Evaluation of Summer Seining in Kansas Reservoirs

Data from August samples of fish in quarter (900 arc) hauls of a 15.2- X 1.8m bag seine were analyzed to determine effectiveness of seining for detecting species presence, forecasting future relative abundance of larger length classes of the same species, and assessing the value of seining as an indicator of prey availability for piscivores in Kansas reservoirs. The data set contained 98 reservoir-years of samples from 24 impoundments with 2-7 years of data per reservoir. The median number of hauls per reservoir and year was 19; the range was 10-30. Bag seines effectively sampled only small fish, most < 140 mm. Presence was accurately detected in 100% of the reservoir-years sampled for gizzard shad and ranged from 90% to 97% for minnows, white bass, lepomid sunfishes, and freshwater drum. Presence was detected correctly from 80% to 90% ofthe time for red shiner, largemouth bass, channel catfish, brook silverside, and bluegill but <80% of the time for other species. Gizzard shad, minnows, lepomid sunfishes, and red shiner were the only species or groups that could be effectively sampled in most reservoirs with a geometric mean of 25 or fewer hauls per year. Effective sampling was defined as the capability of detecting 100% changes in mean catch with 80% certainty at a = 0.05. Correlations of mean catch with reservoir physicochemical characteristics suggested some reasons for the wide variation in catch among reservoirs but provided little insight into types of reservoirs most appropriate for seining. Poor sampling effectiveness was associated with low abundance of fishes vulnerable to seining, small sample areas (0.018 ha) per haul, and the necessity of sampling only areas with gently sloping, unobstructed bottoms. Seine catches were of no value for predicting the future relative abundance of the same species in larger length classes, and of limited value for predicting walleye and gizzard shad recruitment to a 25.4-mm mesh gill net. In Melvern Reservoir, seining underestimated densities of most species and median lengths of gizzard shad compared with estimates from 2 coverotenone samples. Length frequencies and numbers of gizzard shad in seine catches provided some indication of growth, potential for recruitment, and availability to young piscivores. Seine catch was an easily obtained, although poor indicator, of prey availability.

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