Effects of capture method and handling time on the physiological stress responses of a benthic elasmobranch

Marine animals are increasingly exposed to anthropogenic disturbances that disrupt their behaviour and induce physiological stress. In vertebrates, stressors such as anthropogenic disturbances increase the production of glucocorticoid hormones. Although sharks are one of the most threatened groups of marine animals, relatively little is known about their glucocorticoid physiology. We investigated how different capture methods (hand capture and rod and reel) affected physiological stress responses of Port Jackson sharks (Heterondontus portusjacksoni). We measured lactate and glucose levels immediately following capture and over 60-min in the field using point-of-care (POC) devices. We then validated our glucose and lactate measurements using traditional laboratory assays. Additionally, we measured two hormones associated with glucocorticoid physiology (adrenocorticotropic hormone and corticosterone). Point-of-care devices could reliably measure lactate levels of Port Jackson sharks, but not glucose levels. Lactate and corticosterone levels increased over the 60-min holding period post-capture. Sharks captured by hand had higher corticosterone levels but similar lactate levels to sharks caught by rod and reel. While the use of hooks can lead to physical injuries when capturing sharks, our findings challenge the assumption that capturing sharks by hand is less stressful than rod and reel with heavy tackle. Our study highlights the potential use of POC devices to measure metrics associated with physiological stress responses in sharks and increases our understanding of the effects of capture methods and anthropogenic disturbances on shark stress responses.