Efficiency of Baited Hoop Nets for Sampling Catfish in Southeastern U.S. Small Impoundments

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1 American Fisheries Society Symposium 77: , by the American Fisheries Society Efficiency of Baited Hoop Nets for Sampling Catfish in Southeastern U.S. Small Impoundments BENJAMIN C. WALLACE 1 AND DANIEL M. WEAVER North Carolina Cooperative Fish and Wildlife Research Unit, Department of Biology North Carolina State University, Campus Box 7617 Raleigh, North Carolina 27695, USA THOMAS J. KWAK* U.S. Geological Survey, North Carolina Cooperative Fish and Wildlife Research Unit Department of Biology, North Carolina State University, Campus Box 7617 Raleigh, North Carolina 27695, USA Abstract. Many U.S. natural resource agencies stock catfish (Ictaluridae) into small impoundments to provide recreational fishing opportunities. However, effective standardized methods for sampling catfish in small impoundments have not been developed for wide application, particularly in the southeastern United States. We evaluated the efficiency of three bait treatments (i.e., soybean cake, sunflower cake, and no bait) of tandem hoop nets in two North Carolina small impoundments during the fall of 2008 and spring of 2009 in a factorial experimental design. The impoundments were stocked with catchable-size channel catfish Ictalurus punctatus at contrastingly low (5.5 fish/ha) and high (90.0 fish/ha) rates prior to our sampling. Nets baited with soybean cake consistently sampled more channel catfish than any other treatment. Channel catfish catch ranged as high as 3,251 fish per net series during the fall in nets baited with soybean cake in the intensively stocked impoundment and was up to 8.5 and 15.3 times higher during the fall than in the spring in each impoundment. Nets baited with soybean cake sampled significantly (12 and 24 times) more channel catfish than those with no bait in the two impoundments. These trends did not occur among other catfish species. Nonictalurid fish and turtle catch was higher during spring compared to that of fall, corresponding with low channel catfish catches. Our results indicate that tandem hoop nets baited with soybean cake during the fall is a more efficient method for sampling channel catfish compared to nets baited with sunflower cake or no bait in spring or fall. Our findings validate this technique for application in southeastern U.S. small impoundments to assess catfish abundance to guide management and evaluate the success of catfish stocking programs. Introduction Catfishes (Ictaluridae) are the second most sought after sport fish throughout the United States behind sunfishes (Centrarchidae; USDIFWS et al. 2006). In 2006, approximately 7 million anglers fished for catfishes and bullheads for an average of 14 d of the year. In 1998, 60% of North American fisheries agencies considered catfishes to be either moderately or highly important to anglers, with the highest importance to Midwestern or southern U.S. anglers (Michaletz and * Corresponding author: tkwak@ncsu.edu 1 Present address: Iowa Department of Natural Resources, Black Hawk Fish Management District, Lake View, Iowa 51450, USA Dillard 1999). The rising popularity and demand for catfish fisheries in the United States compels effective fishery assessment and management to ensure sustainable quality angling opportunities. Despite their popularity among anglers, only 34 states manage specifically for catfish, and most of these efforts are directed toward channel catfish Ictalurus punctatus in small impoundments and involve some level of stocking (Michaletz and Dillard 1999). In 1998, 33 states reported that they conduct routine stocking of catfish with channel catfish most commonly stocked. Many of these stockings are to support put-and-take fisheries, where catfish are stocked at a length that is readily available for harvest. In 581

2 582 WALLACE ET AL. some states, channel catfish are stocked at a standard rate regardless of the amount of fishing pressure and harvest each lake receives (Mitzner 1999). As a result, lakes with low fishing pressure may experience an overaccumulation of channel catfish. Hill (1984) found that impoundments in Iowa that received maintenance stockings of channel catfish became overpopulated, resulting in slow growth of the fish. Proper assessment of a lake s fish population is required to ensure that cost benefit ratios of stocked fish are high enough to justify stocking. However, in surveys of state fisheries agencies, only eight states had found a satisfactory sampling method for channel catfish (Vanderford 1984), and Michaletz and Dillard (1999) concluded that effective sampling methods for catfishes remain elusive, especially for sampling in small impoundments and reservoirs. The lack of adequate sampling and population assessment methods has been a critical limitation to effective management of catfish fisheries. Until the past decade, gill netting and electrofishing have been considered the most common techniques employed to sample catfish populations (Michaletz and Dillard 1999). Since then, numerous evaluations of the effectiveness of different sampling gears for catfish have been conducted in both lotic and lentic systems (e.g., Robinson 1999; Sullivan and Gale 1999; Vokoun and Rabeni 1999; Michaletz and Sullivan 2002; Flammang and Schultz 2007). Among these evaluated techniques, baited hoop nets have been successfully used to estimate age and growth, movement, size structure, and abundance expressed as catch per unit effort of channel catfish populations (Hubert 1996; Vokoun and Rabeni 1999). Baited tandem hoop nets yielded channel catfish catch rates up to 5.6 times greater than those of experimental gill nets based upon personnel hours expended (Sullivan and Gale 1999). Furthermore, they were found to be effective for sampling channel catfish populations with very low densities with limited bycatch mortality, contrary to results associated with gill nets (Michaletz and Sullivan 2002). A study in Iowa concluded that channel catfish were sampled with the least amount of effort using tandem hoop nets baited with soybean cake during summer and fall (Flammang and Schultz 2007). However, these evaluations of tandem hoop nets were all conducted in Midwestern states, and no such gear evaluations for channel catfish sampling have been conducted in the southeastern United States where catfish are important to anglers and fisheries management agencies. To our knowledge, baited tandem hoop nets have not been widely used in the southeastern United States to sample catfish populations in small impoundments, nor has the technique been systematically evaluated for its efficiency in the region. In light of recent studies demonstrating the utility of baited tandem hoop nets in Midwestern U.S. water bodies (e.g., Sullivan and Gale 1999; Michaletz and Sullivan 2002; Flammang and Schultz 2007), an evaluation of the efficiency of baited tandem hoop nets in southeastern U.S. small impoundments could enhance the assessment, management, and understanding of catfish fisheries in the region. The identification of suitable catfish sampling techniques is especially needed to guide stocking rates and management of the numerous put-andtake channel catfish fisheries designed to create urban fishing opportunities. The goal of our study was to determine the efficiency of baited tandem hoop nets for sampling catfishes in southeastern U.S. small impoundments. Specifically, we estimated the sampling efficiency of this gear type by catch rate and examined the effects of season, bait type, and catfish population density on efficiency. Study Sites Methods We selected two small impoundments located in the Piedmont physiographic region of North Carolina to evaluate the efficiency of baited tandem hoop nets for sampling catfish. The water bodies were selected to represent typical channel catfish put-and-take fisheries managed by the North Carolina Wildlife Resources Commission (NCWRC) to provide fishing opportunities for urban anglers. Additionally, these impoundments represented widely differing stocking rates and densities of channel catfish for comparison. is a 36-ha impoundment of Walnut Creek, a tributary of the Neuse River, located in Raleigh, North Carolina. Currently, the lake is jointly managed by the NCWRC and North Carolina State University (NCSU). In 2006, the NCWRC and NCSU conducted a comprehensive fish community assessment and developed a lake management plan (NCWRC 2006). Among the various sampling gears used in the 2006 fish assessment (two gill nets, eight trap nets, four 200-m electrofishing transects, and eight seine hauls), only 1 channel catfish was sampled along with 58 other catfish individuals, including blue catfish I. furcatus, white catfish I. catus, brown bullhead Ameiurus nebulosus, and yellow bullhead A. natalis. was historically

3 HOOP-NET SAMPLING EFFICIENCY 583 closed to fishing, but following the 2006 assessment and development of the lake management plan, it was opened to recreational fishing in Since then, receives annual stockings of 200 channel catfish (5.5 fish/ha; 200 to 300 mm total length [TL]). During summer 2008, the fish community assessment was repeated applying the same gear types and effort as the 2006 assessment, and the only catfish species sampled were brown bullhead and yellow bullhead. is a 40-ha impoundment located in Holly Springs, North Carolina, that impounds Basal Creek, a stream in the Neuse River drainage basin. is managed by the NCWRC as a Community Fishing Program (CFP) lake and, as a result, receives annual stockings of 3,600 channel catfish (90.0 fish/ha; 200 to 330 mm TL). Community Fishing Program lakes are routinely sampled by the NCWRC using electrofishing and trap nets to target sunfish species. However those surveys fail to sample adequate numbers of catfish to provide information on population density and size structure (B. J. McRae, North Carolina Wildlife Resources Commission, personal communication). Field Sampling Three series of baited, tandem hoop nets were used to sample catfish in and. A single series of hoop nets consisted of three hoop nets connected by bridles (Michaletz and Sullivan 2002; Flammang and Schultz 2007). Each hoop net consisted of 25.4 mm bar mesh and seven hoops ranging from 53.3 to 76.2 cm in diameter. Throats were placed on the second and fourth hoop of each net. Weights were placed at the openings of the first and second nets, as well as the cod end of the third net. A buoy and line were attached at the opening of the first net to identify the location of each set during sampling. We fished the gear described above in a factorial experimental design as three successive experimental treatments in each lake, varying the use of bait within nets, during late October and early November 2008 (fall) and May 2009 (spring). The first treatment consisted of three series of hoop nets with no bait, which served as a control. The second treatment was three series of hoop nets baited with soybean cake, and the third consisted of the same nets baited with sunflower cake. Each series was set parallel to the shoreline to avoid sinking into deeper water and to ensure that each net in the series was set at the same depth (Flammang and Schultz 2007). Each of the three series was fished for 72 h (Michaletz and Sullivan 2002; Flammang and Schultz 2007). Treatments were applied successively to minimize any temporal effects due to water temperature. Sampling sites within each lake were chosen randomly within a depth stratum of 1 6 m. A Yellow Springs Instruments meter (model 85) was used to measure benthic dissolved oxygen at each sampling location to ensure that it exceeded 1.0 mg/l, the lower tolerance limit for channel catfish (Hubert 1999). The same sampling sites were used for the control and soybean cake treatments, as no residual bait would remain after the control treatment. New sampling sites were selected for the sunflower cake treatment to avoid any bias that may result from residual soybean cake left in the area. All catfish collected from each treatment were identified to species, measured for total length to the nearest millimeter, and weighed to the nearest gram. Nonictalurid fish catch were also identified to species, measured, and weighed. In instances where large numbers of fish were collected, a subsample of 50 fish of each species was measured and weighed and remaining fish were counted. Any turtles captured were identified and counted. Instances of observed acute mortality of fish and turtles were recorded, and all live fish and turtles were released back into the impoundment away from the sampling site. Statistical Analysis We analyzed our catch data using a series of threefactor analyses of variance (ANOVA) as a factorial design. Factors included lake, season, and bait type. Our dependent variables included total catch by number for (1) channel catfish, (2) other catfish species (i.e., blue catfish, white catfish, and bullheads), (3) other fish species (i.e., nonictalurids), (4) total fish, and (5) turtles. We examined Tukey HSD (honestly significant difference) multiple contrasts for any statistically significant bait type main effect or interactions between factors. Results Among parameters examined, hoop-net catch rates were significantly different between lakes, as well as among seasons and bait types (Tables 1 3). Overall, highest channel catfish catch rates occurred in during the fall in nets baited with soybean cake. Channel catfish catch ranged up to 57 fish per net series in and 3,251 fish per net se-

4 584 WALLACE ET AL. TABLE 1. Mean number and biomass (kg) of channel catfish caught in each hoop net series with no bait, soybean cake, and sunflower cake treatments in and during fall 2008 and spring Number Biomass (kg) Lake or season Mean SE Range Mean SE Range No bait Spring Fall Spring Fall Soybean cake Spring Fall 1, , ,549.8 Spring Fall Sunfl ower cake Spring Fall Spring Fall ries in (Table 1). We sampled as many as 15.3 and 8.5 times more channel catfish in the fall compared to spring, corresponding to 7.4 and 25.8 times more biomass in each hoop-net series for Lake Raleigh and, respectively. Nets baited with soybean cake consistently caught more channel catfish than those baited with sunflower cake or unbaited, and nets baited with sunflower cake caught more channel catfish than those without bait. Nets baited with soybean cake sampled 8.6 and 15.4 times as many channel catfish as those with no bait in the fall and spring in and, similarly, 31.0 and 17.0 times as many channel catfish in the fall and spring in, respectively. We did not observe any clear seasonal or bait type trends corresponding to total catch of other catfish species (Table 2). Significant main effects of lake, season, and bait type, as well as several interactions between these factors, were detected by ANOVA (Table 3). For channel catfish, other fish, and total fish catch by number, we found a significant interaction between bait type and lake, indicating that the three bait types caught fish at different rates between the two lakes. For channel catfish and total fish catch, bait type was identified as a significant main effect by ANOVA. Tukey HSD multiple comparisons found channel catfish and total fish catch using soybean cake significantly higher than that using no bait; no differences were detected between sunflower cake and the other two bait treatments. With respect to treatment interactions, channel catfish and total fish catch from hoop nets fished in with soybean cake was significantly higher than that of all other lake and bait combinations, and no differences were detected among other lake and bait combinations. ANOVA results confirmed a lack of significant lake, season, or bait effect on catch of other catfishes. Catch of nonictalurid fish species and turtles and their mortality varied widely among all treatments examined (lake, season, and bait type). Nonictalurid fish catch was primarily comprised of black crappie Pomoxis nigromaculatus and bluegill Lepomis macrochirus. Turtle catch was primarily common

5 HOOP-NET SAMPLING EFFICIENCY 585 TABLE 2. Mean number and biomass (kg) of other catfish species (excluding channel catfish) caught in each hoop net series with no bait, soybean cake, and sunflower cake treatments in and during fall 2008 and spring Number Biomass (kg) Lake or season Mean SE Range Mean SE Range No bait Spring Fall Spring Fall Soybean cake Spring Fall Spring Fall Sunfl ower cake Spring Fall Spring Fall snapping turtle Chelydra serpentina and yellowbellied slider Trachemys scipta. Nonictalurid fish and turtle catch was higher during the spring compared to the fall, which was confirmed by highly significant ANOVA season main effects (P = 0.003; Table 3). Nonictalurid fish catch averaged 39.5 (11.1 SE) fish per net series during spring versus 15.7 (6.8 SE) fish per net series during fall, among all lakes and baits. Turtle catch averaged 3.9 (1.6 SE) turtles per net series during spring versus 0.2 (0.2 SE) turtles per net series during fall. We observed no acute catfish mortality, and nonictalurid mortality ranged TABLE 3. Factorial analysis of variance (35 total degrees of freedom) results, including main effects and all significant interactions and corresponding P values for the number of channel catfish, other catfish, other fish, total fish, and turtles. Bold font indicates significant P values (P < 0.05). Main effect P Significant interactions Catch parameter Lake Season Bait type Effects P Channel catfish (number/net series) Bait type lake Other catfish (number/net series) Other fish (number/net series) Bait type lake Bait type lake season Total fish (number/net series) Bait type lake Turtles (number/net series) Bait type season 0.025

6 586 WALLACE ET AL. from 0% to 22% and averaged 5.4% (2.3% SE) during spring and 6.5% (3.3% SE) during fall. Turtle mortality ranged 0 100% and was higher during the spring (92.1%, 4.1 SE) associated with higher turtle catch rates, compared to the fall when no turtle mortality was observed. Discussion The results of our study provide valuable insight into developing effective methods for sampling catfish in small impoundments in the southeastern United States. Overall, we sampled the highest numbers of channel catfish during the fall using soybean cake bait with minimal fish and turtle mortality, compared to other treatments. Our catch of other catfish species, however, did not appear to be influenced by bait type or season, suggesting they exhibit different behavior and gear susceptibility. Our results indicate that the number of catfish stocked, and thus fish density, influences the efficiency of tandem hoop nets baited with soybean cake, as indicated by the significant interaction between bait type and lake on channel catfish catch rates. During fall, we sampled an average of 1,628 channel catfish per net series in and 31 channel catfish per net series in using soybean cake. Bass Lake and are similar in surface area and depth; however, is stocked with 18 times more channel catfish than each year. This effect may be related to channel catfish already caught in the nets attracting other conspecifics. This suggests that hoop-net sampling effort may be adjusted depending on the intensity of stocking and existing fish density. In fact, our maximum catch rate of more than 3,200 channel catfish per net series in during fall (Table 1) was rather excessive, requiring substantial effort and personnel time to process. In such cases of high fish density, fishing the gear with no bait or for a reduced duration (e.g., 24 h versus 72 h) may be a practical alternative to attain reasonable population samples. While we did not have an estimate of the true channel catfish population size in either lake sampled, we suggest that our catch represents an index of channel catfish density. Our catch rates of channel catfish differed between lakes, generally corresponding to the level of stocking that each lake receives (e.g., Michaletz and Sullivan 2002). Common fish sampling methods, such as trap nets and boat electrofishing, do not appear to capture adequate sample sizes of catfish in North Carolina small impoundments (McRae, personal communication), which limits inferences on their population size structure, age and growth, and condition, as well as angling pressure. Other studies have found gill nets to be effective for sampling channel catfish (Nelson and Little 1988; Robinson 1999); however, prior gill-net sets on failed to capture channel catfish numbers similar to those we obtained using hoop nets. In addition, high fish mortality associated with gill-net sampling reduces their applicability for sampling stocked catfishes in small impoundments, especially in urban areas, as substantial sampling gear mortality would reduce fish availability to anglers at a direct cost to the agency and may lead to negative public perceptions. We observed no acute catfish mortality, similar to findings of other studies with very low to no channel catfish mortality (Sullivan and Gale 1999; Michaletz and Sullivan 2002). When fishing nets that are completely submerged for 72 h, there is potential for turtle mortality. Turtle catch was lower during fall when hoop nets were baited with soybean cake and channel catfish catches were higher. Turtles are ectotherms and become torpid during fall and winter when water temperatures are too low to maintain normal activity (Buhlman and Vaughan 1991). Although turtles appear to be attracted by soybean cake, more so than sunflower cake or no bait, their reduced activity level in cooler water during the fall likely minimizes their catch in a passive fishing gear. The development of effective sampling methods for catfishes has received much needed attention recently, but their application in southeastern small impoundments has not been adopted and is not a standard sampling protocol. Our study expands the use of baited tandem hoop nets for sampling catfishes in a region where these fisheries are rising in popularity. Management agencies are directing more attention to these fisheries and their constituents. Given the economic expenditures, labor, and effort required to maintain quality angling opportunities, sound management practices based on effective population monitoring will enhance the ability to meet fisheries objectives and goals (Michaletz and Dillard 1999; Arterburn et al. 2002). For example, the NCWRC currently manages 43 community fishing lakes stocked annually with channel catfish as part of their goal to enhance public fishing opportunities for urban residents, especially youth, elderly, and physically challenged individuals (NCWRC 1998), similar to programs in other southeastern states. A creel

7 HOOP-NET SAMPLING EFFICIENCY 587 survey conducted by the NCWRC found that 84% of anglers were satisfied with the fishing in CFP lakes and that 97% planned to fish there again (R. K. Wong and C. T. Waters, North Carolina Wildlife Resources Commission, unpublished data). From 2005 to 2009, NCWRC stocked an average of 190,500 channel catfish weighing 26,048 total kilograms per year in those 43 small impoundments (NCWRC 2009). Mean annual stocking per lake was 4,600 hatchery-reared catchable-size channel catfish ( mm TL), but stocking rates for individual lakes were adjusted according to lake area. A cursory search of state fisheries agencies Web sites revealed that other southeastern states, including Virginia, Tennessee, South Carolina, Georgia, Alabama, Mississippi, Florida, and Louisiana, also stock channel catfish into reservoirs and small impoundments. These extensive catfish stocking programs throughout the southeastern United States could be managed more efficiently and effectively if suitable sampling techniques were evaluated and available. Our findings validate baited tandem hoop nets for application in southeastern U.S. small impoundments to assess catfish abundance to guide management and evaluate the success of catfish stocking programs. Acknowledgments We thank Brian McRae, Kyle Briggs, and Russell Wong of the North Carolina Wildlife Resources Commission (NCWRC) for their assistance in the field and insight on North Carolina s Community Fishing Program. Others that assisted with field sampling include Patrick Cooney, Kyle Rachels, Jeremy Remmington, Alexandra Chaytor, Jim Wallace, and Mike Waine. We also thank Matt Rudolf and Piedmont Biofuels of Pittsboro, North Carolina for their contribution of soybean and sunflower cake and Andrew McMahan of Central Carolina Community College of Pittsboro, North Carolina for the use of his grain press. Holly Springs Parks and Recreation Department graciously provided access to their facilities at. Brian McRae and Josh Raabe provided constructive manuscript reviews. The North Carolina Cooperative Fish and Wildlife Research Unit is jointly supported by North Carolina State University, NCWRC, U.S. Geological Survey, U.S. Fish and Wildlife Service, and Wildlife Management Institute. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. References Arterburn, J. E., D. J. Kirby, and C. R. Berry, Jr A survey of angler attitudes and biologist opinions regarding trophy catfish and their management. Fisheries 27(5): Buhlman, K. A., and M. R. Vaughan Ecology of the turtle Pseudemys concinna in the New River, West Virginia. Journal of Herpetology 25: Flammang, M. K., and R. D. Schultz Evaluation of hoop-net size and bait selection for sampling channel catfish in Iowa impoundments. North American Journal of Fisheries Management 27: Hill, K Classification of Iowa lakes and their fish standing stock. Iowa Conservation Commission, Federal Aid in Sport Fish Restoration, Completion Report F-90-R, Des Moines. Hubert, W. A Passive capture techniques. Pages in B. R. Murphy and D. W. Willis, editors. Fisheries techniques, 2nd edition. American Fisheries Society, Bethesda, Maryland. Hubert, W. A Biology and management of channel catfish. Pages 3 22 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. Michaletz, P. H., and J. G. Dillard A survey of catfish management in the United States and Canada. Fisheries 24(8):6 11. Michaletz, P. H., and K. P. Sullivan Sampling channel catfish with tandem hoop nets in small impoundments. North American Journal of Fisheries Management 22: Mitzner, L Assessment of maintenance-stocked channel catfish populations in Iowa lakes. Pages 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. NCWRC (North Carolina Wildlife Resources Commission) North Carolina Wildlife Resources Commission, Division of Inland Fishes, Community Fishing Program. North Carolina Wildlife Resources Commission, Raleigh. NCWRC (North Carolina Wildlife Resources Commission) management plan. North Carolina Wildlife Resources Commission, Raleigh. NCWRC (North Carolina Wildlife Resources Commission) Warmwater and coolwater statewide stocking summary. North Carolina Wildlife Resources Commission, Raleigh.

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