Stress response and postrelease mortality of blacktip sharks (Carcharhinus limbatus) captured in shore-based and charter-boat-based recreational fisheries

In the coastal waters of the southeastern United States, the black-tip shark (Carcharhinus limbatus) is targeted by recreational anglers and is currently one of the most often captured large coastal shark species. We estimated postrelease mortality (PRM) rates for blacktip sharks captured on rod and reel by shore-based and charter-boat-based fishermen by using acoustic transmitters (number of sharks=81). Additionally, 24 blacktip sharks were tagged with pop-off satellite archival tags (PSATs) to validate the survivorship obtained through analysis of data from the acoustic transmitters. The stress response associated with both recreational capture methods was quantified by using numerous blood chemistry characteristics. Overall, 18.5% of blacktip sharks died postrelease (17.1% and 20.0% of those captured from shore and from charter boats, respectively). The results of survivorship analysis based on data from transmitters are consistent with results inferred from data from PSATs, supporting our use of acoustic transmitters to assess PRM in blacktip sharks. Fight time had a significant effect on blood pH, lactate, hematocrit, potassium, and glucose for sharks caught from shore but only on lactate for sharks caught from charter boats. In general, the blood chemistry characteristics assessed were poor predictors of PRM. Fifty percent of foul-hooked sharks (i.e., sharks hooked anywhere but the jaw) died postrelease, indicating the importance of the effect of hook placement on PRM.