Catch rates and selectivity among three trap types in the US South Atlantic black sea bass commercial trap fishery

摘要

We compared selectivity and catch rates of black sea bass Centropristis striata between two experimental trap types: back-panel traps (50.8-mm-mesh back panels; 38.1-mm mesh in all other panels), which represent the new legal minimum mesh configuration; and all-panel traps (50.8-mm mesh in all panels), which are electively used by a subset of fishers. Catches in both experimental trap types were compared with catches in control traps (38.1-mm mesh in all panels). Traps were fished from October 2006 to March 2007 in waters 12-30 m deep in Onslow Bay, North Carolina. Correlation analyses were used to examine postrelease condition of discarded black sea bass in relation to fish density in traps and capture depth. We found that mean catch rates of sublegal-sized black sea bass (<254 mm total length) were lower for control traps than for both experimental traps and were lower for back-panel traps than for all-panel traps; however, catch rates of legal-sized fish were not different among trap types. Median black sea bass size increased with trap mesh size. Modeled selectivity for each experimental trap type was relatively knife-edged (i.e., characterized by a narrow selection range); both experimental trap types caught smaller proportions of sublegal-sized fish and higher proportions of legal-sized fish than did control traps. Estimated immediate mortality rates of black sea bass discards were 3.7 (control), 1.1 (back panel), and 0.7% (all panel). Less-favorable release condition was positively correlated with fish density and depth. Combining immediate discard mortality over observed depths (common depths for this fishery) and losses from observable barotrauma, the assumed mortality rate of discarded black sea bass in the U.S. South Atlantic commercial trap fishery (15%) may be too high.