Effects of Handling Methods of Gravid Channel Catfish on Cortisol Response and Reproductive Performance to Produce Hybrid Catfish Fry

Abstract

There is a need to optimize production protocols to improve the efficiency of embryo production in commercial catfish hatcheries for hybrid catfish (female Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus). The present study compared two methods of handling broodfish from a Channel Catfish population while they are being transferred from pond to hatchery. Sexually mature females (average weight = 3.9 kg/fish) were seined and transported in a hauling truck to the hatchery prior to being injected with hormones. The fish that were placed in soft mesh bags (confined) were compared with fish that were allowed to swim freely (nonconfined) in the hauling truck and raceway in the hatchery. The fish were bled at seining (0 h), after transport to the hatchery (1 h), and while in the raceway at 4 and 24 h, respectively, and plasma levels of cortisol were measured. The broodfish that were suspended in soft mesh bags were monitored for ovulation and strip-spawned to determined their relative fecundity (eggs/kg of body weight) and fry/kg body weight. The results showed that cortisol levels were high after seining in both groups. The cortisol concentrations were significantly lower (P < 0.05) at 1 and 4 h in the nonconfined than in the confined group. By 24 h, the cortisol levels had decreased in both of the treatment groups. The average relative fecundity (9,617 versus 8,576) and the number of fry/kg body weight (3,039 versus 2,710) were significantly higher (P < 0.05) for the nonconfined fish than for the confined fish. Minimizing handling and confining stress of gravid Channel Catfish after seining during transport to the hatchery and holding them in hatchery tanks for 4 h prior to hormone injection appears to be beneficial to the hatchery production of hybrid catfish fry.