Use of Hematological Markers to Assess Physiological Condition and Health Status in Free-Ranging Sand Tiger Sharks (Carcharius taurus)

The contents of blood can provide information about the physiological condition and health of vertebrates. This study seeks to better understand the stress physiology and blood bacteria presence of the sand tiger shark (Carcharius taurus), as sharks are known to have unique physiology and immune systems. In this study the blood metabolites glucose, lactate, and ketones (3-hydroxybuteric acid and acetoacetate), were used to understand how biotic and abiotic factors affect the acute stress response to capture and handling. Metabolite concentrations from blood plasma were analyzed using colorimetric assays. Glucose and ketones showed no significant responses to capture and handling stressors, while lactate increased with longline soak time. There was an interactive effect of fork length and sex on the ketone acetoacetate at the time of longline capture. Bacteria in the blood of sand tiger sharks was quantified using blood culture methods. Sharks that were positive for blood bacterial growth had near significant lower levels of lactate during capture compared to sharks negative for bacterial growth. Blood bacteria presence did not differ between sexes or across fork lengths. The results from this study demonstrate that while sand tiger sharks respond metabolically to longline capture, they may be physiologically robust to capture. While none of the bacterial results were statistically significant, they represent potentially interesting trends that should be investigated further in future studies. More studies are necessary to better understand the implications of abiotic and biotic factors on the stress response of sand tiger sharks.