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 dr um Sciaenops ocellatus L. to create a recreational fishery in Biscayne Bay, FL, USA, was assessed. Cohorts were reared in ponds to an early juvenile s ize of approximate to 50 mm total length. Fish were then harvested and tran sported 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 stre ssors operating before or during pond harvest were predetermining toleratio n of transport. Seine sampling 1-6 days after cohorts were released indicat ed that fish 'disappeared' from release sites faster than the rates of mort ality observed for their siblings monitored in food-rich, predator-free tan ks. Visual and immunological analyses of gut contents suggested that juveni le great barracuda Sphyraena barracuda (Walbaum) and adult redfin needlefis h Strongylura notata (Poey) were the major predators. Strategies for reduci ng pre- and post-release mortality and directions for future research are s uggested. Discontinuing the release of unmarked organisms of any type is st rongly recommended.