Abstract
Abstract.— Different sizes of catfish fingerlings understocked in multiple‐batch production may result in different survival, yield, cost, and economic risk. A pond production study was conducted to compare net yield, growth, survival, costs, and economic risk of understocking 7.6‐cm, 12.7‐cm. or 17.8‐cm channel catfish Ictalurus punctatus fingerlings in growout ponds. Fingerlings were understocked at 15,000/ha with 1,369 kg/ha carryover fish averaging 0.58 kg. Mean growth rate increased significantly with size of fingerling understocked (1.4 ± 0.2 g/d, 1.8 ± 0.07 g/ d, and 2.2 ± 0.06 g/d for 7.6‐cm, 12.7‐cm, and 17.8‐cm understocked fingerlings, respectively). Mean individual weights at harvest also increased significantly with size at stocking but none of the understocked fingerlings reached minimum market size (0.57 kg) over the 201‐d study period. Survival of the smallest (7.6‐cm) understocked fingerlings was significantly lower, but there was no difference in survival between the two other treatments. Net yields were highest for the two treatments understocked with 12.7‐ and 17.8‐cm catfish and significantly lower for the treatment understocked with 7.6‐cm fish. Growth of large carryover fish was significantly less in the treatment understocked with 17.8‐cm fingerlings. Breakeven production costs were highest for the treatment understocked with 7.6‐cm fish and lower for the other two treatments. The risk analysis showed that it was very likely that the 12.7‐ and 17.8‐cm understocked fish could be grown profitably (very little risk of costs exceeding $ 1.32/kg—$1.65/kg). However, the risk of growing out 7.6‐cm understocked fish at costs above market prices increased sharply. This static analysis indicated that the preferred size to understock in growout ponds would be 12.7 cm; however, additional work is needed in a dynamic framework to quantify the benefit of 17.8‐cm fingerlings reaching market size earlier in the second year.
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