ORGANIZED GROUP-SPAWNING OF DOMESTICATED STRIPED BASS Morone saxatilis

Striped bass (Morone saxatilis) and their hybrids (M. saxatilis x M. chrysops) are the fourth most valuable finfish aquaculture species in the United States and are also important to recreational fisheries. To date, successful reproduction of captive female striped bass has relied on gonadotropin releasing hormone (GnRH) or human chorionic gonadotropin (hCG) treatment following ovarian biopsy. Organized reproductive group spawning of domesticated striped bass is a strategy based on volitionally spawning many female and male fish together in one large tank using limited or no hormones. Using this method, we effectively and consistently spawned approximately half the female striped bass in the National Program for Genetic Improvement and Selective Breeding for the Hybrid Striped Bass Industry and produced millions of fry. Following the group spawning trials, females that failed to spawn volitionally could have been induced to do so with hCG or GnRH.

Four group-spawning trials were conducted (Table 1). Males (2.21 + 0.28 kg) were warmed to 15-16°C, injected with 165 IU/kg hCG to maintain adequate spermiation, and transferred to a 6.1 m diameter (32,176 L) group-spawning tank with flow-through water, and equipped with two upwelling (200 L) egg collectors. One to two days later, females (4.10 + 0.35 kg) were warmed to near spawning temperature (approximately 16°C) and added to the group-spawning tank. The water was gradually warmed to 18-20°C and spawning began an average of 53 + 27 hours after addition of the females.

This is the first report of spawning female striped bass with appreciable fry production without hormone treatment. The method is particularly advantageous because it is commercially scalable, does not require technical expertise in staging oocytes and avoids the handling stress associated with biopsying and injecting pre-spawning fish.