World Aquaculture 65 the fingerlings are not likely to perform well in terms of growth or survival. As channel catfish grow, feed intake as percent of body weight (biomass) decreases. But their feed conversion ratio increases with size. The amount of feed it takes to produce a kilogram of fish increases as fish get larger. It takes 1.1 kg of feed to produce 1.0 kg of gain in 15-cm catfish, and 1.9 kg of feed for 1.0-kg of gain in 38-cm catfish (Robinson et al. 1998), 73 percent more feed for the same amount of growth in 38-cm catfish. Because juvenile channel catfish smaller than 200 g are growing much faster, require more feed, and convert feed to weight gain more efficiently; producers must do their best job of feeding when fish are young (Wurts 2001). It is likely that under-stocked juvenile catfish do not compete effectively with larger fish for larger, floating feed pellets. An alternative feeding practice could improve growth, survival and health of channel catfish fingerlings in a mixed size-class population (multiple-batch production), promoting the development of a more sustainable channel catfish production system. A sinking feed with a smaller pellet size could be used to increase the availability of food for fingerlings. The amount fed would be adjusted in accordance with the rapid growth rate of fingerlings. A smaller sinking feed (Wurts 2001, Li and Robinson 2008) could be simultaneously offered to fingerlings along with the floating pellets for larger fish. Satiation feeding with floating feed would be used for larger fish. Table 1. Channel catfish fingerling survival in multiple batvh production ponds. Study Fingerling Size (g) Density fiingerlings/ha Survival (%) Engle and Valderarma, 2001x 6 15,000 50 Engle and Valderarma, 2001x 12 15,000 76 Engle and Valderarma, 2001x 37 15,000 68 Southworth et al., 2006ay 19 8,600-34,600 24-36 x1369 kg/ha carryover biomass, average initial fish weght = 0.58 kg each. Mean harvest weights for fingerlings stocked = 0.28-0.46 kg after 203 days. y2268 kg/ha carryover biomass, average initial fish weights = 0.37-0.45 kg each. Mean harvest weights for fingerlings stocked = 0.32-0.35 kg after 196 cays. This sequnce of photographs (right and below) shows larger catfish, not quite harvest size, feeding aggressively. (All photos by Charles Weibel at Kentucky State University)
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