Stress response and post-release mortality of blacktip sharks (Carcharhinus limbatus) captured in shore-based and charter boat-based recreational fisheries
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Weber, David Nicholas
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Abstract
The number of recreational anglers, including those participating in a specialized method of recreational fishing targeting large coastal sharks from beaches (i.e. shore-based fishing), has increased in recent decades. While recreational fishing pressure has increased, the physiological stress experienced by captured sharks, and the associated post-release mortality (PRM) rates, remain poorly understood. Estimates of PRM can have significant impacts on total fishery mortality estimates, and are thus critical to effective management plans. In the coastal waters of the southeastern U.S., the blacktip shark (Carcharhinus limbatus) is targeted by recreational anglers, and is currently the most commonly captured large coastal shark species. We estimated PRM rates for blacktip sharks captured on rod-and-reel by shore-based and charter boat-based fishermen using acoustic transmitters (n = 81). Additionally, 24 individuals were double-tagged with pop-off satellite archival tags (PSATs) to validate the survivorship results obtained from the acoustic transmitters. The stress response associated with both recreational capture methods was quantified using numerous blood chemistry parameters. PRM rates were 7.5% (charter boat-based) and 12.2% (shore-based). The survivorship results inferred from acoustic transmitters were consistent with results inferred from PSATs, validating our use of acoustic transmitters to assess PRM in blacktip sharks. Blood lactate, potassium, and glucose increased with disturbance time, and the effect of disturbance time on lactate and potassium differed significantly between capture methods. Hook location was the best predictor of PRM, and 50% of foul-hooked sharks (i.e. sharks hooked anywhere but the jaw) died post-release.