27° 38.400 88° 21.294 27° 38.740 88° 21.934

CH-2007-158 22-Aug-07 AT340 PN 1 D

CH-2007-159 22-Aug-07 AT340 TT D

27° 38.470 88° 21.414 27° 38.460 88° 21.402

27° 38.516 88° 21.610 27° 38.970 88° 22.381

CH-2007-160 22-Aug-07 AT340 TT TW 27° 38.589 88° 21.721 27° 39.007 88° 22.591

CH-2007-161 22-Aug-07 AT340 TT N 27° 38.343 88° 21.277 27° 38.667 88° 22.243

CH-2007-162 22-Aug-07 AT340 5 GB N 27° 38.607 88° 22.151 27° 38.607 88° 22.151

CH-2007-163 22-Aug-07 AT340 TT

CH-2007-164 22-Aug-07 AT340 TT

CH-2007-165 23-Aug-07 AT340 TT

N

N

N

27° 38.353 88° 21.046 27° 38.676 88° 21.893

27° 38.392 88° 21.217 27° 39.118 88° 22.124

27° 38.166 88° 20.877 27° 38.715 88° 21.805

CH-2007-166 23-Aug-07 AT340 TT N

CH-2007-167 23-Aug-07 AT340 5 GB N

27° 38.339 88° 21.034 27° 38.768 88° 21.906

27° 38.412 88° 21.200 27° 38.412 88° 21.200

CH-2007-168 23-Aug-07 AT340 TT N 27° 38.544 88° 21.363 27° 38.880 88° 22.181

CH-2007-169 23-Aug-07 AT340 TT TW 27° 38.481 88° 21.438 27° 38.924 88° 22.252

CH-2007-170 23-Aug-07 AT340 PN 1 N 27° 38.396 88° 21.268 27° 38.578 88° 21.641

CH-2007-171 23-Aug-07 AT340 TT TW 27° 39.344 88° 22.858 27° 39.795 88° 23.663

CH-2007-172 23-Aug-07 AT340 TT D 27° 38.466 88° 21.212 27° 38.755 88° 21.748

CH-2007-173 23-Aug-07 AT340 TT D 27° 39.085 88° 21.980 27° 39.430 88° 22.802

52

171

421*

180

140

0

63

160

0

130

429

422

0

842

984

0

359

627*

224

0

0

0

1291

0

1503

0

194

542

539

CH-2007-174 23-Aug-07 AT340 5 GB D

CH-2007-175 23-Aug-07 AT340 TT

CH-2007-176 23-Aug-07 AT340 TT

D

D

CH-2007-177 23-Aug-07 AT340 PN 1 D

CH-2007-178

CH-2007-179

CH-2007-180

CH-2007-181

CH-2007-182

23-Aug-07

23-Aug-07

23-Aug-07

23-Aug-07

23-Aug-07

AT340

AT340

AT340

AT340

AT340

TT

5 GB

TT

PN 2

TT

D

D

D

D

D

Table 1 cont.

27° 39.034 88° 21.969 27° 39.034 88° 21.969

27° 38.006 88° 20.645 27° 38.178 88° 21.475

27° 38.657 88° 21.842 27° 38.890 88° 22.623

27° 38.640 88° 21.781 27° 38.872 88° 22.582

27° 38.400 88° 21.216 27° 38.765 88° 22.082

27° 38.383 88° 21.177 27° 38.383 88° 21.177

27° 39.436 88° 23.669 27° 39.813 88° 24.614

27° 39.326 88° 23.419 27° 39.653 88° 24.196

27° 38.522 88° 21.466 27° 38.879 88° 22.379

CH-2007-183 23-Aug-07 AT340 TT TW 27° 38.343 88° 21.041 27° 38.728 88° 21.036

CH-2007-184 23-Aug-07 AT340 TT N 27° 38.169 88° 20.947 27° 38.559 88° 21.804

CH-2007-185 23-Aug-07 AT340 PN 2 N 27° 38.183 88° 20.712 27° 38.226 88° 20.129

CH-2007-186 23-Aug-07 AT340 TT N

CH-2007-187 23-Aug-07 AT340 PN 2 N

CH-2007-188 24-Aug-07 AT340 TT

CH-2007-189 24-Aug-07 AT340 TT

N

N

CH-2007-190 24-Aug-07 AT340 5 GB N

27° 38.280 88° 21.203 27° 38.819 88° 22.169

27° 38.235 88° 20.784 27° 38.434 88° 21.485

27° 38.566 88° 21.511 27° 38.941 88° 22.385

27° 38.460 88° 21.314 27° 38.848 88° 22.197

27° 38.291 88° 20.933 27° 38.291 88° 20.933

CH-2007-191 24-Aug-07 AT340 TT

CH-2007-192 24-Aug-07 AT340 TT

N

N

27° 38.463

27° 38.832

88° 21.357

88° 22.322

27° 38.837

27° 39.206

88° 22.285

88° 23.222

CH-2007-198 24-Aug-07 AT340 TT TW 27° 38.767 88° 21.397 27° 39.120 88° 22.339

CH-2007-199 24-Aug-07 AT340 TT

CH-2007-200 24-Aug-07 AT340 TT

N

N

CH-2007-201 24-Aug-07 AT340 PN 2 N

CH-2007-202 24-Aug-07 AT340 TT N

CH-2007-203 24-Aug-07 AT340 PN 2 N

CH-2007-204 24-Aug-07 AT340 TT

CH-2007-205 24-Aug-07 AT340 TT

N

N

CH-2007-206 24-Aug-07 AT340 PN 2 N

27° 38.718 88° 21.795 27° 39.237 88° 22.684

27° 38.611 88° 21.584 27° 39.101 88° 22.504

27° 38.335 88° 21.133 27° 38.665 88° 21.757

27° 38.640 88° 21.675 27° 39.095 88° 22.586

27° 38.387 88° 21.184 27° 38.757 88° 21.929

27° 38.644 88° 21.662 27° 39.110 88° 22.691

27° 38.706 88° 21.715 27° 39.100 88° 22.662

27° 38.415 88° 21.190 27° 38.819 88° 21.964

53

267

261

292

114

540

0

410

0

572

395

0

134

633

0

382

0

285

278

0

0

511

253

0

321

0

484

0

669

CH-2007-210 25-Aug-07 AT340 TT D

Table 1 cont.

27° 38.651 88° 21.414 27° 38.828 88° 22.558

CH-2007-211 25-Aug-07 AT340 TT D 27° 39.026 88° 24.074 27° 39.195 88° 25.116

CH-2007-213 25-Aug-07 AT340 TT TW 27° 38.782 88° 21.433 27° 38.881 88° 22.279

CH-2007-214 25-Aug-07 AT340 TT TW 27° 38.600 88° 21.459 27° 38.857 88° 22.587

CH-2007-215 25-Aug-07 AT340 PN 2 N

CH-2007-216 25-Aug-07 AT340 TT N

CH-2007-217 25-Aug-07 AT340 PN 2 N

CH-2007-218 25-Aug-07 AT340 TT N

CH-2007-219 25-Aug-07 AT340 TT N

CH-2007-220 25-Aug-07 AT340 TT N

CH-2007-221 25-Aug-07 AT340 PN 2 N

27° 38.479

27° 38.573

27° 38.577

27° 38.649

27° 38.777

27° 38.802

88° 21.082

88° 21.399

88° 21.421

88° 21.746

88° 21.981

88° 22.198

27° 38.785

27° 38.848

27° 38.838

27° 38.834

27° 39.923

27° 38.998

88° 22.031

88° 22.497

88° 22.485

88° 22.774

88° 23.041

88° 23.552

27° 38.565 88° 20.778 27° 38.698 88° 21.596

142*

868

354

307

0

528

0

579

78

1149

0

54

Table 2. The total number of all midwater fishes, invertebrates and autotrophs examined in dietary analyses from the North-central GOM. GCA = gut content analysis. SIA = stable isotope analysis, SL range = standard length size range for fish species (mm). Fish species marked with an * were grouped at family level for all analyses. Fish species marked with ^ were grouped at genera for stable isotope analyses.

FISH

Gonostomatidae


1 46

Cyclothone alba

Cyclothone braueri

Cyclothone pallida

Cyclothone pseudopallida

290 5 10-33

319 11-28

362 10 12-51

332 10 12-45


Sternoptychidae

Argyropelecus aculeatus

Argyropelecus hemigymnus

Sternoptyx diaphana^

30 10 8-30

Sternoptyx pseudobscura^


147 15 13-30

Phosichthyidae

Pollichthys mauli

Vinciguerria poweriae 155 15 12-35

Stomiidae

Astronesthes macropogon*

Astronesthes similus*

Bathophilus longipinnis*

1 31

Bathophilus pawneei*

Chauliodus sloani

Eustomias lipochirus*

Eustomias schmidti*

Leptostomias bilobatus*

Melanostomias biseriatus*

Melanostomias valdiviae*

Photonectes margarita*

1 1 80

1 1 80

1 1 105

1 40

1 31

Photostomias guernei*

Stomias affinis*

Stomias longibarbatus*

1 86

Myctophidae

Benthosema suborbitale

234 6 10-30

Ceratoscopelus warmingii

55

Table 2 cont.

Diaphus lucidus^

Diaphus mollis^

Diaphus problematicus

Hygophum benoiti


111 12-22

Lepidophanes guentheri

157 10 14-66

Myctophum affine

Notolychnus valdiviae

343 11-22

Melamphaidae

Melamphaes simus*

Melamphaes typhlops*

Scopelogadus mizolepis*

Anchylomera blossevillei

1 24

AMPHIPODA

Phrosinidae

1

Platyscelus sp.

2

Pronoidae

Parapronoe sp.

1

CEPHALOPODA

Bolitaenidae

Japetella diaphana

1

Enoploteuthidae

Ancistrocheirus lesuerii

1

Histioteuthidae

Stigmatoteuthis arcturi

3

CNIDARIA

Rhopalonematidae

Colobonema sericeum

1

Atolla vanhoeffeni

1

Megacalanidae

Bathycalanus princeps

4

Pontellidae

Labidocera sp.

2

DECAPODA

Benthesicymidae

Gennadas valens

14

56

Table 2 cont.

Oplophoridae


Systellaspis debilis

5

7

Sergestidae

Sergia sp.

1

Euphausiidae

Nematoscelis megalops

3

Thysanopoda sp.

2

Thysanopoda tricuspida

2

GASTROPODA

Cavoliniidae

Cavolinia tridentata

Diacavolinia sp.

1

2

SALPIDA

Salpidae

Salpa cylindrica

Salpa sp.

4

6

AUTOTROPH

Sargassaceae

Sargassum fluitans

2

Sargassum sp.

10

Detritus 5

57

Table 3. Results of ANOSIM comparing effects of size, time of day, depth and location on the general prey categories consumed for each fish species. Differences are considered significant when R > 0.40 and p < 0.05.

Species




Ceratoscopleus warmingii

Cyclothone alba




Diaphus mollis


Hygophum benoiti



Myctophum affine


Pollichthys mauli


Size Time of day Depth Location

Global R p Global R p Global R p Global R p

Significant differences

0.19 0.05 -0.06 0.64 -0.03 0.56 -0.09 0.89 No

0.24 0.10 -0.04 0.56 0.55 0.02 -0.21 0.88 Depth

0.06 0.06 0.00 0.48 -0.03 0.69 -0.06 0.84 No

0.01 0.44 -0.11 0.80 -0.01 0.55 0.07 0.12 No

-0.02 0.84 -0.01 0.56 0.02 0.37 -0.01 0.67 No

-0.06 1.00 0.03 0.19 -0.05 0.73 -0.02 0.77 No

-0.14 0.90 -0.17 1.00 -0.04 1.00 -0.11 1.00 No

0.06 0.13 0.05 0.15 0.12 0.05 -0.02 0.58 No

-0.11 0.87 0.15 0.17 0.00 0.47 0.03 0.32 No

0.06 0.22 -0.09 0.69 0.03 0.34 0.07 0.13 No

-0.03 0.68 0.34 0.06 No

-0.01 0.52 -0.17 0.97 0.03 0.30 -0.07 0.85 No

0.17 0.03 0.07 0.19 0.04 0.20 0.02 0.33 No

-0.10 0.72 -0.21 0.88 -0.20 0.93 0.25 0.09 No

0.03 0.24 -0.07 0.96 0.09 0.01 0.06 0.01 No

0.38 0.00 0.01 0.39 -0.02 0.52 0.18 0.18 No

0.47 0.12 -0.02 0.58 -0.16 0.72 -0.20 1.00 No

-0.07 0.94 -0.02 0.67 0.07 0.11 0.03 0.15 No

0.10 0.01 0.22 0.01 0.01 0.45 0.03 0.09 No Vinciguerria poweriae

58

Table 4. Percent volume and frequency of prey items consumed by Chauliodus sloani collected from three sites in the Gulf of Mexico

(AC601, GC852, AT340) separated by time of day. Night = 2030 to 0530 hr CDT, Day = 0730 to 1830 hr CDT, Twilight = 0530 to

0730 and 1830 to 2030; n = total number of stomachs analyzed; E = number of stomachs empty.

AC601 GC852 n = 2

E = 2 n = 8

E = 7 n = 37

E = 30

AT340

Twilight Twilight n = 2

E = 1 n = 5

E = 5 n = 7

E = 6 n = 2

E = 1

FISH

Bregmaceros spp.

Myctophidae

Unidentified fish parts

CRUSTACEA

Unidentified crustacean parts

OTHER

Organic material

Unidentified animal parts

100.0 100.0 86.5 28.6 100.0 100.0 100.0 100.0

100.0

67.5 14.3

19.0 14.3 100.0 100.0 100.0 100.0

<0.1 14.3

13.0 57.1

0.5 14.3

100.0 100.0

59

Table 5. Percent volume and frequency of prey items consumed by Gonostoma elongatum collected from three sites in the Gulf of

Mexico (AC601, GC852, AT340) separated by time of day. Night = 2030 to 0530 hr CDT, Day = 0730 to 1830 hr CDT, Twilight =

0530 to 0730 and 1830 to 2030; n = total number of stomachs analyzed; E = number of stomachs empty.

Food Item

AMPHIPODA

Amphipoda

AC601 GC852 AT340

Day n = 0

E = 0 n = 2

E = 0 n = 28

E = 11 n = 3

E = 0 n = 3

E = 0 n = 42

E = 10 n = 10

E = 0

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

0.7 11.8

Scina pusilla

CHAETOGNATHA

Heterokrohnia sp.

CNIDARIA

Cnidaria

COPEPODA

Aetideus acutus

Calanoida

Candacia longimana

Copepoda

Corycaeus furcifer

Corycaeus sp.

Eucalanidae

Gaetanus pileatus

Haloptilus

sp.

Pareucalanus attenuatus

Pleuromamma xiphias

Rhincalanus cornutus

Temora stylifera

0.4 5.9

0.5 17.6

0.1 11.8

18.0 20.0

0.1 3.1

0.3 9.4 3.6 10.0

<0.1 3.1

60

Unidentified copepod parts

CRUSTACEA


Table 5 cont.

0.2 11.8 0.3 12.5

7.3 41.2 14.0 100.0 41.3 33.3 3.4 46.9 25.3 40.0

7.3 41.2 14.0 100.0 41.3 33.3 3.4 46.9 25.3 40.0

DECAPODA

Decapoda

EUPHAUSIACEA

Euphausiidae

Thysanoessa

sp.

Thysanopoda sp.

MYSIDICEA

Lophogastridae

OSTRACODA

Halocyprididae

Myodocopida

Ostracoda

OTHER

Organic material


2.1 5.9

0.6

17.8 11.8 14.7

33.3

33.3

86.9

2.1

6.3

9.4

0.1 11.8 <0.1 3.1

0.1 3.1

<0.1 5.9

100.0 100.0 66.0 64.7 23.4 100.0 58.7 100.0 4.0 62.5 56.7 90.0

100.0 100.0 63.7 52.9 23.4 100.0 58.7 100.0

2.3 11.8

3.4

0.6

62.5 56.7 90.0

3.1

61

Table 6. Percent volume and frequency of prey items consumed by Stomiidae collected from three sites in the Gulf of Mexico



AC601 GC852 AT340

Food Item

COPEPODA

Oncaea sp.


DECAPODA

Decapoda

Penaeidae

FISH

Diaphus mollis

Myctophidae


OTHER

Invertebrate

Nematoda

Organic material

Unidentified animal parts n = 1

E = 1 n = 5

E = 2 n = 13

E = 9 n = 3

E = 2 n = 0

E = 0 n = 8

E = 6 n = 6

E = 5

%V %F %V %F %V %F %V %F

0.1

0

0.1 33.3

61.4

61.4 33.3

8.3 25.0

25.0

80.7

50.0

100.0

7.5 66.7 27.5 25.0

44.2

36.4

50.0

50.0 100.0 100.0

31.1

<0.1 33.3

3.3 33.3 64.2 50.0

27.7 33.3 58.7 50.0

5.5 50.0

19.3 100.0

19.3 100.0

62

Table 7. Percent volume and frequency of prey items consumed by Cyclothone alba collected from three sites in the Gulf of Mexico



AC601 GC852 AT340 n = 2 n = 37

E = 2 E = 26 n = 97

E = 66 n = 41

E = 28 n = 58

E = 39 n = 34

E = 22 n = 21

E = 15

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

COPEPODA

Aetideidae

Calanoida

Copepoda

Cyclopoida

48.3 45.5 75.1 48.4 52.8 30.8 95.7 73.7 80.3 50.0 48.2 33.3

10.1 9.1 34.5 25.8 21.1 15.8 15.5 16.7 14.2 16.7

Euchirella curticauda

Euchirella

sp.

Heterorhabdidae 4.6

Lubbockia aculeata

Pleuromamma robusta

Pleuromamma

sp.


Poecilostomatoida

34.3 9.1 17.2 6.45 17.5 10.5 58.6 8.3

CRUSTACEA copepod 2.7 9.1 1.6 9.7 11.1 15.4 4.9 21.1 4.8 25.0

40.9 27.3 13.0 25.8 42.1 53.8 2.3 21.1 2.3 16.7 crustacean 40.9 27.3 13.0 25.8 42.1 53.8 2.3 21.1 2.3 16.7

DECAPODA

Decapoda

OSTRACODA

Halocyprididae

Myodocopida

63

OTHER

Nematoda


Table 7 cont.

4.1 36.4 3.0 25.8 5.0 30.8 2.0 10.5 17.4 41.7 51.8 66.7

4.0 27.3 3.0 22.6 5.0 30.8 2.0 10.5 6.5 33.3 49.6 66.7

0.1 9.1 0.1 6.5 1.7 25.0 2.3 33.3

9.1 8.3

64

Table 8. Percent volume and frequency of prey items consumed by Cyclothone braueri collected from three sites in the Gulf of



COPEPODA


Calanoida

Copepoda

Corycaeus sp.

Cyclopoida

AC601 GC852 AT340

Day n = 2

E = 2 n = 18

E = 14 n = 100

E = 77 n = 49

E = 34 n = 55

E = 47 n = 58

E = 41 n = 37

E = 35

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

100.0 100.0 64.3 39.1 53.0 66.7 42.4 87.5 69.2 52.9 7.0 50.0

57.2 25.0 19.7 13.3 16.2 25.0

10.9 8.7 2.6 6.7 5.3 25.0 36.6 17.6 7.0 50.0


Miracia efferata

Pleuromamma

sp.


CRUSTACEA

33.8 100.0 18.1 13 30.7 46.7 19.7 25.0 32.2 29.4

OSTRACODA

Conchoecinae

Ostracoda

OTHER

1.2 4.35 35.2 20.0 57.6 25.0

35.2

11.5 39.1 11.8 20.0 3.2 29.4 93.0 50.0

11.5 39.1 7.6 13.3 3.2 29.4 93.0 50.0

65

Table 9. Percent volume and frequency of prey items consumed by Cyclothone pseudopallida collected from three sites in the Gulf of



Food Item

COPEPODA

AC601 GC852 AT340

Twilight Twilight n = 12

E = 11 n = 90

E = 71 n = 95

E = 70 n = 34

E = 25 n = 46

E = 37 n = 34

E = 22 n = 21

E = 20

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

100.0 100.0 87.5 52.6 47.8 48.0 39.5 55.6 86.3 77.8 92.1 75.0 100.0 100.0


Aetideidae

Chiridus sp.

Copepoda

Harpacticoida


10.4 18.9 33.3 77.3 66.7 44.4 33.3 100.0 100.0

34.4

Lubbockia squillimana

Lubbockia

Oithona

sp.

Lucicutia sp.

sp.

Rhincalanus

Mormonilla phasma

sp.

0.0 4.0

0.5 4.0


Pleuromamma sp.

Valdiviella minor

Unidentified copepod parts 100.0 100.0 3.3 10.5 35.9 16.0

CRUSTACEA


16.7 8.3

22.2 2.0

6.0 5.3 4.5 24.0 53.2 22.2 2.0 16.7

66

OSTRACODA

Conchoecinae

Halocyprididae

Myodocopida

Ostracoda

OTHER

Animalia

Nematoda


Table 9 cont.

3.4 5.3 5.8 22.2 8.7 11.1 5.9 8.3

0.6 11.1 8.7 11.1

3.0 36.8 29.0 32 1.6 22.2 5.0 22.2 <0.1 8.3

<0.1

3.0 31.6 28.9 28.0 1.3 11.1 2.3 11.1 <0.1 8.3

0.3 11.1

67

Table 10. Percent volume and frequency of prey items consumed by Hygophum benoiti collected from three sites in the Gulf of



AC601 GC852 AT340 n = 6

E = 6 n = 23

E = 23 n = 37

E = 37 n = 10

E = 10 n = 7

E = 6 n = 27

E = 11 n = 1

E = 1

AMPHIPODA

Amphipoda

COPEPODA

Calanoida

Candacia curta

Candacia pachydactyla

Cyclopoida

Farranula gracilis

CRUSTACEA

DECAPODA

Decapoda

MOLLUSCA

Bivalvia

OSTRACODA

Myodocopida

Ostracoda

OTHER

Organic material 34.0 75.0

68

Table 11. Percent volume and frequency of prey items consumed by Valenciennellus tripunctulatus collected from three sites in the

Gulf of Mexico (AC601, GC852, AT340) separated by time of day. Night = 2030 to 0530 hr CDT, Day = 0730 to 1830 hr CDT,

Twilight = 0530 to 0730 and 1830 to 2030; n = total number of stomachs analyzed; E = number of stomachs empty.

Night Twilight n = 1

E = 0 n = 3

E = 0 n = 37

E = 4 n = 24

E = 3 n = 9

E = 4 n = 44

E = 12 n = 29

E = 2

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

AMPHIPODA

Amphipoda

COPEPODA

Aegisthus mucronatus amphipod

1.2 100.0 28.8 33.3 24.8 51.5 58.4 85.7 84.8 80.0 40.0 62.5 59.2 77.8

Aetideidae

Calanoida 0.2

Candacia curta

Copepoda

Corycaeus sp.

Cyclopoida

Euchaeta

sp.

Harpacticoida


Lubbockia sp.


Oithonidae

1.2 100.0 0.3 9.1 0.8 14.3 2.1 20.0 0.9 9.4 0.2 7.4

0.8 9.1

Pleuromamma abdominalis

Pleuromamma piseki


Pleuromamma sp.

0.9 3.0 6.5 23.8 19.6 60.0 4.3 12.5 7.8 25.9

69


Poecilostomatoida

Rhincalanus cornutus

Rhincalanus sp.


CRUSTACEA


EUPHAUSIACEA

Euphausiidae

OSTRACODA

Archiconchoecinae

Conchoecinae

Halocyprididae

Myodocopida

Myodocopina

Ostracoda

OTHER

Nematoda


Table 11 cont.

3.4

0.4 0.9 22.2

22.0 39.4 17.8 47.6 19.6 40.0 31.5 50.0 17.0 33.3

74.1 100.0 32.2 66.7 67.8 81.8 27.1 66.7 2.1 20.0 32.0 56.3 23.5 63.0

74.1 100.0 32.2 66.7 67.8 81.8 27.1 66.7 2.1 20.0 32.0 56.3 23.5 63.0

0.6 33.3 2.6 21.2 0.8 28.6 0.3 20.0 2.0 18.8 0.9 14.8

0.6 33.3 0.1 3.0 0.4 19.0 0.3 20.0 1.0 6.3 0.5 3.7

0.4 3.0 0.2 3.7

24.7 100.0 38.4 33.3 4.8 33.3 6.8 42.9 12.8 40.0 26.0 56.3 16.5 44.4

24.7 100.0 38.4 33.3 4.7 24.2 6.8 42.9 12.8 40.0 25.9 53.1 16.4 40.7

0.2 9.1 <0.1 4.8 0.1 3.1 <0.1 3.7

<0.1 3.7

70

Table 12. Percent volume and frequency of prey items consumed by Diaphus mollis collected from three sites in the Gulf of Mexico



AC601 GC852 AT340 n = 1

E = 0 n = 0

E = 0 n = 14

E = 0 n = 3

E = 2 n = 4

E = 0 n = 10

E = 1 n = 2

E = 0

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

CHAETOGNATHA

Sagittoidea

Unidentified chaetognath parts

COPEPODA

Calanoida

28.1 25.0

12.5 25.0 <0.1 11.1

63.4 100.0 15.3 57.1 12.8 100.0 12.5 25.0 20.9 77.8 79.0 100.0


Pleuromamma

sp.


62.3 100.0 9.3 7.1

3.7 21.4 12.8 100.0

11.6 22.2 78.7 50.0

7.4 44.4 0.1 50.0

100.0

Unidentified crustacean parts 36.6 100.0

DECAPODA

4.8 50.0 12.8 100.0 17.0 55.6 9.8 50.0

Decapoda 7.1

EUPHAUSIACEA

Euphausiidae

FISH

25.0

34.4

MOLLUSCA

Gastropoda

71

Table 12 cont.

OSTRACODA

Conchoecinae

Myodocopida

Ostracoda

Unidentified ostracod parts

Organic material

Nematoda


100.0 11.1

100.0 100.0

0.9 28.6 <0.1 11.1

78.4 85.7 68.0 100.0 25.0 25.0 53.5 77.8 1.4 100.0

<0.1 14.3 <0.1 11.1

72

Table 13. Percent volume and frequency of prey items consumed by Cyclothone pallida collected from three sites in the Gulf of



AC601 GC852 AT340 n = 18

E = 15 n = 115

E = 109 n = 95

E = 84 n = 32 n = 58

E = 32 E = 58 n = 40

E = 39 n = 4

E = 4

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

AMPHIPODA 9.09

Unidentified amphipod parts

COPEPODA

29.9 9.09

68.4 33.3 71.6 16.7 3.11 9.09

22.6

Haloptilus oxycephalus

68.4 33.3 49.0 16.7


OSTRACODA

9.4 16.7

23.1 33.3 9.4 33.3 24.9 18.2

Halocyprididae 23.1 33.3 3.8 16.7

Myodocopida

Unidentified ostracod parts 14.9 9.09

OTHER

Organic material

8.5 33.3 9.5 33.3 42.1 63.6 100.0 100.0

8.5 33.3 9.5 33.3 42.1 63.6 100.0 100.0

73

Table 14. Percent volume and frequency of prey items consumed by Vinciguerria poweriae collected from three sites in the Gulf of



AC601 GC852 AT340

Primno latreillei n = 2

E = 0 n = 6

E = 4 n = 72

E = 21 n = 19

E = 14 n = 7

E = 3 n = 45

E = 8 n = 4

E = 2

AMPHIPODA 14.3 25.0

Brachyscelus crusculum

Brachyscelus sp.

Eupronoe armata

Hyperiidea

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

4.7 2.0

0.2 2.0

1.6 2.0

2.2 2.0

Themistella fusca

Tryphana malmi

COPEPODA

Calanoida

Candaciidae

Candacia bipinnata

4.5

46.7 100.0 13.2 37.3 4.7 40.0 5.1 25.0 21.6 67.6

4.9 16.2

Candacia varicans

Copepoda

Corycaeus sp.

Cyclopoida

20.0 0.1 2.7

20.0

0.5 7.8 0.8


Lubbockia sp.

Paracandacia bispinosa

Paracandacia simplex

<0.1

2.5 2.0

74

Pleuromamma sp.

Sapphirina sp.

Temora sp.

Table 14 cont.

20.0

0.1 2.0

Undinula vulgaris

CRUSTACEA

4.3 54.1

100.0 100.0 21.6 58.8 7.0 20.0 48.9 73.0 crustacean 100.0 100.0

DECAPODA

21.6 58.8 7.0 20.0

12.6

48.9 73.0

0.7 2.7

Decapoda 12.6 decapod

EUPHAUSIACEA

Euphausiidae

50.0

Myctophidae


MOLLUSCA

Gastropoda

OSTRACODA

Archiconchoecinae

53.3 50.0 0.1 2.0 12.7 40.0

0.1 2.0

0.1 2.7

0.1 2.0

11.2 41.2 19.3 60.0 82.0 100.0 18.1 29.7 11.0 50.0

Conchoecinae

Halocyprididae

Halocypridinae

4.8 13.7 18.8 40.0 13.6 50.0 7.6 8.1

50.0

0.7 5.9

Halocypris sp.

Myodocopida

Myodocopina

Sarsiellidae

0.6 3.9

0.9 0.4 8.1

2.0 21.6

75

OTHER


Table 14 cont.

14.9 35.3 1.6 20.0 8.8 21.6 0.8 50.0

14.8 33.3 1.6 20.0 8.8 18.9 0.8 50.0

<0.1 7.8 <0.1 2.7

76

Table 15. Percent volume and frequency of prey items consumed by Myctophum affine collected from three sites in the Gulf of



AC601 GC852 AT340 n = 1

E = 0 n = 10

E = 9 n = 40

E = 21 n = 6

E = 2 n = 0

E = 0 n = 4

E = 0 n = 0

E = 0

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

AMPHIPODA 48.2

Amphipoda

Hyperiidea

Paratyphis

sp.

Unidentified amphipod parts

CHAETOGNATHA

25.4

7.6 5.3

15.2

26.0 25.0 26.0 25.0

6.2 25.0

6.2 25.0

COPEPODA 70.4 18.6

Calanoida 2.5

Candaciidae

Copepoda

Corycaeidae

6.9 5.3

0.4

0.7 100 <0.1

12.0


Microsetella rosea

Oncaeidae

Temora

sp.


0.3

0.2 25.0

3.9 25.0

100.0

100.0 100 4.6 36.8 3.3 25.0 6.6 50.0

CRUSTACEA


6.2

6.2 47.4 24.5 25.0 3.9 50.0

77

Table 15 cont.

DECAPODA

Decapoda

1.5 50.0

1.5 50.0

MOLLUSCA

Gastropoda

OSTRACODA

10.9

Conchoecinae

Halocyprididae

Myodocopida

Ostracoda

0.1 5.3

<0.1

9.8 5.3

50.0

<0.1 Animalia

Organic material

Phytoplankton


26.1 100.0

3.5 100.0

0.1 5.3

16.9 47.4 49.5 50.0

<0.1 5.3

40.1 75.0

78

Table 16. Percent volume and frequency of prey items consumed by Argyropelecus aculeatus collected from three sites in the Gulf of



AC601 GC852 AT340

AMPHIPODA

Amphipoda


Eusiridae

Gammaridea

Hyperiidea

Phronima

sp.

Primno evansi

Primno

sp.

n = 3

E = 0 n = 0

E = 0 n = 22

E = 7 n = 0

E = 0 n = 4

E = 1 n = 8

E = 2 n = 3

E = 0

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

0.4 33.3 7.2 26.7 5.1 33.3 0.4 33.3 28.4 100.0

0.4 33.3 1.5 6.7 0.1 16.7 3.0 33.3

Scina oedicarpus amphipod

CHAETOGNATHA

Sagittoidea

COPEPODA

Aetideus acutus

Calanoida

Copepoda

31.1 100.0 2.6 46.7 7.48 66.7 22.6 50.0 9.1 66.7

9.4 33.3 0.5 6.67 3.6 16.7 3.5 66.7

10.6 33.3 1.1 33.3 5.1 33.3 9.0 50

Corycaeus sp.

Cyclopoida 1.5 66.7 0.7 33.3


Paracalanidae

79

Table 16 cont.

Paracalanus aculeatus



Poecilostomatoida


CRUSTACEA

Crustacea

1.8 33.3

0.1 66.7

33.4 80.0

1.7 33.3 2.0 33.3

17.7 66.7 31.1 83.3 13.7 66.7

DECAPODA decapod

EUPHAUSIACEA

1.8 33.3 31.5 80.0 17.7 66.7 30.9 83.3 13.7 66.7

Euphausiidae

MOLLUSCA

Gastropoda

0.1 3.4

6.7 33.3

OSTRACODA

Archiconchoecinae

Conchoecinae

Halocypridinae

Halocypris sp.

Myodocopida

Ostracoda

42.1 100.0 9.4 53.3 59.5 100.0 19.0 50.0 16.7 66.7

25.1 66.7 3.5 20.0 23.8 66.7 6.7 16.7 16.2 66.7

12.4 33.3 2.4 26.7 11.9 33.3 11.2 33.3

OTHER ostracod

24.7 33.3 31.5 60.0 6.8 33.3 26.9 83.3 18.4 66.7


24.7 33.3 25.6 60.0 6.8 33.3 26.9 83.3 18.3 66.7

5.9 6.7 0.2 33.3

80

Table 17. Percent volume and frequency of prey items consumed by Argyropelecus hemigymnus collected from three sites in the Gulf of Mexico (AC601, GC852, AT340) separated by time of day. Night = 2030 to 0530 hr CDT, Day = 0730 to 1830 hr CDT, Twilight =


COPEPODA

Calanoida

Copepoda


Lubbockia

sp.

AC601 n = 1

E = 1 n = 2

E = 0 n = 8

E = 5 n = 7

E = 4 n = 3

E = 1 n = 6

E = 5 n = 3

E = 3

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

AMPHIPODA amphipod

GC852 AT340

Night Twilight

38.8 100.0 19.4 100.0 48.6 100.0 52.3 100.0 25.9 100.0

11.9 50.0 17.6 66.7 40.3 66.7 3.3 100.0 18.5 100.0

26.8 50.0 0.1 33.3 0.8 66.7 48.6 50.0


Unidentified copepod parts 1.7 33.3 0.3 50.0 2.47 100.0

CRUSTACEA

EUPHAUSIACEA

3.5 66.7 13.5 66.7 3.0 50.0

Nematoscelis microps

OSTRACODA

Conchoecinae

Myodocopida

Ostracoda

47.7 50.0 10.0 66.7 1.2 100.0

50.0


OTHER

Organic material

1.2 66.7 0.6 50.0

13.4 100.0 12.1 100.0 37.8 100.0 42.6 100.0 74.1 100.0

13.4 100.0 12.1 100.0 37.8 100.0 42.6 100.0 74.1 100.0

81

Table 18. Percent volume and frequency of prey items consumed by Pollichthys mauli collected from three sites in the Gulf of Mexico



AC601 GC852 AT340

Day Day n = 0

E = 0 n = 0

E = 0 n = 2

E = 0 n = 0

E = 0 n = 15

E = 6 n = 21

E = 4 n = 25

E = 5

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

AMPHIPODA

Amphipoda

COPEPODA

Calanoida

8.7 50.0 79.8 77.8 7.3 41.2 32.6 35.0

Copepoda

Corycaeus

sp.

Cyclopoida

Harpacticoida

0.8 50.0 0.1 11.8 2.4 5.0

0.0 5.9 10.0 5.0

Pleuromamma borealis


Pleuromamma sp.

CRUSTACEA

7.9 50.0 39.5 66.7 0.5 11.8 1.0 10.0

11.9 58.8 10.1 55.0

11.9 58.8 10.1 55.0

DECAPODA

EUPHAUSIACEA

Euphausiidae

Nyctiphanes capensis

Stylocheiron sp.

61.6

82

Thysanopoda sp.

OSTRACODA

Conchoecinae

Halocyprididae

Myodocopida

Ostracoda

OTHER

Organic material

Table 18 cont.

27.8 50.0 17.9 11.1 15.0 29.4 38.1 35.0

11.9 50.0 12.7 11.8 18.0 15.0

17.9 11.1 1.8 11.8 7.8 20.0

15.9 50.0 0.5 11.8 4.4 10.0

2.2 11.1 4.2 17.6 3.2 20.0

2.2 11.1 4.2 17.6 3.2 20.0

83

Table 19. Percent volume and frequency of prey items consumed by Benthosema suborbitale collected from three sites in the Gulf of



AC601 GC852 AT340 n = 13

E = 4 n = 9

E = 7 n = 64

E = 33 n = 7

E = 4 n = 21

E = 9 n = 74

E = 15 n = 46

E = 34

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

3.2


3.2

Platysceloidea amphipod

ANNELIDA

Polychaeta

CHAETOGNATHA

8.3

COPEPODA 51.9 77.8 100.0 100.0 30.7 45.2 32.9 33.3 75.8 33.3 22.6 54.2 43.7 41.7

Candacia bipinnata

Candaciidae

Corycaeus

(

Urocorycaeus

)

furcifer

Corycaeus sp.

11.0 22.2

Cyclopoida

Euchaetidae

0.9 3.2

7.0

1.1 5.1

<0.1 <0.1

Labidocera

sp.


84

Pleuromamma borealis


Pleuromamma

sp.

Sapphirina metallina

Temora stylifera


Table 19 cont.

55.6 50.0 7.0 3.2 1.4 1.7 10.2 8.3

8.6 33.3 2.0 12.9 32.9 33.3 23.4 25.0 8.3 32.2 24.2 33.3

24.3 44.4 17.7 38.7 7.9 66.7 11.2 8.3 19.9 49.2 8.4 33.3

DECAPODA 3.2

Decapoda 3.2

EUPHAUSIACEA 0.1

Euphausiidae

FISH

Myctophidae

OSTRACODA

Archiconchoecinae

Conchoecinae

Halocyprididae

Halocypris

sp.

2.7 33.3 7.2 25.8

1.8

1.8

3.0 16.7 5.0 20.3 1.3 8.3

0.8 0.3

Ostracoda


OTHER


15.4 55.6

15.4 55.6

0.8 6.5 2.3 13.6

18.0 45.2 59.2 66.7 8.8 33.3 23.5 67.8 15.9 58.3

18.0 45.2 59.2 66.7 7.9 25.0 23.5 66.1 15.9 58.3

<0.1 3.2 0.9 8.3 <0.1 1.7

85

Table 20. Percent volume and frequency of prey items consumed by


collected from three sites in the Gulf of



AC601 GC852 AT340 n = 6

E = 0 n = 5

E = 3 n = 25

E = 4 n = 12

E = 4 n = 3

E = 0 n = 16

E = 4 n = 5

E = 0

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

AMPHIPODA

Amphipoda

Gammaridea

Hyperiidea

Lestrigonus sp.

1.8

0.1 4.8

3.3 4.8

COPEPODA

Aetideus acutus

34.9 83.3 28.3 100 20.3 52.4 7.8 37.5 59.2 100.0 22.5 66.7 15.4 40.0

Candacia longimana

Copepoda

Corycaeus sp.

Eucalanus sp.

Oncaea sp.



Pleuromamma sp.

CRUSTACEA

Crustacea

0.5 4.8

5.9 4.8

8.4 8.3

22.4 33.3 60.9 50.0 40.0 47.6 60.8 50.0 40.8 33.3 28.5 83.3

0.1 4.8

86


DECAPODA

Decapoda

EUPHAUSIACEA

Euphausiidae

Nematoscelis sp.

FISH

Unidentified parts

OSTRACODA

Conchoecinae

Halocyprididae

Myodocopida

Ostracoda

SALPIDA

Salpidae

OTHER

Nematoda

Table 20 cont.

22.4 33.3 60.9 50.0 40.0 42.9 60.8 50.0 40.8 33.3 28.5 83.3

4.5 4.8

4.5 4.8

5.8 4.8

<0.1

<0.1

16.7

33.3

0.4 9.5

0.3 4.8

87

Table 21. Percent volume and frequency of prey items consumed by Lepidophanes guentheri collected from three sites in the Gulf of



AC601 GC852 AT340

AMPHIPODA

Amphipoda

Gammaridea

Hyperiidea

Phronima sp.

COPEPODA

Aetideus acutus

Calanoida

Candacia curta

Candacia sp.

Copepoda

Corycaeus sp.

Cyclopoida


Harpacticoida

Oncaea sp.


Pleuromamma gracilis


Pleuromamma sp.

n = 15

E = 0 n = 4

E = 1 n = 36

E = 11 n = 7

E = 2 n = 25

E = 8 n = 57

E = 9 n = 13

E = 7

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

6.5 4.0

75.9 86.7 12.1 66.7 28.5 76.0 <0.1 20.0 10.7 53.3 24.2 62.5 22.9 50.0

3.9 4.0

2.2 26.7 0.3 12.0 0.9 12.5

0.3 4.0

0.2 33.3 0.5 24.0 <0.1 20.0 <0.1 6.3

0.3 4.0

88

CRUSTACEA

Crustacea

DECAPODA

Decapoda

EUPHAUSIACEA

Euphausiidae

Thysanopoda sp.

FISH

Unidentified parts

MOLLUSCA

Gastropoda

OSTRACODA

Conchoecinae

Halocyprididae

Myodocopida

Ostracoda

SALPIDA

Salpidae

OTHER

Nematoda

Table 21 cont.

24.4 53.3 8.47 33.3 9.7 40.0 8.0 29.4 1.1 16.7 5.5 33.3

6.2 13.3 17.7 28.0 80.3 40.0 36.8 17.6 54.6 47.9 20.9 16.7

6.2 13.3 17.7 28.0 80.3 40.0 36.8 17.6 54.6 47.9 20.9 16.7

0.3 4.0

71.1 16.7

0.2 13.3 71.1 33.3 7.6 16.0 0.6 2.1

0.5 20.0 1.2 12.0 16.7 16.7

0.3 4.0 0.1 8.3

5.2 40.0 0.5 12.0 1.1 10.4

9.6 53.3 1.86 33.3 4.7 48.0 19.7 80.0 13.2 35.3 6.9 35.4 39.4 50.0

9.6 46.7 1.86 33.3 4.7 40.0 19.6 60.0 13.2 35.3 6.9 35.4 39.4 50.0

<0.1 6.7 <0.1 8.0 0.1 40.0

89

Table 22. Percent volume and frequency of prey items consumed by Notolychnus valdiviae collected from three sites in the Gulf of



AC601 GC852 AT340

CHAETOGNATHA

COPEPODA

Calanoida

Candaciidae

Copepoda

Corycaeidae

Cyclopoida

Euchaeta

sp.

Harpacticoida n = 1

E = 0 n = 14

E = 2 n = 92

E = 23 n = 30

E = 13 n = 71

E = 32 n = 94

E = 35 n = 41

E = 21

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

22.3 33.3 39.4 52.2 36.0 41.2 62.4 61.5 52.3 67.8 72.8 55.0

<0.1 8.3 18.1 20.3 3.3 5.9 4.3 10.3 8.5 13.6 1.7 5.0

5.9 2.6

5.9 2.6


Oncaea

sp.

0.1 2.9 0.2 3.4 0.3 5.0


Pleuromamma gracilis


Pleuromamma sp.

3.0

0.8


Poecilostomatoida


CRUSTACEA

8.2 16.7 4.2 23.2 31.1 29.4 16.8 30.8 14.8 23.7 48.5 25.0

51.0 58.3 18.7 43.5 54.3 58.8 0.1 2.6 25.0 33.9 11.3 25.0

51.0 58.3 18.7 43.5 54.3 58.8 0.1 2.6 25.0 33.9 11.3 25.0

90

Table 22 cont.

DECAPODA

EUPHAUSIACEA

Euphausiidae

OSTRACODA

Conchoecinae

Halocyprididae

Halocypridinae

Myodocopida

Myodocopina

Ostracoda

OTHER

Animalia

Nematoda


100.0 100.0 <0.1 8.3 4.4 27.5 2.4 17.6 4.5 2.6 9.9 28.8 1.3 10.0

0.5 2.9 0.3 5.9 0.2 1.7

<0.1 8.3 1.6 4.3 6.7 6.8

0.8 2.9 2.1 11.8 0.8 6.8

100.0 100.0 1.0 8.7 4.5 2.6 1.2 8.5

0.5 5.8 0.5 5.1 0.3 5.0

26.6 16.7 14.0 27.5 7.3 23.5 14.1 20.0

26.6 16.7 14.0 27.5 7.3 23.5 32.8 43.6 2.0 10.2 14.0 10.0

0.1 2.6

91

Table 23. Percent volume and frequency of prey items consumed by Ceratoscopelus warmingii collected from three sites in the Gulf of Mexico (AC601, GC852, AT340) separated by time of day. Night = 2030 to 0530 hr CDT, Day = 0730 to 1830 hr CDT, Twilight =


AC601 GC852 AT340

CNIDARIA

Hydrozoa

COPEPODA

Calanoida n = 5

E = 1 n = 6

E = 4

AMPHIPODA

Amphipoda

%V %F %V %F %V %F %V %F %V %F %V %F %V %F

54.6 50.0 8.8 31.6 0.4 33.3 0.8 13.2

54.6 50.0 0.7 10.5 0.6 13.2

Hyperiidea 1.7 10.5 0.4 33.3 0.2 2.63

Phronima stebbingii amphipod

ANNELIDA

CHAETOGNATHA

1.7 15.8 0.2 33.3 1.5 7.89

1.7 15.8 0.2 33.3 1.5 7.89

34.6 100.0

2.4 25.0 n = 23

E = 4 n = 5

E = 2 n = 6

E = 3 n = 39

E = 1 n = 4

E = 1

3.7 47.4 1.2 66.7 13.4 100.0 9.5 65.8 2.3 66.7

2.6 5.3 0.3 33.3 0.7 33.3 1.0 5.26

Candacia sp.

Copepoda

Corycaeidae

Corycaeus

sp.

Cyclopoida

Harpacticoida

0.8 26.3 0.8 33.3 2.8 55.3 0.4 66.7

Microsetella rosea

Miracia efferata

92

Table 23 cont.

Miraciidae

Temora stylifera

CRUSTACEA

Crustacea

19.5 25.0 0.0 10.5 7.1 33.3 5.5 21.1

46.8 50.0 3.6 36.8 16.7 66.7 8.4 33.3 2.7 31.6

46.8 50.0 3.3 31.6 16.7 66.7 8.4 33.3 2.6 31.6 38.7 66.7

DECAPODA

Caridea

Decapoda

EUPHAUSIACEA

Euphausiidae

FISH 0.1

MOLLUSCA

Bivalvia

Cephalopoda

Gastropoda

Mollusca

6.9 10.5 1.1 7.89 52.5 33.3

25.0 5.6

Conchoecinae

Halocyprididae

Myodocopida 5.9 25.0 0.5 21.1 5.2 33.3 0.7 15.8

Ostracoda 33.3 10.5

Platycopida

SALPIDA

Salpida

3.3 10.5 0.2 7.89

93

OTHER


Table 23 cont.

53.2 50.0 68.2 78.9 76.3 100.0 0.9 33.3 79.0 97.4 6.4 33.3

53.2 50.0 65.0 73.7 76.3 100.0 0.9 33.3 73.5 94.7

3.2 10.5 5.4 10.5 6.4 33.3

94

Table 24. Mean (± 1 standard error) δ 13 C and δ 15 N values for midwater fishes, invertebrates and carbon sources collected from each site (AC601, AT340, GC852). n = number in parentheses, * = multiple fish species grouped together

δ 15 N δ 13 C

FISH

Gonostomatidae


Cyclothone alba

Cyclothone pallida 8.44 ± 0.28 (5)

7.32 ± 0.32 (5)

9.97 (1)

9.52 (1)

8.56 ± 0.63 (4) -19.22 ± 0.12 (5)

-19.53 ± 0.12 (5)

-18.10 (1)

-18.45 (1)

-18.82 ± 0.15 (4)

Cyclothone pseudopallida 7.61 ± 0.17 (4) 7.82 ± 0.21 (3) 7.64 ± 0.28 (3) -19.48 ± 0.41 (4) -18.77 ± 0.29 (3) -18.74 ± 0.35 (3)


Sternoptychidae

8.96 ± 0.27 (6) 7.22 ± 0.23 (6) -18.87 ± 0.31 (6) -18.84 ± 0.11 (6)


7.90 ± 0.44 (5) 8.68 ± 0.24 (5) -18.83 ± 0.10 (5) -17.94 ± 0.41 (5)


Sternoptyx spp.*

7.82 (1) 7.80 ± 0.22 (9)

8.60 ± 0.26 (7) 6.99 ± 0.89 (2)

-18.63 (1) -18.72 ± 0.18 (9)

-19.75 ± 0.12 (7) -19.49 ± 0.16 (2)


9.15 ± 0.09 (5) 9.06 ± 0.21 (5) 8.57 ± 0.28 (5) -19.97 ± 0.14 (5) -19.73 ± 0.16 (5) -18.76 ± 0.41 (5)

Phosichthyidae

Pollichthys mauli

Vinciguerria poweriae

Stomiidae*

Chauliodus sloani

7.94 ± 0.10 (10)

8.03 ± 0.24 (5)

6.60 ± 0.19 (10)

7.59 ± 0.32 (5)

8.37 ± 0.26 (11) 7.90 ± 0.95 (6)

9.11 (1)

Myctophidae



Diaphus spp.*

-18.60 ± 0.10 (10)

-19.60 ± 0.09 (10) -18.98 ± 0.09 (5)

-19.24 ± 0.32 (11) -18.86 ± 0.37 (6)

-19.95 ± 0.54 (5) -17.92 (1)

6.80 ± 0.42 (3) 7.26 ± 0.49 (3) -19.60 ± 0.30 (3) -18.57 ± 0.19 (3)

6.36 ± 0.29 (3) 7.21 ± 0.33 (5) 6.43 ± 0.63 (4) -19.60 ± 0.26 (3) -19.34 ± 0.21 (5) -18.98 ± 0.35 (4)

8.41 (1) 8.76 ± 0.71 (5) -19.18 (1) -19.33 ± 0.28 (5)




Myctophum affine

9.20 (1) 7.97 ± 0.26 (6) -19.23 (1) -18.33 ± 0.08 (6)

7.91 ± 0.22 (3) 8.48 ± 0.19 (7) 7.49 ± 0.29 (5) -19.52 ± 0.22 (3) -19.51 ± 0.13 (7) -18.95 ± 0.19 (5)

7.94 ± 0.25 (4)

5.87 ± 0.28 (10)

6.75 ± 0.23 (6) -19.22 ± 0.10 (4)

-21.32 ± 0.22 (10)

-18.42 ± 0.04 (6)

95

Melamphaidae*

CNIDARIA

Atollidae

Atolla vanhoeffeni

Colobonema sericeum

8.27 ± 0.21 (5) 8.22 ± 0.63 (4)

Rhopalonematidae

12.81 (1)

15.47 (1)

Table 24 cont.

8.77 (1)

8.52 (1)

SALPIDA

Salpidae

Salpa cylindrica

Salpa

sp.

CEPHALOPODA

1.62 ± 0.61 (4)

4.16 ± 1.63 (3) 1.08 ± 0.14 (3)

Bolitaenidae

Japetella diaphana

5.67 (1)

Enoploteuthidae

-19.73 ± 0.07 (5) -19.42 ± 0.31 (4) -18.87 (1)

-19.73 (1)

-19.11 (1)

-18.74 (1)

-18.25 ± 0.22 (4)

-19.91 ± 0.71 (3) -17.88 ± 0.43 (3)

-19.55 (1)

Ancistrocheirus lesuerii

Histioteuthidae

6.19 (1)

Stigmatoteuthis arcturi 10.39 ± 1.04 (3)

GASTROPODA

Cavoliniidae

Cavolinia tridentata

Diacavolinia

sp.

CHAETOGNATHA

1.41 (1)

1.55 (1)

-0.29 (1)

8.84 ± 1.24 (5)

-19.25 (1)

-20.71 ± 0.10 (3)

-19.26 (1)

-19.43 (1)

-20.25 (1)

-19.98 ± 0.19 (5)

AMPHIPODA

Phrosinidae

Anchylomera blossevillei 3.95 (1)

Platyscelidae

Platyscelidae

sp.

Platyscelus sp.

6.51 ± 0.02 (2)

6.03 (1)

-20.68 (1)

-19.12 ± 0.10 (2)

-17.91 (1)

96

Table 24 cont.

Pronoidae

Parapronoe

sp.

7.59 (1)

COPEPODA 3.70 (1) 7.00 ± 1.53 (5) -19.14 (1)

-19.33 (1)

-19.57 ± 0.32 (5)

Megacalanidae

Bathycalanus princeps

9.06 ± 0.57 (4)

Pontellidae

-20.58 ± 0.34 (4)

Labidocera sp.

EUPHAUSIACEA

Euphausiidae

Nematodcelis megalops

Thysanopoda

sp.

3.65 ± 0.29 (2) -18.96 ± 0.18 (2)

5.97 ± 0.66 (4) 6.65 ± 0.25 (2) 4.98 ± 0.23 (5) -19.57 ± 0.26 (4) -19.16 ± 0.002 (2) -19.14 ± 0.24 (5)

6.60 ± 0.33 (3)

7.74 ± 0.61 (2)

Thysanopoda tricuspida 2.90 ± 0.50 (2)

DECAPODA

-19.50 ± 0.46 (3)

-19.10 ± 0.54 (2)

-17.74 ± 0.41 (2)

Benthesicymidae

Gennadas valens 6.83 ± 0.12 (4) 7.50 ± 0.32 (6) 6.49 ± 0.10 (4) -19.16 ± 0.39 (4) -18.47 ± 0.31 (6) -18.26 ± 0.14 (4)

Oplophoridae


Systellaspis debilis

7.78 ± 0.63 (4)

6.30 (1)

6.98 (1)

5.93 ± 0.29 (6)

Sergestidae

Sergia sp.

ZOOPLANKTON

7.79 (1)

-17.50 ± 0.14 (4)

-17.17 (1)

-19.10 (1)

-18.41 (1)

-17.84 ± 0.07 (6)

5.96 ± 2.17 (2) 7.43 ± 0.99 (5) 4.34 ± 1.36 (4) -19.19 ± 0.06 (2) -20.37 ± 0.70 (5) -19.57 ± 0.61 (4)

AUTOTROPH

Sargassaceae

Sargassum

spp.

1.40 ± 0.33 (3) 1.88 ± 1.00 (5) -0.37 ± 0.41 (4) -17.48 ± 0.65 (3) -17.60 ± 1.05 (5) -18.48 ± 0.29 (4)

Detritus

Phytoplankton 3.82 ± 0.57 (5) 2.36 ± 0.68 (8)

3.60 ± 2.08 (5)

5.25 ± 0.35 (8) -20.01 ± 0.78 (5) -19.78 ± 0.83 (8)

-9.95 ± 0.92 (5)

-19.36 ± 0.69 (8)

97

Table 25. Percent of prey contributions for each midwater fish species using IsoSource. *Results for M. affine are based on the inclusion of chemosynthetic material, as this species was not bound by the photosynthetic based prey sources.

Family

Gonostomatidae

Species

Cyclothone alba




Sternoptychidae



Sternoptyx spp.


Phosichthyidae

Pollichthys mauli


Stomiidae Chauliodus sloani

Stomiidae

Myctophidae






Myctophum affine*

Melamphaidae Melamphaidae

Zooplankton Cnidaria Pterapoda Salpida Cephalopoda

1-99 %ile 1-99 %ile 1-99 %ile 1-99 %ile 1-99 %ile

0.26-0.72 0-0.18 0.12-0.46 0-0.12 0-0.28

0-0.46 0-0.36 0-0.30 0-0.38 0-0.56

0-0.50 0-0.28 0-0.42 0-0.46 0-0.46

0-0.36 0-0.28 0-0.28 0-0.42 0-0.40

0-0.14 0-0.14 0-0.16 0-0.28 0-0.18

0-0.30 0-0.26 0-0.30 0-0.50 0-0.34

0.94-0.98 0.00 0.02-0.06 0.00 0-0.02

0.18-0.78 0-0.34 0-0.32 0-0.12 0-0.52

0.48-0.90 0-0.10 0-0.20 0-0.06 0-0.18

0-0.46 0-0.24 0-0.5 0-0.50 0-0.38

0-0.18 0-0.16 0-0.20 0-0.34 0-0.22

0-0.70 0-0.32 0-0.44 0-0.26 0-0.52

0-0.28 0-0.22 0-0.36 0-0.56 0-0.32

0-0.28 0-0.12 0-0.42 0-0.42 0-0.20

0.30-0.86 0-0.24 0-0.32 0-0.12 0-0.38

98

Decapoda Euphausiid Fish POM Chemo

1-99 %ile 1-99 %ile 1-99 %ile 1-99 %ile 1-99 %ile

Table 25 cont.

0-0.06 0-0.28

0-0.48 0-0.56

0-0.38 0-0.64

0-0.52 0-0.52 0-0.38

0.52-0.84 0-0.24

0.06-0.62 0-0.46

0.00 0.00

0-0.10 0-0.34

0.06-0.50 0-0.30

0-0.14 0-0.50 0-0.52

0-0.04 0-0.16 0-0.34

0.02-0.58 0-0.58 0-0.28

0-0.34 0-0.58

0-0.20 0-0.48 0-0.38

0.42-0.78 0-0.28

0-0.18 0-0.64

0.02-0.54 0-046

0-0.24 0-0.32 0-0.50

0-0.08 0-0.34

99

Table 26. Mean trophic position (TP), one standard deviation (Stdev), range (minimum – maximum) and number of fish (n) for each midwater fish species collected in the north-central Gulf of Mexico, using data from stable isotope and gut content analyses. Trophic positions were calculated using modified equations from Vander Zanden et al. (1996) (see methods).

GCA SIA

Cyclothone alba







Sternoptyx

Stomiidae

Diaphus

spp.

Chauliodus sloani

Diaphus problematicus spp.


Melamphaidae


Pollichthys mauli




Hygophum benoiti



Myctophum affine

3.87

3.06

3.14

3.17

3.02

3.04

3.05

3.05

3.04

Mean TP Stdev

3.04 0.13

Range

3.00 - 3.50 n

57

Mean TP

2.64

Stdev

0.36

3.00

3.00

3.01

0.00

0.00

0.07

3.00 - 3.00

3.00 - 3.00

3.00 - 3.50

60

9

51

3.30

2.82

0.48

0.18

3.18

3.07

3.03

3.01

3.06

3.07

4.00

0.27

0.15

0.12

0.05

0.15 3.00 - 3.50 34

0.21 3.00 - 4.00 69

0.00

3.00 - 3.94

3.00 - 3.50

3.00 - 3.38

3.00 - 3.49

4.00 - 4.00

29

25

11

87

5

3.02

3.12

2.88

3.10

3.44

2.28

2.89

3.09

Range

2.26 - 3.01 n

5

2.39 - 3.96 10

2.57 - 3.07 10

0.54

0.43

2.28 - 3.93 12

2.08 - 3.59 10

0.31 2.46 - 3.23 10

0.40 2.16 - 3.49 9

0.26 2.74 - 3.82 15

0.30

0.24

0.32

1.85 - 2.78

2.39 - 3.22

2.73 - 3.83

10

15

6

0.23

0.19

0.27

0.33

3.50 - 4.00

3.00 - 4.00

2.90 - 4.00

3.00 - 4.00

8

83

56

27

0.08 3.00 - 3.27 13

0.13 3.00 - 3.50 46

0.14

0.20

0.14

2.94 - 3.50

2.99 - 4.00

3.00 - 4.00

91

24

151

3.08

2.50

2.35

3.05

3.33

3.00

2.59

1.92

3.13

0.91 1.60 - 3.67 11

0.37 2.05 - 2.93 6

0.46 1.57 - 2.94 12

0.37 2.67 - 3.58 7

0.33

0.34

0.40

0.44

2.76 - 3.69

2.44 - 3.55

1.90 - 3.16

1.19 - 2.48

6

15

10

10

0.41 2.51 - 3.65 10

100

Figure 1. Sampling areas in the North-central Gulf of Mexico for midwater fauna, 9-25 August

2007. The three cold seep sites (AT340, GC852, AC601) were located on the continental slope at depths > 1000 m. Each dot represents one station.

101

Figure 2. Multidimensional scaling (MDS) plot documenting the differences among the gut contents of midwater fishes. Data were based on the Bray-Curtis similarity matrix calculated from standardized, square root transformed, mean volumes of prey (12 general categories).

Colors represent the different fish families, red = Gonostomatidae, Orange = Sternoptychidae,

Green = Phosichthyidae, Blue = Stomiidae, Purple = Myctophidae. Ca =

Cyclothone alba,

Cb =

Cyclothone braueri , Cp = Cyclothone pallida, Cps = Cyclothone pseudopallida, Ge =

Gonostoma elongatum,

Aa =


, Ah =


, Vt =


, Pm =

Pollichthys mauli

, Vp =

Vinciguerria poweriae,

Cs =

Chauliodus sloani

, St = Stomiidae, Bs =


, Cw =


, Dm =

Diaphus mollis

, Hb =

Hygophum benoiti

, La =


, Lg =


, Ma =

Myctophum affine,

Nv =


. Clusters are defined at 30% (solid black line) and 60% (dashed black line) similarities.

102

Figure 3. Relationships among stomach fullness, mean depth of capture and time for midwater fishes.

Data were compiled from all sites and excluded specimens that lacked depth data. A)

C. alba,

B)

C. braueri , C) C. pseudopallida , D) C. pallida , E) A. hemigymnus , F) V. tripunctulatus, G) G. elongatum, H) A. aculeatus , I) P. mauli , J) V. poweriae , K) B. suborbitale , L) C. warmingii , M) D. mollis,

N)

H. benoiti

, O)

L. alatus

, P)

L. guentheri,

Q)

N. valdiviae

, R)

M. affine

, S)

C. sloani

, T)

Stomiidae.

103

A

B

C

Time

00:00 04:00 08:00 12:00 16:00 20:00 00:00

500

700

900

1100

1300

100

300

500

700

900

1100

1300

Cyclothone alba

(n = 231)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

100

300


(n = 233)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

100

300

500

700

900

1100

1300 Cyclothone pseudopallida

(n = 310)

104

D

E

F

100

300

500

700

900

1100

1300

Time

00:00 04:00 08:00 12:00 16:00 20:00 00:00

500

700

900

1100

1300

100

300

500

700

900

1100

1300


(n = 328)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

100

300

Argyropelecus hemigymnus (n = 14)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

Valenciennellus tripunctulatus (n = 135)

105

I

G

H

100

300

500

700

900

1100

1300

500

700

900

1100

1300

Time

00:00 04:00 08:00 12:00 16:00 20:00 00:00

100

300

500

700

900

1100

1300


(n = 78)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

100

300


(n = 29)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

Pollichthys mauli

(n = 58)

106

J

K

L

100

300

500

700

900

1100

1300

Time

00:00 04:00 08:00 12:00 16:00 20:00 00:00

100

300

500

700

900

1100

1300


(n = 139)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

100

300

500

700

900

1100

1300 Benthosema suborbitale

(n = 193)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

Ceratoscopelus warmingii (n = 75)

107

M

N

O

Time

00:00 04:00 08:00 12:00 16:00 20:00 00:00

300

500

700

900

1100

1300

100

300

500

700

900

1100

1300

Diaphus mollis

(n = 30)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

100

Hygophum benoiti

(n = 104)

500

700

900

00:00 04:00 08:00 12:00 16:00 20:00 00:00

100

300

1100

1300 Lampanyctus alatus (n = 63)

108

P

Q

R

Time

00:00 04:00 08:00 12:00 16:00 20:00 00:00

300

500

700

900

1100

1300

100

300

500

700

900

1100

1300


(n = 127)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

100


(n = 312)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

700

900

1100

1300

100

300

500

Myctophum affine

(n = 40)

109

S

T

Time

00:00 04:00 08:00 12:00 16:00 20:00 00:00

700

900

1100

1300

100

300

500

700

900

1100

1300 Chauliodus sloani

(n = 52)

00:00 04:00 08:00 12:00 16:00 20:00 00:00

100

300

500

Stomiidae (n = 26)

110

14

12

10

8

6

4

2

Cyclothone alba







Sternoptyx spp.

Pollichthys mauli


Chauliodus sloani

Stomiidae (6 spp.)




Diaphus spp.



Myctophum affine

Melamphaidae (3 spp.)

Cavoliniidae

Cephalopoda

Chaetgnatha

Cnidaria

Salpidae

Amphipoda

Copepoda

Euphausiacea

Zooplankton


Gennadas valens

0 Systellaspis debilis

Phytoplankton

-22 -21 -20 -19 -18 -17

Sargassum spp.

Figure 4. Plot of the average δ 15 N values against the average δ 13 C values (± 1 standard error) for midwater fishes, invertebrates and primary producers collected in the north-central GOM. Shades of blue represent the different families of midwater fishes, dark red represents non-crustaceans, bright red represents small crustaceans, orange represents large crustaceans (Decapoda) and green represents primary producers. Due to small sample sizes, Stomiidae, Melamphaidae, and all invertebrates (with the exception of decapods) contain multiple species. Detritus (not pictured) had greatly enriched carbon, but did not appear to contribute to the food web. Dashed lines represented approximate trophic levels.

111

8.0

7.8

7.6

7.4

7.2

7.0

6.8

10

A B

8.5

8.0

7.5

7.0

6.5

R

2

= 0.223

p = 0.646

6.0

18 20 22 24 26 28 30 32 34 36

C

10.5

10.0

9.5

9.0

8.5

8.0

7.5

7.0

6.5

6.0

25

D

30

8.4

8.2

10.0

9.5

E

10.0

20 30

9.0

8.5

8.0

7.5

7.0

40

R

2

= 0.736

p = 0.002

6.5

50

6.0

0

9.0

F

50

35

100

40

150

R 2 = 0.367

p = 0.064

45

R 2 = 0.618

p = 0.002

50

200

9.5

9.0

8.5

8.0

8.5

8.0

7.5

7.5

7.0

7.0

6.5

R

2

= 0.274

p = 0.329

6.5

R 2 = 0.400

p = 0.068

6.0

6.0

0 10 20 30 40 50 60 0 10 20 30 40

Figure 5. Relationship between δ 15

SL (mm)

N and SL for midwater fish species. A)

Cyclothone alba,

B)

Cyclothone pallida, C) Cyclothone pseudopallida, D) Gonostoma elongatum, E) Argyropelecus aculeatus

, F)


, G)

Sternoptyx spp., H)


,

I)

Pollichthys mauli

, J)


K)

Chauliodus sloani

, L) Stomiidae, M)


, N)


, O)

Diaphus spp., P)

Diaphus problematicus , Q) Lampanyctus alatus , R) Lepidophanes guentheri , S) Myctophum affine, T)

Melamphaidae. The lines correspond to linear regressions.

112

7.5

7.0

6.5

6.0

G

9.5

9.0

8.5

8.0

7.5

7.0

6.5

6.0

0

I

8.0

10 20 30 40

H

10.0

R 2 = 0.509

p = 0.128

50

7.5

60

7.0

16

9.0

J

9.5

9.0

8.5

8.0

8.5

8.0

7.5

7.0

18 20 22 24

R 2 = 0.123

p = 0.399

26 28

5.5

5.0

24

K

9.5

9.0

8.5

8.0

29 34

R

2

= 0.331

p = 0.082

6.5

39

6.0

18

L

12.0

11.0

10.0

9.0

8.0

7.0

20 22 24 26 28

R 2 = 0.614

p < 0.001

30 32

7.5

R 2 = 0.852

6.0

5.0

R 2 = 0.355

7.0

0 50 100 150 200

Figure 5 cont. Relationship between δ 15 p = 0.009

250

4.0

0

SL (mm)

50 100 150 200 p = 0.053

250 300

N and SL for all midwater fish species. A)

Cyclothone alba, B) Cyclothone pallida, C) Cyclothone pseudopallida, D) Gonostoma elongatum, E)


, F)


, G)

Sternoptyx spp., H)


, I)

Pollichthys mauli

, J)


K)

Chauliodus sloani

, L)

Stomiidae, M)


, N)


, O)

Diaphus spp., P)

Diaphus problematicus , Q) Lampanyctus alatus , R) Lepidophanes guentheri , S) Myctophum affine,

T) Melamphaidae. The lines correspond to linear regressions.

113

M N

8.0

7.5

7.0

6.5

R 2 = 0.735

p = 0.307

6.0

18 19 20 21 22 23 24 25 26 27 28

O

8.50

8.00

7.50

7.00

6.50

6.00

5.50

5.00

4.50

4.00

P

0

10.0

9.5

10 20 30

R 2 = 0.356

p = 0.149

40 5 0

9.5

9.0

9.0

8.5

8.5

8.0

8.0

7.5

R 2 = 0.838

p = 0.029

7.5

R 2 = 0.738

p = 0.013

Q

7.0

25 35 45 55 65 75

7.0

40

9.00

R

45 50 55 60 65 70 75 80

9.5

9.0

8.50

8.00

8.5

7.50

8.0

7.00

7.5

6.50

7.0

6.00

6.5

6.0

25 30 35 40 45

R 2 = 0.113

p = 0.220

50

5.50

5.00

55

30

SL (mm)

35 40 45 50 55 60

R

2

= 0.652

p = 0.138

65

Figure 5 cont. Relationship between δ 15 N and SL for all midwater fish species. A)

Cyclothone

70 alba, B) Cyclothone pallida, C) Cyclothone pseudopallida, D) Gonostoma elongatum, E)


, F)


, G)

Sternoptyx spp., H)


, I)

Pollichthys mauli

, J)


K)

Chauliodus sloani

, L)

Stomiidae, M)


, N)


, O)

Diaphus spp., P)

Diaphus problematicus , Q) Lampanyctus alatus , R) Lepidophanes guentheri , S) Myctophum affine,

T) Melamphaidae. The lines correspond to linear regressions.

114

S

7.5

T

10.0

7.0

9.5

6.5

9.0

8.5

6.0

8.0

5.5

7.5

5.0

7.0

4.5

R

2

= 0.408

p = 0.047

6.5

R

2

= 0.687

p = 0.003

4.0

6.0

13 14 15 16 17 18 19 12 14 16 18 20 22 24 26

Figure 5 cont. Relationship between δ

SL (mm)

15 N and SL for all midwater fish species. A) Cyclothone alba, B) Cyclothone pallida, C) Cyclothone pseudopallida, D) Gonostoma elongatum, E)

Argyropelecus aculeatus, F) Argyropelecus hemigymnus, G) Sternoptyx spp., H)

Valenciennellus tripunctulatus, I) Pollichthys mauli, J) Vinciguerria poweriae, K) Chauliodus sloani, L) Stomiidae, M) Benthosema suborbitale, N) Ceratoscopelus warmingii, O) Diaphus spp., P) Diaphus problematicus, Q) Lampanyctus alatus, R) Lepidophanes guentheri, S)

Myctophum affine, T) Melamphaidae. The lines correspond to linear regressions.

28

115

TROPHIC STRUCTURE OF MIDWATER FISHES OVER COLD SEEPS IN THE... CENTRAL GULF OF MEXICO Jennifer P. McClain-Counts

δ

∑

Related documents

Products

Support

TROPHIC STRUCTURE OF MIDWATER FISHES OVER COLD SEEPS IN THE... CENTRAL GULF OF MEXICO Jennifer P. McClain-Counts

δ

∑

Related documents

Add this document to collection(s)

Add this document to saved

Suggest us how to improve StudyLib