Effects of capture on adrenal steroid and vasopressin concentrations in free-ranging bottlenose dolphins (Tursiops truncatus)

Marine mammals are routinely caught in the wild in an effort to monitor their health. However, capture-associated stress could potentially bias various biochemical parameters used to monitor the health of these wild caught animals. Therefore, the effects of capture were quantified by measuring plasma adrenal steroids and arginine vasopressin (AVP) in free-ranging bottlenose dolphins (Tursiops truncatus) (n=31). Total capture and restraint times were also correlated to hormone concentrations to quantify the effects of capture. Significant, positive correlations between corticosterone and cortisol (R=0.752; P<0.0001), and between corticosterone and aldosterone (R=0.441; P=0.045) were demonstrated. Significant correlations between capture and restraint time and hormone levels were not observed. Animals restrained for less than 20 min exhibited hormone levels similar to those for animals restrained for more than 20 min. The positive correlations among the adrenal steroids suggest that release of these steroids was stimulated by adrenocorticotropin (ACTH). The lack of a correlation between cortisol and AVP indicates that AVP did not influence ACTH-induced cortisol release in this situation. The study suggests that (1) a typical hypothalamic-pituitary-adrenal axis is present in these animals, and (2) the relatively short capture and restraint times did not induce a significant neuroendocrine stress response.