The Effect of Two Initial Diet Sizes on Growth of Channel Catfish Stocked into Ponds as Single-Size or Mixed-Size Populations

Effects on growth of initially feeding a small-diameter (3.2 mm) fingerling diet compared to a standard-size growout diet (6.4 mm) on growth in single-size and mixed-size catfish ponds were evaluated. Ponds (0.1 ha) were stocked with either fingerlings-only (19 g initial weight) or mixed-size populations of 85% fingerlings and 15% third-year (307 g initial weight) fish. All fish were fed to satiation, once daily. At week 6, ponds receiving the smaller diet.were switched to the standard-size diet for the remainder of the 21-week study. Under mixed-size culture, no differences (P >0.05) were observed in final weight gain due to initial diet size for either fingerlings or third-year fish. Likewise, there was no difference (P >0.05) in weight gain due to diet size for fingerlings grown under single-size culture. After 21 weeks of culture, fingerlings produced under the single-batch scenario weighed 42% more than fingerlings cultured with larger fish. Total diet consumption in the mixed-size ponds was similar, whether initially fed the smaller diet or not. However, under single-size culture, overall diet consumption was 2.85 kg/ha/d less in ponds initially fed the smaller diet, even though final weight gains were unaffected by initial diet size. Regardless, savings associated with the decreased diet consumption of the smaller-diameter ration were offset by its higher cost. The practice of initially feeding a smaller-diameter ration in ponds understocked with moderately-sized fingerlings fed to satiation appears to offer no advantage with respect to fingerling growth.