Hyatt, M.W.; Anderson, P.A., and O'Donnell, P.M., 2018. Influence of temperature, salinity, and dissolved oxygen on the stress response of bull (Carcharhinus leucas) and bonnethead (Sphyrna tiburo) sharks after capture and handling.

Capture and handling stress can induce acidosis in sharks. This response, endured during commercial bycatch and in catch-and-release recreational fisheries, could be exacerbated in certain environmental conditions. To assess environmental influence on stress response, changes in acid-base, blood gas, and metabolite analytes (pH, pCO2, and lactate) measured with the i-STAT portable clinical analyzer were evaluated immediately after capture and removal from gillnets among wild bull (Carcharhinus leucas) and bonnethead (Sphyrna tiburo) sharks caught in waters of differing temperature (T), salinity (Sal), and dissolved oxygen (DO). Time from capture to blood collection (C-BD) was also recorded. Effects of T, Sal, DO, and C-BD on acid-base physiology were evaluated by modeling their ability to predict pH, pCO2, and lactate concentrations using ordinal logistic regression (OLR). The OLR models suggest that C. leucas sharks experienced a mixed metabolic and respiratory acidosis in warmer waters and at the low end of their salinity tolerance, and that S. tiburo sharks experienced a metabolic acidosis in warmer waters with a potential for respiratory acidosis at the high end of their salinity tolerance. In S. tiburo, capture and handling time exacerbated acidosis. Based on these findings, it is recommended that commercial and catch-and-release fisheries conduct operations cautiously during times of the year when water temperatures are high and salinities are at either extreme, by decreasing soak times, using the strongest proper tackle gear to reduce fight times, and releasing sharks as soon as possible after capture and detection.

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