Economic Interactions Between Feeding Rates and Stocking Densities in Intensive Catfish Ictalurus punctatus Production

Feed represents the largest cost input in intensive catfish Ictalurus punctatus production. Daily feed rations are generally related to stocking densities, up to a point a t which high feeding rates begin to affect water quality. There has been no prior research to analyze the economic interactions between feeding and stocking rates. Econometric techniques were used to estimate a Just-Pope catfish production function, which was used to compute marginal products of inputs, and to identify stocking and feeding rates associated with the boundaries between Stages I, 11, and I11 of the production function. Survey data collected by USDA National Animal Health Monitoring System were used for this analysis. Maximum yield, when accounting for both stocking and feeding rates, occurred at about 30,000 fingerlingdha. However, profit-maximizing stocking densities ranged between 16,942 and 21,312 fingerlingdha, depending upon expected catfish and feed prices. Farmers stocking at higher rates could be attempting to maximize yield instead of profit. Feed, fingerlings, and labor are the three largest cost inputs (45%, 8%, and 9% of total costs, respectively) in intensive catfish Zctulurus punctutus production (Engle and Kouka 1996). Daily feed rations are generally related to the stocking density and size of catfish in a pond. Feed rations typically increase with increased stocking density until high feed rates begin to result in deterioration of water quality. High stocking densities with limited feed may result in reduced growth of individual fish and reduced average yield. Economic theory indicates that output of a product (in this case catfish) increases as input levels increase until a point of maximum yield is reached. If inputs are increased beyond this point, yield will deI Corresponding author. crease (Kay and Edwards 1994). This production function relationship can be estimated econometrically using farm-level data and is characterized by three distinct stages. Stage I1 zones are uniquely associated with the profit maximization objective in perfectly competitive input and output markets (Beattie and Taylor 1985). Profit maximizing input levels within Stage I1 can be derived from the production function, conditional on input and output prices and other factors. Earlier economic analyses of catfish production determined that feed, length of growing season, level of capital intensity, and stocking density significantly affected average yield (Lacewell et al. 1973; Panayotou et al. 1982; Neme et al. 1990). However, these production function analyses were based on datasets with limited obQ Copyright by the World Aquaculture Society 2wO