Variable Responses of Channel Catfish Populations to Stocking Rate: Density-Dependent and Lake Productivity Effects

Abstract

Put–grow–take fisheries for channel catfish Ictalurus punctatus are popular in many small impoundments but are costly because fingerling (>175 mm total length [TL]) stockings are usually necessary to maintain these fisheries. Stocking the appropriate number of fish is important for making efficient use of these hatchery products and for creating desirable fisheries. The effect of stocking rate on channel catfish populations was evaluated by examining 60 small impoundments that had been assigned to one of three annual stocking rates (12, 37, or 74 fingerlings/ha). As channel catfish stocking rate increased, catch per unit effort (CPUE, number of fish per 3-d tandem hoop-net series) and total annual mortality increased, while proportional size distribution (PSD, formerly proportional stock density), PSD for fish 508 mm or longer, relative weight, and annual growth increments decreased; these results suggest that density-dependent processes were important. However, 10-fold differences in CPUE and threefold differences in size structure indices and growth increments were common among lakes stocked at the same rate. Further analysis revealed that CPUE and lake productivity (indexed by chlorophyll-a concentration) were important variables in explaining differences in size structure, condition, and growth among populations. Because of the highly variable response, appropriate stocking rates need to be determined for each lake. I propose comparing growth increments of individuals within a lake to a statewide standard to determine the relative growth rate for the lake. Stocking rates should be reduced for channel catfish populations that are growing slowly but could be increased for fast-growing populations.