Outdoor Tank and Pond Spawning of Cobia, Rachycentron canadumin Coastal South Carolina

Abstract

Research was conducted at the South Carolina Department of Natural Resources Waddell Mariculture Center to evaluate the potential for captive reproduction of cobia, Rachycentron canadumin outdoor tanks and ponds. In May 2001, adult cobia (3 males, 1 female, and 1 suspected female) obtained from a local high salinity estuary were stocked into an outdoor tank (32,000-L) receiving ambient estuary water. Spawning occurred within 2 days after stocking. Over the course of 3 consecutive days, a total of 3.6 million eggs were collected with roughly equal numbers collected during each 24-hour period. Mean fertilization rate was 58.1%. Hatching occurred at approximately 24 hours after initiation of each spawning event. Mean percent hatch was 27.5%. Fish were relocated to a 0.25-ha circular pond 10 days after tank spawning activity ended. One female received pelleted GnRHa before stocking. Eggs were observed 3 days after stocking and at 12 days after hatching, approximately 50,000 larvae were harvested. In May and June 2002, three groups of recently caught adult cobia, each consisting of 3 males and 1 female, were placed in one of three outdoor tanks. Spawning occurred within 2–4 days after stocking of Tanks 1 and 2. During a single spawning event, a total of 2.1 million and 560,000 eggs were collected from Tanks 1 and 2, respectively. Relative batch fecundity of females stocked in Tanks 1 and 2 was estimated to be 79.2 and 20.9 eggs/g, respectively. No fertile eggs were collected from Tank 2. Percent fertilization and hatch of eggs collected from Tank 1 was 3.2% and 1.5%, respectively. No spawning activity of fish stocked in Tank 3 occurred. Findings reveal that naturally conditioned recently caught adult cobia can readily spawn soon after capture and that ponds can be utilized for reproduction of this species in the U.S.

Key Words:

• Rachycentron canadum
• cobia
• reproduction
• spawning