No abstract

This range-finding study determined the optimum concentration of copper sulfate (CuSO4) for fungus control on eggs of channel catfish Ictalurus punctatus. The study consisted of five CuSO4 concentrations (2.5, 5, 10, 20, and 40 mg/L) and an untreated control in a flow-through system. A single spawn was used for each replication (N=4). Eggs were treated daily until the embryos reached the eyed stage. When hatching was complete for all viable eggs, fry were counted to determine the percent survival in each treatment. Fungal growth was severe in the untreated controls; survival of hatched fry in the control group was approximately 2%. The optimum CuSO4 treatment, as determined by percent survival of hatched fry, was 10 mg/L daily (69% survival); survival for this treatment group was significantly different from that for the controls. Very little fungus was present in treatments receiving 10-mg/L CuSO4 or higher except in one replication that had approximately 40% unfertilized eggs. The average survival rates in the 0-, 2.5-, 5-, 10-, 20-, and 40-mg/L CuSO4 treatments were 2, 34, 50, 69, 59, and 51%, respectively.

Within a three-phase production strategy for farming channel catfish Ictalurus punctatus, the second phase, fingerling to stocker production, was evaluated. A complementary economic analysis compared the cost of producing stockers, food-size fish net returns, and overall cost of production for a three-phase production system with that of the traditional multiple-batch system. Pond run fingerlings (mean length ¼ 10.7 cm; mean weight ¼ 10 g) were stocked into 0.05-ha experimental earthen ponds at densities of 98,840, 123,550, and 148,260 per hectare. They were fed floating fingerling feed with 36% crude protein to satiation during a 180-d grow-out period. At harvest, mean survival (63.7-72.6%) and mean feed conversion ratio (1.5-1.6) did not differ significantly among treatments. Mean harvested biomass (kg/ha) ranged from 5,766.5 to 9,135.6 and increased as density increased. Mean harvest weight (85.8-94.3 g) decreased as density increased but was not statistically different among treatments. Stocker cost of production was US$0.17, $0.18, and $0.22 per stocker for the highest, medium, and lowest initial fingerling stocking treatments, respectively. For the higher stocking rates, total food-size cost of production (variable and fixed costs) was $1.37/kg, which was $0.02/kg to $0.28/kg less than the production costs of food-size catfish in multiple-batch production systems. The mean harvest weight goal of 113.5 g was not achieved in any treatment, but a slightly larger fingerling stocking size combined with seasonal water temperatures should produce the desired weight for stocking into the third phase (final grow out) of production. The estimated production cost for the three-phase system appears to be less than that of the multiple-batch system. In addition, the three-phase system offers other advantages, such as better inventory control and minimal loss from bird depredation. This broad management concept has the flexibility to be modified to meet the needs of individual operations.

No abstract