Evaluation Of LHRHa Implants and Injections on the Production of Channel Catfish (Ictalurus punctatus) Female X Blue Catfish (Ictalurus furcatus) Male Fry

Abstract

The hybrid produced from the channel catfish (Ictalurus punctatus) female and the blue catfish (I. furcatus) male has better culture traits than the primarily cultured channel catfish. Producing hybrid catfish has been limited because of the low number of fry per kilogram produced. Increasing the number of fry per kilogram of female by using different LHRHa treatments to induce ovulation and increase sperm production were the goals of these experiments. Two treatments, 100µg/kg implants and 30/150 injections, yield the greatest number of fry/kg. Of those two, 100 µg/kg implants was the most consistent treatment, and had the maximum mean fry/kg. Late in the spawning season 75 µg/kg implanted females had both higher ovulation rate and egg quality compared to females implanted with 100 µg/kg of LHRHa. Latency time decreased with increasing temperatures. Females exposed directly or indirectly to males had higher fry per kilogram than females with no exposure. During 2005, females that were directly exposed to males, although consistent with the first year, had an increased latency of about 6 hours. Higher doses of injections and implants, in general, tended to result in greater relative fecundity and greater numbers of eggs stripped from the females than lower doses of injections, and resulted in greater relative fecundity than lower doses of injections. Indirect contact and, therefore, probable pheromone communication increased hatch rate and fry/kg by about 3X. In 2004, hatch of the first 4 egg masses stripped from an individual fish was essentially equivalent (20.7-23.2% hatch), and then hatch rate rapidly decreased for egg masses 5-7, 14.0, 7.6 and 6.5%, respectively. Effects of egg mass order were more dramatic in 2005. The first 3 egg masses had 28.6-31.2 % hatch, egg mass 4 had 12.2 % hatch and egg masses 5-6 4.1-4.4% hatch. The first 3-4 egg masses should give consistent and good hatch. Strain of blue catfish had larger effects on reproduction than implantation. Large strain differences existed for sperm/g of testes, sperm/kg male body weight and hatching percentage. Application of the best treatments examined in these experiments could result in commercial levels of hybrid fry production. Utilization of this hybrid would then have a positive impact on the economics of the American catfish industry.