Age and growth of blue catfish, Ictalurus furcatus (Lesueur, 1840), among
three exploited and one unexploited waterbodies in Tennessee
David R. Stewart, Jr.
A thesis submitted to the graduate faculty in partial fulfillment
of the requirements for the degree of
Master of Science
Middle Tennessee State University
May 2009
ii
Age and growth of blue catfish, Ictalurus furcatus (Lesueur, 1840), among three
exploited and one unexploited waterbodies in Tennessee
David Randall Stewart, Jr.
Approved:
George W. Benz, Ph.D., Major Professor
Dennis M. Mullen, Ph.D., Committee Member
Brian T. Miller, Ph.D., Committee Member
George G. Murphy, Ph.D., Chair, Department of Biology
Michael D. Allen, Ph.D., Dean, College of Graduate Studies
iii
Age and growth of blue catfish, Ictalurus furcatus (Lesueur, 1840), among three
exploited and one unexploited waterbodies in Tennessee
David R. Stewart Jr.
Abstract
The blue catfish, Ictalurus furcatus, is an important sport and commercial resource in
Tennessee. Recently, the species has been designated a Tennessee sportfish, allowing the
Tennessee Wildlife Resources Agency to apply for federal sportfishery enhancement
funding to support its management. However, few studies have been published on blue
catfish in Tennessee that contain biological data of interest to fishery managers.
Furthermore, at least some of the results of the publications of interest are considered
dubious, as more recent research has indicated that they are based on older and less
reliable methods of analysis. With this in mind, the present study was conducted to
primarily gather weight-length relationship data, relative weight estimates, and
preliminary age and growth information for blue catfish in four Tennessee waterbodies:
Lake Barkley, Kentucky Lake, the Mississippi River, and Fort Loudoun Reservoir. In
this study, a total of 779 blue catfish were collected from fall 2006 to fall 2008 from fish
wholesalers and commercial fishermen and biologists (Lake Barkley 169 fish sampled,
Kentucky Lake 172 fish sampled, Mississippi River 248 fish sampled, Fort Loudoun
Reservoir 190 fish sampled). Standard weight-length relationships for each waterbody,
as well as a preliminary state-wide relationship based on pooled data provided good to
excellent predictive power, with r2 values for the Kentucky Lake, Mississippi River, Fort
iv
Loudoun Reservoir, and the state-wide weight-length relationships all equaling 0.95 or
higher and that of Lake Barkley equaling 0.74. Statistical differences in weight-length
relationship slopes or intercepts were found between the following waterbodies: Lake
Barkley vs. Kentucky Lake (Kentucky Lake fish adding body weight more rapidly with
increasing body length than Lake Barkley fish), Lake Barkley vs. Fort Loudoun
Reservoir (Fort Loudoun Reservoir fish adding body weight more rapidly with increasing
body length than Lake Barkley fish), Kentucky Lake vs. the Mississippi River (Kentucky
Lake fish adding weight more rapidly with increasing body length than Mississippi River
fish), Mississippi River vs. Fort Loudon Reservoir (Fort Loudoun Reservoir fish adding
weight more rapidly with increasing body length than Mississippi River fish), Lake
Barkley vs. the Mississippi River (Lake Barkley fish weighing more overall than
Mississippi River fish, but adding body weight at a similar rate per increase in body
length), and Kentucky Lake vs. Fort Loudoun Reservoir (Kentucky Lake fish weighing
more overall than Fort Loudoun Reservoir fish, but adding body weight at a similar rate
per increase in body length). Calculations of relative weight revealed that blue catfish of
all sizes in Lake Barkley and Kentucky Lake were above the species weight standard (by
21 and 12 percent, respectively); whereas, fish from the Mississippi River and Fort
Loudoun Reservoir collections were below the standard (by 6 and 14 percent,
respectively). Blue catfish aged in this study (using otoliths as the aging structure)
ranged from 0 to 34 years old and 70 to 1,115 mm total length, with the 34-year-old
individual representing the oldest blue catfish reported to date by any published study.
Significant differences in growth were detected between some of the study waterbodies,
with blue catfish in Kentucky Lake generally being longer per age than those in Fort
v
Loudoun Reservoir, in the Mississippi River generally being longer per age than those in
Fort Loudoun Reservoir, in Lake Barkley generally being longer per age than those in the
Mississippi River, in Lake Barkley generally exhibiting similar length at age as fish in
Kentucky Lake, except for age 4 catfish, and in Lake Barkley generally being longer per
age than those in Fort Loudoun Reservoir. This study was designed to detect and
describe patterns, rather than reveal the processes underlying them. Consequently, the
causes of the aforementioned differences and similarities in weight-length relationships,
relative weight estimates, and age and growth patterns remain unknown. Nonetheless,
the results provided by this study should prove valuable to fisheries managers in
Tennessee as they consider how best to manage the state’s catfish resources.
vi
Acknowlegements
I thank Cool Cats Fish Market, Harts Fish Market, B & F Fish Market, and Quillens Fish
Market, and especially Danny Shelton, Tim Case, and Andy Eldridge (all Cool Cats Fish
Market), Dennis Duncan and family (Harts Fish Market), and Jimmy Quillen (Quillens
Fish Market), for their unmeasurable assistance and hospitality throughout the project. I
thank George Scholten (Commercial and Reservoir Coordinator, Tennessee Wildlife
Resources Agency, TWRA) for the opportunity to study catfish age and growth,
guidance, and assistance regarding project and non-project matters; and Jackie Childress
and Reggie Wiggins (both TWRA) for providing valuable assistance as we braved the
commercial wholesalers in the midst of an all too hot summer to gather samples from
Lake Barkley and Kentucky Lake. I thank Eric Ganus (TWRA) for assistance with
sample collection and catfish aging, Pat Black (TWRA) for help with statistical software
as well as asistance in the field, the TWRA big head carp round-up squandron (Bobby
Wilson, George Scholten, Doug Peterson, Pat Black, Frank Fiss, Mike Bramlett, Mike
Jolley, John Hammonds, Steve Henegar, Jim Negus, Rob Lindbom) and others I may
have forgotten who assisted with sample collection in the Mississippi River; and Ed Scott
(formerly with the Tennessee Valley Authority) for help with sample collection from Fort
Loudoun Reservoir. A unquantifiable thanks is extended to Dr. George W. Benz (Middle
Tennessee State University, MTSU) for valuable guidance and support during various
stages of the project, and Drs. George W. Benz, Brian T. Miller, and Dennis M. Mullen
(all MTSU) for constructive comments regarding this thesis. Special thanks go to Shirley
and Randy Stewart for moral, loving, and financial support during my graduate program
vii
at MTSU. This project was partially funded by the Tennessee Wildlife Resources
Agency, a George G. Murphy Research Scholarshp, a J. Gerald Parchment Biological
Field Station Scholarship, and travel support from the MTSU Department of Biology,
College of Basic and Applied Sciences, and the College of Graduate Studies, for which I
am grateful.
viii
Table of Contents
Abstract ..................................................................................................................... iii
Acknowledgements ................................................................................................... vi
Table of Contents ...................................................................................................... viii
List of Tables ............................................................................................................ x
List of Figures ........................................................................................................... xii
Introduction ............................................................................................................... 1
Materials and Methods .............................................................................................. 5
Catfish Harvest Report .............................................................................. 5
Waterbodies Studied ................................................................................. 7
Sample Collection .................................................................................... 8
Otolith Removal and Processing .............................................................. 10
Data Anaylses ........................................................................................... 11
Results ....................................................................................................................... 14
Catfish Harvest Report ............................................................................. 14
Samples Collected .................................................................................... 16
Weight-length Relationships and Relative Weights ................................. 17
Age and Growth ....................................................................................... 19
Discussion ................................................................................................................. 22
Catfish Harvest Report ............................................................................. 23
Weight-length Relationships and Relative Weights ................................. 24
Age and Growth ....................................................................................... 26
ix
Conclusions. ............................................................................................. 30
References ................................................................................................................. 34
Tables ........................................................................................................................ 39
Figures ....................................................................................................................... 56
x
List of Tables
Table 1. Sport fishery creel survey analysis results for catfish (blue catfish,
Ictalurus furcatus; channel catfish, I. punctatus; flathead catfish, Pylodictis
olivaris) and bullheads (black bullhead, Amerius melas; yellow bullhead,
A. natalis) caught in three Tennessee waterbodies during 1998-2006. .............. 39
Table 2. Monthly 2005 commercial catfish harvest (kg) for 17 Tennessee
waterbodies calculated from Tennessee Wildlife Resources Agency commercial
fishing data. ......................................................................................................... 41
Table 3. Sport and commercial harvest of catfish (blue catfish, Ictalurus furcatus;
channel catfish, I. puntatus; and flathead catfish, Pylodictis olivaris) for 22
waterbodies for the year 2006. . ........................................................................... 42
Table 4. Number of blue catfish, Ictalurus furcatus, sampled from four study
waterbodies. ........................................................................................................ 44
Table 5. Parameters of log10 transformed weight-length linear regressions for
four studied Tennessee waterbodies and log10 transformed weight-length linear
regression for pooled data from the same four waterbodies used to represent
Tennessee. ............................................................................................................ 47
Table 6. Overall and mean relative weights for five size classes of blue catfish, Ictalurus
furcatus, sampled from four Tennessee waterbodies. ......................................... 48
Table 7. Mean total length at age (mm) for blue catfish, Ictalurus furcatus, in four
Tennessee waterbodies. ....................................................................................... 49
xi
Table 8. Fishery mileposts for blue catfish, Ictalurus furcatus, in four Tennessee
waterbodies. ....................................................................................................... 50
Table 9. Comparison of blue catfish, Ictalurus furcatus, length age data
stemming from studies in Lake Barkley (Tennessee and Kentucky). ................ 51
Table 10. Comparison of blue catfish, Ictalurus furcatus, length age data
stemming from studies in Kentucky Lake (Tennessee and Kentucky). .............. 52
Table 11. Comparison of blue catfish, Ictalurus furcatus, length age data
stemming from studies in Mississippi River (Tennessee and Louisianna). ........ 54
Table 12. Comparison of blue catfish, Ictalurus furcatus, length age data
stemming from studies in Fort Loudoun Reservoir (Tennessee), Lake Hugo
(Oklahoma), Lake Ellsworth (Oklahoma), and Lake Eufaula (Oklahoma). ....... 55
xii
List of Figures
Figure 1. Major river systems of Tennessee. ........................................................... 56
Figure 2. Location and removal of sagittal otoliths from catfish. ............................ 57
Figure 3. Epoxy casts containing catfish otoliths. ................................................... 58
Figure 4. Weight-length relation for blue catfish, Ictalurus furcatus, collected from Lake
Barkley (Tennessee portion of lake; formula for log10 transformed weight-length
linear regression and r2 value provided at upper left). ........................................ 59
Figure 5. Weight-length relation for blue catfish, Ictalurus furcatus, collected from
Kentucky Lake (Tennessee portion of lake; formula for log10 transformed weightlength linear regression and r2 value provided at upper left). .............................. 60
Figure 6. Weight-length relation for blue catfish, Ictalurus furcatus, collected from the
Mississippi River (formula for log10 transformed weight-length linear regression and
r2 value provided at upper left). ........................................................................... 61
Figure 7. Weight-length relation for blue catfish, Ictalurus furcatus, collected from Fort
Loudoun Reservoir (formula for log10 transformed weight-length linear regression
and r2 value provided at upper left). .................................................................... 62
Figure 8. Weight-length relation for blue catfish, Ictalurus furcatus, collected from four
Tennessee waterbodies (Lake Barkley, Kentucky Lake, Mississippi River, Fort
Loudoun Reservoir; formula for log10 transformed weight-length linear regression
and r2 value provided at upper left). .................................................................... 63
Figure 9. Blue catfish, Ictalurus furcatus, von Bertalanffy growth curve and model
parameters for four Tennessee waterbodies. ........................................................ 64
xiii
Figure 10. Blue catfish, Ictalurus furcatus, von Bertalanffy growth curve and model
parameters for Lake Barkley. ............................................................................... 65
Figure 11. Blue catfish, Ictalurus furcatus, von Bertalanffy growth curve and model
parameters for Kentucky Lake. ............................................................................ 66
Figure 12. Blue catfish, Ictalurus furcatus, von Bertalanffy growth curve and model
parameters for Mississippi River. ........................................................................ 67
Figure 13. Blue catfish, Ictalurus furcatus, von Bertalanffy growth curve and model
parameters for Fort Loudoun Reservoir. .............................................................. 68
1
Introduction
Ictalurids (Ictaluridae) are among the most frequently fished freshwater fishes in the
United States. The National Survey of Fishing, Hunting, and Wildlife-Associated
Recreation reported that, in 2006, seven million US anglers fished 98.2 million days for
catfish (USFWS and USCB 2006). Catfish (blue catfish, Ictalurus furcatus (Lesueur
1840); channel catfish, I. punctatus (Rafinesque 1818); flathead catfish, Pylodictis
olivaris (Rafinesque 1818); black bullhead, Ameiurus melas (Rafinesque 1820); and
yellow bullhead, A. natalis (Lesueur 1819)), formed the third most sought after fish
group, behind black bass (Micropterus spp.) and panfish (some non-bass members of
Centrarchidae) (USFWS and USCB 2006). In Tennessee, blue catfish, channel catfish,
and flathead catfish comprised the third most sought after group of fishes, behind black
bass and crappie (black crappie, Pomoxis nigromaculatus (Lesueur 1829) and white
crappie, P. annularis (Rafinesque 1818); (USFWS and USCB 2006; Pat Black,
Tennessee Wildlife Resources Agency, unpublished report).
The blue catfish is the largest ictalurid and can reach 165 cm total length (TL) and 68
kg in weight (Etnier and Starnes 1993). Although the species may sometimes be
confused by anglers with other catfishes (unpublished observations of author), I. furcatus
is easily differentiated from its congeners by the following characteristics: 30-36 anal fin
rays, distinctive coloration (pale grey, white to blue dorsally; white ventrally), and a
lower jaw that never extends beyond the upper jaw (Etnier and Starnes 1993). Blue
catfish are native to 29 states within the Mississippi, Missouri, and Ohio river drainages,
where they most commonly inhabit large bodies of water (Etnier and Starnes 1993). Blue
2
catfish generally mature at 35-66.2 cm TL and 4 or 5 years of age in the South and 38.148 cm TL and 6 or 7 years of age in the North (Graham 1999).
Fourteen states, including Tennessee, support recreational and commercial fisheries
for catfish (Graham 1999). Recreational angling for catfish has recently become more
popular, as evidenced by increased media exposure, such as fishing-related television
programming and sports magazines (Graham 1999). This increase in popularity has
manifested itself in Tennessee as well, and in 2008 In-fisherman Magazine included
Tennessee’s Cumberland River system as one of the ten best blue catfish fisheries in the
nation (Hoffman 2008). Associated with this catfish angling invigoration, the
International Game Fish Association has recognized four world-record blue catfish since
1996. The current all-tackle world record for the species, 56 kg and 147.3 cm TL (which
broke the previous record by 1.4 kg) was caught in the Mississippi River near Alton, IL
in 2005. Other large blue catfish have generated further attention, such as those landed at
a 2008 Memphis, TN based Mississippi River catfish tournament, where for the first
time, two catfish of any species weighing > 45 kg were brought to the scales (Brasher
2007).
In Tennessee, there were 237 resident and 6 non-resident commercial fishing licenses
issued in 2008 permitting holders to harvest catfish. Commercially harvested catfish
(blue catfish, channel catfish, and flathead catfish) in Tennessee are sold to commercial
fish wholesalers who distribute the flesh for human consumption. As of October 2008,
the harvest price for catfish in Tennessee was US$0.45 per lb (Dennis Duncan, Hart’s
Fish Market, personal communication). Blue catfish comprises the heaviest annual
3
commercial catch, followed by channel catfish, and flathead catfish (George Scholten,
Tennessee Wildlife Resources Agency, personal communication). Regarding the two
most-harvested catfishes, blue catfish are typically more desirable to commercial
fishermen because consumers prefer their white flesh, which lacks the off-colored tint
typically exhibited by flesh of channel catfish (Danny Shelton, Cool Cats Fish Market,
personnel communication).
Catfish (Ictalurus spp. and P. olivaris) were primarily managed as commercial
species in Tennessee prior to 2003, and sportfishermen harvesting them were only
required to hold a valid sportfishing license. The commercial harvest was regulated
through license and gear restrictions, i.e., commercial fishermen were required to hold a
valid general commercial fishing license and were restricted from fishing within 91 m
(300 ft) of a river mouth or within 914 m (3,000 ft) downstream of any Tennessee Valley
Authority or US Army Corps of Engineers dam (George Scholten, Tennessee Wildlife
Resources Agency, personnel communication). In 2001, Arterburn et al. (2001) reported
results of a comprehensive catfish angler survey within the greater Mississippi River
basin that documented a widespread desire by anglers for increased management of
catfish to enhance sportfishing. The Arterburn et al. (2001) survey results, along with the
public’s growing interest in recreational catfish angling, prompted the Tennessee Wildlife
Resources Agency (TWRA) to initiate a series of angler opinion surveys (2000, 2001,
2005) regarding catfish management (George Scholten, Tennessee Wildlife Resources
Agency, unpublished data). Results of these surveys indicated that Tennessee’s catfish
anglers supported the concept of TWRA managing catfish as sportfish by using a variety
4
of fisheries practices (George Scholten, Tennessee Wildlife Resources Agency,
unpublished data). Those results, supported by attention that the catfishery received in
association with the International Ictalurid Symposium (Irwin et al. 1999), prompted
TWRA to re-evaluate catfish management within the state. Based on that process and
subsequent deliberations, Tennessee’s catfish harvest regulations were modified as
follows in March 2003: 1) catfish < 86.4 cm (< 34 in) TL could be harvested by
commercial and sportfishermen, 2) sportfishermen could additionally harvest one catfish
per day ≥ 86.4 cm TL, but only possess two catfish ≥ 86.4 cm TL at any one time, and 3)
commercial fishermen could not fish within 91 m of a river mouth or within 914 m
downstream of any Tennessee Valley Authority or US Army Corps of Engineers dam.
After intense lobbying by commercial fishermen to establish parity with the sport fishery,
commercial regulations were modified in 2006 such that commercial fishermen could
also harvest one catfish per day ≥ 86.4 cm TL but only possess two catfish ≥ 86.4 cm TL
at any one time. The Tennessee Wildlife Resources Commission reclassified blue
catfish, channel catfish, and flathead catfish as sport and commercially fished species in
fall 2007, a decision that allowed federal sportfish restoration funds to be utilized for
catfish management. Some efforts by TWRA since that decision have been aimed at
collecting basic information about catfish populations in Tennessee to aid in the
assessment of the aforementioned management regulations.
Age and growth data and weight-length relationships are used by biologists in a
number of analytical assessments (e.g., estimation of growth rates, length and age at
maturity, age at time of fishery recruitment, and duration fishes spend within a fishery) to
5
enhance fishery management and monitoring (Beverton and Holt 1957; Ricker 1975).
Few age and growth data exist regarding catfish in Tennessee waters, with only two
reports focusing on blue catfish. Conder and Hoffarth (1965) reported on the age and
growth of blue catfish in Barkley Reservoir and Kentucky Lake and Hale and Timmons
(1990) reported on age and growth of blue catfish in Kentucky Lake. Unfortunately,
these studies assigned fish ages based on assessments of growth marks on pectoral fin
spines, a methodology now considered unreliable because it results in the
underestimation of the age of older fish (Buckmeier et al. 2002). Although age and
growth data exist for blue catfish outside of Tennessee (but the majority of these based on
fishes aged using fin spines) (Graham 1999), observed differences in age and growth of
blue catfish amongst various waterbodies (Boxrucker and Kuklinski 2006) strengthens an
argument in favor of obtaining waterbody specific data within Tennessee to support stock
monitoring and management decisions. With the above in mind, the purpose of this study
was to gather information useful to TWRA’s fishery managers regarding age and growth,
weight-length relationships, and relative weight of blue catfish in three exploited and one
unexploited Tennessee waterbodies. In addition, unpublished TWRA harvest data that
was used to support the planning of the aforementioned study is also presented.
Materials and Methods
Catfish Harvest Report
The catfish harvest component of this study was carried out to help identify waterbodies
of interest regarding the catfish age and growth studies that form the bulk of this report
and to provide TWRA with some preliminary metrics regarding Tennessee’s catfish
6
harvest. Hence, no effort was made to measure harvest data variance or gather data in a
manner that supported any statistical analyses. Tennessee Wildlife Resources Agency
1998-2006 creel survey data for blue catfish, channel catfish, and flathead catfish were
collected and assessed, as available, for Lake Barkley, Kentucky Lake, and Fort Loudoun
Reservoir. Specifically, annual creel data were reviewed and two annual species
averages were calculated across the nine years for each waterbody: average mean total
weight caught (kg) and average mean total weight harvested (kg). Annual TWRA creel
data for blue catfish, channel catfish, flathead catfish, and the bullheads Amerius melas
and A. natalis were combined to obtain average of the number of angler hours fished and
the number of catfish caught per hour for each of the years 1998-2006. The 2005 TWRA
commercial catfish harvest data (reported in lb for the following 17 waterbodies: Lake
Barkley, Kentucky Lake, Mississippi River, Nolichucky River, Obion River, Perryville
River, Reelfoot Lake, Chickamauga Lake, French Broad River, Hatchie River, Lake
Nickajack, Old Hickory Reservoir, Watts Barr Reservoir, Cheatham Lake, Lake Douglas,
Lake Guntersville, Hiwassee River) were converted to kg and tallied by month for four
groups (blue catfish, channel catfish, flathead catfish, and catfish spp., the latter group
referring to an unidentified mixture of individuals representing the three aforementioned
species). The dollar value of the harvest was estimated by applying a US$0.45 per lb
(US$ 0.992 per kg) multiplier (a value in line with information supplied by wholesale
representatives, see above). Lastly, the total catfish harvest (kg; for blue catfish, channel
catfish, and flathead catfish combined) for 22 Tennessee waterbodies (Chickamauga
Lake, Lake Barkley, Kentucky Lake, Reelfoot Lake, Pickwick Lake, Watts Bar
Reservoir, Old Hickory Lake, Lake Douglas, Percy Priest Reservoir, Lake Cherokee,
7
Normandy Lake, Woods Reservoir, Boone Lake, Tims Ford Lake, Norris Lake, Melton
Hill Lake, Dale Hollow Lake, Lake Watauga, Center Hill Lake, South Holston Reservoir,
Fort Loudoun Reservoir, Tellico Lake) was calculated by combining values for the sport
harvest and commercial harvest for the year 2006 (George Scholten, Tennessee Wildlife
Resources Agency, unpublished data). From this data, the contribution of the sport
catfish and commercial catfish harvests were each be expressed as a percent of the total
catfish harvest for each waterbody and for Tennessee as a whole, as was the harvest (kg)
per ha for each waterbody.
Waterbodies Studied
Lake Barkley, Kentucky Lake, and the Mississippi River were selected for study as
exploited waterbodies based on their high levels of catfish harvest in recent years (as
determined from the catfish harvest analysis and discussion with TWRA staff). Fort
Loudoun Reservoir was added to the study to represent an unexploited reservoir. Fort
Loudoun Reservoir has been closed to commercial and recreational harvest since 1979
because of polychlorinated biphenyls (PCB) contamination (Bobby Wilson, Tennessee
Wildlife Resources Agency, personnel communication).
Lake Barkley is an impoundment of the Cumberland River possessing a 1,616-km
shoreline (Tennessee portion of the lake has a surface area of 7,406 ha) located in
southwestern Kentucky and north-central Tennessee (Figure 1). Kentucky Lake is the
largest reservoir in Tennessee, with a surface area of 43,794 ha and over 3,322 km of
shoreline extending from Stewart County to Hardin County, TN (Figure 1). The
Mississippi River is the second longest river in North America and it borders Tennessee
8
for 269 km from Dyer County to Shelby County, TN (Figure 1). The Mississippi River is
one of the most heavily fished rivers in North America. During 2005, Tennessee waters
of the Mississippi River supported a commercial catfish harvest of 65,315 kg, with blue
catfish comprising 78 percent (50,794 kg) of said harvest (Tennessee Wildlife Resources
Agency, unpublished data). Fort Loudoun Reservoir is a 5,908 ha impoundment of the
Tennessee River, with a 610-km shoreline in East Tennessee, West of Knoxville (Figure
1).
Sample Collection
Catfish samples from Lake Barkley and Kentucky Lake were collected by visiting
commercial fish wholesalers (Hart’s Fish Market, Paris, TN; B&F Fish Market,
Perryville, TN; Quillen’s Fish Market, Paris, TN; Cool Cats Fish Market, McKinnon,
TN) during 2007 (May-October) and 2008 (May-October). Commercial fishermen
selling to the wholesalers fished mainly with gill nets, but they occasionally used trotlines to harvest catfish. Gill net mesh sizes varied from 7.62-10.16 cm stretched mesh,
with nets fished overnight. A minimum of ten fish per 25-mm length interval (intervals
starting at 200 mm TL) was sought by unselectively gathering catfish from swim tanks at
the commercial fish wholesalers or from the live wells of commercial fishing boats as
catches were being offloaded at the wholesalers. In addition, six catfish from Kentucky
Lake were obtained from commercial fisherman during the 2008 paddlefish (Polyodon
spathula (Walbaum, 1792)) season; catfish comprise most of the paddlefish harvest bycatch. Because paddlefish are harvested using 15-cm stretched mesh gill nets, sampling
that by-catch facilitated the collection of samples from catfish that were larger than those
9
normally seen at the commercial catfish wholesalers. All collected fish were measured
(TL, nearest mm), weighed (nearest g), tagged in the head with a uniquely numbered tag
(Floy® T-bar anchor tag, Floy Tag and Mfg., Inc., Seattle, WA), and decapitated.
Processing procedures used by the commercial fish wholesalers precluded efforts to
gather fish sex information. Sagittal otoliths were removed (see below) from each tagged
head at the end of each sampling trip.
Mississippi River sampling occurred during four days in November 2006 and 2007.
Three sampling methods were used at each of the three collection locations along the
Mississippi River (Caruthersville, MO; Ashport, TN; and Randolph Point, TN). Boat
electrofishing using low-frequency pulsed-DC (15 pulses per s) was carried out in 10-min
passes around wing dikes, rip-rap, and sand bars, with the electrofishing boat
accompanied by two chase boats to increase netting efficiency. A 4.88-m knotless
shrimp trawl (complete shrimp trawl, model number TRL16C, Memphis Net and Twine
Co., Inc, Memphis, TN) was towed for 5 min around wing dikes, rip-rap, and sand bars.
Two experimental gill nets (one a 46-m net with stretched mesh sizes ranging 2.54-10.16
cm and the second a 55-m net with stretched mesh sizes ranging 6.35-8.89 cm) were
fished behind wing dikes for 4-8 hr during the day. Similar to the sampling methods used
for Lake Barkley and Kentucky Lake, a minimum total of ten catfish per 25-mm length
interval was sought as a combined sample from the three sample locations. All blue
catfish were measured (TL, nearest mm), weighed (nearest g), and sexed (gonad
inspection), prior to having their sagittal otoliths removed (see below).
10
Fort Loudoun Reservoir was sampled in January and February of 2007 using 38-91 m
long trot-lines set at various locations within the reservoir. A total of nine lines were set
at one time (total of 36 sets) and various baits (threadfin shad, Dorosoma petenense
(Günther, 1867); common carp, Cyprinus carpio L., 1758; and flathead minnow,
Pimephales promelas Rafinesque, 1820) were fished on 2/0 hooks hanging from 61-cm
trotters. Trotters were spaced 152 cm apart and lines were fished overnight at depths
ranging from 0.91-15.24 m. All blue catfish were measured (TL, nearest mm), weighed
(nearest g), and sexed (gonad inspection), and sagittal otoliths were removed (see below)
from each fish.
Otolith Removal and Processing
Sagittal otoliths (otoliths) were removed by transversly sectioning the supraoccipital bone
3-5 mm anterior to a plane bridging the locked pectoral spines (Figure 2; Buckmeier et al.
2002). Otoliths from each catfish were placed in an individual coin envelope bearing
data regarding collection location, sample date, fish length, fish weight, fish sex, and tag
number. Otoliths were allowed to dry in the envelopes for 2 weeks before soft tissue and
debris were cleaned from them using sharp-tipped forceps. Clean otoliths were
embedded in 2-part epoxy (EasyCast Epoxy resin and hardner, Fields Landing, CA) in a
plastic mold (maroon 21 flat embedding mold, model number 2449M-AB, SPI Supplies,
West Chester, PA) and allowed to harden for 3 days. Four steps were used to embed
otoliths in the epoxy molds. First, the molds were slightly filled with 2-part epoxy and
allowed to set for 3 days. Second, clean otoliths were aligned longitudinally in the epoxy
mold (Figure 3). Each mold provided its own individual identification number. Lastly,
11
the epoxy molds were filled completely with the 2-part epoxy and allowed to set for 3
days. A LECO®VC-50 low-speed isomet saw was used to section otoliths just anterior to
the anti-rostrum on the rostral side of the otolith (Figure 3). After sectioning, otoliths
(still embedded in epoxy) were ground to the central portion of the sulcus toward the
post-rostrum side of the otolith using 320 grit sand paper (Figure 3). Otoliths were
examined under a stereo-microscope at 50× using fiber-optic lights to provide side
illumination. Catfish ages were assigned using standard enumeration of growth rings as
described by Buckmeier et al. (2002). An otolith “reading” training period during which
the author read catfish otoliths with experienced TWRA biologists preceded the formal
age assignment portion of the analysis.
Data Analyses
Throughout the data analysis, parametric statisical tests were used for data sets with
normally distributed data. In instances when data were not normally distributed, data sets
were either tranformed using standard methods for each analysis or nonparametric
statistical tests were employed (as noted below).
Association between catfish weight and length was determined using linear weightlength regressions generated by Statistical Analysis Software, (SAS; SAS Institute 2008),
according to the following equation.
linear equation: log10 (W) = -a + b log10 (TL)
where:
W = weight in (g)
TL = total length in (mm)
12
a and b = the intercept and slope, respectively, of the weight-length
regression
Analysis of covariance (ANCOVA, using SAS) was used to test for significant
differences in the weight-length regression slopes between pairs of study lakes (every
possible pair being tested). In instances when a significant difference between slopes was
not found, a subsequent ANCOVA using an equal slope (a dummy variable) for each
waterbody was used to test for significant differences in weight-length regression
intercepts according to methods fully explained in Pope and Kruse (2007).
The relative weight index (Wr; see Wege and Anderson 1978) was calculated for
catfish ≥ 160 mm TL from each of the four waterbodies according to the following
equation.
Wr = (W/Ws) × 100
where:
W = observed weight (g)
Ws = length specific standard weight (g) predicted from the species
specific weight-length regression (see Anderson and
Neumann 1996)
Analysis of variance (ANOVA, using SAS) was used to test for significant differences in
Wr between waterbodies that were sampled using similar capture methods (i.e., Kentucky
Lake and Lake Barkley). A Kruskall-Wallis test (using SAS) was used to test for
significant differences in Wr amonst the following five catfish length intervals for each
waterbody: stock fish (fish ≥ 301 and ≤ 510 mm TL), quality fish (fish ≥ 511 and≤ 760
mm TL); preferred (fish ≥761 and ≤ 890 mm TL); memorable (fish ≥ 891 and ≤ 1,140
mm TL); and trophy (fish ≥ 1,140 mm TL).
13
Catfish growth was assessed using the von Bertalanffy growth model (see Ricker
1975) according to the following equation.
Lt = L∞ {1 - e-k(t-to)}
where:
t = age
Lt = mean total length at age
L∞ = theoretical maximum total length
k = Brody growth coefficient
to = hypothetical age at length zero
The model was fit for each waterbody using the software package, Fisheries Analyses
and Simulation Tools (FAST) (Slipke and Maceina 2003), with the model parameter L∞
assigned as the length of the largest fish collected in each waterbody. FAST was also
used to calculate mean length at age directly from the aged samples. Analysis of
covariance (ANCOVA, using SAS) was used to compare the slopes of the log10
transformed mean TL at age regressions for Kentucky Lake, Mississippi River, and Fort
Loudoun Reservoir, and a Tukey multiple comparison test (using SAS) was subsequently
used to identify significant growth differences amongst these waterbodies. Because the
convergence criteria for the Lake Barkley log10 transformed age regression failed (thus
precluding the use of a SAS ANCOVA analysis), an unpaired Student’s t-test (using
SAS) was used to evaluate mean total length at age for Lake Barkley vs. the remaining
three waterbodies.
14
Results
Catfish Harvest Report
The creel survey analysis results indicated that the 1998-2006 mean total weight caught
and mean total harvest for blue catfish, channel catfish, and flathead catfish were each
highest (by far) in Kentucky Lake vs. Lake Barkley or Fort Loudoun, with the Kentucky
Lake mean total weight caught equaling 92.9, 93.9, and 97.8 percent of the total mean
total weight caught of blue catfish, channel catfish, and flathead catfish (respectively) for
the three waterbodies combined (Table 1). Although a consideration of these means
based on total fishing effort within the three waterbodies was not undertaken, the
Kentucky Lake catch casually appeared disproportionately high when waterbody size
(surface area in ha) was considered (Table 1). Mean total harvest accounted for 0-266
percent of the mean total weight caught for blue catfish, channel catfish, and flathead
catfish within the three waterbodies. The 0 percent value stemmed from the lack of
harvest in Fort Loudoun Reservoir associated with fishing advisory warnings, and the
value of 266 percent (calculation double-checked for accuracy) for channel catfish in
Lake Barkley obviously indicated an error or errors in the TWRA creel survey database.
Although the analysis was not designed to statistically test any calculated values, it seems
notable that the levels of retention (i.e., mean total harvest as a percent of mean total
catch) for Lake Barkley and Kentucky Lake were within 10 percent for blue catfish,
channel catfish, and flathead catfish (Table 1).
In 2005, commercial fishermen harvested 892,827 kg of catfish from 17 Tennessee
waterbodies at an estimated wholesale value of US$885,755, with blue catfish
15
comprising 70 percent (623,402 kg) and US$618,464, channel catfish comprising 25
percent (220,805 kg) and US$219,056, flathead catfish comprising 3 percent (29,322 kg)
and US$29,089, and unidentified catfish spp. comprising 2 percent (19,298 kg) and
US$19,146 of said take (Table 2). The greatest combined harvest of catfish occurred
during the month of May (12 percent of the 2005 annual harvest; 108,681 kg), with most
of the reported fish categories indicating the same (Table 2). Total catfish harvest
increased 50.1 percent (36,270 kg) from April to May and decreased 22.2 percent (24,174
kg) May to June (Table 2). Blue catfish harvest exhibited similar changes during the
same periods, i.e., a 67.7 percent (31,395 kg) increase and a 21.3 percent (16,604 kg)
decrease, respectively (Table 2). During the fall, blue catfish harvest rose 27.9 percent
(11,065 kg) from September to October before harvest decreased by 12.9 percent (6,548
kg) from October to November (Table 2). Channel catfish harvest exhibited an initial
increase, 23.4 percent (4,308 kg), from February to March and remained high through
May, before decreasing by 26.7 percent from May to June. Harvest then rose by 21.2
percent (3,418 kg) from June to August before plummeting 35.1 percent (6,873 kg) in
September and oscillating through the fall and early winter (Table 2). Although overall
harvest levels of flathead catfish were not as high as those of blue or channel catfish,
flathead catfish harvest also exhibited a large increase from April to May, i.e., 93.5
percent (1,965 kg), and another large increase from September to October, i.e., 180.7
percent (3,432 kg). Although January and December 2005 exhibited low overall catfish
harvests (i.e., 7.0 percent and 7.1 percent of the annual harvest, respectively), September
exhibited the lowest harvest (6.1 percent of the annual harvest). Here it seems notable
16
that even during September, Tennessee’s commercial catfish harvest represented a
US$53,967 wholesale enterprise.
Amongst the 22 waterbodies for which annual harvest for the year 2006 was assessed,
catfish harvest ranged from a high of 17.4 kg per ha in Chickamauga Lake to a low of 0
kg per ha in Tellico Lake (Table 3). The highest sport harvest per ha occurred in
Chickamauga Lake (3.44 kg per ha) as did the highest commercial harvest (13.95 kg per
ha) (Table 3). Regarding waterbodies reported on in this study, Lake Barkley was
Tennessee’s second most heavily exploited reservoir (13.4 kg catfish per ha) during the
post-2000 annual harvest assessment (Table 3). That take, totaling 99,390 kg, was
comprised of 7.2 percent sport harvest (0.97 kg per ha) and 92.8 percent commercial
harvest (12.44 kg per ha) (Table 3). During that same period, Kentucky Lake was ranked
Tennessee’s third most heavily exploited reservoir (9.2 kg per ha) for catfish harvest,
with said take (totaling 403,313 kg) consisting of 22.7 percent sport harvest (2.09 kg per
ha) and 77.3 percent commercial harvest (7.11 kg per ha) (Table 3). Fort Loudoun
Reservoir, open to fishing under a consumption advisory, naturally exhibited a negligible
catfish harvest (Table 3).
Samples Collected
A total of 779 blue catfish were collected during this study from fall 2006 to fall 2008
from the four studied waterbodies. The Lake Barkley sample consisted of 169 fish
ranging in length from 275-1,115 mm TL (Table 4). The Kentucky Lake sample
consisted of 172 fish ranging in length from 266-1,191 mm TL (Table 4). The
Mississippi River sample consisted of 248 fish ranging in length from 70-830 mm TL
17
(Table 4). The Fort Loudoun Reservoir sample consisted of 190 fish ranging in length
from 255-1,105 mm TL (Table 4). Success in collecting 10 fish in each of the 25 mm
study intervals was “good to excellent” in all waterbodies for intervals ranging from 451
to 650 mm, and spotty regarding size intervals consisted of fish < 451 or > 650 mm
(Table 4). Of the fish collected, all except 12 fish from Kentucky Lake were aged (these
unaged fish were, however, used in the weight-length and relative weight analyses).
Additionally, the six large aged fish from Kentucky Lake (representing the entire sample
collected by commercial paddlefishermen) were not used in any analysis because
attempts to fit the von Bertalanffy growth model using these fish resulted in nonconvergence failure of model parameters, an indication that these larger fish were
significantly dissimilar from the smaller individuals comprising the bulk of the Kentucky
Lake sample.
Weight-length Relationships and Relative Weights
Linear regressions of log10 transformed weight-length data resulted in slopes ranging
from 2.87 to 3.46 and intercepts ranging from -4.6 to -6.21 for the four waterbodies and a
slope of 3.21 and intercept of -5.59 for pooled data considered to represent Tennessee
(Table 5; Figures 4-8). More than 95 percent of the variation in log10 weight was
described by the log10 length in the regressions of Kentucky Lake, the Mississippi River,
Fort Loudoun Reservoir, and Tennessee overall; whereas, 74 percent of the same
variation was described by log10 length in the regression representing Lake Barkley
(Table 4). Analysis of covariance revealed weight-length regressions of the following
pairs of waterbodies to be significantly different based on comparisons between their
18
slopes: Lake Barkley vs. Kentucky Lake (F = 18.40, df = 1, P < 0.0001; Kentucky Lake
fish adding body weight more rapidly with increasing body length than Lake Barkley
fish), Lake Barkley vs. Fort Loudoun Reservoir (F = 17.01, df = 1, P < 0.0001; Fort
Loudoun Reservoir fish adding body weight more rapidly with increasing body length
than Lake Barkley fish), Kentucky Lake vs. Mississippi River (F = 16.06, df = 1, P <
0.0001; Kentucky Lake fish adding body weight more rapidly with increasing body
length than Mississippi River fish), Mississippi River vs. Fort Loudoun Reservoir (F =
15, df = 1, P < 0.0001; Fort Loudoun Reservoir fish adding body weight more rapidly
with increasing body length than Mississippi River fish). Comparisons between weightlength regression slopes revealed insignificant differences for Lake Barkley vs.
Mississippi River (F = 3.43, df = 1, P > 0.0648) and Kentucky Lake vs. Fort Loudoun
Reservoir (F = 0.57, df = 1, P > 0.04510). Subsequent ANCOVA testing for significant
differences between weight-length regression intercepts for the last two pairs of
waterbodies revealed that the intercepts of Lake Barkley and the Mississippi River were
significantly different (dummy slopes = 3.08, t = -5.36, df = 1, P < 0.0001; Lake Barkley
fish weighing more overall than Mississippi River fish, but adding body weight at a
similar rate per increase body length) as were the intercepts of Kentucky Lake and Fort
Loudoun Reservoir (dummy slopes = 3.43, t = -12.85, df = 1, P < 0.0001; Kentucky Lake
fish weighing more overall than Fort Loudoun Reservoir fish, but adding body weight at
a similar rate per increase body length). In the latter two cases, the overall weight of
catfish for Lake Barkley (intercept = -5.187) was larger than that of the Mississippi River
(intercept = -5.279), and the overall catfish weight for Kentucky Lake (intercept = 6.112) was larger than that of Fort Loudoun Reservoir (intercept = -6.229). The weight-
19
length regression for Tennessee (i.e., a regression of pooled data from all four studied
waterbodies) had a slope of 3.21 and an intercept of -5.59 and differed (i.e., different
slope) significantly from the regressions of each of the four waterbodies (TN vs. Lake
Barkley, F = 9.01, df = 1, P < 0.0028; TN vs. Kentucky Lake, F = 7.08, df =1, P <
0.0079; TN vs. Mississippi River, F = 7.02, df = 1, P < 0.0082; TN vs. Fort Loudoun
Reservoir, F = 5.70, df = 1, P < 0.0171).
Lake Barkley catfish had an overall Wr of 121 and Wr values among the stock,
quality, preferred, and memorable length intervals (Table 6) did not differ significantly
(χ2 = 5.70, df = 4, P > 0.2223). Kentucky Lake catfish had an overall Wr of 112 and a
significant difference existed among Wr values of the stock, quality, preferred, and
memorable length intervals (χ2 = 16.92, df = 4, P < 0.0020) (Table 6). Mississippi River
catfish had an overall Wr of 94 and no significant difference existed among Wr values of
the stock, quality, and preferred length intervals (χ2 = 4.13, df = 4, P > 0.2477) (Table 6).
Fort Loudoun Reservoir catfish had an overall Wr of 86 and no significant difference
existed among Wr values of the stock, quality, preferred, and memorable length intervals
(χ2 = 9.06, df = 4, P > 0.0597) (Table 6). Kentucky Lake and Lake Barkley catfish
overall Wr values were not significantly different from one another (F = 0.68, df = 1, P >
0.4087).
Age and Growth
The estimated age of blue catfish ranged from 0-34 years overall in the four study lakes,
with age ranges for each waterbody as follows: Lake Barkley, 2-18 years; Kentucky
Lake, 2-14 years; Mississippi River, 0-21 years; and Fort Loudoun Reservoir, 5-34 years
20
(Table 7; Figure 9). The 34-year old blue catfish from Fort Loudoun Reservoir (874 mm
TL female) represents the oldest estimated age reported for this species (a 24-year-old
blue catfish was reported by Holley (2006)). Parameters for the von Bertalanffy growth
equation were as follows for the four study lakes: Lake Barkley, L∞ = 1,115 mm TL, k =
0.11, t0 = -0.693 (Figure 10); Kentucky Lake, L∞ = 940 mm TL, k = -0.126, t0 = -1.217
(Figure 11); Mississippi River, L∞ = 830 mm TL, k = -0.145, t0 = -1.019 (Figure 12); and
Fort Loudoun Reservoir, L∞ = 1,105 mm TL, k = -0.044, t0 = -1.227 (Figure 13).
The von Bertalanffy equation predicted that blue catfish spend roughly 11 years in the
fishery in Lake Barkley, entering at age 1.5 and reaching the trophy size limit at age 12.5
(Figure 10). Blue catfish in Kentucky Lake recruited the fishery at about 1.5 years old
and remain within the fishery until at least age 11 (i.e., the age of the oldest samples used
in the analysis) (Figure 11). In the Mississippi River, blue catfish entered the fishery at
about 1.5 years old and remain in the fishery until they were at least 21 years old (i.e., the
age of the oldest samples used in the analysis) (Figure 12). In Fort Loudoun Reservoir
blue catfish entered the fishery at age 3.5 and remain in the fishery until age 34 (Figure
13). Estimated ages of blue catfish at the memorable size (890 mm TL) were 15 and 34
years old in Lake Barkley and Fort Loudoun Reservoir, respectively (Figures 10, 13).
The weight of catfish as they recruited the fishery ranged from 58 to 228 g in the four
waterbodies, with entry-sized catfish in Kentucky Lake weighing the most and those in
Fort Loudoun Reservoir weighing the least (Table 8; Figures 4-13). The weight of blue
catfish at the midpoint age within the fishery and weight at the age when leaving the
fishery could only be estimated from the populations sampled in Lake Barkley and Fort
21
Loudoun Reservoir (Table 8; Figures 4, 10; 7, 13). Lake Barkley blue catfish exhibited a
fishery midpoint weight of 1,778 g and a fishery exit weight of 6,761 g; whereas, Fort
Loudoun Reservoir catfish exhibited a fishery midpoint weight of 1,659 g and a fishery
exit weight of 7,244 g. However, fishery midpoint blue catfish within Lake Barkley were
estimated to be 6 years old, whereas, those in Fort Loudoun Reservoir were estimated to
be 15 years old. Furthermore, fishery exit blue catfish within Lake Barkley were
estimated to be 13 years old, whereas, those in Fort Loudoun Reservoir were estimated to
be 34 years old.
Analysis of covariance revealed a significant difference in the log10 transformed mean
TL at age regressions among Kentucky Lake, Mississippi River, and Fort Loudoun
Reservoir (F = 35.01, df = 2, P < 0.0001), and a subsequent Tukey multiple comparisons
test indicated significant differences in catfish total length at age between Kentucky Lake
and Fort Loudoun Reservoir (Tukey HSD 33.372, P < 0.05; with blue catfish in
Kentucky Lake generally being longer at a given age than those in Fort Loudoun
Reservoir) and Mississippi River vs. Fort Loudoun Reservoir (Tukey HSD 48.388, P <
0.05; with blue catfish in the Mississippi River generally being longer at a given age than
those in Fort Loudoun Reservoir); whereas, no significant difference in catfish total
length at age was discovered between Kentucky Lake and the Mississippi River (Tukey
HSD 16.016, P > 0.05). Results of Student’s t-tests between Lake Barkley and
Mississippi River blue catfish revealed significant differences for 2-year-old catfish (t =
2.36, df = 19P < 0.029), 4-year-old catfish (t = 2.41, df = 51, P < 0.020), and 5-year-old
catfish (t = 5.06, df = 87, P < 0.0001; with blue catfish in Lake Barkley generally being
22
longer at a given age than those in the Mississippi River). Similar testing between Lake
Barkley and Kentucky Lake blue catfish 2-10 years old revealed mean total length to only
be different for age 4 catfish (t = 2.22, df = 36, P < 0.033; with age 4 blue catfish in
Kentucky Lake being longer than those in Lake Barkley), while similar testing between
Lake Barkley and Fort Loudoun Reservoir catfish 5-11 years old revealed mean total
length to be different between waterbodies for all seven ages (age 5; t = 4.65, df = 18, P <
0.0002: age 6; t = 7.00, df = 27, P < 0.0001: age 7; t = 5.09, df = 55, P < 0.0001: age 8; t
= 4.62, df = 22, P < 0.0001: age 9; t = 6.23, df = 12, P < 0.0001: age 10; t = 6.04, df = 16,
P < 0.0001: age 11; t = 3.78, df = 6, P < 0.0092; with blue catfish in Lake Barkley being
generally longer at a given age than those in Fort Loudoun Reservoir).
Discussion
The blue catfish is a highly sought sport and commercial species (Graham 1999). In
Tennessee, the commercial blue catfish harvest is typically sold to commercial fish
wholesalers or small restaurants (Hale and Timmons 1990). However, despite the sport
and commercial interest in catfish in Tennessee, biological information on Ictalurus spp.
in the state is limited, with only six such reports published in the primary literature
(Schoffman 1954; Carroll and Hall 1964; Conder and Hoffarth 1965; Hargis 1966; and
Hale and Timmons 1990). Of these, only two studies focused on blue catfish (Conder
and Hoffarth 1965; and Hale and Timmons 1990). In addition, the grey literature
supplies little more information on Ictalurus spp. in Tennessee other than occurrence
records, with some of this information having been repackaged for publication in the
peer-reviewed literature (e.g., Conder and Hoffarth 1965; Hale and Timmons 1990).
23
Commercial Harvest Report
A comprehensive review by Graham (1999) revealed blue catfish to be recreationally
important in 21 states and within 14 of said states (including Tennessee) they were
considered to be commercially important as well. Graham (1999) reported commercial
harvests of blue catfish (for an undesignated year or years) from nine states (Arkansas,
Illinois, Indiana, Kentucky, Louisiana, Mississippi, Missouri, South Carolina, and
Tennessee), with harvests ranging from < 22,222 kg (Indiana) to 4,888,889 kg
(Louisiana). In Graham’s report, Tennessee’s commercial blue catfish harvest was
411,153 kg, a value that placed it fifth amongst the nine reporting states regarding total
harvest. However, Graham (1999) reported Tennessee’s blue catfish sport harvest of
1,381,409 kg (i.e., 335 percent of the Tennessee commercial harvest) as the highest sport
take of any of the five states for which sportfishing data were available. The Tennessee
commercial catfish harvest in 2005 totaled 892,827 kg, with blue catfish comprising 70
percent (623,402 kg) of said take. And, regardless of the limitations of the harvest data
reported herein, the typical annual blue catfish commercial harvest in Tennessee likely
totals more than several hundred thousand kilograms, with a wholesale value of at least
several hundred thousands of dollars. Nationally, Miranda (1999) reported the highest
mean sportfishing harvest of Ictalurus spp. (i.e., channel and blue catfish) between 1946
and 1988 to be 26.7 kg per ha (waterbody not specified). That harvest rate pertained to
channel and blue catfish, and thus is not directly comparable to data reported herein.
However, it is notable that Tennessee’s waterbodies experienced a total annual blue
catfish harvest as high as 17.4 kg per ha (Chickamauga Lake), with the highest
commercial harvest within any Tennessee waterbody reported here equaling 13.95 kg per
24
ha (Chickamauga Lake) and with the highest sport harvest also coming from that same
lake (3.44 kg per ha). In the Tennessee waterbodies fished commercially and for which
data were gathered, the sport harvest per ha ranged from 3.99 percent (Reelfoot Lake) to
128.87 percent (Lake Douglas) of the commercial harvest per ha in the same waters.
According to the monthly 2005 commercial catfish harvest reported herein, commercial
catfishing in Tennessee is a 12-month per year activity, with even the smallest monthly
harvest having a wholesale value of US$53,964. Fluctuations in monthly harvest noted
above could be related to a variety of biological (e.g., fish migration, reproduction),
physical (e.g., water temperature, flow regime), and socioeconomic (e.g., changes in
fishing effort as fishermen are diverted to other higher value enterprises, such as
paddlefish harvest, during certain seasons) factors.
Weight-length Relationships and Relative Weights
The weight of fishes and various biomass-related data are important information
regarding fisheries management, and the standard weight-length relationship in particular
is an important tool used in assessing harvest (Ricker 1975). Overall, the log10
transformed weight-length relationships for each of the four waterbodies provided a high
level of explanation of catfish weight based on length, with r2 values for Kentucky Lake,
Mississippi River, and Fort Loudoun Reservoir all above 0.95, and Lake Barkley equal to
0.74. Increased sampling within Lake Barkley (n = 168) probably would have resulted in
a better weight-length fit, as several small fish in that sample displayed high weights (see
Figure 4). Furthermore, when the data were pooled for the Tennessee-wide weightlength analysis (n = 773), an r2 value of 0.95 resulted. Two types of differences were
25
exhibited in the weight-length relationships of the four waterbodies. First, there were
significant differences in the slopes of the weight-length regressions between; Lake
Barkley and Kentucky Lake, Lake Barkley and Fort Loudoun Reservoir, Kentucky Lake
and the Mississippi River, and the Mississippi River and Fort Loudoun Reservoir. Such
differences denoted different rates of association between weight and length between
waterbodies. Second, there were significant differences in overall weights (i.e.,
intercepts) despite the fact that the weight-length slopes were similar (this type of
difference was exhibited between Lake Barkley and the Mississippi River, and Kentucky
Lake and Fort Loudoun Reservoir). Possible biological explanations for the two types of
difference are many (e.g., growth associated genetic differences between catfish
populations, differences in forage bases between waters, etc.) and both types of
difference could result from a similar cause. Although Lake Barkley and Kentucky Lake
are only about 15-km apart and run roughly parallel to one another for 80 km (and thus
might generally be considered to possess many environmental and biological
similarities), blue catfish in Kentucky Lake gained weight at a faster rate than blue catfish
in Lake Barkley. Although the pooled data analysis resulted in a Tennessee-wide weightlength relationship with a high fit, this relationship differed from each of the four
waterbodies. Because of those differences, I believe that “lake specific” weight-length
relationships (when available) should be used for management purposes (e.g., conversion
of length data to biomass data or for yield modeling purposes).
Relative weight indices are now commonly used in fisheries management to compare
the weights of fishes from various waters to one another and to a species specific
26
standard (Anderson and Neumann 1996). In the present study, the relative weight of
catfish in the Mississippi River and Fort Loudoun Reservoir exhibited values 6 percent
and 14 percent below (respectively) the species standard while Lake Barkley and
Kentucky Lake exhibited values 21 percent and 12 percent higher (respectively) than the
species standard. An expansion of this analysis might point to waters such as Lake
Barkley (especially) and Kentucky Lake as holding potential for designation as trophy
blue catfish fisheries.
Age and Growth
Studies of fish age and growth arguably provide some of the most useful biological
fisheries management data (e.g., see Beverton and Holt 1957; Ricker 1975). Blue catfish
have been aged by interpreting annual growth marks on pectoral spines (primarily; e.g.,
Conder and Hoffarth 1965; Porter 1969; Freeze 1977; Hale and Timmons 1989, 1990)
and otoliths (more recently; e.g., Holley 2006). However, to date neither of these two
aging methods have been validated for blue catfish. Buckmeier et al. (2002) did validate
the use of otoliths as an accurate aging structure in channel catfish in an aging study of
known age, 1-4 year-old fish. In that study, the use of pectoral spines as an aging
structure (two methods: cut spines and basal–articulatory process) was also assessed.
Overall, the use of pectoral spines was considered to be less accurate than the use of
otoliths, with age estimates stemming from the cut spine method generally agreeing with
otolith estimates for 1-3 year-old fish, but tending to underestimate the age of catfish over
3 years of age. The use of the basal-articulatory process of pectoral spines was shown to
result in erratic and relatively inaccurate age estimates. Based on their results,
27
Buckmeier et al. (2002) recommended that otoliths be used as the standard aging
structure to estimate the age of channel catfish. More recently, Sakaris and Irwin (2008)
validated the use of otoliths for the study of daily growth increments for young-of-theyear channel catfish as old as 119 days post-hatch, with considerable accuracy in fishes
up to 60 days old.
Ideally, age and growth studies of fishes are conducted with multiple “readers” (age
interpreters) so that individual biases can be identified and an assessment of aging
precision can be conducted (e.g., Isermann et al. 2003). However, given the exigencies
facing fishery management agencies, some aging efforts rely on single readers, as was the
case in the present study. While this presents an increased level of uncertainty regarding
the assigned ages, the bias injected into an aging study by any individual reader should be
consistent such that general comparisons between populations of the same species are not
invalidated. Although a single reader was used to assign ages in this study, recently, a
second reader (Eric Ganus, Tennessee Wildlife Resources Agency) independently
estimated the ages of a subset (n = 40) of the blue catfish otoliths used in this study from
Kentucky Lake. All 40 of those estimates agreed with the ages assigned to the same fish
by this study. Thus, conclusions presented here regarding the major differences in blue
catfish growth (length at age) amongst the four studied waterbodies are likely robust.
Notably, blue catfish in Fort Loudoun Reservoir grew at a considerably slower rate than
conspecifics in Lake Barkley, Kentucky Lake, and the Mississippi River (Figure 9).
To date, no growth assessment of various year classes (through the use of age and
growth back-calculation methods; see Ricker 1975) of blue catfish has been reported for
28
any waterbody. The method of assessing growth used in the present study (i.e., a nonback calculation method) assigned length at age to individual catfish based on the length
and age at the time of capture. Although such a method facilitates the rapid accumulation
of length at age data and requires less expensive aging equipment (such that the method
is preferred by some agency biologists for some studies), this method injects two sources
of potential bias into the growth analysis. For one, if fishes from different waterbodies
are captured at significantly different growth periods during the year (e.g., spring vs. fall
of the same year), differences in growth since last annulus formation (year mark) on the
aging structure can confound the analysis by increasing the variance associated with the
length at age model. In the present study this bias was likely spread evenly amongst the
studied waterbodies, as for the most part, sample collection from the study lakes
proceeded similarly throughout the overall sampling period. A second bias that gets
interjected by a non-back calculation method of aging is that each length at age value is
specific to a particular year class of fish. Hence, if significant differences in growth
amongst year classes within a waterbody exist, the overall variance associated with the
growth model becomes inflated. The ability to determine just how egregious this type of
bias is can only be determined in light of a concurrent assessment of the growth of each
year class within the pooled sample. Thus, results stemming from a non-back calculation
study of growth do not directly correlate to mean length at age data stemming from the
averaging of length at age data of independent year classes, and the results of
comparisons between the two must be considered tentative.
29
In light of the above, direct comparisons of blue catfish growth estimates reported by
the present study with those reported by others must be interpreted with caution.
Furthermore, based on the results of Buckmeier et al. (2002) one might expect studies
that employed pectoral spines as the aging structure to report somewhat inflated values
for length at age of catfish older than age 3. Blue catfish growth reported by this study
within the Tennessee portion of Lake Barkley was faster for age 1-5 fish compared to
blue catfish growth reported by Freeze (1977) for the Kentucky portion of the lake (Table
9). Age 6 and age 7 catfish in the Kentucky portion of the lake were estimated to be
longer (Freeze 1977) than those reported by this study for the Tennessee portion of the
lake. The difference in the general rate of growth between these two studies may have
resulted from age underestimation of catfish deemed age 5 and age 6 by Freeze (1977),
age overestimation of catfish deemed age 5 and age 6 by the present study, differences in
growth between different regions of the lake, differences in growth over the 30 years
separating these two studies, differences in sample size between studies, or combinations
of these variables.
Blue catfish growth reported by this study for Kentucky Lake was faster than any of
the previous five studies of blue catfish growth in this lake in either Tennessee or
Kentucky waters (Table 10). An inspection of growth increments (see Table 10)
indicates some possible aging errors in the previous studies (i.e., what appear as large
departures from the expected lessening of growth increments with age). However, a
combination of year class and sample size effects can sometimes produce such
appearances. Also, Hale and Timmons (1990) documented differences in growth
30
between blue catfish within the lacustrine and riverine portions of this lake in Tennessee
waters, with the lacustrine catfish exhibiting faster growth (Table 10). Hale and
Timmons (1990) proposed that a higher mortality rate (associated with high fishing
mortality) within the lacustrine portion of the lake was the cause of this difference. Some
evidence also exists that blue catfish in Kentucky waters of Kentucky Lake grew slower
than those in Tennessee waters of the lake (cf. growth data of Hale and Timmons 1989
and 1990, as reported in Table 10).
Blue catfish growth reported by this study for the Mississippi River exhibited slower
growth than that reported by Kelley and Carver (1966) in their study of catfish (sample
size of only 57 fish) in the Mississippi River Delta (Table 11). In addition to the
dissimilarity in sample size and aging method between these two studies, the notable
difference in growth could have been attributed to the lower Mississippi River possessing
a longer growing season, higher prey density, or many other factors.
Blue catfish in Fort Loudoun Reservoir (the slowest growing catfish in the present
study) exhibited slower growth than blue catfish in three Oklahoma lakes purported to
exhibit slow growth due to stunting associated with overpopulation (Boxrucker and
Kuklinski 2006; Table 12), while blue catfish growth rates for Lake Barkley, Kentucky
Lake, and the Mississippi River were all faster than the slow-growth Oklahoma lakes (cf.
length at age data in Tables 9-12).
Conclusions
The present study focused on three exploited (Lake Barkley, Kentucky Lake, Mississippi
River) and one recently unexploited (Fort Loudoun Reservoir) waterbodies. Unexploited
31
waters are often studied in conjunction with exploited waters in fisheries studies in hope
of using them to define natural mortality and to otherwise consider the effects of fishing
harvest on fish populations (e.g., see Beckwith et al. 1986). However, in the present case,
although differences in the weight-length relationship, relative weight, and length at age
between Fort Loudoun Reservoir and at least some of the exploited waters were
documented by this study, the differences are not necessarily related to the unexploited
status of Fort Loudoun Reservoir. For example, differences between blue catfish in Fort
Loudoun Reservoir and the exploited waterbodies could be related to “lake specific” nonfishery-related factors such as lake productivity or forage base. To robustly consider the
effects of exploitation, multiple unexploited waters are typically studied along with
multiple exploited waters; and, it is further desirable to assess exploited waters in light of
their relative levels of exploitation (e.g., see Beckwith et al. 1986).
Because this study was designed to detect and describe patterns rather than reveal the
biological processes underlying them, the causes of the differences and similarities in
weight-length relationships, relative weight estimates, and age and growth patterns
remain unknown. That said, the results of this study, although preliminary, should prove
immediately valuable as baseline data for fisheries managers in Tennessee as they
consider how best to manage the state’s catfish resources. With that task in mind,
following are some recommendations regarding future studies in support of catfish
management in Tennessee. One could argue that two primary research agendas should
exist regarding catfish management in Tennessee: defining the fishery and gathering
biological information necessary for sound management.
32
The state would benefit from continued assessments aimed at defining the monthly
and annual sport and commercial harvest in waters throughout the state. Such
assessments should include harvest as well as some metric of effort. Potentially
important ancillary data (e.g., water temperature, wholesale price of catfish, type of gear
fished by sport and commercial fishermen, etc.) should also be routinely gathered. As
Tennessee is generally known as a state of opportunity regarding a quality catfishing
experience (Hoffman 2008), the state might also consider greater promotion of catfishing
to increase tourism and stimulate other economic benefits. Studies aimed at defining the
economic impact of catfishing relative to other types of fishing within the state might also
help to properly prioritize catfish management in relation to other fisheries exigencies.
Several studies would be beneficial to gathering biological information required to
manage catfish in Tennessee. For example, to date no report exists that validates otolith
aging methods in blue catfish. Given the life history of Ictalurus spp., such a validation
study should be designed to investigate possible differences between male and female
catfishes, as mature males may develop false annuli associated with the periods during
which they guard the developing eggs. Such a study would be relatively easy to design
and would lend confidence to studies requiring age assessments. Similarly, differences in
growth amongst year classes of fishes can be pronounced (for results of a recent study
focusing on flathead catfish see Jones and Noltie (2007)) and yet no data regarding this
phenomenon exists for blue catfish. With this in mind, a study in one to several of
Tennessee’s most important reservoirs should investigate possible variations in blue
catfish growth associated with sex and year class. Valuable too would be investigations
33
of possible association between sex and weight-length relationships and relative weight,
fecundity at age, age and length at maturity, and studies aimed at estimating numbers and
biomass of blue catfish in waters throughout the state, especially as these numbers relate
to variable year class strength and other metrics affecting recruitment to the fishery. The
ultimate goal of these studies would be to set the stage for a more ambitious statewide
study that focuses on yield modeling (Beverton and Holt 1957; Ricker 1975; Beckwith et
al. 1986) to assess changes in catfish biomass associated with various real or hypothetical
management changes (e.g., alterations of harvest size limits). Certainly studies such as
these will generate a better understanding of blue catfish as an important renewable
natural resource within Tennessee.
34
References
Anderson, R. O., and R. M. Neumann. 1996. Length, weight, and associated structural
indicies. Pages 447-482 in B. R. Murphy, and D. W. Willis, editors. Fisheries
techniques, second edition. American Fisheries Society, Bethesda, Maryland.
Arterburn, J. E., D. J. Kirby, and C. R. Berry, Jr. 2001. Biologist opinions and angler
attitudes concerning catfish and their management in the Mississippi River basin.
Mississippi Interstate Cooperative Resources Association, Final Report, Des Moines,
Iowa.
Beckwith, Jr., E. E., G. W. Benz, and R. P. Jacobs. 1986. Stock assessment of
largemouth bass (Micropterus salmoides) in selected lakes with special reference to
the 305 mm minimum size limit. Final Federal Report 1980-1986. Dingle-Johnson
Project No. F-57-R. Connecticut Department of Environmental Protection, Hartford,
Connecticut.
Beverton, R. J. H., and S. J. Holt. 1957. On the dynamics of exploited fish populations.
Chapman and Hall, London, U.K.
Boxrucker, J., and K. Kuklinski. 2006. Abundance, growth, and mortality of selected
Oklahoma blue catfish populations: implications for management of trophy fisheries.
Proceedings of the Annual Conference of the Annual Associates of the Fish and
Wildlife Agencies 60:152-156.
35
Brasher, B. 2007. Monster catfish highlights victory. Memphis commercial appeal.
Available: http://www.commercialappeal.com/news/2007/nov/05/monster-catfishhighlights-victory/.
Buckmeier, D. L., E. R. Irwin, R. K. Betsill, and J. A. Prentice. 2002. Validity of
otoliths and pectoral spines for estimating ages of channel catfish. North American
Journal of Fisheries Management 22:934-942.
Caroll, B. B., and G. E. Hall. 1964. Growth of catfishes in Norris Reservoir, Tennessee.
Journal of Tennessee Academy of Science 39:86-91.
Conder, J. R., and R. Hoffarth. 1965. Growth of channel catfish, Ictalurus punctatus,
and blue catfish, Ictalurus furcatus, in the Kentucky Lake portion of the Tennessee
River in Tennessee. Proceedings of the Annual Conference of the Southeastern
Association of Game and Fish Commissioners 16:348-354.
Etnier, D. A., and W. C. Starnes. 1993. The fishes of Tennessee. University of
Tennessee Press, Knoxville, Tennessee.
Freeze, T. M. 1977. Age and growth, condition, and length-weight relationships of
Ictalurus furcatus and Ictalurus punctatus from Lake Barkley and Kentucky Lakes,
Kentucky. Master’s thesis. Murray State University, Murray, Kentucky.
Graham, K. 1999. A review of the biology and management of blue catfish. Pages 3749 in E. R. Irwin, W. A. Hubert, C. F. Rabeni, H. L. Schramm, Jr., and T. Coon,
editors. Catfish 2000: proceedings of the international ictalurid symposium.
American Fisheries Society, Symposium 24, Bethesda, Maryland.
36
Hale, R. S., and T. J. Timmons. 1989. Comparative age and growth of blue catfish in the
Kentuck portion of Kentucky Lake between 1967 and 1985. Transactions of the
Kentucky Academy of Science 50:22-26.
Hale, R. S., and T. J. Timmons. 1990. Growth of blue catfish in the lacustrine and
riverine areas of the Tennessee portion of Kentucky Lake. Journal of the Tennessee
Academy of Science 65:86-90.
Hargis, H. L. 1966. Haul seine and trap net development and improvement based on
related biological fishery research in Tennessee reservoirs. Job Completion Report 45-R-1, Tennessee Game and Fish Commision, Nashville, Tennessee.
Hoffman, S. 2008. Top blue cat waters. In-Fisherman. Available: http://www.infisherman.com/magazine/exclusives/if2807_cats/.
Holley, M. P. 2006. An evaluation of the catfish fishery in Wilson Reservoir, Alabama.
Masters thesis. Auburn University, Auburn, Alabama.
Irwin, E. R., W. A. Hubert, C. F. Rabeni, H. L. Schramm, Jr., and T. Coon, editors.
1999. Catfish 2000: proceedings of the international ictalurid symposium. American
Fisheries Society, Symposium 24, Bethesda, Maryland.
Isermann, D. A., J. R. Meerbeek, G. D. Scholten, and D. W. Willis. 2003. Evaluation of
three different structures used for walleye age estimation with emphasis on removal
and processing times. North American Journal of Fisheries Management 23:625-631.
37
Jones, B. D., and D. B. Noltie. 2007. Flooded flatheads: evidence of increased growth in
Mississippi River Pylodictis olivaris (Pisces: Ictaluridae) following the great midwest
flood of 1993. Hydrobiologia 592:183-209.
Kelley, Jr., J. R., and D. C. Carver. 1966. Age and growth of blue catfish, Ictalurus
furcatus (LeSuer 1840) in the recent delta of the Mississippi River. Proceedings of
the Annual Conference Southeastern Association of Game and Fish Commissioners
19:296-299.
Miranda, L. E. 1999. Recreational harvest in reservoirs in the USA. Fisheries
Management and Ecology 6:499-513.
Pope, K. L., and C. G. Kruse. 2007. Condition. Pages 423-471 in C. S. Guy, and M. L.
Brown, editors. Analysis and interpretation of freshwater fisheries data. American
Fisheries Society, Bethesda, Maryland.
Porter, M. E. 1969. Comparative age, growth, and condition studies on the blue catfish,
Ictalurus furcatus (LeSuer), and the channel catfish, Ictalurus punctatus
(Rafinesque), within the Kentucky waters of Kentucky Lake. Master’s thesis.
Murray State University, Murray, Kentucky.
Ricker, W. E. 1975. Computation and interpretation of biological statistics of fish
populations. Bulletin of the Fisheries Research Board of Canada 191:1-382.
Sakaris, P. C., and E. R. Irwin. 2008. Validation of daily ring deposition in the otoliths
of age-0 channel catfish. North American Journal of Fisheries Management 28:212218.
38
SAS Institute. 2008. User’s guide, version 9.1.3. SAS Institute, Cary, North Carolina.
Schoffman, R. J. 1954. Age and growth of the channel catfish in Reelfoot Lake,
Tennessee. Journal of the Tennessee Academy of Science 39:2-8.
Slipke, J. W., and M. J. Maceina. 2003. Fishery analysis and simulation tools (FAST
3.0). Department of Fisheries and Allied Aquacultures, Auburn University, Auburn,
Alabama.
USFWS (Fish and Wildlife Service), and USCB (Census Bureau). 2006. National
Survey of Fishing, Hunting, and Wildlife-Associated Recreation. U.S. Department of
the Interior and U.S. Department of Commerce, Washington, D.C.
Wege, G. J., and R. O. Anderson. 1978. Relative weight (Wr): a new index of condition
for largemouth bass. Pages 79-91 in G. D. Novinger, and J. G. Dillard, editors. New
approaches to the management of small impoundments. American Fisheries Society,
North Central Division, Special Publication 5, Bethesda, Maryland.
39
Table 1. Sport fishery creel survey analysis resultsa for catfish (blue catfish, Ictalurus furcatus; channel catfish, I. punctatus; flathead catfish, Pylodictis
olivaris) and bullheads (black bullhead, Amerius melas; yellow bullhead, A. natalis) caught in three Tennessee waterbodies during 1998-2006. Values
in parentheses represent percent of corresponding grand total.
Reservoir
Species
Mean total
weight
caught (kg)
Mean total
harvest (kg)
Mean total harvest
as percent of mean
total weight caught
Lake
Barkley
Angler hours
fished for
catfish and
bullheads
Number of catfish
and bullheads
caught hr-1
17,567
1.52
Mean total weight
caught ha-1 (kg ha-1)
7,359
(6.3%)
6,071
82%
0.99
Channel
catfish
2,411b
(6.1%)
6,409b
266%
0.32
Flathead
catfish
114
(2.2%)
98
86%
0.015
Kentucky
Lake
399,254
1.05
Blue catfish
107,917
(92.9%)
99,224
92%
2.46
Channel
catfish
36,999
(93.9%)
32,779
89%
0.84
Flathead
catfish
5,179
(97.8%)
4,228
82%
0.19
Table 1. Continued on Subsequent Page
Blue catfish
39
40
Table 1. Continued.
Reservoir
Species
Mean total
weight
caught (kg)
Mean total
harvest (kg)
Mean total harvest
as percent of mean
total weight caught
Fort
Loudoun
Reservoirc
Blue catfish
931 (0.8%)
0d
Grand
Total
Angler hours
fished for
catfish and
bullheads
Number of catfish
and bullheads
caught hr-1
9,806
0.22
0%
0.99
426,627
Blue catfish
116,207
105,295
Channel
catfish
39,410
39,188
Flathead
catfish
5,293
4,326
Mean total weight
caught ha-1 (kg ha-1)
0.32
0.015
2.46
a
Data analyzed from Tennessee Wildlife Resources Agency creel surveys, 1998-2006.
A reported harvest > the corresponding catch (both calculated values double checked for accuracy) indicates a reporting error in the TWRA creel survey.
c
Blue catfish were the only species of catfish reported, other catfishes are not generally considered abundant in this reservoir.
d
Lack of harvest corresponds to a period when the reservoir was under a fishery advisory warning regarding fish consumption.
b
40
41
Table 2. Monthly 2005 commercial catfish harvest (kg) for 17 Tennessee waterbodies calculated from Tennessee Wildlife Resources Agency commercial
fishing data.a
2005 Monthly Commercial Harvest (kg)
Harvested
group
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sept.
Oct.
Nov.
Dec.
Blue
catfish
623,402
44,809
51,245
45,292
46,351
77,746
61,142
52,149
65,061
39,719
50,784
44,236
44,868
Channel
catfish
220,805
15,890
18,390
22,698
21,958
22,029
16,153
16,205
19,571
12,698
17,489
21,703
16,021
Flathead
catfish
29,322
652
819
1,575
2,100
4,065
3,351
2,907
3,499
1,899
5,331
2,041
1,083
Catfish
spp.b
19,298
722
1,075
1,829
2,002
4,841
3,861
1,201
732
82
18
1,775
1,160
Totals
892,827
62,073
71,529
71,394
72,411
108,681
84,507
72,462
88,863
54,398
73,622
69,755
63,132
a
Waterbodies: Lake Barkley, Kentucky Lake, Mississippi River, Nolichucky River, Obion River, Perryville River, Reelfoot Lake, Chickamauga Lake,
French Broad River, Hatchie River, Lake Nickajack, Old Hickory Reservoir, Watts Barr Reservoir, Cheatham Lake, Lake Douglas, Lake Guntersville,
Hiwassee River
b
Catfish spp. refers to a mixture of blue catfish, channel catfish, and flathead catfish not identified by species when reported.
41
42
Table 3. Sport and commercial harvest of catfish (blue catfish, Ictalurus furcatus; channel catfish, I. punctatus; and flathead catfish, Pylodictis
olivaris) for 22 Tennessee waterbodies for the year 2006.a
Sport
harvest
(kg)
Commercial
harvest (kg)
Total
harvest
(kg)
Sport
harvest
(% of
total)
Commercial
harvest (% of
total)
Sport
harvest
ha-1 (kg)
Commercial
harvest ha-1 (kg)
Harvest ha-1
(kg)
Chickamauga Lake
13,962
47,991
194,780
242,771
19.8
80.2
3.44
13.95
17.4
Lake Barkleyb
7,406
7,147
92,243
99,390
7.2
92.8
0.97
12.46
13.4
Kentucky Lake b
43,794
91,727
311,586
403,313
22.7
77.3
2.09
7.11
9.2
Reelfoot Lake
4,220
1,028
25,348
26,376
3.9
96.1
0.24
6.01
6.3
Pickwick Lake
2,492
2,590
11,879
14,469
17.9
82.1
1.04
4.77
5.8
Watts Bar Reservoir
15,783
23,477
38,861
62,338
37.7
62.3
1.49
2.46
3.9
Old Hickory Lake
9,105
5,104
21,976
27,080
18.8
81.2
0.56
2.41
3.0
Lake Douglas
12,383
15,440
11,975
27,415
56.3
43.7
1.25
0.97
2.2
Percy Priest
Reservoir
5,747
4,869
0
4,869
100
0
0.85
0
0.85
Lake Cherokee
12,262
4,914
0
4,914
100
0
0.40
0
0.4
Normandy Lake
1,233
441
0
441
100
0
0.36
0
0.36
Woods Reservoir
1,481
282
0
282
100
0
0.19
0
0.19
Boone Lake
1,829
289
0
289
100
0
0.16
0
0.16
Table 3. Continued on Subsequent Page
Surface
area (ha)
Waterbody
42
43
Table 3. Continued.
Surface
area (ha)
Sport
harvest
(kg)
Commercial
harvest (kg)
Total
harvest
(kg)
Sport
harvest
(% of
total)
Commercial
harvest (% of
total)
Sport
harvest ha-1
(kg)
Commercial
harvest ha-1
(kg)
Harvest ha-1
(kg)
Tims Ford Lake
4,290
312
0
312
100
0
0.07
0
0.07
Norris Lake
13,840
823
0
823
100
0
0.06
0
0.06
Melton Hill Lake
1,898
108
0
108
100
0
0.06
0
0.06
Dale Hallow Lake
7,069
525
0
525
100
0
0.07
0
0.07
Lake Watauga
2,602
82
0
82
100
0
0.03
0
0.03
Center Hill Lake
7,373
175
0
175
100
0
0.02
0
0.02
South Holston
Reservoir
2,564
26
0
26
100
0
0.01
0
0.01
Fort Loudoun
Reservoirc
5,908
27
0
27
100
0
0.005
0
0.005
Tellico Lake
6,498
0
0
0
100
0
0
0
0
207,377
708,648
916,025
22.6%
77.4%
0.61±0.18
2.28±0.88
2.93±1.03
Waterbody
Total
Mean (± SE)
a
Data primarily from unpublished records of the Tennessee Wildlife Resources Agency (see text for details).
Heavily exploited reservoir included in study.
c
Lightly exploited reservoir included in study.
b
43
44
Table 4. Number of blue catfish, Ictalurus furcatus, sampled from four study waterbodies.
Number of Fish per Total Length Interval
≤ 225
≥ 226
≤ 250
≥ 251
≤ 275
≥ 276
≤ 300
≥ 301
≤ 325
≥ 326
≤ 350
≥ 351
≤ 375
≥ 376
≤ 400
≥ 401
≤ 425
≥ 426
≤ 450
≥ 451
≤ 475
≥ 476
≤ 500
Lake
Barkley
169
0
0
1
0
1
2
4
6
6
5
12
12
Kentucky
Lake
172
0
0
3
2
1
2
2
7
3
7
13
12
Mississippi
River
248
43
5
6
5
2
3
16
15
21
16
17
19
Fort
Loudoun
Reservoir
190
0
0
3
3
1
4
4
5
0
10
14
6
Total
779
43
5
13
10
5
11
26
33
30
38
56
49
Table 4. Continued on Subsequent Page
Waterbody
Total
number
of fish
sampled
44
45
Table 4. Continued.
Number of Fish per Total Length Interval
≥ 501
≤ 525
≥ 526
≤ 550
≥ 551
≤ 575
≥ 576
≤ 600
≥ 601
≤ 625
≥ 626
≤ 650
≥ 651
≤ 675
≥ 676
≤ 700
≥ 701
≤ 725
≥ 726
≤ 750
≥ 751
≤ 775
≥ 776
≤ 800
Lake
Barkley
17
14
20
7
11
9
14
4
2
5
10
2
Kentucky
Lake
11
8
17
13
14
9
6
5
7
7
5
0
Mississippi
River
23
16
4
10
7
4
6
3
1
2
0
1
Fort
Loudoun
Reservoir
13
7
22
14
12
11
5
9
7
3
3
6
Totals
64
45
63
44
44
33
31
21
17
17
18
9
Table 4. Continued on Subsequent Page
Waterbody
45
46
Table 4. Continued.
Number of Fish per Total Length Interval
Waterbody
≥ 801
≤ 825
≥ 826
≤ 850
≥ 851
≤ 875
≥ 876
≤ 900
≥ 901
≤ 925
≥ 926
≤ 950
≥ 951 ≤
975
≥ 976 ≤
1,000
≥ 1,001
Lake
Barkley
0
0
0
1
1
0
0
0
3
Kentucky
Lake
1
2
0
2
0
3
0
0
10
Mississippi
River
2
1
0
0
0
0
0
0
0
Fort
Loudoun
Reservoir
2
8
6
4
1
1
1
2
3
Totals
5
11
6
7
2
4
1
2
16
46
47
Table 5. Parameters of log10 transformed weight-length linear regressions for four studied Tennessee
waterbodies and log10 transformed weight-length linear regression for pooled data from the same four
waterbodies used to represent Tennessee.
Weight-Length Parameters
Waterbody
Slope ± 95% CI
y-intercept ± 95% CI
r2
Lake Barkley
2.87 ± 2.61-3.13
-4.60 ± -5.32--3.88
0.74
Kentucky Lake
3.46 ± 3.35-3.57
-6.20 ± -6.50--5.90
0.96
Mississippi River
3.10 ± 2.5-3.17
-5.33 ± -5.51--5.15
0.97
Fort Loudoun Reservoir
3.41 ± 3.23-3.59
-6.16± -6.45--5.87
0.96
Tennessee
3.21 ± 3.17-3.26
-5.59 ± -5.72--5.46
0.95
48
Table 6. Overall and mean relative weights for five size classes of blue catfish, Ictalurus furcatus, sampled from four Tennessee waterbodies.a
Mean Relative Weights (Wr)
Overall Wr
Stock (≥ 300 to ≤ 509 mm
TL)
Quality (≥ 510 to ≤
759 mm TL)
Preferred (≥ 760 to ≤
889 mm TL)
Memorable (≥ 890 to ≤
1,139 mm TL)
121
156.45
98.06
102.81
105.85
Kentucky Lake
112
106.18
114.53
121.17
103.62
Mississippi River
94
95.85
89.27
105.42
Fort Loudoun Reservoir
86
86.83
86.1
87.09
Waterbody
Lake Barkley
a
78.5
Lack of data prevented calculation of trophy size interval values.
48
49
Table 7. Mean total length at age (mm) for blue catfish, Ictalurus furcatus, in four Tennessee waterbodies.
Age
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
32
33
34c
Number of
fish
a
Lake Barkleya
Kentucky Lakea
318
405
479
559
547
575
631
681
709
693
787
271
535
525
550
560
595
670
704
740
1079
1092
1144
108
236
271
376
428
471
522
558
602
664
679
650
688
812
1115
1035
830
169
172
Heavily exploited reservoir included in study.
Lightly exploited reservoir included in study.
c
Oldest blue catfish “aged” to date.
b
Mississippi Rivera
248
Fort Loudoun
Reservoirb
329
281
317
382
445
446
441
472
474
508
527
579
592
602
636
625
718
710
729
667
759
826
812
839
837
900
874
190
50
Table 8. Fishery mileposts for blue catfish, Ictalurus furcatus, in four Tennessee waterbodies.a Note
that values for some mileposts could not be estimated for some waters because of a lack of data.
Waterbody
Lake Barkley
Number
of years
within
fishery
Age (yr)
leaving
fisheryc
Weight
(g)
entering
fishery
Weight
(g) at
midpoint
within
fishery
Weight
(g)
leaving
fishery
1.5
11
12.5
158
1,778
6,761
1,659
7,244
Kentucky Lake
1
228
Mississippi River
1
138
Fort Loudoun Reservoir
a
Age (yr)
entering
fisheryb
3.5
30.5
34
58
Age estimations calculated using waterbody specific von Bertalanffy model parameters (see Figures 1013) as described by Slipke and Maceiana (2006). Weight estimations calculated using waterbody specific
weight-length associations (see Figures 4-7).
b
Age entering fishery calculated as corresponding to a total length of 205 mm.
c
Age leaving fishery calculated as corresponding to a total length of 864 mm.
51
52
Table 9. Comparison of blue catfish, Ictalurus furcatus, length age data stemming from studies in Lake Barkley (Tennessee and Kentucky).
Length at Age (mm)
(Growth Increment from Previous Age; mm)
Waterbody
(State)
Study
Aging Structurea
1
2
3
4
5
6
7
(TN)
Present studyb
O
190
290
(100)
372
(82)
450
(78)
519
(69)
581
(62)
637
(56)
(KY)
Freeze (1977)c
P
76
188
(112)
302
(114)
376
(74)
455
(79)
584
(129)
658
(74)
Lake Barkley
a
O = otoliths, P = pectoral spines.
Length at age and growth increment values as predicted by the waterbody specific von Bertalanffy growth model (see Figure 10).
c
Length at age and incremental growth values derived from reported mean length at age values.
b
51
53
Table 10. Comparison of blue catfish, Ictalurus furcatus, length age data stemming from studies in Kentucky Lake (Tennessee and Kentucky).
Length at Age (mm)
(Growth Increment from Previous Age; mm)
Waterbody
(State)
Study
Aging
Structurea
1
2
3
4
5
6
7
8
9
10
11
(TN)
Present Studyb
O
229
313
(84)
388
(75)
453
(65)
511
(58)
561
(50)
606
(45)
646
(40)
681
(35)
711
(30)
873
(27)
(TN)
Hale and Timmons (1989)c
P
132
221
(89)
274
(53)
318
(44)
363
(45)
424
(61)
485
(61)
549
(64)
584
(35)
607
(23)
693
(86)
(TN)
Hale and Timmons (1990)c
P
142
229
(87)
287
(58)
343
(56)
401
(58)
447
(46)
500
(53)
423
(-77)
551
(128)
587
(36)
(TN)
Hale and Timmons (1990)c
P
145
239
(94)
295
(56)
356
(61)
427
(71)
483
(56)
551
(68)
627
(76)
671
(44)
(KY)
Conder and Hoffarth (1965)c
P
135
198
(63)
252
(54)
297
(45)
356
(59)
429
(73)
513
(84)
582
(69)
699
(117)
Kentucky
Lake
846
(147)
52
54
Table 10. Continued.
Length at Age (mm)
(Growth Increment from Previous Age; mm)
Waterbody
(State)
Study
Aging
Structurea
1
2
3
4
5
6
7
8
9
10
11
(TN)
Present Studyb
O
229
313
(84)
388
(75)
453
(65)
511
(58)
561
(50)
606
(45)
646
(40)
681
(35)
711
(30)
873
(27)
(KY)
Porter (1969)c
P
117
213
(96)
310
(97)
391
(81)
480
(89)
559
(79)
627
(68)
(KY)
Freeze (1977)c
P
76
165
(89)
239
(74)
302
(63)
311
(9)
432
(121)
483
(51)
564
(81)
666
(102)
Kentucky
Lake
a
O = otoliths, P = pectoral spines.
Length at age and growth increment values as predicted by the waterbody specific von Bertalanffy growth model (see Figure 11).
c
Length at age and incremental growth values derived from reported mean length at age values.
b
53
55
Table 11. Comparison of blue catfish, Ictalurus furcatus, length age data stemming from studies in Mississippi River (Tennessee and Louisiana).
Length at Age (mm)
(Growth Increment from Previous Age; mm)
Waterbody
(State)
Study
Aging
Structurea
1
2
3
4
5
6
(TN)
Present Studyb
O
211
294
(83)
367
(73)
429
(62)
483
(54)
530
(47)
(LA)
Kelley and Carver (1966)c
P
191
386
(195)
508
(122)
638
(130)
749
(111)
848
(99)
Mississippi
River
a
O = otoliths, P = pectoral spines.
Length at age and growth increment values as predicted by the waterbody specific von Bertalanffy growth model (see Figure 12).
c
Length at age and incremental growth values derived from reported mean length at age values.
b
54
56
Table 12. Comparison of blue catfish, Ictalurus furcatus, length age data stemming from studies in Fort Loudoun Reservoir (Tennessee), Lake Hugo
(Oklahoma), Lake Ellsworth (Oklahoma), and Lake Eufaula (Oklahoma).
Length at Age (mm)
(Growth Increment from Previous Age; mm)
Waterbody
(State)
Study
Aging
Structurea
1
2
3
4
5
6
7
8
9
10
11
12
13
Fort Loudoun
Reservoir (TN)
Present Studyb
O
103
146
188
227
265
301
336
369
400
431
460
488
514
(43)
(42)
(39)
(38)
(36)
(35)
(33)
(31)
(31)
(29)
(28)
(26)
Lake Hugo
(OK)
Boxrucker and
Kuklinski
(2006)c
223
273
320
331
371
412
450
474
487
(55)
(50)
(47)
(11)
(40)
(41)
(38)
(24)
(13)
Lake Ellsworth
(OK)
Boxrucker and
Kuklinski
(2006)c
186
222
234
253
274
298
321
339
384
394
414
382
(20)
(36)
(12)
(19)
(21)
(24)
(23)
(18)
(45)
(10)
(20)
(-32)
Lake Eufaula
(OK)
Boxrucker and
Kuklinski
(2006)c
203
256
295
273
351
357
375
415
427
473
479
491
(47)
(53)
(39)
(-22)
(78)
(6)
(18)
(40)
(12)
(46)
(6)
(12)
P
P
P
168
166
156
a
O = otoliths, P = pectoral spines.
Length at age and growth increment values as predicted by the waterbody specific von Bertalanffy growth model (see Figure 13).
c
Length at age and incremental growth values derived from reported mean length at age values.
b
55
57
1
3
2
4
Figure 1. Major river systems of Tennessee. Blue catfish (Ictalurus furcatus) samples were collected from the following four
waterbodies as part of this study: Lake Barkley (1), Kentucky Lake (2), Mississippi River (3), and Fort Loudoun Reservoir (4).
56
58
B
A
C
D
Figure 2. Location and removal of sattigal otoliths from catfish. A. Otoliths
are located within a plane (dashed line) lying just anterior to (ca. 3-5 mm) a
transverse plane (solid line) bridging the proximal ends of the locked
pectoral spines. B. Sawblade lying along plane of section used to expose
otoliths. C. Catfish head being sectioned to expose otoliths. D. Right
sagittal otolith being removed with a forceps. Figure 2A and 2B modified
from Buckmeier et al. (2002).
59
r
ar
ss
Figure 3. Epoxy casts containing catfish otoliths. For aging purposes, the
sagittal otolith was transversely sectioned just anterior to the antirostrum (ar)
on the rostrum side (r) using a low-speed isomet saw. Sand paper (200-500
grit) was then used to grind the otolith to the ventral sulcus (s).
60
log10 W = -4.60 + 2.87log10TL
r2 = 0.74
n = 168
Figure 4. Weight-length relationship for blue catfish, Ictalurus furcatus, collected
from Lake Barkley (Tennessee portion of lake; formula for log10 transformed weightlength linear regression and r2 value provided at upper left).
61
log10 W = -6.21 + 3.46log10TL
r2 = 0.96
n = 166
Figure 5. Weight-length relationship for blue catfish, Ictalurus furcatus, collected
from Kentucky Lake (Tennessee portion of lake; formula for log10 transformed
weight-length linear regression and r2 value provided at upper left).
62
log10 W = -5.33 + 3.10log10TL
r2 = 0.97
n = 205
Figure 6. Weight-length relationship for blue catfish, Ictalurus furcatus, collected
from the Mississippi River (formula for log10 transformed weight-length linear
regression and r2 value provided at upper left).
63
log10 W = -6.16 + 3.41log10TL
r2 = 0.96
n = 190
Figure 7. Weight-length relationship for blue catfish, Ictalurus furcatus, collected
from Fort Loudoun Reservoir (formula for log10 transformed weight-length linear
regression and r2 provided value at upper left).
64
log10 W = -5.59 + 3.21log10TL
r2 = 0.95
n = 773
Figure 8. Weight-length relationship for blue catfish, Ictalurus furcatus, collected
from four Tennessee waterbodies (Lake Barkley, Kentucky Lake, Mississippi River,
Fort Loudoun Reservoir; formula for log10 transformed weight-length linear
regression and r2 value provided at upper left).
65
864 mm TL (Trophy size limit)
A
C
D
B
A) Lake Barkley
B) Kentucky Lake
C) Mississippi River
D) Fort Loudoun Reservoir
Figure 9. Blue catfish, Ictalurus furcatus, von Bertalanffy growth curves for four
Tennessee waterbodies.
66
1,115 mm TL (L∞)
864 mm TL (TN trophy size limit)
Lt = 1,115 {1 – e -0.11(t +0.693)}
r2 = 0.83
n = 169
Figure 10. Blue catfish, Ictalurus furcatus, von Bertalanffy growth curve and model
parameters for Lake Barkley.
67
940 mm TL (L∞)
864 mm TL (TN trophy size limit)
Lt = 940 {1 – e -0.126(t +1.217)}
r2 = 0.92
n = 155
Figure 11. Blue catfish, Ictalurus furcatus, von Bertalanffy growth curve and model
parameters for Kentucky Lake.
68
864 mm TL (TN trophy size limit)
830 mm TL (L∞)
Lt = 830 {1 – e -0.145(t +1.019)}
r2 = 0.97
n = 207
Figure 12. Blue catfish, Ictalurus furcatus, von Bertalanffy growth curve and model
parameters for Mississippi River.
69
1,105 mm (L∞)
864 mm TL (TN trophy size limit)
Lt = 1,105 {1 – e -0.044(t +1.227)}
r2 = 0.96
n = 190
Figure 13. Blue catfish, Ictalurus furcatus, von Bertalanffy growth curve and model
parameters for Fort Loudoun Reservoir.