Oklahoma Digital Prairie
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W 2800.7 F532r no.26 1992/94 c.3 OKLAHOMA o FISH RESEARCH AND SURVEYS FOR OKLAHOMA LAKES AND RESERVOIRS FLATHEAD CATFISH ECOLOGY AND POPULATION STRUCTURE IN OKLAHOMA PRAIRIE STREAMS MAY 1, 1992 through FEBRUARY 28, 1994 JOB TITLE: Flathead catrlSh ecology and population structure in Oklahoma prairie streams. CONTRACT PERIOD: May 1, 1992 through February 28, 1994 I. Proeram Narrative Objective Number 26: To determine population structure and associations between biotic and abiotic variables with abundance and distribution of the flathead catfISh, Pylodictis olivaris, in Oklahoma prairie streams. II. Introduction: The flathead catfISh Pylodictis olivaris is native to the larger rivers of the Mississippi, Missouri, and Ohio basins from the Great Lakes, Gulf of Mexico coastal plain, and Rio Grande drainage into northeastern Mexico (Lee et al. 1980; Young and Marsh 1990; Quinn 1991). Non-native distribution from introductions and subsequent movements includes Florida, South Carolina, Idaho, Oregon, Washington, Arizona and California (Lee and Terrell 1987; Young and Marsh 1990). Flathead catfISh are an important fIShery resource throughout much of its range (Young and Marsh 1990; Pugibet and Jackson 1991), due to its fighting ability (McCoy 1955), large size (Quinn 1991), and palatable flesh (Jordan and Evermann 1920). Investigations of flathead catfISh populations from lotic waters have primarily centered around age and growth, population structure, movement, and food habits (Funk 1955; Cross and Hasting 1956; Minckley and Deacon 1959; Mayhew 1969; Cross and Hastings 1956; Guier et al 1981; Weeks and Combs 1981; Dames et al. 1989; Quinn 1988; Young and Marsh 1990; Coon and Dames 1991; Quinn 1991; Insaurralde 1992). Major accounts of flathead catfISh habitat use have typically been descriptive (Minckley and Deacon 1959; Cross 1967; Miller and Robison 1973; Pflieger 1975; but see Coon and Dames 1991; Insaurralde 1992) and have not discussed the habitat requirements of young-of-year flathead catfISh in streams lacking riffles (Lee and Terrell 1987). In Oklahoma, the flathead catfISh is a highly preferred sport species (Summers 1990), reaching a weight of 48 kilograms. It is typically described as being common in larger lakes and streams (Miller and Robison 1973). Based on a 1990 survey of state game wardens (unpublished data, Oklahoma Department of Wildlife Conservation) it was suspected that significant fIShing pressure is being placed on flathead catfISh stocks in rivers and streams. Methods employed include rod and reel, trotline, limb line, bank sets, and noodling. In 1991 the Oklahoma Department of Wildlife Conservation (ODWC) imposed a statewide 508 mm minimum length limit to an existing daily creel limit of 10 flathead catfISh. It was reasoned the additional limits were warranted based upon the popularity of the species. Despite its popularity, little ecological information is available on stocks of flathead catfISh in Oklahoma (Gilliland 1987) or other paris of the Southwest (Young and Marsh 1990). The available information concerning Oklahoma flathead catfISh stocks is primarily based on reservoir sampling (McCoy 1955; Jenkins 1954; Turner and Summerfelt 1971a; Turner and Summerfelt 1971b; Weeks and Combs 1981; Gilliland 1988). Flathead catfish may be as vulnerable to overharvest as other species, such as largemouth bass (Quinn 1991). The purpose of this study was to determine habitat use, population structure, and length-weight relationships of the flathead catfISh in selected Oklahoma prairie stream systems. Electrofishine survey.-- Road surveys of six Oklahoma prairie streams for areas of suitable boat access and suitable electrofishing locations were conducted from 19 May to 9 June 1992. During these road surveys angler access to these streams from public roads was also recorded. From 18 June 1992 to 16 March 1993, flathead catflSh were sampled from Oklahoma prairie stream systems. Six streams were sampled by electrofishing from 18 reach access locations chosen during the road surveys (Table 1). One hundred forty-five sites were electroflShed for flathead catflSh abundance and habitat relationships. ElectroflShing was conducted with a Smith-Root 5.0, gas powered pulsator (GPP). The GPP was mounted in a 4.3 m, flat bottom, aluminum boat. Eight anodes, constructed of 100 cm long stainless steel cable, were attached to a ring 50 cm in diameter. The ring was mounted on a 180 cm boom, extending from the front of the boat. The hull of the boat served as the cathode. Effective electrofishing settings encountered for flathead catfish were 15 pulses per second (pps) at 2-9 amps. These settings were also appeared effective for electrofishing blue catflSh Ictalurns furcatus. A site was electrofished for 3 minutes with the boat stationary, while a second boat with two personnel was used to collect surfacing flathead catfish. In addition to the 145 stationary electroflShing sites, other areas within a reach were electroflShed for flathead catfish with the GPP boat moving. Estimates of forage fish were made within the reach sections by electroflShing with a pulse setting of 120 pps. Other flSh species surfacing during electroflShing efforts were recorded. Also, presence of anglers at time of sampling was recorded. Twenty-six variables were recorded at each of the 145 stationary electrofishing sites along with 8 variables recorded at the reach level. Due to daily fluctuations, water temperature was initially eliminated from the analyses. Based on preliminary correlation analyses, twenty of the original variables were chosen for the final analyses (Table 2). Continuous variables were log-transformed (JOgIO(Nor N+ 1» to meet the assumptions of nonnality and constant variance (Sokal and Rohlf 1981). The variables and transfonnations (N+ 1) were: average depth (measured with a LCR depth finder), average width, number of debris piles (N+ 1), number of isolated logs (N+ 1), number of blue catfish (N+l), altitude (obtained from 1:24,000 scale topographic maps), conductivity, secchi depth, Julian date (N+ 1), (for the following categorical variables: 0 = not a maj or component; 1 = was a major component) current, slope, shade, stability, mud, clay, sand, boulders/riprap, submerged debris (estimated using a LCR depth finder), angler pressure (bank/trotlines), and shad abundance. Flathead catfish collected during stationary and moving electrofishing were measured for total length (mm), weighed (g) and released. Flathead catfISh observed surfacing, but not collected, were recorded with an estimate of total length. For analyses the observed catfISh were subsequently placed into 3 broad length groups: ~349 mm, 350-509 mm, ~510 mm. Relationships were investigated for 112 stationary electrofishing sites from 19 reach samples. Sites with no flathead catfISh were eliminated since absence of fISh during electroflShing could be due to reasons not associated with the variables recorded. For one reach that was sampled twice (E18 and EI8a), both samples were included since they were separated by substantial time (57 days) and the environmental conditions had changed drastically (personal observation). Prior to analyses flathead catfISh were classified into two groups: juveniles « 350 mm) and adults ~350 mm), based on the minimum maturity length for flathead catfish in rivers (Turner and Summerfelt 1971a). The abundance data were log-transformed (lOgIO(N+ 1)) prior to analyses to improve homogeneity of variances and normalities (Sokal and Rohlf 1981). All categorical data were included in the analyses as dummy variables generated by effects coding (for two groups = -1, + 1). This method produces parameter estimates that are differences from both groups taken as an aggregate, since neither group is designated as a reference group (Cohen and Cohen 1983). Relationships between juvenile and adult abundances and habitat use were evaluated by forward stepwise multiple linear regression. Because the 112 sites were obtained from 19 reach samples, they cannot be considered statistically independent. Thus, we used a method that analyzes for within-reach variation after removing the effect of reaches (Robertson et aI. 1993). This was accomplished by initially forcing into the model effects coded dummy variables for each reach sample. This produced reach coefficients (RCs) that characterized between-reach differences. We then analyzed for between-reach variation by entering as the dependent variable the RCs against the variables recorded for each reach, along with the mean of variables recorded at each site. During all analyses alpha-to-enter and alpha-to-remove was set at 0.15. Only variables with P ~ 0.05 were included in the final models. Juvenile and adult abundance data were compared among reaches and rivers using a one-way analysis of variance (ANOVA). Post hoc pairwise multiple comparisons were made using the Tukey-Kramer HSD test. Population structure data was analyzed after combining lengths of flathead catfISh collected into the broad length categories of observed flathead catfish ~349, 350-509, L510 mm). Percentages of fish in each broad length group were compared between rivers, using pairwise G-tests of independence (Sokal and Rohlf 1981). To control the tablewide alpha level, probabilities were adjusted using the sequential Bonferroni technique (Rice 1989). Flathead catfish size structure was also analyzed using the length categorization system presented by Gabelhouse (1984). The indices proportional stock density (PSD) and Relative stock density (RSD)