Role of Stocking Sequence on Survival of Fingerling Channel Catfish Cultured in Mixed-Size Populations

Replacement channel catfish Ictalurus punctatus are typically stocked as fingerlings into commercial grow-out ponds following partial harvest of large fish. To determine if timing of subsequent stocking of fingerlings into mixed-size populations influences fingerling survival, we examined the effects of stocking large and small fish 2 weeks after initial stocking of large fish. Fifty large (mean weight = 374 g) and 50 small (25 g) catfish were stocked into two 1,323-L tanks. Tank 1 was stocked with large fish and maintained for 14 d; on day 14, small fish were added. Tank 2 was stocked with large and small fish simultaneously on day 14. A third tank was stocked with 100 small fish only on day 14. Three ponds (0.05-ha each) were also used in the same design with large fish (240 g) and small fish (30 g). On day 15, all fish were harvested and counted to determine 24-h survival. This procedure was replicated over three trials in both the tank and pond studies. Survival of small fish stocked 14 d after stocking of large fish in tanks and ponds was significantly less (P ≤ 0.05) than survival of small fish stocked concurrently with large fish or stocked alone. These results suggest that replacement fingerlings should be stocked as soon as possible following partial harvest.