Threadfin Shad Use as Supplemental Prey in Reservoir White Crappie Fisheries in Kentucky

Prey bases in two Kentucky reservoirs were supplemented with stocked prespawn adult threadfin shad Dorosoma petenense during 1991–1993 to improve fisheries for white crappies Pomoxis annularis by increasing their growth and shifting population size structure toward larger fish. Abundance of age-0 threadfin shad produced was lower than native age-0 gizzard shad D. cepedianum, but threadfin shad provided late-season prey by spawning later than gizzard shad in both reservoirs. In Rough River Lake, threadfin shad stocking rates of 15–28 fish/ha produced peak densities of 0.04 ± 0.01 to 0.46 ± 0.10 fish/m3 (mean ± SE) that represented 3. 5, and 0.3% of the annual peak gizzard shad densities from 1991 through 1993, respectively, but neither white crappie growth nor population size structure were improved. In Dewey Lake, threadfin shad stocking rates of 121–285 fish/ha produced peak threadfin shad densities of 0.40 ± 0.15 to 0.66 ± 0.08 fish/m3 that represented 89, 23, and 20% of peak gizzard shad densities from 1991 through 1993, respectively. Available shad prey smaller than 5 cm were primarily threadfin shad after mid-June. Shad consumption and growth by white crappies larger than 18 cm in Dewey Lake increased during shad stocking years; however, population improvement was minimal and growth of age-0 white crappies concurrently decreased. Supplementing the prey base did not substantially improve white crappie populations in either reservoir, and this practice is no longer used to manage crappie fisheries in Kentucky. In large Kentucky reservoirs and other aquatic systems, benefits of threadfin shad stocking may be limited to fully piscivorous predators in the presence of low densities of fast-growing gizzard shad. Even under these conditions, my data suggest that high stocking rates (at least 125 fish/ha) and careful community monitoring may be required for management success. Otherwise, contributions to prey resources and sportfish responses are likely to be minimal; moreover, community integrity may be compromised.