Cat Fish Stock

8/9/2019 Cat Fish Stock

1/11

1191

North American Journal of Fisheries Management 25:11911201, 2005 [Article] Copyright by the American Fisheries Society 2005DOI: 10.1577/M03-251.1

Population Abundance and Stock Characteristics of Flathead

Catfish in the Lower St. Joseph River, Michigan

DANIEL J. DAUGHERTY AND TRENT M. SUTTON*

Department of Forestry and Natural Resources, Purdue University,

195 Marsteller Street, West Lafayette, Indiana 47907-1159, USA

Abstract.Little information exists regarding the biological attributes and stock dynamics of

flathead catfish Pylodictis olivaris in lotic systems throughout the northern United States. We

examined the population abundance, annual survival, growth, condition, size structure, and age

structure of flathead catfish in the lower St. Joseph River, Michigan, to direct future management

efforts in this system and increase our knowledge of northern flathead catfish stocks. Fish were

collected by means of electrofishing during June through September 2002 and 2003. Population

abundance was estimated at 5,452 individuals (range, 3,9857,277 fish), and annual survival was

estimated at 67%. Analysis of pectoral spine cross sections revealed that growth was greatest for

fish younger than age 6 (range, 8398 mm/year) and decreased among older age-classes (range,1870 mm/year). Relative weight was greatest for individuals less than 300 mm total length (TL;

115%) and declined with increasing fish length. The size structure and age structure of flathead

catfish were dominated by fish less than 400 mm TL and younger than age 4 (89% and 79%,

respectively), although individuals greater than 1,100 mm TL and up to age 17 were present in

the population. Relative stock density estimates indicated that 58% of fish greater than the minimum

stock size were of quality length, while flathead catfish of preferred, memorable, and trophy sizes

represented 28, 7, and 1% of fish collected, respectively. Despite their presence on the northern

fringe of the species geographic distribution, the flathead catfish in the lower St. Joseph River

exhibited biological characteristics and stock dynamics that were similar to those reported for

other lightly exploited stocks throughout the midwestern United States.

Flathead catfish Pylodictis olivaris are an im-

portant component of the North American catfish

fishery (Jackson 1999). This species is native to

the Mississippi River, Mobile River, and Rio

Grande River drainages, the Laurentian Great

Lakes basin, and northeastern Mexico (Hubbs and

Lagler 1947; Lee and Terrell 1987; Jackson 1999)

and supports recreational and commercial fisheries

throughout much of its geographic distribution

(Moss and Tucker 1989; Grussing et al. 2001). In

many states, flathead catfish offer anglers an op-

portunity to catch fish by means other than hook

and line (e.g., handgrabbing, bankpoling, etc.),while giving commercial fishers a high-quality

product preferred by many consumers (Quinn

1993; Grussing et al. 2001; Jackson 1999). Despite

the popularity of this species, knowledge regarding

the population characteristics of flathead catfish

stocks is limited. This lack of information is most

prevalent in moderate-size rivers, streams, and

creeks, where fisheries managers have found as-

sessment of catfish populations difficult due to the

solitary nature and low population abundances of

* Corresponding author: [email protected]

Received December 22, 2003; accepted January 12, 2005

Published online August 2, 2005

catfish (Stauffer et al. 1996; Vokoun and Rabeni

1999).Although a number of studies have examined

the population characteristics of flathead catfish in

lotic environments, most have focused on size

structure, age distribution, and growth in systems

throughout the southern United States (Purkett

1958; Minckley and Deacon 1959; Mayhew 1969;

Guier et al. 1984; Pisano et al. 1983; Young and

Marsh 1990; Grussing et al. 2001). Purkett (1958)

reported that flathead catfish grew an average of

76 mm/year in the Salt River, Missouri, and

reached a mean total length (TL) of 300 mm byage 4. Flathead catfish grew more slowly in the

Salt River system than in the Mississippi River

(IllinoisIowa and MissouriIowa), where fish

reached 381 and 432 mm TL, respectively, at the

age 4 (Barnickol and Starrett 1951). Similarly,

Minckley and Deacon (1959) reported that flathead

catfish reached 483 mm TL by age 4 in the Big

Blue River, Kansas. However, Guier et al. (1984)

reported faster growth in the Cape Fear River,

North Carolina, where individuals reached a mean

TL of 580 mm at the same age. The results of these

studies indicate that growth of flathead catfish issystem specific and that the length of the growing

season may not be a reliable predictor of growth

rate.


2/11

1192 DAUGHERTY AND SUTTON

Whereas southern stocks of flathead catfish have

received attention from fisheries managers, little

information exists regarding the characteristics of

populations in the upper Midwest and Great Lakes

regions. Historically, northern populations haveexperienced lower exploitation rates and less an-

gling pressure than those in the south (Topp et al.

1994; Stauffer et al. 1996). These fishery char-

acteristics may result in differences in abundance,

growth, condition, age structure, and size structure

for flathead catfish stocks between northern and

southern systems. Stauffer et al. (1996) found that

growth rates of flathead catfish in the Minnesota

River, Minnesota, were 1352% lower than those

of fish in the southern United States. The authors

also noted that a high abundance of large fish was

present in the population: 20% of flathead catfishsampled were greater than 910 mm TL. These re-

sults suggest that differences in population char-

acteristics exist between northern and southern

flathead catfish stocks, supporting the need for ad-

ditional studies on fish in northern systems.

The popularity of recreational and commercial

fisheries for flathead catfish has increased sub-

stantially throughout their geographic range in re-

cent years (Summers 1986; Gilliland 1988; Quinn

1993; Cunningham 1995; Stauffer et al. 1996;

Jackson 1999). This trend is especially evident inthe northern United States, where flathead catfish

have historically attracted little angler interest

(Topp et al. 1994; Stauffer et al. 1996). Because

flathead catfish may be susceptible to overharvest

due to such factors as their low abundance and

aggressive behavior, knowledge of the life history

characteristics and population status of this species

is important for the implementation of appropriate

management strategies (Quinn 1993; Grussing et

al. 2001; Jackson 1999). Without this information,

management of flathead catfish populations would

be difficult, particularly as angling pressure in-

creases (Stauffer et al. 1996).

The flathead catfish population in the St. Joseph

River, a Lake Michigan tributary located in south-

western Michigan and northeastern Indiana, has

experienced an increase in angling pressure over

the past decade (J. Dexter, Michigan Department

of Natural Resources, personal communication).

Prior to 1996, an average of 14 flathead catfish

caught from the St. Joseph River each year was

entered into the annual state master angler award

program. Over the past 7 years, the average num-ber of entries submitted each year has decreased

by 50%. This decline in the catch of trophy fish

suggests an increase in the exploitation rate of flat-

head catfish in the St. Joseph River. However, the

current status of this fishery and the biological

attributes of the population remain unknown. The

objective of this study was to provide information

regarding the population characteristics and stockdynamics of flathead catfish in the St. Joseph River

system. Such information can be used to direct

future management efforts and i ncrease our knowl-

edge of flathead catfish populations in the northern

United States.

Study Site

The 338-km main-stem St. Joseph River is

joined by 2,641 km of tributaries, discharging an

average of 130 m3 /s from a watershed that drains

approximately 7,770 km2 in Michigan and 4,364

km2 in Indiana. The free-flowing (hereafter re-ferred to as lower) section of the St. Joseph River

is a 37.6-km reach between the Berrien Springs

Dam and the mouth of the river at Lake Michigan

(Figure 1). Because flathead catfish are not found

above the Berrien Springs Dam (J. Dexter, Mich-

igan Department of Natural Resources, personal

communication), the boundaries of this river reach

served as the upstream and downstream limits of

the sampling area. We divided the lower St. Joseph

River into four 9.4-km sampling sections to fa-

cilitate collection of flathead catfish (Figure 1).Sampling sections 1 and 2 are dominated by gravel

substrates and have a low to fair gradient (00.9

m/km), whereas sections 3 and 4 are dominated

by sand substrates and have a low gradient (0 0.5

m/km). Riparian land cover in the reach is dom-

inated by hardwood forests, although urban de-

velopment dominates section 4 as the river ap-

proaches Lake Michigan.

The lower St. Joseph River supports a resident

warmwater fish community; the most abundant

species are flathead catfish, channel catfish Ictal-

urus punctatus, freshwater drum Aplodinotus grun-

niens, common carp Cyprinus carpio, and gizzard

shad Dorosoma cepedianum (Wesley and Duffy

1999). Mean channel width in the lower St. Joseph

River is 130 m (range, 50250 m), and mean water

depth is 1.6 m (range, 0.38.2 m), although lateral-

scour pools with water depths in excess of 7 m

occur throughout the reach. Midsummer (June

August) water temperature can be as high as 28C;

mean dissolved oxygen is 9.6 mg/L (range, 6.9

14.1 mg/L) and turbidity is 16.5 nephelometric

turbidity units (NTU; range, 1127 NTU). In-stream habitat is composed primarily of woody

debris and rip-rap; few aquatic macrophytes exist

in the system.


3/11

1193ST. JOSEPH RIVER FLATHEAD CATFISH

FIGURE 1.Map of the lower, free-flowing reach of the St. Joseph River, Michigan. Lines bisecting the river

indicate the upper and lower boundaries of the four sections used for the sampling of flathead catfish.

Methods

Flathead catfish were collected during June

through September 2002 and 2003. We used the

modified predator approach defined by Vokoun and

Rabeni (1999). Fish were sampled once per week

from each section of the study area by use of 24

38-V AC produced by a three-bar magnetic motor,

as described by Morris and Novak (1968). Al-

though sampling efforts were conducted in all hab-

itat types (i.e., main-channel pools, riffles, and

runs with and without structure), efforts were con-

centrated in structural habitats typically selected

by flathead catfish (e.g., large woody debris jams,

timbered channels, undercut banks, rip-rap, etc.;

Cunningham 2000). At each sampling location,two 18-gauge insulated wires (each 6.1 m in

length) with the distal ends connected to

aluminum-bar electrodes (30.5 cm long and 2.5

cm wide) were deployed approximately 45 m up-

stream and downstream of the boat. Electrical cur-

rent was applied continuously for 90 s at each

sampling location. During August 2003, flatheadcatfish were also sampled from section 4 by means

of low-frequency (20% pulse width), low-pulse

(7.5 pulse/s) DC boat electrofishing, as described

by Stauffer and Koenen (1999). A chase boat was

used during all sampling periods in 2003 to ca pture

flathead catfish that surfaced downstream of the

boat carrying the electrofishing unit.

Population characteristics.All captured flat-

head catfish were measured for TL (nearest 1 mm)

and wet weight (nearest 1 g). The spine of the left

pectoral fin was removed and dried for subsequentage and growth analyses in the laboratory. Ab-

solute population abundance of flathead catfish

was calculated by use of the Schnabel estimator


4/11


for closed populations (Schnabel 1938). Because

assessments of flathead catfish movement in the

lower St. Joseph River indicated that individuals

remained within the study reach during the entire

study period (Daugherty and Sutton 2005), we as-sumed the population to be geographically closed.

Ninety-five percent confidence intervals (CIs)

were calculated with the Poisson distribution by

substituting the confidence limits for the number

of marked individuals at large in the population

(R) into the Schnabel estimator (Van Den Avyle

1993). Flathead catfish density (i.e., the number of

individuals per river kilometer [rkm]) was calcu-

lated by dividing the estimate of absolute abun-

dance by the length of the study reach.

In the laboratory, pectoral spines were sectioned

by use of a rotary tool fitted with a diamond-coated

cutting disk. To avoid potential fish age underes-

timation due to erosion of the central lumen (Turn-

er 1982; Nash and Irwin 1999), multiple cross sec-

tions were cut between the distal end of the basal

recess and the proximal end of the spine dentations

(Layher 1981; Crumpton et al. 1987). Spine sec-

tions were then visually examined and discarded

until enlargement of the central lumen was no lon-

ger obvious (Munger et al. 1994). Cross sections

of each spine were mounted on microscope slides

and viewed with transmitted light at 36135magnification under a zoom stereomicroscope fit-

ted with a digital camera. Images of each spine

were analyzed with IPLab 3.6 image analysis soft-

ware (Scanalytics, Fairfax, Virginia), which was

used to determine the number of annuli present,

the length of the spine radius, and the radial dis-

tance to each annulus for back-calculation of

length at age. All measurements were recorded to

the nearest 0.01 mm. Each spine image was ana-

lyzed independently by two readers, and disagree-

ments between readers were reconciled with a sub-sequent concert read.

Length at age for each flathead catfish was back-

calculated by means of a modification of the Fras-

erLee method (DeVries and Frie 1996). Back-

calculated length-at-age estimates were used to de-

termine the age at which flathead catfish were re-

cruited to the harvestable fishery (minimum length

limit, 381 mm TL) and to calculate age-specific

annual growth rates (mm/year). A von Bertalanffy

growth model was constructed for the population

in FAST 2.0 (Auburn University, Auburn, Ala-bama). Mean TL and age-at-capture data were used

to estimate the theoretical maximum fish length

(L

), Brody growth coefficient (K), and time period

when fish body length equals 0 mm (to) for the

von Bertalanffy growth model.

Fish condition was calculated as relative weight

(Wr). Length-specific standard weights (Ws) for

flathead catfish were derived from the standard-weight equation, log10(Ws) 5.542 3.23log10(TL)

(Bister et al. 2000). Relative weight was not cal-

culated for flathead catfish less than 130 mm in

length because the standard-weight equation ex-

cluded smaller individuals due to variance-to-

mean errors greater than 0.02 (Bister et al. 2000).

Relative stock density (RSD) indices (e.g., quality

[Q], preferred, memorable, and trophy) were cal-

culated based on length categories developed by

Bister et al. (2000). Minimum TLs for each cat-

egory were as follows: 350 mm for stock length,

510 mm for quality length, 710 mm for preferredlength, 860 mm for memorable length, and 1,020

mm for trophy length.

Due to variable capture rates of flathead catfish

ages 512, annual survival was estimated based

on the Robson and Chapman (1961) method.

Ninety-five percent CIs for these estimates were

calculated by use of the methods described by

Ricker (1975). The estimate of annual survival ob-

tained from the Robson and Chapman (1961)

method was used to calculate the instantaneous

total mortality rate Z. Confidence intervals for Zwere calculated by substituting the confidence lim-

its of the annual survival rate into the calculation

of Z. Age-classes younger than the first age-class

fully recruited to the sampling gear, as well as age-

classes with limited sample sizes (N 5), were

omitted from the estimation of annual survival

(Ricker 1975; Van Den Avyle 1993).

Data analysis.Piecewise linear regression was

used to determine the relationship between mean

annual growth increment and fish age. Simple lin-

ear regression was employed to determine the re-

lationship between relative condition and fish TL.

Mean TL of flathead catfish in the lower St. Joseph

River was regressed as a function of fish age, and

analysis of covariance (ANCOVA) was used to

compare this regression with growth relationships

for nine other flathead catfish populations. Signif-

icant differences among regression coefficients

were determined by the Tukeys honestly signifi-

cant difference test. All statistical analyses em-

ployed a significance level of 0.05.

Results

A total of 653 flathead catfish were collected

from 759 sites on 32 sampling occasions during

June through September 2002 and 2003. One-


5/11


FIGURE 2.Length-frequency distribution of flathead

catfish collected from the lower St. Joseph River, Mich-

igan, during 2002 and 2003.

FIGURE 3.Age-frequency distribution of flathead

catfish collected from the lower St. Joseph River, Mich-

igan, during 2002 and 2003.

hundred forty-six flathead catfish were collected

by low-frequency electrofishing during 15 d of

sampling in 2002. In 2003, 447 individuals were

collected during 17 sampling occasions. An ad-

ditional 60 fish were collected during August 2003

by means of DC boat electrofishing.

Six percent (N 40) of the flathead catfish

tagged during the study period were recaptured

during subsequent sampling occasions. The ab-

solute abundance of flathead catfish in the lowerSt. Joseph River was estimated at 5,452 individ-

uals (95% CI 3,9857,277). The density of flat-

head catfish was estimated at 145 fish/rkm. Annual

survival of flathead catfish in the lower St. Joseph

River was 0.672 (95% CI 0.6700.673). The Z

derived from this approach was 0.397 (95% CI

0.3960.400).

Flathead catfish captured during the study

ranged from 87 to 1,132 mm TL (Figure 2). In-

dividuals less than 100 mm TL represented 1% of

fish sampled, whereas flathead catfish ranging

from 100 to 400 mm TL made up the greatest

proportion of fish collected (89%). Capture rates

of flathead catfish greater than 400 mm TL varied

among length-classes (Figure 2). Fish ranging

from 500 to 600 mm TL composed 3% of the catch,

whereas fish that were 700800 mm TL repre-

sented 7% of fish sampled. Flathead catfish 900

mm TL and larger made up 5% of the population.

Pectoral spine cross sections were examined for

94% (N 612) of the collected fish. Age and

growth analyses were omitted for 41 individuals

either because of missing or broken pec toral spinesor because of pectoral spine size. Pectoral spines

collected from individuals less than 130 mm TL

were too small to accurately cross-section. The age

of flathead catfish ranged from 1 to 17 years (Fig-

ure 3). Age-1 flathead catfish represented 22% of

the fish sampled, age-2 fish represented 36%, age-

3 fish represented 15%, and age-4 fish represented

6%; these data indicate that the fish did not become

fully vulnerable to the sampling gear until age 2.

Capture rates of age-512 flathead catfish varied

among age-classes (Figure 3). Age-9 flathead cat-

fish composed the greatest proportion (4%) of fish

captured within this age range. Fish older than age12 made up 2% of the population (Figure 3).

Length-at-age estimates for flathead catfish in

the lower St. Joseph River indicated that flathead

catfish reached a mean TL of 102 mm by age 1

and were recruited to the harvestable fishery by

age 4, when the mean TL was 401 mm (Figure 4).

The mean length at age of fish in the oldest age-

class (age 17) was 1,016 mm TL. Based on the

von Bertalanffy growth equation, the predicted age

at which flathead catfish were recruited to the har-

vestable fishery was 4 years, while the maximum

attainable TL of flathead catfish in the St. Joseph

River was estimated at 1,174 mm (Figure 4).

Mean annual growth increments of flathead cat-

fish were greatest among fish younger than age 6

(range, 8398 mm/year). The slope of the linear

regression relationship over this age range indi-

cated that annual growth declined by less than 5

mm/year during this period (Figure 5). The great-

est declines in the annual growth rate of flathead

catfish in the lower St. Joseph River were observed

between ages 6 and 8 (range, 4270 mm/year).

Piecewise regression of these age-classes indicatedthat annual growth declined by approximately 14

mm/year. Annual growth rates declined little

among fish older than age 8; however, fish growth


6/11


FIGURE 4.Mean length at age and fitted von Ber-

talanffy growth equation (t age in years; lt length

at time t) for flathead catfish collected from the lower

St. Joseph River, Michigan, during 2002 and 2003. Errorbars represent 95% confidence intervals about the mean

length at age. Confidence intervals were not calculated

for age 16 because only one fish was collected.

FIGURE 6.Relationship between mean relative

weight (Wr) and total length (TL) for flathead catfish

collected from the lower St. Joseph River, Michigan,

during 2002 and 2003. Individuals were pooled into 100-

mm length groups. Error bars represent 95% confidence

intervals. Confidence intervals were not calculated for

the 1,100-mm size-class because only one fish was col-

lected.

FIGURE 5.Relationship between age (X) and calcu-

lated mean annual growth increment (Y) for each age-

class (i) of flathead catfish collected from the lower St.

Joseph River, Michigan, during 2002 and 2003. Error

bars represent 95% confidence intervals.

TABLE 1.Comparative relative stock density (RSD)

indices for flathead catfish in the lower St. Joseph River

(SJ), Michigan, the Flint River (FL), Georgia, and the

Cape Fear River (CF), North Carolina.

Indexcategory

MinimumTL (mm)

SJfrequency

(%)a

FLfrequency

(%)b

CFfrequency

(%)c

Quality 510 58 57 49

Preferred 710 28 28 21

Memorable 860 7 14 9

Trophy 1,020 1 5 1

a This study.b Quinn (1988).c Ashley and Buff (1986).

was less than 30 mm/year for these older age-

classes.

An inverse relationship was observed between

Wr and TL of flathead catfish in the lower St. Jo-

seph River (r2 0.75; P 0.001; Figure 6). Fish

condition was similar for individuals less than 300

mm TL (Wr

115%), whereas condition variedamong 300700-mm fish. Mean Wr of 300399-

mm fish was 98%, while the mean Wr for 400

700-mm fish was 113%. Relative weight was low-

est for flathead catfish greater than 700 mm TL

(mean, 88%).

The RSD estimates indicated that 58% of fish

greater than the minimum stock size (350 mm TL)

were quality length (510 mm TL; Table 1). Flat-

head catfish in the preferred-size range (710 mm

TL) composed 28% of the stock, while memorable-

size individuals (860 mm TL) made up 7% of

fish collected. Trophy fish (1,020 mm TL) rep-resented 1% of fish captured during the study pe-

riod.

Discussion

Unexploited fish stocks are characterized by

high population abundance, a low rate of annual

mortality, a broad range of fish age-classes and

length-classes, and decreased annual growth (Cla-

dy et al. 1975; Goedde and Coble 1981). In ad-

dition, the presence of large fish with reduced con-

dition further suggests little or no exploitation due


7/11


to increased competition for suitable prey resourc-

es and the increased occurrence of senescence

(Van Den Avyle 1993). Previous studies have char-

acterized the flathead catfish as a long-lived spe-

cies (

15 years) that exhibits relatively fastgrowth (approximately 100 mm/year; Barnickol

and Starrett 1951; Layher and Boles 1979; Guier

et al. 1984; Jackson 1999; Nash and Irwin 1999).

In addition, flathead catfish are known to reach

TLs in excess of 900 mm in systems with low rates

of exploitation (Hesse 1994; Stauffer et al. 1996).

Our study results suggest that the population char-

acteristics and stock dynamics of flathead catfish

in the lower St. Joseph River are similar to those

of other midwestern stocks that receive low ex-

ploitation rates.

Absolute population abundance estimates offlathead catfish in lotic systems have not been re-

ported; therefore, we could not make direct com-

parisons with other studies. However, the esti-

mated density (145 fish/rkm) of flathead catfish in

the lower St. Joseph River was comparable to den-

sities reported for other systems. Marsh et al.

(1988) estimated that the density of flathead catfish

ranged from 155 to 259 fish/km in the lower Col-

orado River, Arizona. Similarly, flathead catfish

density estimates ranged from 159 to 249 fish/km

in the Missouri River, Nebraska (Tondreau 1988).Therefore, our estimate of flathead catfish density

demonstrates that the lower St. Joseph River sup-

ports fish numbers similar to those seen in other

riverine systems.

Survival rates for flathead catfish have not been

quantified in lotic systems because of the limited

data availability and an overreliance on length- and

age-frequency distributions to qualitatively de-

scribe fish survival. For example, Stauffer et al.

(1996) attempted to estimate survival and mortal-

ity rates for flathead catfish and found that the

number of captured fish from each age-class did

not decline with increasing age. As a result, these

authors concluded that flathead catfish survival

was high. Although estimates of flathead catfish

survival are not available, the annual survival of

fish in the lower St. Joseph River (67%) was in

agreement with estimates for lightly exploited

populations of channel catfish. For example, Ku-

beny (1992) determined that the annual survival

of channel catfish was 74% in the James River,

South Dakota, whereas annual survival rates as

high as 87% have been reported for some Iowastreams (Paragamian 1990). Similarly, Gerhardt

and Hubert (1991) estimated the annual survival

of channel catfish to be 77% in the Powder River,

Wyoming; high survival was attributed to a low

rate of exploitation. The similarity in annual sur-

vival rate between the lower St. Joseph River and

these previously studied systems further suggests

relatively low exploitation of flathead catfish inthe St. Joseph River.

Because flathead catfish are long-lived and have

relatively low fecundity (approximately 6,900

11,300 eggs/female), the size structure and age

structure of populations of this species may be

altered by excessive harvest (Jenkins and Burk-

head 1994; Stauffer et al. 1996; Jackson 1999).

Overexploited populations of flathead catfish have

been characterized by the presence of large num-

bers of small fish (400 mm TL) and the absence

of larger individuals. In contrast, populations that

receive little harvest pressure possess a more uni-form length-frequency distribution over a greater

range of fish length-classes. Hesse (1994) reported

that the percentage of flathead catfish greater than

the legal length limit (457 mm TL) in the highly

exploited Missouri River was less than 5% be-

tween 1974 and 1993. In contrast, greater than

25% of flathead catfish collected in the lightly ex-

ploited Flint River, Georgia, were greater than this

length (Quinn 1989). Flathead catfish greater than

500 mm TL represented 47% of fish sampled in

the Minnesota River (Stauffer et al. 1996), whereexploitation of flathead catfish has been estimated

at less than 1% (Leitch and Baltezore 1987). Al-

though a large proportion (89%) of the flathead

catfish collected in the lower St. Joseph River were

less than 400 mm, the relative frequency of fish

greater than this length and the presence of fish as

old as age 17 suggest high survival and a low rate

of exploitation in this system. However, the sharp

decline in abundance between ages 3 and 4, which

corresponds to the age at which most fish were

recruited to the harvestable fishery (381 mm

TL), suggests that flathead catfish do experience

some harvest pressure in the lower St. Joseph Riv-

er.

The RSD estimates of flathead catfish in the low-

er St. Joseph River were within the range reported

for other populations of this species (Table 1).

Quinn (1989) reported the RSD-Q of flathead cat-

fish in the Flint River fishery to be 57%, whereas

fish in the Cape Fear River had a RSD-Q of 49%

(Ashley and Buff 1986). The proportions of pre-

ferred, memorable, and trophy sizes of fish in the

lower St. Joseph River were also similar to pro-portions reported for these stocks. In other lotic

systems receiving low rates of exploitation, trophy

fish have been found to make up less than 5% of


8/11


TABLE 2.Comparative regression relationships based on mean length-at-age data, mean annual regional surface air

temperature (MAST), and geographic location for flathead catfish populations in 10 U.S. rivers. The MAST data were

based on 19711999 averages published by the National Oceanic and Atmospheric Administration. Regression equations

with common letters were not significantly different (ANCOVA: F 3.59; df 9, 69; P 0.001). Fish older than

age 12 were not included in the analysis because of small sample sizes (N 5 fish) or limited availability among

populations.

River CoordinatesMAST

(C) Regression r2 N P

Minnesota River (Minnesota)a 44N, 94W 7.5 TL 111.7 69.4 (Age) z 0.96 12 0.0001

St. Joseph River (Michigan)b 42N, 86W 7.5 TL 69.2 73 (Age) z 0.96 12 0.0001

Mississippi River (IowaIllinois)c 41N, 90W 10 TL 98.9 71.7 (Age) z 0.99 11 0.0001

Salt River (Missouri)d 40N, 92W 12.5 TL 34.6 61.7 (Age) z 0.99 9 0.0001

Missouri River (Nebraska)e 40N, 95W 10 TL 43.4 80.5 (Age) z 0.93 7 0.0004

Blue River (Kansas)f 39N, 96W 12.5 TL 46.0 108.4 (Age) y 0.99 7 0.0001

Flint River (Georgia)g 33N, 83W 17.5 TL 147.6 105.3 (Age) y 0.97 7 0.0001

Cape Fear River (North Carolina)h 35N, 79W 15 TL 117.7 101.5 (Age) y 0.97 8 0.0001

Colorado River (ArizonaCalifornia)i 32N, 114W 22.5 TL 6.6 112.9 (Age) y 0.99 9 0.0001

Rio Grande River (Texas)j 30N, 101W 20 TL 72.3 107.9 (Age) y 0.99 7 0.0001

a Stauffer et al. (1996).b This study.c Barnickol and Starrett (1951).d Purkett (1958).e Holz (1969).f Minckley and Deacon (1959).g Quinn (1988).h Guier et al. (1981).i Young and Marsh (1990).j Pate (1980).

flathead catfish populations (Hesse et al. 1978;

Pugibet and Jackson 1991; Insaurralde 1992).

These studies corroborate our results, indicatingthat the size structure of flathead catfish in the

lower St. Joseph River provides further evidence

of low rates of exploitation.

Length-at-age data for flathead catfish in the

lower St. Joseph River were within the range of

growth estimates reported for other midwestern

populations of this species. However, fish growth

was slower than that reported for populations

throughout the southern United States (Table 2).

The growth of fish in our system most closely re-

sembled the growth of flathead catfish in the Mis-

sissippi River, IowaIllinois, and the Minnesota

River, whereas the average growth rate of flathead

catfish in southern systems was 35% greater than

that of St. Joseph River fish (Table 2). Similar

latitudinal trends in growth have been reported for

other fish species (Power and McKinley 1997;

Braaten and Guy 2002). Our results suggest that

the thermal gradient and length of the growing

season associated with geographic location are re-

liable indicators of flathead catfish growth rates.

The declines in annual growth rates observed

for flathead catfish in the lower St. Joseph Riverhave been observed for other flathead catfish

stocks throughout the species range. Purkett

(1958) found that the mean annual growth incre-

ment of age-14 flathead catfish was 68 mm/year,

while the growth of fish older than age 4 decreased

by 26%. Stauffer et al. (1996) estimated that thegrowth rate of age-15 flathead catfish in the Min-

nesota River averaged 120 mm/year. In contrast,

the mean annual growth increment for fish aged

610 in this system decreased to 50 mm/year,

whereas the growth of fish older than age 10 av-

eraged 34 mm/year. Mayhew (1969) reported that

annual growth increments were greater than 120

mm/year for fish younger than age 3, whereas the

growth of older age-classes declined to less than

40 mm/year by age 7. Previous studies have de-

termined that flathead catfish become reproduc-

tively mature between ages 3 and 5 (Barnickol and

Starrett 1951; Minckley and Deacon 1959; Turner

and Summerfelt 1971). Although the onset of re-

productive maturity in flathead catfish may con-

tribute to declines in the annual growth rate, the

variation among populations suggests that addi-

tional factors (e.g., population density, prey avail-

ability, etc.) may also affect annual growth on a

system-specific basis.

The relationship between Wr and TL of flathead

catfish in the lower St. Joseph River contrasted

with results reported for other populations of flat-head catfish. Guier et al. (1984) and Lemmons

(1995) found that the condition of flathead catfish

increased with body length. Although food habits


9/11


and relative abundance of prey types for flathead

catfish were not examined in our study, the decline

in Wr with increasing length may indicate a lack

of adequate prey sizes for larger fish. Adult flat-

head catfish are known to be highly piscivorous(Minckley and Deacon 1959; Turner and Sum-

merfelt 1971; Jackson 1999); forage fish make up

as much as 95% of the diet of fish greater than

600 mm TL (Weller and Robbins 1999). Studies

by Brown and Dendy (1961) and Haas et al. (2001)

found a positive relationship between prey size and

the TL of flathead catfish, suggesting that larger

fish selected larger forage. The high relative abun-

dance of large flathead catfish in the lower St. Jo-

seph River, which results from low exploitation

and high survival, may limit the availability of

prey items selected by these fish. Future studiesshould assess flathead catfish diet and the popu-

lation structure and proportional stock densities of

forage fishes to provide a better understanding of

predatorprey dynamics in this system.

The results of our study indicate that flathead

catfish in the lower St. Joseph River are compa-

rable in biological attributes and stock dynamics

to populations throughout the midwestern United

States. The survival rate, size structure, and age

distribution of flathead catfish in the lower St. Jo-

seph River were comparable to those of stocksknown to receive low exploitation rates, suggest-

ing that harvest pressure is relatively low in this

system. However, little information exists regard-

ing system-specific biotic and abiotic factors that

influence the stock characteristics and population

dynamics of flathead catfish. For example, future

studies should attempt to determine factors that

influence the abundance, growth, and condition of

flathead catfish. As angler attitudes and interests

change regarding this species, efforts must be un-

dertaken to quantify exploitation rates and sub-

sequent impacts on flathead catfish survival and

population structure. Studies that examine flathead

catfish recruitment would increase our understand-

ing of stock structure and describe annual vari-

ability in year-class strength and recruitment dy-

namics. These data would provide fisheries man-

agers with the information necessary to develop

appropriate management strategies for flathead

catfish populations throughout the species geo-

graphic range.

Acknowledgments

We would like to thank S. Donabauer, L. Zurita,

R. Wyld, A. Gima, and S. Reed for their assistance

with field data collections. J. Wesley and J. Dexter,

Michigan Department of Natural Resources, Fish-

eries Division, provided assistance with project

development and sampling equipment. Construc-

tive comments on earlier drafts of this manuscript

by A. Benson, M. Hansen, P. Hrodey, R. Swihart,H. Weeks, and two anonymous reviewers im-

proved this manuscript. Funding for this project

was provided by the Great Lakes Fishery Trust and

Purdue University Department of Forestry and

Natural Resources. This research was approved for

publication as manuscript number 17405 by the

Purdue University Agricultural Research Pro-

grams.

References

Ashley, K. W., and B. Buff. 1986. Determination of

current food habits of flathead catfish in the CapeFear River. North Carolina Wildlife Resources

Commission, Raleigh.

Barnickol, P. G., and W. C. Starrett. 1951. Commercial

and sport fishes of the Mississippi River between

Caruthersville, Missouri, and Dubuque, Iowa. Bul-

letin of the Illinois Natural History Survey 25:267

350.

Bister, T. J., D. W. Willis, M. L. Brown, S. M. Jordan,

R. M. Neumann, M. C. Quist, and C. S. Guy. 2000.

Proposed standard weight (Ws) equations and stan-

dard length categories for 18 warmwater nongame

and riverine fish species. North American Journal

of Fisheries Management 20:570574.Braaten, P. J., and C. S. Guy. 2002. Life history attri-

butes of fishes along the latitudinal gradient of the

Missouri River. Transactions of the American Fish-

eries Society 131:931945.

Brown, B. E., and J. S. Dendy. 1961. Observations on

the food habits of the flathead and blue catfish in

Alabama. Proceedings of the Annual Conference

Southeastern Association of Game and Fish Com-

missioners 15(1961):210222.

Clady, M. D., D. E. Campbell, and G. P. Cooper. 1975.

Effects of trophy angling on unexploited popula-

tions of smallmouth bass. Pages 425429 in R. H.

Stroud and H. Clepper, editors. Black bass ecologyand management. Sport Fishing Institute, Washing-

ton, D.C.

Crumpton, J. E., M. M. Hale, and D. J. Renfro. 1987.

Aging of three species of Florida catfish utilizing

pectoral spine sites and otoliths. Proceedings of the

Annual Conference Southeastern Association of

Fish and Wildlife Agencies 38(1984):335341.

Cunningham, K. K. 1995. Comparison of stationary and

mobile electrofishing for sampling flathead catfish.

North American Journal of Fisheries Management

15:515517.

Cunningham, K. K. 2000. Influence of environmental

variables on flathead catfish electrofishing catch.

Proceedings of the Annual Conference Southeastern

Association of Fish and Wildlife Agencies

52(1998):125135.

Daugherty, D. J., and T. M. Sutton. 2005. Seasonal


10/11


movement patterns, habitat use, and home range of

flathead catfish in the lower St. Joseph River, Mich-

igan. North American Journal of Fisheries Man-

agement 25:256269.

DeVries, D. R., and R. V. Frie. 1996. Determination of

age and growth. Pages 483512 in B. R. Murphyand D. W. Willis, editors. Fisheries techniques, 2nd

edition. American Fisheries Society, Bethesda,

Maryland.

Gerhardt, D. R., and W. A. Hubert. 1991. Population

dynamics of a lightly exploited channel catfish stock

in the Powder River system, WyomingMontana.


11:200205.

Gilliland, E. 1988. Telephone, microelectronic, and

generator-powered electrofishing gear for collecting

flathead catfish. Proceedings of the Annual Con-

ference Southeastern Association of Fish and Wild-

life Agencies 41(1987):221229.Goedde, L. E., and D. W. Coble. 1981. Effects of fishing

on a previously fished and an unfished warmwater

fish community in two Wisconsin lakes. Transac-

tions of the American Fisheries Society 110:594

603.

Grussing, M. D., D. R. DeVries, and R. A. Wright. 2001.

Stock characteristics and habitat use of catfishes in

regulated section of four Alabama Rivers. Proceed-

ings of the Annual Conference Southeastern As-

sociation of Fish and Wildlife Agencies 53(1999):

1534.

Guier, C. R., L. E. Nichols, and R. T. Rachels. 1984.

Biological investigation of flathead catfish in the

Cape Fear River. Proceedings of the Annual Con-

ference Southeastern Association of Fish and Wild-

life Agencies 35(1981):607621.

Haas, J. J., L. A. Jahn, and R. Hilsabeck. 2001. Diets

of introduced flathead catfish (Pylodictis olivaris) in

an Illinois reservoir. Journal of Freshwater Ecology

16:551555.

Hesse, L. W. 1994. The status of Nebraska fishes in the

Missouri River, 4. Flathead catfish, Pylodictis oli-

varis, and blue catfish, Ictalurus furcatus (Ictaluri-

dae). Transactions of the Nebraska Academy of Sci-

ences 21:8998.

Hesse, L. W., C. R. Wallace, and L. Lehman. 1978. Fish-

es of the channelized Missouri River: agegrowth,

lengthfrequency, lengthweight, coefficient of

condition, catch curves and mortality of 25 species

of channelized Missouri River fishes. Nebraska

Game and Parks Commission, Technical Series

Number 4, Norfolk.

Hubbs, C. L., and K. F. Lagler. 1947. Fishes of the Great

Lakes region. Cranbrook Institute of Science, Bul-

letin 26, Bloomfield Hills, Michigan.

Insaurralde, M. S. 1992. Environmental characteristics

associated with flathead catfish in four Mississippi

streams. Doctoral dissertation. Mississippi State

University, Mississippi State.

Jackson, D. C. 1999. Flathead catfish: biology, fisheries,

and management. Pages 2335 in E. R. Irwin, W.

A. Hubert, C. F. Rabeni, H. L. Schramm, Jr., and T.

Coon, editors. Catfish 2000: proceedings of the in-

ternational ictalurid symposium. American Fisher-

ies Society, Symposium 24, Bethesda, Maryland.

Jenkins, R. E., and N. M. Burkhead. 1994. Freshwater

fishes of Virginia. American Fisheries Society, Be-

thesda, Maryland.

Kubeny, S. 1992. Population characteristics and habitatselection of channel catfish (Ictalurus punctatus) in

the lower James River, South Dakota. Masters the-

sis. South Dakota State University, Brookings.

Layher, W. G. 1981. Comparison of annulus counts of

pectoral and dorsal spines in flathead catfish. Pro-

gressive Fish-Culturist 43:218219.

Layher, W. G., and R. J. Boles. 1979. Growth of Py-

lodictis olivaris (Rafinesque) in a Kansas Reservoir.

Transactions of the Kansas Academy of Sciences

82:3648.

Lee, L. A., and J. W. Terrell. 1987. Habitat suitability

index models: flathead catfish. U.S. Fish and Wild-

life Service, Biological Report 82, Washington,D.C.

Leitch, J. A., and J. F. Baltezore. 1987. Attitudes of

Minnesota anglers. Final report by the Center for

Environmental Studies, North Dakota State Uni-

versity, to the Minnesota Department of Natural Re-

sources, Division of Fish and Wildlife, St. Paul.

Lemmons, R. P. 1995. Habitat and populational char-

acteristics of flathead catfish in six Oklahoma

stream systems. Masters thesis. University of

Oklahoma, Norman.

Marsh, P. C., W. L. Minckley, and K. L. Young. 1988.

Commercial potential of flathead catfish in the Col-

orado, Gila, Salt, and Verde rivers, Arizona. Ari-zona Fish and Game Department, Final Report,

Phoenix.

Mayhew, J. K. 1969. Age and growth of flathead catfish

in the Des Moines River, Iowa. Transactions of the

American Fisheries Society 98:118121.

Minckley, W. L., and J. E. Deacon. 1959. Biology of

the flathead catfish in Kansas. Transactions of the

American Fisheries Society 88:344355.

Morris, L. A., and P. F. Novak. 1968. The telephone

generator as an electrofishing tool. Progressive

Fish-Culturist 30:110112.

Moss, J. L., and W. H. Tucker. 1989. Growth and harvest

of flathead catfish in three Alabama public lakes.Proceedings of the Annual Conference Southeastern


42(1988):149156.

Munger, C. R., G. R. Wilde, and B. J. Follis. 1994.

Flathead catfish age and size at maturation in Texas.


14:403408.

Nash, M. K., and E. R. Irwin. 1999. Use of otoliths

versus pectoral spines for aging adult flathead cat-

fish. Pages 309316 in E. R. Irwin, W. A. Hubert,

C. F. Rabeni, H. L. Schramm, Jr., and T. Coon, ed-

itors. Catfish 2000: proceedings of the international

ictalurid symposium. American Fisheries Society,Symposium 24, Bethesda, Maryland.

Paragamian, V. L. 1990. Characteristics of channel cat-

fish populations in streams and rivers of Iowa with


11/11


varying habitats. Journal of the Iowa Academy of

Science 97:3745.

Pisano, M. S., M. J. Inansci, and W. L. Minckley. 1983.

Age and growth and lengthweight relationship for

flathead catfish, Pylodictis olivaris, from Coachella

Canal, southeastern California. California Fish andGame 69:124128.

Power, M., and R. S. McKinley. 1997. Latitudinal var-

iation in lake sturgeon size as related to the thermal

opportunity for growth. Transactions of the Amer-

ican Fisheries Society 126:549558.

Pugibet, E. E., and D. C. Jackson. 1991. Sampling flat-

head catfish in small streams. Proceedings of the



Purkett, C. A., Jr. 1958. Growth of the fishes in the Salt

River, Missouri. Transactions of the American Fish-

eries Society 87:116131.

Quinn, S. P. 1988. Investigations into the biology of theflathead catfish (Pylodictis olivaris) in the lower

Flint River and the promotion of this species as a

fisheries resource for the Flint River fishermen.

Georgia Department of Natural Resources, Game

and Fish Division, Federal Aid in Sport Fish Res-

toration, Project F-28- 15, Atlanta.

Quinn, S. P. 1989. Flathead catfish abundance and

growth in the Flint River, Georgia. Proceedings of

the Annual Conference Southeastern Association of


Quinn, S. P. 1993. Development of a multiuse fishery

for flathead catfish. North American Journal of Fish-

eries Management 13:594599.Ricker, W. E. 1975. Computation and interpretation of

biological statistics of fish populations. Fisheries

Research Board of Canada Bulletin 191.

Robson, D. S., and D. G. Chapman. 1961. Catch curves

and mortality rates. Transactions of the American

Fisheries Society 90:181189.

Schnabel, Z. E. 1938. The estimation of the total fish

population of a lake. American Mathematical

Monographs 45:348368.

Stauffer, K. W., and B. D. Koenen. 1999. Comparison

of methods for sampling flathead catfish in the Min-

nesota River. Pages 329339 in E. R. Irwin, W. A.

Hubert, C. F. Rabeni, H. L. Schramm, Jr., and T.




Stauffer, K. W., R. C. Binder, B. C. Chapman, and B.

D. Koenen. 1996. Population characteristics and

sampling methods of flathead catfish Pylodictis oli-

varis in the Minnesota River. Minnesota Department

of Natural Resources, Division of Fish and Wildlife,

Section of Fisheries, Study IV, Job 389, St. Paul.

Summers, G. L. 1986. Oklahoma anglers opinion survey

1985. Oklahoma Department of Wildlife Conser-vation, Federal Aid in Sport Fisheries Restoration,

Project F-37-R, Bulletin 18, Oklahoma City.

Tondreau, R. 1988. A population study of flathead cat-

fish in the channelized Missouri River near Sioux

City, Iowa. Iowa Department of Natural Resources,

Final Report, Sioux City.

Topp, D. H., H. Drewes, M. Henry, G. Huberty, and P.

Jacobson. 1994. Assessment of the Red River fish-

ery, with special emphasis on channel catfish. Min-

nesota Department of Natural Resources, Study IV,

Job 242 Completion Report, St. Paul.

Turner, P. R. 1982. Procedures for age determination

and growth rate calculations of flathead catfish. Pro-

ceedings of the Annual Conference Southeastern


34(1980):253262.

Turner, P. R., and R. C. Summerfelt. 1971. Food habits

of adult flathead catfish, Pylodictis olivaris (Rafin-

esque), in Oklahoma reservoirs. Proceedings of the


Game and Fish Commissioners 24(1970):387401.

Van Den Avyle, M. J. 1993. Dynamics of exploited fish

populations. Pages 105135 in C. C. Kohler and W.

A. Hubert, editors. Inland fisheries management in

North America. American Fisheries Society, Be-

thesda, Maryland.

Vokoun, J. C., and C. F. Rabeni. 1999. Catfish samplingin rivers and streams: a review of strategies, gears,

and methods. Pages 271286 in E. R. Irwin, W. A.

Hubert, C. F. Rabeni, H. L. Schramm, Jr., and T.




Weller, R. R., and C. Robbins. 1999. Food habits of

flathead catfish in the Altamaha River System,

Georgia. Proceedings of the Annual Conference

Southeastern Association of Fish and Wildlife

Agencies 53(1999):3441.

Wesley, J. K., and J. E. Duffy. 1999. St. Joseph River

assessment. Michigan Department of Natural Re-sources, Fisheries Division, Special Report 24, Ann

Arbor.

Young, K. L., and P. C. Marsh. 1990. Age and growth

of flathead catfish in four southwestern rivers. Cal-

ifornia Fish and Game 76:224233.

Cat Fish Stock

Documents

Transcript of Cat Fish Stock