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Circulating adrenocorticotropic hormone levels, lactate levels, hematocrit and osmolality in relation to capture stress in Atlantic sharpnose sharks, Rhizoprionodon terraenovae

Fuller, Lauren, Stell, Ehlana, Leary, Christopher, Parsons, Glenn
Comparative biochemistry and physiology 2020 v.243 pp. 110655
Rhizoprionodon, blood sampling, corticotropin, glucocorticoids, hematocrit, lactic acid, osmolality, population dynamics, sharks, sport fishing, stress response
Incidental capture of sharks during commercial and recreational fishing is of major conservation concern because of the potential effects it can have on physiological stress responses and survival. Endocrine aspects of the stress response are, however, poorly understood in elasmobranchs because of difficulties in measuring the primary glucocorticoid (1α-hydroxycorticosterone). Here, we combined measures of plasma adrenocorticotropic hormone (ACTH), the highly conserved pituitary hormone responsible for stimulating the release of adrenal/interrenal glucocorticoids, with measures of plasma lactate, osmolality, hematocrit, and behavior to gain a greater understanding of the capture stress response in Atlantic Sharpnose sharks, Rhizoprionodon terraenovae. Individuals were subject to a non-repeated measures blood sampling protocol in which blood samples were obtained following exposure to capture stress for <3 min (designated baseline), and 15, 30, 45 and 60 min, after which behavior was categorized during release. Results revealed that ACTH was significantly higher at 15, 30, 45, and 60 min than at baseline. Lactate levels were highest at 45 and 60 min whereas osmolality and hematocrit did not differ significantly among the sampling periods. Lactate was the only variable to significantly predict the shark's behavior upon release with higher lactate levels correlating with sluggish behavior. Measurements of stress indicators are important in understanding the effects of capture on shark populations, which has been implicated in population declines.