Refrigerated storage and cryopreservation of sperm for the production of red snapper and snapper hybrids

Abstract

The red snapper Lutjanus campechanus is an economically valuable sport and commercial fishery, and because of its high market value and limited commercial harvest, red snapper have received considerable attention as a candidate for marine aquaculture and stock enhancement programs. The goal of this thesis was to improve hatchery techniques for artificial spawning of red snapper Lutjanus campechanus. The objectives were to: 1) refine protocols for collecting, handling, transport, and holding of mature red snapper broodstock for induced spawning; 2) establish methods for strip-spawning of red snapper to optimize egg quality; 3) develop procedures for the collection, storage, and use of refrigerated and cryopreserved sperm of red snapper and gray snapper, and 4) evaluate the overall effects of gamete and larval quality on rearing success. The techniques developed were practical methods that hatchery managers can use to collect high-quality broodstock, to preserve sperm, and to collect and incubate eggs. Red snapper broodstock (N = 101; 1.0 to 3.8 kg) were collected during the 2000 and 2001 spawning seasons (May to August) off coastal Louisiana by hook and line sampling. The reproductive condition of females was evaluated through samples of oocytes collected by intraovarian biopsy. Females with oocytes ranging in size from 350 to 550 µm were considered good candidates for hormone induced spawning. Female snapper were induced to ovulate with injections of human chorionic gonadotropin. Females were monitored for oocyte maturation and were stripped after ovulation. In a series of 2 x 2 trials, refrigerated and cryopreserved sperm with motilities above 80% were compared to evaluate fertilization and hatching success. Eggs were incubated in plastic bags (200 eggs per L) and fertilization was assessed as embryos developed through 8-cell, neurulation, and hatch. Fertilization and hatch rates ranged from 7 to 99% and were highly correlated (r2 = 0.92). Refrigerated sperm yielded fertilization rates of 52 ± 23% (mean ± SD) and cryopreserved sperm yielded fertilization rates of 44 ± 22%. Use of refrigerated and cryopreserved sperm improved efficiency within the hatchery and each were effective for the fertilization of eggs and production of larvae.