ENHANCEMENT OF RECRUITMENT AND NURSERY FUNCTION
BY HABITAT CREATION IN PENSACOLA BAY, FLORIDA
By Carrie Shannon Tomlinson Stevenson
B.S., Samford University, 1998
A thesis submitted to the Department of Biology
College of Arts and Sciences
The University of West Florida
In partial fulfillment of the requirements for the degree of
Master of Science
2007
The thesis of Carrie Shannon Tomlinson Stevenson is approved:
Barbara Ruth, M.S., Committee Member
Date
Philip C. Darby, Ph.D., Committee Member
Date
Richard A. Snyder, Ph.D., Committee Chair
Date
Accepted for the Department/Division:
George L. Stewart, Ph.D., Chair
Date
Accepted for the College:
Jane S. Halonen, Ph.D., Dean
Date
Accepted for the University:
Richard S. Podemski, Ph.D., Dean of Graduate Studies
ii
Date
ACKNOWLEDGMENTS
Special thanks go to all of the volunteers who assisted me with hours of seining,
identifying, collecting, and net cleaning; including A. MacWhinnie, S. Bowen, A. Bloaha,
A. Schrift, J. DuPree, J. Liddle, C. Thompson, C. Power, B. Klein, L. Pennington, C.
Seltrecht, T. Chapman, C. Cox, T. Alvarez, R. Ehlers, S. Marshall, M. Diller, N. Koch, J.
McDonald, J. Cevarny, L. Cates, T. Trent, and W. Adams-Riley. Greatest thanks to my
advisor and committee members for their support, advice, and patience, as well as to
Dr. Patterson and Dr. Pomory for assistance with statistical analysis. To my co-workers
and supervisors at the University of Florida/Escambia County Extension Service and
Department of Environmental Protection, my deepest appreciation for equipment and
encouragement, as well as allowing me the time to work on this project. Enormous
thanks to my parents, for accountability, confidence, and repeatedly asking me, “How’s
your thesis going?” Most of all, this project is dedicated to my husband, son, and
daughter for their understanding, help, and tolerance of all of the odd hours and years it
took to complete this undertaking.
iii
TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS .............................................................................................. iii
LIST OF TABLES ............................................................................................................v
LIST OF FIGURES ........................................................................................................ vi
ABSTRACT .................................................................................................................. viii
CHAPTER I.
ESTUARINE HABITAT VALUE ...............................................1
A. Salt Marshes ............................................................................2
B. Seagrasses................................................................................4
C. Oyster Reefs ............................................................................5
D. Open Bottom ...........................................................................6
E. Habitat Diversity and Complexity ..........................................7
F. Restoration and Ecological Engineering ..............................11
CHAPTER II.
STUDY SITE DESCRIPTION ...................................................17
CHAPTER III.
METHODS .................................................................................22
CHAPTER IV.
RESULTS ...................................................................................26
A. Species Abundance ...............................................................27
B. Community Structure ............................................................47
C. Species Richness ...................................................................49
D. Size........................................................................................52
E. DEP Sampling Results ..........................................................61
CHAPTER V.
DISCUSSION .............................................................................68
REFERENCES ...............................................................................................................77
APPENDIX .....................................................................................................................87
iv
LIST OF TABLES
Table
Page
1.
Timeline of construction activity and sampling at study sites ...............................23
2.
Water quality data collected by FDEP ..................................................................27
3.
Water visibility data collected by FDEP ................................................................27
4.
Species collected in this study ..............................................................................28
5.
Rank order chart for four most common species of fish and most common
crustacean ...............................................................................................................33
6.
Comparison of overall abundance data for the frequently occurring species ........34
7.
Rank order for infrequently occurring species at Site 1 ........................................42
8.
Rank order for infrequently occurring species at Site 2 ........................................43
9.
Comparison of four infrequently occurring species...............................................46
10.
Average dissimilarity between habitats .................................................................48
11.
Species richness and diversity ...............................................................................50
12.
Comparison of total L. xanthurus (Spot) results by size class ...............................52
13.
Comparison of total M. cephalus (Striped mullet) results by size class ................55
14.
Comparison of total L. rhomboides (Pinfish) results by size class ........................57
15.
Comparison of total M. peninsulae (Tidewater silverside) results by size class ...59
16.
Species collected during DEP sampling (February-August 2005) ........................62
17.
Summary table of statistical analysis for four dominant species ..........................67
v
LIST OF FIGURES
Figure
Page
1.
Study area in relation to the greater Gulf of Mexico region .................................17
2.
The sampling sites along the shoreline of Pensacola Bay as seen in preproject conceptual design map for Project Greenshores .......................................19
3.
Aerial photo of Sites 1 and 2.................................................................................20
4.
Timeline of overall faunal abundance by site .......................................................31
5.
Comparison of total faunal abundance between sites by sampling date ...............32
6.
The total abundance of fish species recovered at the sampling locations over
entire course of the study ......................................................................................35
7.
Difference in total abundance of all species in Site 1 as a percentage
Difference from total abundnce at Site 2 ..............................................................36
8.
Leiostomus xanthurus (Spot) abundance comparison...........................................38
9.
Mugil cephalus (Striped mullet) abundance comparison......................................38
10.
Menidia peninsulae (Tidewater silverside) abundance comparison .....................38
11.
Lagodon rhomboides (Pinfish) abundance comparison........................................38
12.
Callinectes sapidus (Blue crab) abundance comparison ......................................40
13.
Comparative abundance for all infrequently occurring species ............................44
14.
Comparison of abundance for four infrequently occurring species ......................45
15.
2-D Multi-dimensional scaling plot ......................................................................47
16.
Species richness comparison using mean number of species captured
during repeated hauls ............................................................................................51
vi
17.
L. xanthurus (Spot) representation for Class 1 (0-4.5 cm) ...................................54
18.
L. xanthurus representation for Class 2 (4.5-9.5 cm) ...........................................54
19.
L. xanthurus representation for Class 3 (10-20 cm) .............................................54
20.
M. cephalus (Striped mullet) representation for Class 1 (0-4.5 cm) ....................56
21.
M. cephalus representation for Class 2 (4.5-9.5 cm) ............................................56
22.
M. cephalus representation for Class 3 (10-20 cm) ..............................................56
23.
L. rhomboides (Pinfish) representation for Class 1 (0-4.5 cm).............................58
24.
L. rhomboides representation for Class 2 (4.5-9.5 cm) ........................................58
25.
L. rhomboides representation for Class 3 (10-14.5 cm)........................................58
26.
M. peninsulae (Tidewater silverside) representation for Class 1 (0-4.5 cm) ........60
27.
M. peninsulae representation for Class 2 (4.5-9.5 cm) .........................................60
28.
M. peninsulae representation for Class 3 (10-14.5 cm) ........................................60
29.
Comparison of species of abundance from DEP sampling in 2005......................63
30.
Total abundance comparison by date for L. rhomboides (Pinfish) in DEP
sampling ................................................................................................................64
31.
Total abundance comparison by date for L. xanthurus (Spot) in DEP
sampling ................................................................................................................65
32.
Total abundance comparison by date for M. peninsulae (Silverside) in DEP
sampling ................................................................................................................66
vii
ABSTRACT
ENHANCEMENT OF RECRUITMENT AND NURSERY FUNCTION
BY HABITAT CREATION IN PENSACOLA BAY, FLORIDA
Carrie Shannon Tomlinson Stevenson
Urban impacts to estuarine nursery habitats can limit larval recruitment affecting
fisheries production and carrying capacity. A community-sponsored habitat creation
effort, Project GreenShores, in Pensacola Bay, Florida, USA, consists of a limestone
oyster reef/breakwater placed seaward of intertidal areas planted with Spartina
alterniflora. For this thesis, fish and epibenthic crustacean populations were sampled
monthly using a 15.24 m beach seine for fifteen months during and after placement of the
reefs and intertidal marsh to monitor changes. The study used an adjacent open water
area separated by a point of land with similar pre-project characteristics to the marsh
creation area as a control. Dominant fish and crustacean species in both locations were
Mugil cephalus, Leiostomus xanthurus, and Callinectes sapidus. Overall, there were
statistically significant differences between abundance of frequently occurring species
and the community structures in Sites 1 and 2. Diversity was nearly indistinguishable
between sites, but species richness was higher within the developed site. Fish size was
similar between the sites and was consistent with expected presence of juvenile fish
based on seasonal spawning patterns and net avoidance capability of larger fish. The
viii
results are relevant to communities and fisheries managers considering investments in
large-scale habitat development projects.
ix
CHAPTER I
ESTUARINE HABITAT VALUE
Estuaries are some of the most productive ecosystems on earth and over 90% of
saltwater species harvested in the Gulf of Mexico and South Atlantic region spend a
portion of their life cycle in them (Minello 1987, Dawes 1998). The basis of this
productivity lies in part with the diversity and complexity of habitat types included within
estuaries. This study examines the complexity and habitat issue by the analysis of open
water fish and crustacean populations associated with the creation of integrated
oyster/rock reef and intertidal marsh islands separated by subtidal channels.
Estuaries contain essential habitats for many fish and invertebrate species,
particularly juveniles. Salt marshes, seagrasses, and oyster reefs are examples of such
habitats, providing refuges, foraging grounds, and nursery areas (Williamson, King, &
Maher 1994; Chapman, Chapman, & Chandler 1996; Peterson, Comyns, Hendon, Bond,
& Duff 2000). Particular habitats within estuaries, therefore, recruit juveniles and allow
for growth and survival into adulthood (Minello, Able, Weinstein, & Hays 2003).
Habitats with structural complexity provided by the presence of underwater and emergent
vegetation or hard reef can shelter small fish from predators and provide substrate for
epiphytic food sources (Williamson et al. 1994; Hindell, Jenkins, & Keough 2000;
Bystrom, Persson, Wahlstrom, & Westman 2003). The high energy gain possible in a
vegetated area, coupled with protection from predators, can make areas encompassing
1
structure highly productive sites (Baltz, Fleeger, Rakocinski, & McCall 1998). This
property is illustrated by a study from Minello and Rozas (2002), who found a direct
relationship between vegetated intertidal area and increased brown shrimp and blue crab
production. Each type of estuarine habitat has particular advantages to various species
utilizing the area and may vary within species depending on developmental stage.
Salt Marshes
Tidal salt marshes are important habitats for nutrient cycling, primary production,
and production of fish, crustaceans, and macroinvertebrates within estuarine systems
(Broome 1990; Rozas & Minello 1998). Stable isotope studies have been used to
describe the structure of salt marsh food webs and complex interactions between organic
matter and macrofauna (Peterson & Fry 1987; Peterson & Howarth 1987), reinforcing the
role of marshes in estuarine productivity. The extensive root systems of salt marshes
allow them to serve as coastal buffers and their ability to trap sediments and take up
nutrients improves water quality (Reed 1989; Piazza, Banks, & LePeyre 2005).
While salt marshes can be found worldwide (Mitsch & Gosselink 2000), most
research on the ecological role of salt marshes has been conducted in the United States,
particularly in the Southeastern Atlantic and Gulf coasts (Connolly 1999). Many of these
studies focus on the frequent use of this habitat by fish and decapod crustaceans (Minello
& Zimmerman 1992, Minello, Zimmerman, & Medina 1994, Micheli & Peterson 1999)
due to their importance as nursery areas (Rozas & Minello 1998; Minello & Zimmerman
2000; Crinall & Hindell 2004). The density of vegetation within salt marshes provides
2
shelter for juvenile nekton while the shallow water excludes larger predators (Chapman et
al. 1996; O’Connell, Cashner, and Schieble 2005).
Sampling for mobile organisms within these vegetated systems can be difficult
(Rozas & Minello 1997, Connolly 1999) and the diversity of methods used to study
nekton use can complicate comparisons between studies. Sampling tools and methods
include seines (Whaley, Burd, & Robertson 2007), trawls (O’Connell et al. 2004), flume
weirs (Connolly 1999), drop samplers (Rozas & Minello 1998; Meng, Cicchetti &
Chintala 2004), and fyke nets (Cardinale, Brady & Burton 1998; Crinall & Hindell 2004).
Tidal creeks and flats within the marsh are generally easier to sample and are also used
frequently by nekton (Minello et al. 1994), so many studies have focused on these areas.
Tidal creeks within marshes provide a connection to the open bay for flushing to
maintain salinity levels and a means of escape for fish during low tide (Minello,
Zimmerman & Klima 1987; Cardinale et al. 1998). These natural channels provide a
conduit for marine life and create an extensive network of edge throughout a marsh
system (Mense & Wenner 1989; Minello et al. 1994; Desmond 2000). Edges in salt
marshes are important structural elements for fish and crustaceans, providing both food
resources and refuge from open water predators (Chapman et al. 1996; Desmond, Zedler,
& Williams 2000; Bologna & Heck 2002; Teal & Weinstein 2002). Teal and Weinstein
(2002) observed fish at the margin of Spartina alterniflora (Saltmarsh cordgrass) and
open water and found that habitat value decreases as fish leave the marsh with a positive
relationship between higher fish catch numbers and edge habitat. This relationship was
found whether the fish went deeper into the middle of the marsh or further out into open
water (Teal & Weinstein 2002; Minello, Able, Weinstein, & Hays 2003).
3
Seagrasses
While salt marshes provide intertidal habitat, seagrass beds are submerged
vegetated habitats. Seagrasses are sensitive to a number of anthropogenic effects
including boat propeller dredging, net trawling, and thermal pollution as well as natural
phenomena such as tropical storms and overgrazing (Dawes 1998). Water clarity is
crucial for submerged vegetation due to its reliance on unimpeded light penetration for
photosynthetic activity. Seagrasses stabilize loose sediment, dissipate wave energy, and
provide a structural refuge for biota. Seagrasses may also serve as a hydraulic seine
increasing residence time for floating larvae. This effect results in the buildup of an
important food source accumulating mobile taxa to edges, allowing them to recruit and
mature in the grassbeds (Rozas & Minello 1998). The nursery function and predation
refuge in seagrasses is comparable to that of salt marshes (Parrish 1989; Rozas & Minello
1998; Flynn & Ritz 1999). Proximity of grassbeds to differing habitats and physical
structure of seagrasses enhances utilization by diverse species as well (Oviatt & Raposa
2000). Jenkins and Sutherland (1997) found that within seagrass beds fish abundance
increased with the width of leaf blades. Bologna and Heck (2002) found the vertical
structure of algae and seagrass added surface area and therefore more usable habitat when
compared to unvegetated sediments.
Seagrass serves as substrate for epiphytes, a vital food source for many marine
species (Short, Burdick, Short, Davis, & Morgan 2000; Hindell, Jenkins, & Keough 2000;
Heck, Able, Fahay, & Roman 1989). In addition to providing ephiphytic food sources,
some fishes, urchins (Short et al. 2000) and endangered species including West Indian
4
manatees (Trichechus manatus) and green sea turtles (Chelonia mydas) depend on
seagrass blades directly for food (Williams 1988; Provancha & Hall 1991; Thayer,
Bjorndal, Ogden, Williams, & Zieman 1984).
Oyster Reefs
The value of oyster reefs in the estuarine system has been recognized for some
time (Möbius 1877) due to their high productivity and physical structure for biota within
otherwise unconsolidated sediment environments (Piazza et al. 2005). Coen and
Luckenbach (2000) listed as important functions of oyster reefs: 1) their ability to filter
and purify water, 2) stabilize sediment, and 3) provide a refuge for species not found in
sandy bottom habitats. Oyster reefs are important in estuarine biogeochemistry because
they utilize tidal energy carrying suspended particulate matter to create oyster biomass
and shell reefs, as well as concentrate and recycle nutrients (Dame & Patten 1981;
Nestlerode, Luckenbach, & O’Beirn 2007).
The increased structural complexity of oyster reefs due to the intersitial space
between shells and clusters of shells (Meyer & Townsend 2000) provides habitat for
numerous species. Posey, Powell, Alphin, and Townsend (1999) found that both primary
reef residents and transients use the reefs for foraging. They showed oyster reefs were
important Palaemonetes pugio (Grass shrimp) habitat; the shrimp were facultative reef
residents who used the reefs for refuge when hunted, but left the area when herbivores
such as Mugil cephalus (Striped mullet) were present. Opsanus beta (Gulf toadfish) and
5
Gobiesox strumosus (Skilletfish) are exemplary resident fish species that use oyster reefs
and dead shells to lay eggs. In a comparative study of three estuarine habitat types, Coen
and Luckenbach (2000) found that oyster reefs contained twice the number of decapod
species found in seagrasses and 15 times that of marshes. In created oyster reefs, Meyer
& Townsend (2000) attributed high densities of sessile and mobile macrofauna
(particularly crab species) to their structural complexity and ability to reduce turbidity.
Open Bottom
Open bottom habitats typically have the lowest nekton density when compared
with marshes, seagrass beds, or reefs (Rozas & Minello 1998; Jenkins & Wheatley 1998)
and their value is often overlooked relative to other estuarine habitats. Shallow water
benthos can be as productive or more productive than the water column and is critical
habitat for some small fish and many larger nekton (Hindell et al. 2000; Bystrom et al.
2003). Mud flats, for example, may support micro and macroalgae and harbor shellfish,
annelids, and other infauna (Rozas & Minello 1998; Short et al. 2000). These organisms
function as primary producers, deposit feeders, and filterers, producing and cycling
energy to higher trophic levels (Thorpe, Bartel, Ryan, Albertson, Pratt, & Cairns 1997;
Butts & Lewis 1999). Open water is half of the “edge” component found to be crucial in
numerous studies (Minello, Zimmerman, & Medina 1994; Hindell et al. 2000; Bologna &
Heck 2002), and unvegetated channels may be important for migration and spawning of
larger nekton (Minello et al. 1987). Planktonic food sources in marshes have been shown
to increase in density with proximity to open water (Cardinale et al. 1998). Unvegetated
6
bottoms adjacent to vegetated habitat are often undervalued as ecotones providing critical
habitat and are thus more vulnerable to dredging and human influence than wetlands and
seagrasses (Oviatt & Raposa 2000; Meng et al. 2004; Gratwicke & Speight 2005). A
paucity of research exists on the value of the open bottom component. Those studies
done in marsh channels and mud flats, for example, are often undertaken not to examine
importance of open bottom but to focus on the value of adjacent marsh (Connolly 1999).
Habitat Diversity and Complexity
Studies examining the importance of habitat edges have highlighted the
importance of the proximity of several different kinds of habitat for enhancing estuarine
biodiversity and providing critical habitat to a variety of juvenile fish. Rugosity, a
measure of surface topography analyzed by optical intensity video, has positively
correlated complexity with increased species richness, diversity, and abundance
(Shumway, Hofammn, & Dobberfuhl 2007). In an Australian study Jenkins and
Wheatley (1998) observed structure, diversity, and recruitment of fish in seagrass, reefalgal, and unvegetated habitats. They found seagrass and reef had similar fish
assemblages and larger populations than unvegetated sand, demonstrating that habitats
incorporating structure supported higher population densities and species richness. The
more diverse spacing (i.e. complex structure) a habitat possesses, the better it
accommodates larger fish and smaller prey, thus leading to higher species diversity in a
given area (Meng et al. 2004; Gratwicke & Speight 2005; Ribeiro, Almeida, Araujo,
Biscoito, & Freitas 2005). Chapman et al. (1996) also found a positive relationship
7
between species richness, low dissolved oxygen, and structural complexity especially in
rocky crevices and the submerged and emergent vegetated areas along shorelines.
Many species do not select just one form of habitat and often a single ecotone is
not valued over all others (Minello & Zimmerman 2000), emphasizing the importance of
the proximity of diverse habitat types (Gratwicke & Speight 2005) and linkages between
them for maximum recruitment and productivity (Irlandi & Crawford 1997; Micheli &
Peterson 1999; Oviatt & Raposa 2000). Pelagic recruits often live in grassbeds adjacent
to reefs, and Parrish (1989) found the proximity of these habitat types enhanced
recruitment by providing refuge until space availability or fish size allowed migration to
the reef. He suggested more studies on the “effects of proximity of different habitat
types” to clarify their means of interaction and roles in the greater ecology of estuarine
systems.
The premise that increased structure equals increased species abundance and
richness has been widely accepted, but a handful of studies have shown contrary results.
Bartholomew (2002) created an index describing habitat complexity and the relationship
between prey size and space available for hiding, and found that increased cryptic space
availability reduced species richness but noted the possibility that this finding may have
been the result of hidden prey. Glancy, Frazer, Cichra, and Lindberg (2003) emphasized
the importance of structure in their comparison of the relative habitat value of oyster reefs,
seagrasses, and marshes. At an alpha diversity level their study showed a similarity in
species composition in marshes and seagrasses, while oyster reefs harbored a different
community structure. Jenkins and Sutherland (1997) found significantly more species
richness in grass than reef and believed the “structure only” hypothesis was incorrect.
8
They believed the necessary prey and food sources would be found within a vegetated
area, but eventually feeding strategies would be the limiting factor in determining habitat
selection. Bologna and Heck (2002) also investigated this theory but, after sampling in
seagrass patch edges and interiors, found the less densely packed edges of seagrass were
more productive and yielded higher fish catches than the dense interior patches. A similar
finding in freshwater wetlands showed species richness and fish abundance decreased
when measured within the marsh and further from open water (Cardinale et al.1998)
relative to the marsh edge. Some faunal species prefer sandy bottoms to reef or vegetated
structure yet utilize the edges of vegetated or structural habitats for foraging (Jenkins
1998; Hindell et al. 2000). Many of these studies support the idea that ecotones
encompassing several types of habitat complexity will be more productive than those
with little variation.
Predatory pressure also plays a key role in forming essential habitat for juvenile
estuarine species. Chapman et al. (1996) found that nursery function of wetlands is
fundamental because structural complexity can exclude larger fish, whereas open water
does not have those limitations. Structure in the form of a “flexible barrier” (seagrasses,
marsh) or physical impediment (rock, reef) may create some difficulty and potential for
energy loss for predatory fish attempting to swim through it (Bartholomew 2002). In
addition, the lower dissolved oxygen levels found in dense wetlands prevent large
predatory fish from utilizing wetlands as forage areas. Hindell et al. (2000) looked at
small fish assemblages over unvegetated sand and seagrass and found piscivory
decreased as habitats became more complex, although predation varied significantly with
tidal and diel cycles. Even for species that prefer to feed in open water, the proximity of
9
grassbeds, marsh, or reef provides a refuge from larger predators (Hindell et al. 2000;
Ribiero et al. 2005).
Predator strategy and size play key roles in interactions within high complexity
habitats. Flynn & Ritz (1999) found that resident reef fish using a “hide and wait”
approach were more successful in catching prey while the maneuverability of active
searchers was often reduced in highly complex habitats. Habitats normally considered
the lowest predation risk may change based on the sizes of prey and predators present. A
study by Bystrom et al. (2003) found that when predators of a certain size moved into a
marsh, the complex habitat normally assumed to be low risk shifted to higher risk and
sent young of the year L. rhomboides (Pinfish) into open water for refuge. Similar
findings have been found beyond estuarine ecology—in coral reefs a study showed prey
preferred reefs where predators had been excluded regardless of structural complexity,
although when predators were reintroduced recruitment was greater on more complex
reefs (Almany 2004).
The substantial body of evidence showing that proximity to structure and habitat
complexity increases estuarine production (Irlandi & Crawford 1997; Pittman, McAlpine,
& Pittman 2004) has supported numerous efforts to preserve existing habitats, restore
damaged habitats and even to create new habitats (Minello et al. 1997; Meyer &
Townsend 2000; Nestlerode et al. 2007). When attempting to restore lost estuarine
habitats or create new ones, an integrated approach, i.e. incorporating habitat diversity,
may be the most effective means of enhancing biodiversity and production (Parrish 1989;
Bertness & Leonard 1997; Whaley et al. 2007).
10
Restoration and Ecological Engineering
Wetland plantings have been documented in Europe and the United States from as
long ago as the 1920’s and 1930’s to stabilize shores, reclaim land, or reduce channel
siltation. These activities have increased in the recent past (Broome 1990), and
governments and private entities have spent millions of dollars annually reestablishing or
creating wetlands to recover marsh habitat losses (Lewis, 1990). Restoration ecology as
a specific scientific discipline has progressed substantially since the 1990’s (Urbanska
1999) in response to a need for evaluation of efficacy and efficiency in use of public
resources to this end. In addition to scientific evidence of the value of estuarine habitats,
public awareness of marsh, seagrass, and oyster reef habitats’ importance to coastal
ecosystems has increased significantly, and support for attempts to restore and create
habitats has grown (Chabreck 1990). Besides enhancing ecosystem processes, benefits of
healthy estuarine habitats include eco-tourism and environmental education, adding to the
public support for restoring large-scale areas damaged by development, poor water
quality, and subsidence (Connolly 1999; Marcus 2000; FDEP QAPP 2002; Lefeuvre &
Bouchard 2002). In degraded areas, marsh creation can contribute to an overall
ecological boost and addition of new species due to physical proximity of wetlands
(Snograss, Bryan, Lide, & Smith 1996).
The value of these created marshes relative to natural marsh systems has been the
subject of considerable debate. Callinectes sapidus (Blue crab), used as an indicator of
salt marsh habitat value, showed a positive response to restored marshes, moving into the
restored areas quickly and at larger sizes than those utilizing an existing reference marsh
11
(Jivoff & Able 2003). The restored area appeared to enhance recruitment and serve as a
protective refuge for molting. Similarly, macrofaunal density was found to be higher in a
created Salicornia (Glasswort) marsh relative to a natural marsh, although human activity
impacted the reference marsh (Talley & Levin 1999). Significant transport of production
from a restored marsh was found for Fundulus grandis (Gulf killifish) where fish
entering the marsh had stomachs 40% full while those leaving had stomachs 60-80% full
(Teal & Weinstein 2002). Sheridan (2004) noted that newly introduced seagrasses in an
otherwise bare habitat could shelter nekton as effectively as a natural grassbed within six
to thirty-six months, while settlement and faunal use of created oyster reefs has been
found to exceed the density of natural reefs in periods of less than two years (Meyer &
Townsend 2000). A review of 36 restoration projects in the Gulf of Maine showed no
detectable differences for fish assemblages between restored and existing natural marshes
(Konisky, Burdick, Dionne, & Neckles 2006). Conversely, others have shown juvenile
crustacean utilization of restored marshes was less than natural marshes, most likely due
to a lack of benthic organisms and accumulated organic matter (Minello & Zimmerman
1992; Minello & Webb 1993). Incorrect hydrology, poor soil quality, and stunted
vegetation prevented a California wetland restoration from attracting endangered species
and functioned at approximately 60% capacity of a natural reference marsh (Malakoff,
1998).
Shoreline rehabilitation and stabilization has been a major focus of wetland
restoration efforts. Response to eroding shorelines has often involved installation of hard
structures to stabilize sediment, such as riprap or seawalls (Haslett 2000; Bush et al.
2001). Two United States Fish & Wildlife Service (USFWS) studies in the Northeastern
12
U.S. found that approximately 25% (over 100 miles) of the Narragansett Bay (Rhode
Island/Massachusetts) estuary was armored with bulkheads, revetments, and seawalls,
and the Peconic Estuary (New York) had 19 miles of hardened shoreline (Tiner, Begquist,
Siraco, & McClain 2003; Tiner, Huber, Neurminger, & Mandeville 2003). Hardening of
natural shorelines leads to a significant loss of fish habitat and contributes to declining
health and productivity of an estuary (Peterson et al. 2000; Piazza et al. 2005). Dredging,
filling, bulkheads, and seawalls eliminate the intertidal and shallow water ecotone
associated with the natural shoreline. Higher numbers of taxa have been found adjacent
to natural shorelines than hardened ones, leading to a conclusion that a more diverse
population of fish can thrive near a natural shoreline and marsh (Peterson et al. 2000;
Chapman 2003; Seitz, Lipkins, Olmstead, Seebo & Lambert 2006). In the Indian River
Lagoon (Florida) scouring associated with hardened shorelines did not affect subtidal
seagrass distribution (Nielson, Eggers, & Collins 2000). In an urban estuary in Australia
with half its shoreline hardened, abundances of algae and sessile species (polychates,
bivalves, sponges, and sea anemones) within the study were comparable between
seawalls and natural rocky shores, but rare species and 50% of the mobile taxa were
found only on natural shorelines (Chapman 2003).
Many state environmental regulatory agencies encourage planting native
emergent wetland species or seagrasses along shorelines to protect them from erosion as
an alternative to hardened shoreline structures (FDEP Homeowner’s Guide 2002). The
success of these small restoration projects is often contingent upon the location and wave
energy surrounding the shoreline (Butts 1998, Piazza et al. 2005). Projects should be
designed specifically for the site characteristics (Broome 1990; Urbanska 1999).
13
Vegetated shorelines have been documented to be resistant to storm damage and may
help accrete land (Clark 1990; Dawes 1998; Haslett 2000). The ecological success of
small shoreline restoration areas and larger marsh creations is often gauged as a
comparison of habitat value between existing, historical marshes and the newly restored
marshes (Zedler 2000; Jivoff & Able 2003; Konisky et al. 2006).
While the effectiveness of restored or created salt marshes in producing fish has
been well documented, the question of whether an artificial reef—either completely
submerged miles offshore or an intertidal oyster bed—actually serves to produce new fish
populations or just attract and concentrate existing ones remains controversial. True
recruitment would mean the structure provided habitat for fish that would not have
survived otherwise, for larvae are generally produced in numbers greatly exceeding
habitat carrying capacity (Shulman 1984; Parrish 1989). A reef functioning only to
attract would simply collect existing fish into a more central area (Pickering &
Whitmarsh 1996). An analysis of actual productivity requires not just high catch rates or
rapid colonization but evidence of greater catch in the whole region in proportion to
fishing pressure, amount of reef added, and increases in the strength of year classes
(Bohnsack, Harper, McClellan, and Hulsbeck 1994; Pickering & Whitmarsh 1996). The
size of the reef, use by target species, and design in relation to currents are all criteria for
creating a reef that serves to produce and not simply attract new fish (Ribeiro et al. 2005;
Nestlerode et al. 2007).
Many studies have examined the benefits of vegetative or reef habitat compared
with open water, but very few have contrasted two open water habitats for the proximate
effects of created habitat diversity and structure. Minello et al. (2003) analyzed 32
14
studies investigating nekton use of structure, 20 of which were located on the Gulf Coast
involving comparisons with open water (OW) or non-vegetated marsh edge (NVME)
habitat types. Of the 32, however, none of the studies looked at OW versus OW or
purely OW versus NVME. Ten of them included these comparisons within their study
but also looked at seagrass, marsh, creeks, or other biotopes at the same time (Minello et
al. 2003).
Two or more different ecotones are generally analyzed in studies of estuarine
habitat restoration and involve sampling with a seine, trawl, or enclosure device.
Research efforts typically focus on fish or decapod crustaceans for species richness and
abundance. In a review of 26 studies of wetland restoration sites in the 1990’s, fully half
of the papers surveyed showed fish and invertebrate populations were the most widely
used indicators of restoration progress (Zedler & Callway 2000). Most fishes are highly
mobile and can therefore populate a new habitat by choice quickly, and they are
relatively easy to capture, identify, and enumerate. The most useful information is
typically obtained by looking at species richness and dominance, the size distribution of
fish within different habitat types, and gut contents (Cardinale et al. 1998; Desmond et al.
2000; Glancy et al. 2003; Able, Nemerson, & Grothues 2004).
The long-term success of any wetland restoration or creation project cannot be
judged conclusively from faunal use or plant growth within a year or so of installation.
Many projects are scrutinized based on these minimal criteria because they must meet
certain goals within particular time frames based on permit requirements from regulatory
agencies (Zedler 2000). These process constraints shift focus to short-term effects rather
than the long-term potential of the created system (Malakoff 1998). Monitoring of
15
created wetlands is generally short-term (< five years), whereas natural sites used for
reference may be hundreds or thousands of years old. Within the Zedler and Callaway
(2000) survey only 12 of 26 restoration sites were sampled more than six times, and most
were sampled over short periods immediately following restoration. The majority of the
studies were sampled once or twice per year, except for a single study that sampled eight
times in one year to encompass seasonal variability. Due to such limited monitoring, the
researchers suggested that for the years immediately following a wetland restoration, the
terms “progress” or “compliance” be used rather than “success” in the regulatory arena
(Zedler & Callaway 2000).
This study in Pensacola Bay, Florida, included 30 separate sampling events over
15 months to increase the resolution of the information gathered beyond conventional
monthly or seasonal sampling regimes. Information was obtained using similar
evaluation techniques for fish and invertebrates as other estuarine habitat comparison
studies. This report covers the initial short term monitoring and forms a baseline for
future analysis by field biologists with the Florida Department of Environmental
Protection (FDEP).
16
CHAPTER II
STUDY SITE DESCRIPTION
The study site lies along the north-central portion of Pensacola Bay, Florida.
Pensacola Bay, the fifth large estuarine system in Florida (Butts 1998), is located in the
extreme northwestern region of Florida (Figure 1). Several rivers and numerous
freshwater bayous feed the bay, with a tidal inlet to the Gulf of Mexico through
Pensacola Pass. Historical records show the bay contained extensive seagrass meadows,
salt marshes, and harvestable oysters. The influences of overfishing, inadequate sewage
disposal, urban stormwater runoff, industrial discharges, dredging, filling, and shoreline
hardening have led to a depletion and degradation of these natural resources (Thorpe,
Bartel, Ryan, Albertson, Pratt, & Cairns 1997).
Figure 1. Study area in relation to the greater Gulf of Mexico region.
17
In the fall of 2001, the Florida Department of Environmental Protection’s (FDEP)
Ecosystem Restoration Section along with several other local government agencies and
private donors proposed a habitat creation effort (Project GreenShores) aimed at: 1)
enhancing recruitment of larvae and juvenile estuarine species, 2) increasing the carrying
capacity of the system for fish and invertebrate populations, and 3) improving water
quality.
Project GreenShores involved a plan for two phases of construction (Figure 2).
Phase I, totaling 4.85 hectares, included limestone boulder breakwaters in the bay,
approximately 60 m from shoreline between the Pensacola Bay Bridge and the east side
of Muscogee Wharf (Figure 3). This allowed the relatively quiescent area behind the
breakwater/oyster reef to support a tidal marsh along an otherwise open bay/high energy
shoreline (Broome 1990; Piazza et al. 2005). Planted emergent grasses under stress of
incoming waves do not typically survive well if they are not protected during
establishment (Butts 1998). The permanent wave breaks were envisioned to become reef
habitat for fish and oysters (Coen & Luckenbach 2000; FDEP QAPP 2002). Landward
of the oyster beds, sand was pumped in from a nearby dredge spoil site at the mouth of
Bayou Texar to create several large intertidal sandbars. Construction of the new marsh
and oyster reef took place only within the area denoted as “Site 1” in Figures 2 and 3
during the course of this study.
18
Spoil source
Figure 2. The sampling sites along the shoreline of Pensacola Bay as seen in pre-project
conceptual design map for Project GreenShores. The intertidal areas were separated from
the shoreline by a 30 m channel as seen in Fig. 3. No construction activity occurred in
Site 2 during the course of this study. The source of dredge spoil used for intertidal areas
is at the NE corner of diagram.
19
Site 2
Site 1
Intertidal area
Oyster reef
Figure 3. This aerial photo of Sites 1 and 2 (courtesy FDEP) shows the actual position of
the reefs, intertidal marshes, and the approximate location of the sampling sites (stars) for
this study.
The bars are 15-18 m wide, separated by 6 m channels, and follow the contour of
the shoreline. This technique of using dredged sand in intertidal habitat creation has
become a popular method of recycling local spoil material (Minello et al. 1994; Marcus
2000; Teal & Weinstein 2002). S. alterniflora was planted as 36,000 plugs within the
intertidal areas (Butts 1998; FDEP QAPP 2002). This species propagates sexually via
seeds and/or asexually with underground rhizomes (Lewis 1990; Tobe, Burks, Cantrell,
Garland, Sweeley, Hall, & Wallace 1998), and is capable of rapid colonization leading to
good plant survival (Urbanska 1999). Project managers added Juncus roemerianus
(Black needlerush) after sampling for this study was complete and plan to add submerged
aquatic vegetation Halodule wrightii (Shoal grass) and Thalassia testudinum (Turtle grass)
in the tidal creeks of the next phase. Plans for Phase II of the project would expand to the
west of Muscogee Wharf in 2007 (Figure 2). This area was used as the open shoreline
control site for this study, and designated “Site 2”. Using the definitions posed by
20
Minello et al. (2003), Site 1 would be considered a combination of “open water” (OW)
and “non-vegetated marsh edge” (NVME) while Site 2 is considered OW. In this
instance, open water is an area, such as a shallow bay, with a sand bottom and no
vegetative or hard structure. Non-vegetated marsh edge is open sand bottom within 10 m
of marsh vegetation.
In the time since initial planting, the marsh grasses have remained intact through
Hurricanes Ivan (September 16, 2004, Category 3), which passed over the City of
Pensacola, and Dennis (July 7, 2005, Category 3), which passed just east of Pensacola
Bay. The created wetland was largely unaffected by hurricane winds, waves, and storm
surge that partially destroyed the adjacent roadway (Looney & Hobbs 2005).
The objectives of this study were to determine whether the addition and proximity
of structure as limestone breakwater/oyster reef and marsh into a previously sand-bottom,
open water area (Site 1) would result in differences in the abundance and diversity of
juvenile fish and crustaceans as open water nekton when compared to the adjacent open
water (Site 2) without such structural elements.
21
CHAPTER III
METHODS
A bi-monthly survey of the fish and decapod crustacean populations in both Site 1
and Site 2 was conducted from May 2002—July 2003, coinciding with the placement of
the limestone breakwaters and intertidal marsh areas (Table 1). The locations of the
sampling sites were 0.48 km apart but were separated by a large point of land, Muscogee
Wharf (Figures 2, 3).
Site 2 was a sand bottom with occasional oysters and debris and had no emergent
littoral or submerged vegetation. Site 1 began in the same physical condition, but
progressively changed as the rock reef, sand, and plants were added. At the point of
commencement of standardized sampling in May 2002, half of the oyster reef was
constructed at Site 1. From November 8, 2002 to January 21, 2003, dredge spoil material
was pumped into the Site 1 area (30,000-40,000 cubic yards of sand). During these few
months of pumping we experienced an increase in difficulty pulling the seine due to loose
sand settling on the bay bottom; the net often filled up and seining would have to start
again after the net was emptied. In early February 2003, the final rocks and grass
planting occurred. Seining continued throughout the changes. Thirty sampling events,
starting on May 17, 2002, and ending on July 19, 2003 (15 months), were conducted to
encompass the seasonal change and weather events as well as provide comparative
overlap during the summers of 2002 and 2003.
22
Table 1. Timeline of construction activity and sampling at study sites
Date
Activity at Site 1
November 2001
January 22, 2002
May 17, 2002
June 2, 2002
June 15, 2002
July 7, 2002
July 16, 2002
August 3, 2002
August 10, 2002
August 20, 2002
September 7, 2002
September 21, 2002
October 7, 2002
October 19, 2002
November 8, 2002
Construction of limestone breakwater/oyster reef begun
Half of breakwater in place
Began faunal sampling (at both sites)
Sampling event
Sampling event
Sampling event
2000 plants placed along shoreline
Sampling event
Sampling event
Sampling event
Sampling event
Sampling event
Sampling event
Sampling event
Begin pumping 30,000-40,000 cubic yards of sand to create
intertidal sandbars
Sampling event
Sampling event
Sampling event
Sampling event
Sampling event
Sampling event
End pumping of sand
Sampling event
Final rocks placed at breakwater (20,000 tons)
Final grass planting on intertidal sandbars (30,000 plants
Sampling event
Sampling event
Sampling event
Sampling event
Sampling event
Sampling event
Sampling event
Sampling event
Sampling event
Sampling event
Final faunal sampling event (at both sites)
November 10, 2002
November 24, 2002
November 30, 2002
December 2, 2002
January 4, 2002
January 11, 2002
January 21, 2003
January 25, 2003
February 2, 2003
February 3, 2003
February 16, 2003
February 22, 2003
March 9, 2003
March 23, 2003
April 12, 2003
April 27, 2003
May 11, 2003
June 14, 2003
June 29, 2003
July 6, 2003
July 19, 2003
23
Samples were taken using a 15.24 m beach seine net with 6.35 mm mesh wings
and a 1.82 x 1.82 x 1.82 m bag in the middle with 3.17 mm mesh. Consistent sampling
methodology was used throughout the study. Two people waded out 30.5 m offshore and
pulled the net to the beach, resulting in a sample area of approximately 465 cubic meters
each haul. At Site 1 seining began at the edge of an intertidal bar and ended at the shore,
while Site 2 began at a marked point 30.5 m offshore and ended at the beach. Two hauls
were conducted per sampling site (Figure 2). Sampling of both sites occurred within the
same two-hour block of time to remove as much bias as possible from temperature,
salinity, and tidal condition differences at each site. The majority of seine hauls were
conducted during the afternoon at high tide.
After each haul, individual specimens were identified on site (to species level if
possible), enumerated, measured (total length (cm) for fish and shrimp, carapace width
for crabs (cm)), and released into the bay. Unusual species were photographed or
collected for further identification. Attempts were made to release specimens alive,
although young Menidia peninsulae (Tidewater silverside) and M. cephalus (Striped
mullet) suffered losses due to their fragility. Sampling effort was biased towards
juveniles due to the selective nature of the beach seine, but this bias was consistent
between sites.
Species diversity and abundance data were analyzed statistically using Plymouth
Routines in Multivariate Ecological Research (PRIMER v5) software’s 2-way ANOSIM,
SIMPER, and DIVERSE tests, JMP (Version 5) software’s repeated measures test, and
Microsoft Excel’s paired t-test and correlation analyses. Abundances were log
transformed (x+1) when needed to meet homogeneity of variances and assumptions of
24
normality. Water quality data obtained from the local FDEP stations 4 and 6 (Appendix)
by biology laboratory staff represented Sites 1 and 2 respectively. Both stations were
located adjacent to large stormwater outfalls draining urban watersheds. Water quality
data for the sites included turbidity, nitrogen levels, total and fecal coliform bacteria
levels, temperature, dissolved oxygen, salinity, pH, and secchi depth. Sampling was
conducted with a YSI multiprobe meter (water temperature, dissolved oxygen, pH,
salinity). Bacterial samples were collected in autoclaved sterile plastic bottles, while
turbidity, color, and total suspended solids were collected in plastic half gallon bottles.
Nutrients were collected in a 500 mL plastic bottle pre-preserved with sulfuric acid. All
samples were transported on ice and processed according to FDEP standard operating
procedures.
Sources of error and uncontrolled variables included: net snagging on bottom
debris at Site 2, differences in physical ability of volunteers to pull net, and weather
conditions. Attempts were made to nullify these sources as much as possible by using a
consistent, debris-free area to seine and training a pool of assistants who participated
frequently enough to become skilled in the methodology. Sampling dates were on
weekend mornings or afternoons based on volunteer availability. Any biases were
present at both sites—the same people used the net during each sampling event and hauls
were conducted within one hour of each other. Inclement weather was avoided as much
as possible, although the sampling event on January 4, 2003, occurred in 2-3 foot waves
due to an oncoming storm.
25
CHAPTER IV
RESULTS
No significant differences existed between water temperatures, dissolved oxygen,
salinity, pH, turbidity, color, or total suspended solids data collected at both sites between
June 2001 and April 2004 (Tables 2 & 3; Repeated measures ANOVA, p > 0.05 for all
parameters). Water temperatures measured in Pensacola Bay during this time ranged
from 10 C in January to 31 C in July (Table 2). Fecal bacterial samples taken in
October 2002 recorded levels beyond acceptable range or too numerous to count at both
sites (Table 2) but indicated no real differences between sites. The lack of any significant
differences between the two sampling locations suggests any differences in biota were
due to the habitat creation activity at Site 1.
26
Table 2. Water quality data collected by FDEP.
Date
6-Jun-01
6-Jul-01
30-Jan-02
24-Apr-02
17-Jul-02
28-Oct-02
27-Oct-03
21-Jan-04
21-Apr-04
Temp
C
Temp
C
DO
DO
Salinity
Salinity
pH
pH
FC
FC
Site 1
29.56
31.01
18.99
24.48
31.30
24.60
23.40
10.60
21.95
Site 2
29.88
30.59
18.49
24.53
31.20
24.25
23.30
11.00
21.97
1
9.29
8.17
8.82
7.68
5.97
7.74
7.53
7.79
7.27
2
7.97
8.09
8.66
7.56
5.71
7.58
7.86
7.74
8.19
1
20.19
15.35
15.88
15.78
26.51
14.77
22.00
19.80
19.50
2
20.28
15.88
15.80
15.24
25.90
16.44
21.50
19.70
19.90
1
8.03
7.96
8.07
8.14
8.00
7.74
8.04
7.88
7.73
2
8
7.96
8.05
8.11
8.01
7.9
8.08
7.9
7.92
1
0
0
0
50
10
420
70
2
134
2
0
0
0
10
10
1Z*
108
6
100
DO = Dissolved oxygen, FC = Fecal coliform, *Z = Too numerous to count
Table 3. Water visibility data collected by FDEP.
Date
6-Jun-01
6-Jul-01
30-Jan-02
24-Apr-02
17-Jul-02
28-Oct-02
27-Oct-03
21-Jan-04
21-Apr-04
Turbidity
Site 1
3
0
2
2
4
2
1
1
0
Turbidity
Site 2
2
0
5
1
4
3
1
1
0
Color
1
20
0
10
30
15
25
20
10
0
Color
2
30
0
10
30
15
25
20
10
0
TSS
1
31
0
12
11
22
5
17
28
0
TSS
2
27
0
18
10
16
6
22
27
0
TSS = Total suspended solids
Species abundance
Out of 24,387 individual fauna collected over a 15-month period, 31 species of
fish, one mollusk, and three species of decapod crustaceans were captured and identified
in the two sampling areas. Of 35 species, all were commonly occurring estuarine species
(Table 4). A total of 14,256 individual fish, crustaceans or mollusks (33 out of 35 total
species) were captured at Site 1, while 10,131 (29 of 35 species) were caught in Site 2.
27
Table 4. Species collected in this study.
Phylum Mollusca
Class Gastropoda
Order Mesogastropoda
Family Littorinadae
Littorina irrorata
Phylum Arthropoda
Subphylum Crustarea
Class Crustacea
Order Decapoda
Family Paguridae
Pagarus berhardus
Family Palaemonidae
Palaemonetes pugio
Family Portunidae
Callinectes sapidus
Phylum Chordata
Subphylum Vertebrata
Superclass Osteichthyes
Class Actinopterygii
Order Atheriniformes
Family Atherinopsidae
Menidia peninsulae (Goode & Bean)
Order Aulopiformes
Family Synodontidae
Synodus foetens (Linnaeus)
Order Batrachoidiformes
Family Batrachoididae
Opsanus beta (Goode & Bean)
Order Beloniformes
Family Belonidae
Strongylura marina (Walbaum)
Family Hemiramphidae
Hyporhampus unifasciatus (Ranzani)
Order Clupeiformes
Family Clupeidae
Harengula jaguana (Poey)
Order Cyprinodontiformes
Family Fundulidae
Fundulus grandis (Baird & Girard)
Fundulus similis (Baird & Girard)
Family Cyprinodontidae
Cyprinodon variegatus (Lacepede)
Continued next page
28
Table 4, concluded. Species collected in this study.
Order Elopiformes
Family Elopidae
Elops saurus (Linnaeus)
Order Gobiesociformes
Family Gobiesocidae
Gobiesox strumosus (Cope)
Order Perciformes
Family Carangidae
Caranx spp.
Oligoplites saurus (Bloch & Schneider)
Trachinotus carolinus (Linnaeus)
Trachurus lathami (Nichols)
Family Gerreidae
Eucinostomus argenteus (Baird & Girard)
Family Haemulidae
Orthopristis chrysoptera (Linnaeus)
Family Mugilidae
Mugil cephalus (Linnaeus)
Family Sciaenidae
Leiostomus xanthurus (Lacepede)
Menticirrhus americanus (Linnaeus)
Sciaenops ocellatus (Linnaeus)
Family Sparidae
Archosargus probatocephalus (Walbaum)
Lagodon rhomboides (Linnaeus)
Order Pleuronectiformes
Family Paralichthyidae
Citharichthys macrops (Dresel)
Paralichthys albigutta (Jordan & Gilbert)
Paralichthys lethostigma (Jordan &Gilbert)
Family Cynoglossidae
Symphurus minor (Ginsburg)
Order Scorpaeniformes
Family Triglidae
Prionotus tribulus (Cuvier)
Order Siluriformes
Family Ariidae
Arius felis (Linnaeus)
Order Syngnathiformes
Family Syngnathidae
Syngnathus scovelli (Evermann & Kendall)
Order Tetraodontiformes
Family Diodontidae
Chilomycterus schoepfii (Walbaum)
29
Faunal abundance from early sampling conducted during the majority of reef
construction (May-September 2002) in both sites was low, but a greater overall number
of fish and crustacean species were captured in Site 1 over Site 2 (Figure 4). Total
abundance in Site 1 increased to the low hundreds by November 2002, peaking to several
thousand in March 2003 and never dropping below 100 per sampling event through the
conclusion of the study in July 2003 (Figure 5). Overall numbers in Site 2 also increased
in early winter and moved into the thousands by late winter/early spring (January-March
2003) when thousands of young of the year were captured and enumerated. Construction
of the reefs and planting sites were also complete at this point. In April 2003, overall
numbers dropped off significantly through the summer, except for the M. peninsulae
(Tidewater silverside) population, which increased slightly. Sampling ended in mid-July
2003.
Overall abundance of individuals in May-June 2002 was significantly lower than
May-June 2003 (Site 1 p = 0.026; Site 2 p = 0.007). Fewer than ten individuals of any
species were caught in either site during May and June of 2002, and were predominantly
L. rhomboides (Pinfish), E. argenteus (Spotfin mojarra), and L. xanthurus (Spot). Total
faunal abundance in the same months of 2003 were 10 times the previous year’s totals in
both sampling areas, and dominant species were L. xanthurus (Spot), M. peninsulae
(Tidewater silverside), L. rhomboides (Pinfish), T. carolinus (Florida pompano), and M.
cephalus (Striped mullet). Low numbers of previously unseen species appeared in the
summer of 2003 as well.
30
02
2
00
Pl
an
t
s
ng
re
ef
al
o
te
r
fo
fo
ys
H
al
16
/2
4/
7/
/0
1-
-0
2
e
2500
Ju
ay
ac
pl
-500
M
in
Total fauna
3000
ne
-0
2
sh
/8
or
/2
e
00
lin
Au
2
e
Pu
gu
Se
m
st
pt
-0
pi
em
ng
2
be
fo
r
rsa
O
02
ct
nd
1
o
2/
b
/
is
22
er
3/
la
-0
/0
20
nd
2
3
03
s
Sa
b
Fi
D
eg
nd
na
ec
em ins
is
lr
la
oc
be
nd
ks
rs
02
an
co
d
m
pl
pl
an
et
ed
ts
in
pl
ac
e
M
ar
ch
-0
3
Ap
ril
-0
3
M
ay
-0
3
Ju
ne
-0
3
Ju
ly
-0
3
11
11
3500
Site 1
Site 2
2000
1500
1000
500
0
Dates & activities
Figure 4. Timeline of overall faunal abundance by site.
31
/1
7/
6/ 02
2
6/ /0
15 2
6/ /0
27 2
/
7/ 02
7/
8/ 02
3
8/ /0
10 2
8/ /0
20 2
/
9/ 02
7/
9/ 0
21 2
10 /0
/ 2
10 7/
/1 0 2
11 9/
/1 02
11 0/
/2 02
11 4/
/3 02
0
12 /0
/2 2
/
1/ 02
4
1/ /0
11 3
1/ /0
25 3
2/ /0
16 3
2/ /0
22 3
/
3/ 03
9/
3/ 0
23 3
4/ /0
12 3
4/ /0
27 3
5/ /0
11 3
6/ /0
14 3
6/ /0
29 3
/
7/ 03
6
7/ /0
19 3
/0
3
*5
Faunal abundance
4500
4000
Site 1
3500
-500
Site 2
3000
2500
2000
1500
1000
500
0
Dates
Figure 5. Comparison of total faunal abundance between sites by sampling date.
32
The same four fish species were most abundant by rank order for both sites (Table
6). Percentages of total fauna at Sites 1 and 2, respectively, were M. cephalus (Striped
mullet) (42.21%, 39.54%), followed by Leiostomus xanthurus (Spot; 38.46%, 36.39%),
M. peninsulae (10.72%, 19.24%), and Lagodon rhomboides (Pinfish; 3.64%, 1.12%). A
comparison of the relative abundance of these four species can be seen in Figure 6. The
most common crustacean, Callinectes sapidus (blue crab; 0.73%; 0.45%) is also listed
(Table 6).
Table 5. Rank order chart for four most common species of fish and most common
crustacean.
Site 1
Site 1
Site 2
Site 2
Rank
Fish Species
Total
% of
Total
% of
Order
individuals
total
individuals
total
1
Mugil cephalus
6017
42.21
4006
39.54
2
3
Leiostomus xanthurus
Menidia peninsulae
5483
1528
38.46
10.72
3687
1949
36.39
19.24
4
Lagodon rhomboides
519
3.64
113
1.12
Total
13547
95.03
9755
96.29
Rank
Order
Crustacean Species
Site 1
Total
individuals
Site 1
% of
total
Site 2
Total
individuals
Site 2
% of
total
1
Callinectes sapidus
104
0.73
46
0.45
104
0.73
46
0.45
Total
No significant difference in abundance existed for repeated hauls on the same day
at each site so pooled data were used for repeated measures tests. Overall faunal
abundance between sites did not show any significant differences, but individual analyses
of numerically dominant species did. Abundance varied seasonally with water
33
temperature and spawning patterns, and was highly correlated with a positive correlation
coefficient of 0.87. The difference between total abundance at each site was calculated
by dividing the total number of fish caught (by date) at Site 2 by the number at Site 1,
giving the percent difference between site abundances. This data was plotted and shows
a gradual increase (particularly from April to July 2003) in the difference between each
site, with Site 1 having greater abundance (Figure 7).
The five most commonly captured species were analyzed by paired t-test and
showed highly significant differences between abundance in Site 1 and Site 2 (Table 6).
Of these five species, M. cephalus (striped mullet) had the most significantly different
populations between the two sites while C. sapidus (blue crab) had the least.
Table 6. Comparison of overall abundance data for the frequently occurring species
between sites by paired two sample t-test for means. Data was log transformed,
significant if  ≤ 0.05, listed in descending order of significance.
Species
t Statistic
P (T<=t) two-tailed
Mugil cephalus
Lagodon rhomboides
Leiostomus xanthurus
Menidia peninsulae
Callinectes sapidus
3.98157
3.82024
3.14092
2.35407
1.87310
0.00042
0.00062
0.00386
0.02556
0.07117 (NS)
Overall faunal abundance
between sites
NS = not significant
5.92468
1.9588 (NS)
34
Site 1
7000
6000
Site 2
***
**
5000
4000
Total abundance
3000
*
2000
***
1000
0
L. xanthurus
L. rhomboides
M. peninsulae
Species
M. cephalus
Figure 6. The total abundance of dominant fish species recovered at the sampling locations over the entire course of the study.
* ≤ 0.05, ** ≤ 0.01, *** ≤ 0.001
35
36
7/19/03
7/6/03
6/29/03
6/14/03
5/11/03
4/27/03
4/12/03
3/23/03
3/9/03
2/22/03
2/16/03
1/25/03
1/11/03
1/4/03
12/2/02
11/30/02
11/24/02
11/10/02
10/19/02
10/7/02
9/21/02
9/7/02
8/20/02
8/10/02
8/3/02
7/7/02
6/27/02
6/15/02
6/2/02
*5/17/02
% Difference
400
350
300
250
200
Diff %
150
100
50
0
Dates
Figure 7. Difference in total abundance of all species in Site 1 as a percentage difference from total abundance at Site 2.
L. xanthurus (Spot) showed particular variability presumably related to spawning
(Figure 8). These fish were either nonexistent or in very low numbers from May through
December 2002, but increased after the beginning of the year. In January, young of the
year began appearing and were present through the spring, although the population
dropped again in April at both sites and by June none were captured in Site 2. However
low numbers of spot were captured in Site 1 through the end of sampling in August.
Except for large numbers of fish captured in Site 2 in February 2003, this species was
more consistently present and significantly more abundant at Site 1 throughout the
sampling period, although patterns of abundance were highly correlated between sites
(correlation coefficent = 0.81).
M. cephalus (Striped mullet) were found in large numbers in both sampling areas,
starting in January 2003 (Figure 9). Abundance of this species in Site 1 increased from
zero in December 2002 to over 600 in early January 2003. Individual numbers peaked in
March, with over 3,000 juveniles caught, but declined in later spring and summer months.
Abundance in Site 2 was almost completely attributable to fish collected during a single
date in March 2003. Besides this peak, less than ten individual mullet were captured
during any sampling event in Site 2, and overall abundance of this species was
significantly greater at Site 1 compared with Site 2 (Table 6).
37
Faunal abundance
400
300
-100
Faunal abundance
-500
Figure 8. Leiostomus xanthurus (Spot) abundance comparison.
0
*5
/1
7/
6/ 02
2
6/ /02
15
6/ /0
23 2
/
7/ 02
7/
8/ 02
3/
8/ 02
10
8/ /0
20 2
/
9/ 02
7
9/ /02
21
10 /0
/ 2
10 7/
/1 02
10 6/
/1 02
11 9/
/1 02
11 0/0
/2 2
11 4/
/3 02
0
12 /0
/2 2
/
1/ 02
4
1/ /0
11 3
1/ /03
25
2/ /03
16
2/ /0
22 3
/
3/ 03
9
3/ /03
23
4/ /0
12 3
4/ /03
27
5/ /0
11 3
6/ /0
14 3
6/ /03
29
/
7/ 03
6
7/ /0
19 3
/0
3
*5
/1
7/
6/ 02
2
6/ /0
15 2
6/ /0
27 2
/
7/ 02
7/
8/ 02
3/
8/ 0
10 2
8/ /0
20 2
/
9/ 02
7
9/ /0
21 2
10 /0
/ 2
10 7/
/1 02
11 9/
/1 02
11 0/
/2 02
11 4/
/3 02
0
12 /0
/2 2
/
1/ 02
4
1/ /0
11 3
1/ /0
25 3
2/ /0
16 3
2/ /0
22 3
/
3/ 03
9
3/ /0
23 3
4/ /0
12 3
4/ /0
27 3
5/ /0
11 3
6/ /0
14 3
6/ /0
29 3
/
7/ 03
6
7/ /0
19 3
/0
3
Dates
*5
/1
7/
02
6/
15
/0
2
7/
7/
02
8/
10
/0
2
9/
7/
02
10
/7
/0
2
11
/1
0/
02
11
/3
0/
02
1/
4/
03
1/
25
/0
3
2/
22
/0
3
3/
23
/0
3
4/
27
/0
3
6/
14
/0
3
7/
6/
03
6/ 2
2
6/ / 02
15
6/ /02
27
/
7/ 02
7/
0
8/ 2
3
8/ / 02
10
8/ /02
20
/
9/ 02
7
9/ / 02
21
10 /02
/
10 7/0
/1 2
11 9/0
/1 2
11 0/0
/2 2
11 4/0
/3 2
0
12 /02
/2
/
1/ 02
4
1/ / 03
11
1/ /03
25
2/ /03
16
2/ /03
22
/
3/ 03
9
3/ / 03
23
4/ /03
12
4/ /03
27
5/ /03
11
6/ /03
14
6/ /03
29
/
7/ 03
6
7/ / 03
19
/0
3
/0
/1
7
*5
Faunal abundance
1500
1000
Total fauna
3000
4500
2500
4000
Site 1 Total
3500
Site 1
Site 2 Total
2000
0
600
500
Dates
38
Site 2
3000
2500
2000
1500
500
1000
500
0
-500
Dates
Figure 9. Mugil cephalus (Striped mullet) abundance comparison.
700
120
Site 1 Total
100
Site 2 Total
80
Site 1 Total
-20
Site 2 Total
60
200
40
100
20
0
Dates
Figure 10. Menidia peninsulae (Silverside) abundance comparison. Figure 11. Lagodon rhomboides (Pinfish) abundance comparison.
M. peninsulae (tidewater silverside) was one of the few species found in greater
numbers within open water at Site 2 (Figure 10). Very few fish were found in Site 1 or
Site 2 until mid-October, when fish were captured with regularity. Peak numbers
appeared in January. While the highest individual catches were in Site 1, sampling
results showed similar populations in both sites but an overall significant preference for
Site 2 (Table 6; p = 0.026). A total of 1,949 silversides were caught in Site 2, while Site
1 had 1,534.
L. rhomboides (pinfish) abundance never reached the same numbers as the
preceding species in any individual sampling effort, yet had the second most significant
difference of any species analyzed in the study (Table 6). The overall catch of 522
individuals in Site 1 was significantly greater than the 113 caught in Site 2 (Figure 13).
The presence of this species was relatively consistent throughout the year, although their
incidence in Site 2 negatively correlated (correlation coefficient = -0.28) with that of L.
xanthurus (Spot). Pinfish were not found during the winter (November through January)
but was recovered again in March.
C. sapidus (blue crab) was the only crustacean present in numbers large enough to
analyze (Figure 12). Fewer than ten crabs were captured per sampling effort until
January 2003, when more than a dozen small juvenile (0.5-2.0 cm) crabs were captured at
a time in Site 1. Total numbers captured were greater at Site 1 but results from paired t
test show sites were not significantly different ( > 0.05), although the p value was under
0.10 (Table 6). Overall numbers decreased by June.
39
10/4/2002
9/20/2002
9/6/2002
8/23/2002
8/9/2002
7/26/2002
7/12/2002
6/28/2002
6/14/2002
Dates
Figure 12. Callinectes sapidus (Blue crab) abundance comparison.
40
7/11/2003
6/27/2003
6/13/2003
5/30/2003
5/16/2003
5/2/2003
4/18/2003
4/4/2003
3/21/2003
3/7/2003
2/21/2003
2/7/2003
1/24/2003
1/10/2003
12/27/2002
12/13/2002
11/29/2002
11/15/2002
11/1/2002
10/18/2002
-5
5/31/2002
5/17/2002
Total fauna
25
20
Site 1
Site 2
15
10
5
0
The remaining 30 species totaled less than 5% of the overall abundance, with no
other individual species accounting for more than 1.16% of the overall catch. The
infrequently occurring species are listed by rank abundance order and site (Tables 7 & 8).
Several C. variegatus, a typical marsh resident species, occurred in Site 1 but were not
found at Site 2. Four additional species occurring in Site 1 but not Site 2 were
Hyporhampus unifasciatus (Halfbeak), Opsanus beta (Gulf toadfish), Caranx spp. (Jack),
and Sciaenops ocellatus (Red drum). Two species, Arius felis (Hardhead catfish) and
Archosargus probatocephalus (Sheepshead), were found in Site 2 but not Site 1.
Comparative abundance for all of the infrequently occurring species is shown in Figure
13.
Highly significant differences were found between site abundances for
Eucinostomus argenteus (Spotfin mojarra), P. pugio (Grass shrimp), and F. similis
(Longnose killifish) numbers while there were not any significant differences between
the Oligoplites saurus (Leatherjacket) sample numbers (Table 9). All four of these
species occurred more frequently at Site 1 (Figure 14).
Of the 35 species caught, at least seven are of commercial value, including M.
cephalus (Striped mullet), C. sapidus (Blue crab), and two Paralichthys (Flounder)
species. A single juvenile Sciaenops ocellatus (Red drum) was caught by seine.
Important baitfish and crustaceans were present at both sites, including F. similis, L.
rhomboides, and P. pugio.
41
Table 7. Rank order for infrequently occurring species at Site 1.
Rank Order
1
2
3
4
5
6
7
8
9
9
9
10
10
11
11
11
12
13
14
15
15
15
16
16
17
17
17
17
17
18
18
Site 1 Total
individuals
166
114
104
62
49
36
25
17
14
14
14
13
13
10
10
10
9
7
4
3
3
3
2
2
1
1
1
1
1
0
0
709
Species
Eucinostomus argenteus
Fundulus similis
Callinectes sapidus
Palaemonetes pugio
Oligoplites saurus
Synodus foetens
Cyprinidon variegatus
Elops saurus
Chilomycterus schoepfi
Harengula jaguana
Paralichthys albigutta
Pagurus berhardus
Strongylura marina
Symphurus minor
Trachurus lathami
Trachinotus carolinus
Orthopristis chrysoptera
Prionotus tribulus
Syngnathus leptorhynchus
Hyporhamphus unifasciatus
Littorina irrorata
Paralichthys lethostigma
Citharichthys macrops
Gobiesox strumosus
Caranx spp.
Fundulus grandis
Menticirrhus americanus
Opsanus beta
Sciaenops ocellatus
Archosargus probatocephalus
Arius felis
Total
42
Site 1
% of total
1.16
0.8
0.73
0.43
0.34
0.25
0.18
0.12
0.1
0.1
0.1
0.09
0.09
0.07
0.07
0.07
0.06
0.05
0.03
0.02
0.02
0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0
0
4.97
Table 8. Rank order for infrequently occurring species at Site 2.
Rank Order
1
2
3
4
5
5
6
7
8
9
10
11
12
12
12
13
13
13
14
14
15
15
15
15
15
16
16
16
16
16
16
Species
Littorina irrorata
Callinectes sapidus
Oligoplites saurus
Eucinostomus argenteus
Trachinotus carolinus
Trachurus lathami
Strongylura marina
Arius felis
Prionotus tribulus
Palaemonetes pugio
Pagurus berhardus
Syngnathus leptorhynchus
Fundulus similis
Paralichthys albigutta
Synodus foetens
Harengula jaguana
Menticirrhus americanus
Symphurus minor
Chilomycterus schoepfi
Paralichthys lethostigma
Archosargus probatocephalus
Elops saurus
Citharichthys macrops
Gobiesox strumosus
Orthopristis chrysoptera
Caranx spp.
Cyprinidon variegatus
Fundulus grandis
Hyporhamphus unifasciatus
Opsanus beta
Sciaenops ocellatus
Total
Site 2 Total
individuals
97
46
43
42
16
16
15
14
11
10
9
8
7
7
7
5
5
5
4
4
1
1
1
1
1
0
0
0
0
0
0
376
43
Site 2
% of total
0.96
0.45
0.42
0.41
0.16
0.16
0.15
0.14
0.11
0.1
0.09
0.08
0.07
0.07
0.07
0.05
0.05
0.05
0.04
0.04
0.01
0.01
0.01
0.01
0.01
0
0
0
0
0
0
3.72
44
Figure 13. Comparative abundance for all infrequently occurring species.
Palaemonetes pugio
120
Trachurus lathami
140
Synodus foetens
Sygnanthus leptorhynchus
Sciaenops ocellatus
Paralichthys lethostigma
Species
Orthopristis chyrsoptera
Oligoplites saurus
Littorina irrorata
Harengula jaguana
Fundulus similis
Eucinostomus argenteus
Cyprinidon variegatus
Chilomycterus schoepfi
Total abundance
Callinectes sapidus
Archosargus probatocephalus
180
160
Site 1
Site 2
100
80
60
40
20
0
180
*
160
140
***
120
100
Total abundance
80
NS
***
60
40
20
0
Eucinostomus
argenteus
Fundulus similis
Oligoplites saurus
Species
Figure 14. Comparison of abundance for infrequently occurring species.
* ≤ 0.05, ** ≤ 0.01, *** ≤ 0.001, NS = not significant
45
Palaemonetes pugio
Site 1
Site 2
Table 9. Comparison of four infrequently occurring species between the sampling sites
by paired two-sample t-test for means. Data was log transformed, significant if  < 0.05,
listed in descending order of significance.
Species
Fundulus similes
Palaemonetes pugio
Eucinostomus argenteus
Oligoplites saurus
t Statistic
P (T<=t) two-tailed
4.3214
4.2347
2.5507
0.1275
0.000212
0.000212
0.016290
0.899340
46
Community Structure
A highly significant difference (p < 0.001) in the community structure of sampled
fauna from Site 1 and Site 2 over time was found by a 2-way crossed analysis of
similarity (ANOSIM) using PRIMER-E software (Figure 15). Results of the ANOSIM
based on the species present and sampling dates and locations showed that the replicates
within each site were more similar to each other than replicates from different sites,
thereby forming two different community structures between Site 1 and Site 2.
Figure 15. 2-D Multi-dimensional scaling plot representing analysis of similarity
between Site 1 (circles) and Site 2 (triangles) community structure.
47
A SIMPER (similarity percentages) analysis assumes there are no differences
between the two sites (100% similar) and therefore a measure of dissimilarity shows how
the two sites are different. The SIMPER results show to what degree the sites are
different and in this study L. xanthurus (Spot), M. cephalus (Striped mullet), and M.
peninsulae (Tidewater silverside) account for the most variability between the two sites.
The average dissimilarity overall between the two habitats is 78.92, with an average of
15.9 from M. peninsulae and 15.3 from L. xanthurus, and each species accounting for
approximately 20% of the dissimilarity between the two groups. The analysis assumes
there are no differences between the two sites. Just five species of the 35 found
contribute two-thirds of the dissimilarity between the two habitats (Table 10).
Table 10. Average dissimilarity between habitats.
Fig.
10
8
9
11
14
12
14
Site 1
Site 2
Scientific
Average
Average Average
name
abundance abundance
Diss.
M. peninsulae
35.90
32.48
15.96
L. xanthurus
91.40
61.45
15.31
M. cephalus
100.28
66.78
10.95
L. rhomboides
8.67
1.90
7.19
E. argenteus
2.68
0.70
4.13
C. sapidus
1.78
0.75
3.33
F. similis
1.93
0.03
3.19
Between sites
78.92
48
Diss.
/SD
1.13
0.83
0.67
1.04
.64
0.87
0.55
Contrib %
20.22
19.40
13.88
9.11
5.23
4.23
4.04
Cum.
%
20.22
39.61
53.49
62.60
67.84
72.06
76.11
Species Richness
In 28 of 30 sampling events taken during the span of the study, Site 1 had greater
species richness. For the majority of the samples, Site 1 had two to five more taxa (out of
35 total) per haul than Site 2 (Figure 16). Up to 12 different species were found at once
during a single sampling event in Site 1, but the most species for a single seine haul at
Site 2 was eight. Species richness demonstrated an upward trend over time in both
sampling locations, but more noticeably in Site 1. Species associated with hard reef such
as O. beta and Chilomycterus scoepfi (Striped burrfish) along with seagrass-associated
species like Syngnathus leptorhynchus (Bay pipefish) and L. rhomboides (Pinfish) were
found predominantly in Site 1. Using a paired t-test for repeated measures, however,
showed that there was no overall significant difference in the species richness between
the two sites, with p values > 0.05. The lack of statistical significance may be due to the
fact that overall numbers of species were low in both Site 1 and Site 2.
Species richness (d) was consistently higher at Site 1 (Table 11). On average the
Shannon diversity in Site 1 was nearly identical to Site 2. Simpson diversity and Pielou’s
evenness were slightly greater at Site 2.
49
Table 11. Species richness and diversity (determined by the PRIMER biodiversity
analysis DIVERSE).
H1 = Habitat 1/Site 1, H2 = Habitat 2/Site 2, S = sample followed by number
H1S1
H1S2
HI
Average
H2S1
H2S2
H2
Average
Shannon
diversity
Pielou's
(H' log
evenness (J')
e)
0.34211
1.1748
0.41439
1.3658
Simpson
diversity
(1lambda)
0.56745
0.6114
Species
31
27
Total
Individuals
(N)
9051
5205
Species
richness
(d)
3.2929
3.0383
29
25
23
7128
6073
4058
3.1656
2.7549
2.6481
0.37825
0.3799
0.41157
1.2703
1.2229
1.2905
0.5894
0.63199
0.63432
24
5066
2.7015
0.39573
1.2567
0.6332
50
51
7/11/03
6/27/03
6/13/03
5/30/03
5/16/03
5/2/03
4/18/03
4/4/03
3/21/03
3/7/03
2/21/03
2/7/03
1/24/03
1/10/03
12/27/02
12/13/02
11/29/02
11/15/02
11/1/02
10/18/02
10/4/02
9/20/02
9/6/02
8/23/02
8/9/02
7/26/02
7/12/02
6/28/02
6/14/02
5/31/02
5/17/02
Number of species present
12
10
8
6
Site 1 mean
Site 2 mean
4
2
0
Dates
Figure 16. Species richness comparison using mean number of species captured during repeated hauls.
Size
Because the majority of juvenile fish were caught between the winter spawning
peak times during January-April, 2003, these fish were examined more closely to
ascertain whether any particular patterns could be noted in size. The four most common
fish were divided into size classes by measuring total length (TL) and broken into three
classes (Class 1: 0-4.5 cm; Class 2: 5-9.5 cm; Class 3: 10-20 cm) to compare sizes
between sites.
Leiostomus xanthurus (Spot)
Spot were first collected on January 10, 2003. The largest numbers of Class 1
fish were captured in mid February through March in both sites (Figure 17). By April,
Spot were rarely caught. For fish in Class 1 at Site 1, at least six sampling events yielded
more than 500 fish and three events had over 100, while in Site 2 only one event had over
500 fish. This sampling event, however, was a peak of 2500 fish in one haul. Three
samples had over 200 fish, and the overall peaks in population for spot were in February
and March 2003. A paired t test did not show any significant differences between sites
for fish in Class 1 (Table 12).
Table 12. Comparison of total L. xanthurus (Spot) by size class between the sampling
sites by paired two sample t test for means. Data was log transformed, significant if  <
0.05. NS = not significant.
Class
t Statistic
P (T<=t) two-tailed
1
2
3
2.093469
-0.133097
0.5568979
0.069641 (NS)
0.897431 (NS)
0.5911744 (NS)
52
For Class 2, no fish were recovered until February 15 and only five hauls in Site 1
yielded fish, each haul having 25 or fewer individuals (Figure 18). Most hauls in Site 2
had 25 or fewer individuals, except for a peak of 225 fish in February. For the largest
size class, less than ten fish were found at any given site or time, and those caught were
in February (Figure 19). Fifteen fish were caught during two hauls in late February, and
negligible numbers found in either site through March. There were not any significant
differences in site preferences for fish in Classes 2 and 3 (Table 13).
53
2/
03
21
/2
0
(1
3
cm
)
03
/2
0
03
/2
0
03
/2
0
520
26
4/
11
4/
22
3/
20
0
03
/2
0
03
/2
0
03
/0
3
/2
0
8/
3/
21
2/
15
2/
24
10
6
1/
-2
3
-1
20
0
Faunal abundance
3/
20
10 03
/2
0
1/
17 03
/2
0
1/
24 03
/2
0
1/
31 03
/2
00
2/
7/ 3
20
2/
14 03
/2
0
2/
21 03
/2
0
2/
28 03
/2
00
3/
7/ 3
20
3/
14 03
/2
0
3/
21 03
/2
0
3/
28 03
/2
00
4/
4/ 3
20
4/
11 03
/2
0
4/
18 03
/2
0
4/
25 03
/2
00
3
1/
600
400
200
Faunal abundance
800
-400
-20
1/
3/
20
1/
03
10
/2
00
1/
3
17
/2
00
1/
3
24
/2
00
1/
3
31
/2
00
2/
7/ 3
20
2/
03
14
/2
0
2/
03
21
/2
0
2/
03
28
/2
00
3/
7/ 3
20
3/
03
14
/2
0
3/
03
21
/2
0
3/
03
28
/2
00
4/
3
4/
20
4/
03
11
/2
00
4/
3
18
/2
00
4/
3
25
/2
00
3
1/
1400
1/
3/
1/
Faunal abundance
1800
1600
Site 1 Mean
Site 2 Mean
140
1200
120
0
-200
Figure 17. L. xanthurus (Spot) representation for Class 1 (0-4.5 cm TL).
9
8
7
5
Site 1 Mean
Site 2 Mean
4
3
2
1
0
Figure 19. L. xanthurus representation in Class 3 (10-20 cm TL)
54
Site 1 Mean
Site 2 Mean
1000
100
80
60
40
20
0
Figure 18. L. xanthurus representation for Class 2 (5-9.5 cm TL)
Mugil cephalus (Striped mullet)
The majority of striped mullet were found in Site 1, although Class 1 fish peaked
at both sites on March 22, 2003, when an average of 2000 young-of-the-year were
counted in each sampling location. Very few of this size were found after early April
(Fig. 20). A paired t test showed significantly higher numbers recovered at Site 1 for fish
in Class 1 (Table 13).
Table 13. Comparison of total M. cephalus (Striped mullet) by size class between the
sampling sites by paired two sample t test for means. Data was log transformed,
significant if  < 0.05.
Class
1
2
3
NS = not significant
* ≤ 0.05
t Statistic
P (T<=t) two-tailed
2.395685946
1.700262958
0.695381367
0.043468391*
0.12750211 (NS)
0.504373485 (NS)
Mullet in Class 2 were found predominantly in Site 1 only, with only two fish
captured in Site 2 (Figure 21). No more than two fish were ever caught per sampling
effort in Class 3 or higher (Figure 22), most likely due to the larger fishes’ swimming
speed and ability to jump. However, we observed dozens of larger mullet jumping within
both sample areas. There were not any significant differences found between sites for
fish in Class 2 and 3 (Table 13).
55
2/
2
3/
2
00
3
520
(1
)
00
3
00
3
00
3
3
00
00
3
00
3
00
3
3
cm
26
/2
4/
11
/2
4/
22
/2
3/
8/
2
3/
21
/2
2/
15
/2
2/
3
1
24
/2
1/
10
/0
3/
20
10 03
/2
1/
0
17 03
/2
1/
0
24 03
/
1/ 200
31
3
/2
2/ 003
7/
2/ 200
14
3
/
2/ 200
21
3
/
2/ 200
28
3
/2
3/ 003
7/
3/ 20 0
14
3
/
3/ 200
21
3
/
3/ 200
28
3
/2
4/ 003
4/
4/ 200
11
3
/
4/ 200
18
3
/
4/ 200
25
3
/2
00
3
Faunal abundance
1000
500
Faunal abundance
Site 1 Mean
Site 2 Mean
1500
0
-20
Figure 20. M. cephalus (Striped mullet) representation for Class 1 (0-4.5 cm TL).
1.2
0.8
Site 1 Mean
Site 2 Mean
0.6
0.4
0.2
0
Figure 22. M. cephalus representation for Class 3 (10-20 cm TL).
56
1/
1/
4/25/2003
4/18/2003
4/11/2003
4/4/2003
3/28/2003
3/21/2003
3/14/2003
3/7/2003
2/28/2003
2/21/2003
2/14/2003
2/7/2003
1/31/2003
1/24/2003
1/17/2003
1/10/2003
1/3/2003
-500
1/
-0.2
00
3/
2
1/
Faunal abundance
2500
80
2000
70
60
50
Site 1 Mean
Site 2 Mean
40
30
20
10
0
-10
Figure 21. M. cephalus representation for Class 2 (5-9.5 cm TL).
Lagodon rhomboides (Pinfish)
Juvenile pinfish began to be captured after March (Figure 23). Fish in the
smallest size category did not show any significant differences (Table 14). The
population peaked in April but showed a downward trend to almost zero in later sampling
events. By comparison, Class 2 fish were numerous in Site 1 (Figure 24), and showed
highly significant differences (Table 15). A steady rise occurred among fish in this class
from late April through the summer, with a drop in late June but a peak two weeks later
in July. The Class 1 population of juvenile pinfish in Site 1 decreased from in April
concomitant with an increase in Class 2 fish after late April and through the summer.
Table 14. Comparison of total L. rhomboides (Pinfish) by size class between the
sampling sites by paired two sample t test for means. Data was log transformed,
significant if  < 0.05.
Class
t Statistic
P (T<=t) two-tailed
1
2.156237558
2
3.007496176
3
0.127756418
NS = not significant
* ≤ 0.05
0.067984575 (NS)
0.019731848*
0.901934499 (NS)
Fewer than five fish from Class 3 were ever captured in either site, and no significant
differences were noted (Figure 25). Members of the species were found predominantly at
Site 1, so little can be noted about the size distributions at Site 2 except for a slight
increase through the summer for fish in Class 2.
57
-0.5
-1
7/13/2003
7/6/2003
6/29/2003
6/22/2003
6/15/2003
6/8/2003
6/1/2003
5/25/2003
5/18/2003
5/11/2003
5/4/2003
4/27/2003
4/20/2003
3.5
4/13/2003
4
4/6/2003
3/30/2003
3/23/2003
Abundance
20
0
3/
30 3
/2
00
3
4/
6/
20
03
4/
13
/2
00
4/
20 3
/2
00
4/
27 3
/2
00
3
5/
4/
20
03
5/
11
/2
00
5/
18 3
/2
00
5/
25 3
/2
00
3
6/
1/
20
03
6/
8/
20
0
6/
15 3
/2
00
6/
22 3
/2
00
6/
29 3
/2
00
3
7/
6/
20
03
7/
13
/2
00
3
23
/
3/
-5
-10
Figure 23. L. rhomboides (Pinfish) representation for Class 1 (0-4.5 cm TL).
4.5
Site 1 Mean
Site 2 Mean
3
2.5
2
1.5
1
0.5
0
Figure 25. L. rhomboides representation for Class 3 (10-14.5 cm TL).
58
4/6/2003
7/13/2003
7/6/2003
6/29/2003
6/22/2003
6/15/2003
6/8/2003
6/1/2003
5/25/2003
5/18/2003
5/11/2003
5/4/2003
4/27/2003
4/20/2003
4/13/2003
0
3/30/2003
10
Abundance
20
3/23/2003
Abundance
25
Site 1 Mean
Site 2 Mean
60
50
Site 1 Mean
Site 2 Mean
15
40
30
20
5
10
0
Figure 24. L. rhomboides representation for Class 2 (5-9.5 cm TL).
Menidia peninsulae (Tidewater silverside)
The smallest tidewater silversides, Class 1, were present in January 2003 within
both habitats, but no more of these fish were found in Site 2 until April, when a single
fish was captured. Very few members of the species were found at Site 1 until April,
when numbers were recovered to levels similar to January (Figure 26). For Class 2, these
fish were found in larger numbers consistently through February, March, and April
(Figure 27). The majority of fish captured were in Class 2, with peak numbers in January.
Analysis by paired t test showed there was not any significant difference found between
fish sizes at Sites 1 and 2 for Classes 1 or 2 (Table 15).
Table 15. Comparison of total M. peninsulae (Tidewater silverside) by size class between
the sampling sites by paired two sample t test for means. Data was log transformed,
significant if  < 0.05.
Class
1
2
3
NS = not significant
* ≤ 0.05
t Statistic
P (T<=t) two-tailed
1.14663046
-0.799510211
-2.728585736
0.284669987 (NS)
0.447081309 (NS)
0.025902394*
For Class 3, less than ten fish were found in Site 1 between February and April, while
relatively large numbers were found in the Site 2 (Figure 28). Overall, presence in Site 1
was recorded in late February and peaked in April, while a consistent presence and
variety of sizes were captured at Site 2. The average number of silversides found in Site 1
was less than 100, while Site 2 held more than 100 on average. A paired t test showed a
highly significant difference between sites for Class 3 fish (Table 15).
59
-10
-20
4/25/2003
4/18/2003
4/11/2003
4/4/2003
60
3/28/2003
70
3/21/2003
3/14/2003
3/7/2003
2/28/2003
2/21/2003
2/14/2003
2/7/2003
1/31/2003
1/24/2003
1/17/2003
1/10/2003
4/25/2003
4/18/2003
4/11/2003
4/4/2003
3/28/2003
3/21/2003
3/14/2003
3/7/2003
2/28/2003
2/21/2003
2/14/2003
2/7/2003
1/31/2003
1/24/2003
1/17/2003
1/10/2003
1/3/2003
-20
1/3/2003
Faunal abundance
-50
Figure 26. M. peninsulae (Tidewater silverside) representation for Class 1 (0-4.5 cm TL).
80
Site 1 Mean
Site 2 Mean
50
40
30
20
10
0
Figure 28. M. peninsulae representation for Class 3 (10-14.5 cm TL).
60
4/25/2003
4/18/2003
4/11/2003
4/4/2003
Site 1 Mean
Site 2 Mean
3/28/2003
3/21/2003
3/14/2003
3/7/2003
2/28/2003
2/21/2003
2/14/2003
2/7/2003
1/31/2003
0
1/24/2003
20
1/17/2003
40
1/3/2003
60
Faunal abundance
80
1/10/2003
Faunal abundance
100
250
200
Site 1 Mean
Site 2 Mean
150
100
50
0
Figure 27. M. peninsulae representation for Class 2 (5-9.5 cm TL).
DEP Sampling Results
In February, May, and August 2005 the FDEP Ecosystem Restoration Department
responsible for Project GreenShores conducted fish sampling to monitor post-creation
effects of the new marsh and reef. The same seine was used but methodology differed in
that four hauls were conducted per site instead of two and no size data was collected.
Similar species were captured in the DEP study and abundance patterns were consistent
with the findings from 2002-2003 (Figures 29, 30, 31, 32). Sampling on August 25, 2005
was conducted after Hurricane Katrina, and no samples were taken from Site 2 due to
excessive debris in the water. For comparison purposes, repeated measures tests were
run on the overall abundance of the same four species dominating the 2002-2003
sampling. No significant differences were noted between Sites 1 and 2 for overall
abundance (p = 0.377) nor for abundance of M. peninsulae (Tidewater silverside) (p =
0.576), L. rhomboides (Pinfish) (p = 0.607), M. cephalus (Striped mullet) (p = 0.284),
and L. xanthurus (Spot) (p = 0.355).
Overall, 5,481 individual fish were captured, with 4,390 in Site 1 and 1,091 in
Site 2. Thirty species were represented, with 28 at Site 1 but just 11 at Site 2 (Table 16).
Total numbers of individuals for 26 species were higher at Site 1, while Micropogonias
undulatus (Atlantic croaker) and M. peninsulae (Tidewater silverside) dominated the Site
2 catch and outnumbered those in Site 1. While the total species count was similar,
seventeen species were not previously documented in the 2002-2003 sampling. These
included commercially important species Cynoscion nebulosus (Speckled trout), Lutjanus
61
synagris (Lane snapper), and Lutjanus griseus (Mangrove snapper). A single cow nose
ray (Rhinoptera bonasus) was also collected.
Table 16. Species collected during DEP sampling (February-August 2005), abundance
and percentage of total designated by site. * Not recorded in 2002-2003 data.
Species
Lagodon rhomboides
Bairdiella chrysoura*
Mugil cephalus
Leiostomus xanthurus
Micropogonias undulatus*
Menidia peninsulae
Mugil curema*
Harengula jaguana
Eucinostomus argenteus
Fundulus grandis
Arenigobius bifrenatus*
Anchoa mitchilli*
Orthopristis chrysoptera
Sphyraena barracuda*
Opsanus beta
Brevoortia patronus
Cynoscion nebulosus*
Strongylura marina
Penaeus aztecus*
Lutjanus synagris*
Sciaenops ocellatus
Eleotris pisonis*
Cyprinidon variegatus
Lagocephalus laevigatus*
Symphurus spp.
Pomatomus saltatrix*
Lutjanus griseus*
Rhinoptera bonasus*
Penaeus spp.*
Urophycis floridana*
Total
Site 1 Total
Site 1
% Total
abundance
2025
751
550
253
214
159
156
72
53
36
32
21
17
9
8
8
5
4
4
3
2
2
1
1
1
1
1
1
0
0
4390
46.13
17.11
12.53
5.76
4.87
3.62
3.55
1.64
1.21
0.82
0.73
0.48
0.39
0.21
0.18
0.18
0.11
0.09
0.09
0.07
0.05
0.05
0.02
0.02
0.02
0.02
0.02
0.02
0.00
0.00
100
62
Site 2
Total
189
0
4
133
391
308
0
0
25
0
6
20
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
13
1
1091
Site 2
% Total
abundance
17.32
0.00
0.37
12.19
35.84
28.23
0.00
0.00
2.29
0.00
0.55
1.83
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.09
0.00
0.00
0.00
0.00
0.00
0.00
1.19
0.09
100
2500
2000
Site 1
Site 2
1500
Total abundance
1000
500
0
Lagodon rhomboides
Leiostomus xanthurus
Mugil cephalus
Species
Menidia peninsulae
Figure 29. Comparison of species abundances from DEP sampling in 2005; species selected for comparison to 2002-2003 study.
63
2500
2000
Total abundance
1500
1000
Site 1
Site 2
500
0
Feb-05
Mar-05
Apr-05
May-05
Jun-05
Jul-05
-500
-1000
Dates
Figure 30. Total abundance comparison by date for L. rhomboides (Pinfish) in DEP sampling.
64
Aug-05
300
250
200
Abundance
150
Site 1
Site 2
100
50
0
Feb-05
Mar-05
Apr-05
May-05
Jun-05
-50
-100
Dates
Figure 31. Total abundance comparison for L.xanthurus (Spot) in DEP sampling.
65
Jul-05
Aug-05
500
400
Total abundance
300
200
Site 1
Site 2
100
0
Feb-05
Mar-05
Apr-05
May-05
Jun-05
Jul-05
-100
-200
Dates
Figure 32. Total abundance for M.peninsulae (Tidewater silverside) in DEP sampling.
66
Aug-05
Total Abundance
Abundance
p values (paired t test)
Average abundance
Average dissimilarity
Size (Class 1)
p value (paired t test)
Size (Class 2)
p value (paired t test)
Size (Class 3)
p value (paired t test)
Mullet
Site 1
Site 2
6017
4006
Spot
Site 1 Site 2
5483
3687
Silverside
Site 1 Site 2
1528
1949
Pinfish
Site 1 Site 2
519
113
Total
Site 1 Site 2
14256 10131
0.00042*
0.00386*
0.02556*
0.00062*
1.9588
100.28
66.78
91.40
61.45
35.90
32.48
8.67
1.90
10.95
15.31
15.96
7.19
0.0435*
0.0696
0.2847
0.0680
0.1275
0.8974
0.4471
0.0197*
0.5044
0.5912
0.0260*
0.9019
78.92
3.1656 2.7015
Avg. species richness
1.2703 1.2567
Avg. Shannon Diversity
0.5894 0.6332
Avg. Simpson diversity
Table 17. Summary table of statistical analyses for four dominant species. Values repeated for each site if comparison was
between sites, asterisk * if p value is significant (α ≤ 0.05) for location.
67
CHAPTER V
DISCUSSION
This thesis evaluated the importance of habitat complexity for recruitment and
species diversity of mobile estuarine fauna. The study encompasses a time course of
habitat change in one of two similar and adjacent shallow sandy bottom sites. The habitat
change involved placement of a rock reef and creation of intertidal areas planted with S.
alterniflora. Thus, the study provides both a comparison of habitat type and habitat
change over time in addressing the importance of structural complexity and habitat
diversity. With a few exceptions, the addition of habitat complexity and proximity to
newly planted vegetation had consistently enhanced fish and blue crab populations over
the temporal variance observed.
Manmade structures such as artificial reefs have been used since the 17th century
(Hiroshi 1998) to create habitat for fish because they provide refuge and substrate for
vegetative food sources (Pickering & Whitmarsh 1996). Many recent habitat creation
projects have shown that fauna will utilize and respond positively to these sites, often
within 1-2 years of construction (Chabreck 1990; Jenkins & Sutherland 1997; Meyer &
Townsend 2000). Results from the study of open bottom adjacent to the created oyster
reef and marsh within Project GreenShores suggest this site functioned similarly.
Overall abundance at both Sites 1 and 2 increased significantly from May and June 2002
to May and June 2003. This temporal change may represent 1) natural interannual
variation, or 2) an overall improvement for the larger shoreline habitat with the addition
of GreenShores. Interannual variation could be explained by EPA research in Pensacola
68
Bay (Murrell 2003), which showed a strong interannual fluctuation of bacterioplankton
related to freshwater input in the bay, which could in turn affect the amount of oxygen
available for nekton. Allen & Barker (1990) also demonstrated similar effects on larval
fish abundances due to low salinity periods. However, an overall improvement may have
occurred as other research has shown that larger reefs (> 4000 cubic meters) tend to
produce fish, as do those situated within a sandy, structure-free bottom (Borntrager &
Farrell 1992; Bohnsack 1994). The creation site monitored within this thesis fits both of
those criteria. In addition, trends in abundance within both sites increased noticeably in
early 2003, coinciding with both the end of site construction and entrance of young-ofthe-year into the estuary. These findings show potential exists for enhanced fisheries
attraction and production on a regional scale encompassing both the intertidal control and
treatment sites.
Most studies of faunal abundance in estuarine ecosystems fall into two categories:
1) comparison of a structurally complex habitat to one of lesser complexity, or 2)
comparison of restored/created habitats (usually salt marshes) to existing ones (Jenkins &
Wheatley 1998; Rozas & Minello 1998; Minello & Zimmerman 1992). Structure within
these studies includes artificial reef, oyster reef, seagrasses, freshwater and saltwater
marshes, and many combinations thereof. The majority of these studies show positive
responses—increased species diversity and greater abundance—in the sites containing
structure when compared to open bottom (Jenkins & Sutherland 1997; Peterson et al.
2000; Rozas & Zimmerman 2000). Research has shown that created oyster reefs are
colonized in a short time (Meyer & Townsend 2000; Piazza et al. 2005) and restored salt
marshes generally share characteristics of comparable, naturally occurring marshes
69
(Talley & Levin 1999; Jivoff & Able 2003; Able et al. 2004). The research in Pensacola
Bay took a different approach from these studies by comparing two open water habitats
and observing differences over time.
While fish commonly utilize complex habitats, open bottom is also an important
habitat for some species. In addition to foraging areas, sandy bottom has been shown to
be a “staging area” for juveniles before migration (Minello et al. 1987). Several species
within this study—M. peninsulae (Tidewater silverside), L. xanthurus (Spot), and
Symphurus minor (Largescale tonguefish) for example—prefer it for foraging or
camouflage. Two of the most prevalent species, M. cephalus (Striped mullet) and L.
xanthurus (Spot), are also typical residents of open bottom (Rozas & Zimmerman 2000).
While the proximity of structural complexity did not appear to enhance M. peninsulae
(Tidewater silverside) numbers, two other open water species, M. cephalus (Striped
mullet) and L. xanthurus (Spot), were recovered in significantly higher numbers at the
habitat creation site, even at this early stage of construction.
The formation of two significantly different communities within open bottom
over a relatively short period is one of the more notable findings within this study. The
fish assemblages were similar for each site, and statistical analysis showed that the
primary differences in communities lay in the abundances of just three species: L.
xanthurus (Spot), M. cephalus (Striped mullet), and M. peninsulae (Tidewater silverside).
These taxa accounted for over 90% of the total abundance in each site. Previous research
has also shown that differences in community structure and overall abundance can be
attributable to a small number of species (Jenkins & Sutherland 1997; Peterson et al.
2000). While repeated measures tests comparing overall abundance at both sites did not
70
show any significant differences, analysis of the three most frequently occurring species,
and several of the infrequently occurring ones, did show a difference in populations
between Site 1 and Site 2.
Juvenile density in a specific area is an important characteristic of habitat value
(Minello et al. 2003). These young fish may better reflect any site differences due to
adults’ greater mobility, territoriality, and removal by fishing (Rozas & Minello 1997)
and may reflect recruitment trends. Certainly the capture method used in this work was
biased towards juveniles. Abundance in both sites coincided with spawning peaks
(January-March), when thousands of young-of-the-year, especially L. xanthurus (Spot)
and M. cephalus (Striped mullet) were schooling (FWRI 2005; Hill 2005). The highly
correlated nature of the data in both sites is most likely due to the seasonality and
population dynamics of the organisms in the larger bay system. However, within these
seasonal and life history trends, the consistently higher and significantly different overall
density of key species in Site 1 suggests the improved habitat facilitated recruitment.
With the exception of M. peninsulae (Tidewater silverside), which demonstrated a
strong preference for open bottom in sampling efforts in 2002-2003 and 2005, most
specimens were recovered in greater numbers in the vicinity to marsh edge and reef.
Other literature (Rozas & Minello 1998; Minello & Zimmerman 2000) suggests
silversides prefer open water, and our study does not refute that finding. The highly
significant difference in presence of L. rhomboides (Pinfish), a species commonly found
over grassbeds, marshes, and manmade structures such as piers and pilings (Hoese &
Moore 1977; Irlandi & Crawford 1997), at Site 1 indicated fish were differentiating
between the two locations. Young M. cephalus (Striped mullet) were more abundant at
71
Site 1, which could be attributed to their preference for vegetative matter (Odum 1968).
P. pugio and F. similis, species well documented to prefer salt marshes (Connolly 1999;
Oviatt & Raposa 2000; Teal & Weinstein 2002), were found in significantly greater
abundance in Site 1. Juvenile L. xanthurus (Spot) are grazers of benthic sediments
(Phillips, Huish, Kerby, & Moran 1989) and are typically found over sandy and muddy
bottoms (Hill 2005) so their presence was expected in both sites.
The most commonly found crustacean within the study was C. sapidus (Blue
crab). Although more individuals may have been captured if some of the sampling had
taken place at night, this bias would have existed at both sites. A number of studies have
shown blue crabs to be more nocturnally active (Ryer 1987; Mense & Wenner 1989).
Abundance of this species was significantly greater at Site 1, and this may have been due
to availability of prey. As the planted S. alterniflora in Site 1 grew, L. irrorata
(Periwinkle snail) colonized the site in high numbers and were observed climbing the
grass blades. These are a known prey item for blue crabs during high tide (Steele 1979,
West & Williams 1986). Although the numbers of snails recorded were higher in Site 2
(Table 3), the sampling did not include the large number of snails observed living in the
marsh vegetation near Site 1.
Species diversity was actually higher at Site 2, which does not support the theory
that the added structure would increase diversity. This may be a factor of 1) the close
proximity of the two areas, 2) the fact that the reef and marsh were very newly
established and did not yet affect diversity, or 3) that sampling was restricted to open
bottom. In some cases created wetlands cannot achieve the goals anticipated by
restorationists simply because some are mutually exclusive; the most highly productive
72
wetlands are often monocultures and unable to attract a highly diverse faunal population
(Zedler 2000), although diversity and production are often goals stated within the same
projects.
While species richness was higher at almost every sampling event in Site 1 and
greater as measured by the DIVERSE test, repeated measures tests showed it was not a
statistically significant trend over time. One explanation could be that species richness is
generally higher in low nutrient wetlands (Chapman et al. 1996, Zedler 2000) whereas
both sites within this study receive large inputs of nutrients from both natural planktonic
sources and stormwater runoff that might mask site-specific differences (Thorpe et al.
1997). Rozas & Zimmerman (2000) had similar findings, showing species richness and
fish densities were not significantly different when marsh and nonvegetated marsh edge
were compared. Since this investigation targeted open water species in both sites the
similar fish assemblages were anticipated and there may have been no treatment effect.
The majority of fish captured in our study were under 5 cm, and Luckhurst and Luckhurst
(1978) found positive correlations between habitat complexity and species richness only
for fish larger than 5 cm. However, fish surveys taken by Department of Environmental
Protection staff in the same locations in 2005 found an additional ten species exclusively
in Site 1, including reef fish such as Lutjanus synagris (Lane snapper), Rhinoptera
bonasus (Cownose ray) and several species of Coryphopterus (Goby). Underwater
video and anecdotal evidence by fishermen have indicated Lutjanus griseus (Gray
snapper), Mycteroperca spp. (Grouper), and large S. ocellatus (Red drum) are populating
the rock reef area in Site 1. While the three samples taken in 2005 showed no significant
differences in numbers recovered between sites, Site 1 had twice as many species present.
73
Although the later sampling involved greater sampling effort per event, the trend of
increased species richness is a likely outcome of the create habitats maturing with time.
Along with species richness and diversity, site fidelity is another important factor
to consider in the analysis of ecosystem restoration projects. Site fidelity of recruits and
ontogenetic habitat shifts were unknown variables for this study, limiting the ability to
address any differences in production between sites. Increases in fish sizes from
sequential sampling were used to infer growth rates for M. cephalus (Striped mullet) and
L. rhomboides (Pinfish), assuming site fidelity. M. cephalus (Striped mullet) and L.
rhomboides (Pinfish) spawn in late winter and early spring, and juvenile population
increased in March for both species (FWRI 2005). Data suggests recruitment and growth
as abundant Class 1 (0-4.5 cm) fish decreased in April commensurate with an increase in
Class 2 (5-9.5 cm) fish (Figures 24, 25, 27, 28). Mobility of the species sampled was an
impediment to determining any site-specific growth differences, and no individuals were
tagged or tracked to demonstrate site fidelity. Mobile species have many choices within
a large bay to congregate, and could easily have moved between Sites 1 and 2 or to and
from the sites and the larger bay system. In addition, the size spectrum captured can be
affected by predation and net avoidance. Youngest fish tend to be removed faster than
larger fish by predators. Fish larger than 5 cm may also be better at net avoidance. Large
M. cephalus (Striped mullet) in particular were often observed jumping but rarely
captured in the seine.
Given the limitations of the collection method, the data are not intended to be
comprehensive for all species, but a relative reflection of any differences between sites.
Organisms within this study were collected by seine, but the net could roll over
74
burrowing animals, and fast swimmers or those who cling to vegetation or rocks likely
avoided avoid the net altogether (Rozas & Minello 1997; Petrik & Levin 2000).
Assessment of fish populations in clear water areas can be accomplished with visual
surveys, but the typically turbid conditions of estuaries require trapping or catching of
some kind (Williamson et al. 1994; Baltz et al. 1998; Petrik & Levin 2000).
Most studies have found detectable patterns of increased overall abundance and
species diversity for fish and crustaceans in habitats with structure compared with open
bottom or damaged habitat. This study differed in that for open water sampling,
proximity of marsh and reef resulted in no difference in overall abundance and species
diversity. Size differences were generally not significant except for M. cephalus (Striped
mullet) (Class 1), L. rhomboides (Pinfish) (Class 2) in Site 1 and M. peninsulae
(Tidewater silverside) (Class 3) in Site 2. The net excluded most large fish and weights
were not measured in this study. Biomass may have differed between sites, which could
indicate improved foraging success (Hunter-Thomson, Hughes, & Williams 2002).
However, the greater species richness and enhanced recruitment of particular species of
fish at Site 1 indicate the newly created habitat will likely contribute to fish production in
this portion of Pensacola Bay.
A final contribution from this study was the ability to show significant differences
in faunal density over time between sites in close physical proximity to one another.
Williamson et al. (1994) also noted that two adjacent habitats with different physical
characteristics could exhibit a difference in species composition with obvious habitat
preferences among the species present. By targeting open water species in this study the
specific habitat preference was less of an issue than the proximity of habitat and habitat
75
complexity. By adding reef and vegetation to open water and creating complexity,
species abundance improved for the majority of fish and blue crabs recovered. Given the
focus on open water species that would normally be found at both sites, and the
overriding influence of population and seasonal dynamics within the larger bay system,
the ability to detect differences between these two sites based on an immature habitat
creation project is dramatic. This research supports the ideas that increased habitat
complexity improves juvenile recruitment and that the positive effects of marsh and reef
creation can be indirectly carried into open water nekton populations in a shallow bay.
76
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