By Gina Russo
Earlier this fall, a Special Activity License was obtained to collect adult red drum, Sciaenops ocellatus, in the Gulf near Tampa Bay in support of brood fish research for intensive hatcheries. This required close coordination between hatchery staff and a contracted purse seine vessel to be ready when red drum were sighted in coastal waters.
Red drum were spotted two miles west of Bean Point (Anna Maria Island, FL) on September 16, 2016. Two hatchery staff were aboard the vessel to set up oxygen in the vessel holds, to observe and document red drum bailing from the purse seine into the vessel holds, and to monitor the fish, oxygen, pH and temperature in the vessel holds during the return trip to Port Manatee. At Port Manatee, 106 red drum were loaded into live haul trailers for transport to SERF. These fish were stocked into two 1-acre ponds within 30 minutes of unloading from the purse seine vessel at Port Manatee. The transition from the wild to captivity began in the ponds with the acclimation of the red drum to a frozen diet of squid, mackerel, and shrimp. Many of these red drum will move into maturation and spawning tanks in 2017 to continue studies on the effects of tank and population size on reproductive contribution, and to investigate other issues related to spawning in captivity.
An example of other investigations include a novel investigation of the effects of nitrate (which accumulates as a byproduct in recirculating aquaculture systems with minimal water renewal) on marine fish reproduction. During this study, the spawning-season duration, fecundity and quality as measured by red drum embryo size and survival, and larval growth and survival through metamorphosis were determined. Also, oocytes and blood were collected monthly from female red drum to assess histology, and steroid and vitellogenin levels, respectively.
Although the study is not completed, an interesting data trend revealed during this study suggests that spawning-season duration or frequency of spawning might be inversely related to spawning quality. This would have implications on hatchery design and broodstock management and may be an upcoming subject for investigation. Regardless of what is in store for future investigations, the newly acquired red drum adults are eating voraciously and are in good health.