Investigations of Physiological Changes in Gulf of Mexico Sharks during Acute Stress Events with Emphasis on the Atlantic Sharp Nose Shark

Blood samples were taken from seven species of shark found in the Gulf of Mexico. The species examined were Atlantic sharpnose (Rhizoprionodon terraenovae), blacknose (Carcharhinus acronotus), blacktip [Carcharhinus limbatus), bull {Carcharhinus leucas), finetooth {Carcharhinus isodon), spinner (Carcharhinus brevipinna), and tiger (Galeocerdo cuvier). The blood of 63 sharks was collected and analyzed for hematocrit, leukocrit, and plasma percent volume. Plasma osmolality values were also analyzed. Sharks were captured using hook and line (n=24) and longline (n=39). Hook and line captured sharks were submitted to a stress protocol described by Hoffmayer and Parsons (2001) and longline captured sharks were submitted to a stress protocol described in this study. In addition, 27 animals other than elasmobranchs were sampled in order to provide a comparative analysis. This included 5 species of marine teleosts, 2 species of freshwater teleosts, and 2 species of terrestrial mammals. The marine teleosts were cero (Scomberomorus regalis), great barracuda (Sphyraena barracuda), little tunny (Euthynnus alletteratus), king mackerel (Scomberomorus cavalla), and mahi mahl (Coryphaena hippurus). The freshwater teleosts were the white crappie (Pomoxis anularis) and black crappie (Pomoxis nigromaculatus). The terrestrial mammals were the domestic dog (Conisfamiliaris) and the domestic cat (Felis catus). Un-stressed sharpnose, finetooth, spinner, and blacktip sharks were observed to have a higher mean leukocrit (3.21±0.33% total blood volume) than all other marine teleosts (1.24±0.27% total blood volume), fresh water teleosts (1.07±0.26% total blood volume), and terrestrial mammals (0.92±0.14% total blood volume). Sharks were observed to have a lower mean hematocrit (26.87±1.2% of blood volume) than marine teleosts (42.26±7.0% of blood volume), fresh water teleosts (27.29±2.3% of blood volume), and terrestrial mammals (45.89±2.8% of blood volume). Baseline results of mean osmolality of sharpnose, finetooth, spinner, and blacktip (971±62 mOsm) were observed to be higher than fresh water teleosts (344±32 mOsm). The Atlantic sharpnose stress series suggested hemodilutlon (-5.45% decrease by volume), leukoconcentratlon (+1.45% increase by volume), hyperplasma (+4.00% increase by volume), and hyperosmolality (+172 mOsm) at 45 minutes into the stress protocol. This suggests that acute stress may induce an immune response in these sharks. This may also suggest an osmoregulatory disruption due to capture stress. Aggression ratings were recorded at the time of capture with 16 sharks in order to provide a behavioral component to the effect of the stress series. Voluntary bite force was also recorded on 5 sharks subjected to the stress protocol in a study by Dalton (2011) as a supplement to the behavioral study. All sharks that completed the stress protocol fell Into a subdued to docile state at 45-60 minutes into the stress protocol. This study is meant to report effects of potential capture and post-capture mortality on Gulf of Mexico shark species in order to provide a greater understanding of the stress response In elasmobranchs