Red drum, Sciaenops ocellatus L., stock enhancement in Biscayne Bay, FL, USA: Assessment of releasing unmarked early juveniles

The State of Florida's practice of releasing unmarked early juvenile red drum Sciaenops ocellatus L. to create a recreational fishery in Biscayne Bay, FL, USA, was assessed. Cohorts were reared in ponds to an early juvenile size of ≃ 50 mm total length. Fish were then harvested and transported immediately to release locations within 24 h. Substantial mortality often resulted after harvesting and immediate transport of early juveniles. Weak correlations between post-transport mortality, transport conditions and fish characteristics (i.e. age, size and condition) suggested that stressors operating before or during pond harvest were predetermining toleration of transport. Seine sampling 1-6 days after cohorts were released indicated that fish 'disappeared' from release sites faster than the rates of mortality observed for their siblings monitored in food-rich, predator-free tanks. Visual and immunological analyses of gut contents suggested that juvenile great barracuda Sphyraena barracuda (Walbaum) and adult redfin needlefish Strongylura notata (Poey) were the major predators. Strategies for reducing pre- and post-release mortality and directions for future research are suggested. Discontinuing the release of unmarked organisms of any type is strongly recommended.