Effect of temperature on metabolic stress and recovery of two Argyrosomus species from simulated catch-and-release angling

Catch-and-release (C&R) angling has grown in popularity due to increasing numbers of conservation-minded anglers and regulations of recreational fisheries. C&R is often assumed to cause low mortality but can cause physiological and physical impairment. Fish metabolism and temperature interact to play a critical role in the biological functioning of fish. Understanding the relationship between temperature, fish metabolism, and physiological impairment is important for effective fisheries management and conservation, particularly for C&R angling in a changing thermal environment. We used respirometry to quantify post-release metabolic stress and recovery of two popular Namibian angling species (Argyrosomus inodorus and A. coronus) subjected to simulated C&R angling across a range of temperatures. Metabolic stress and recovery time did not differ significantly between warm (A. coronus) and cold-water (A. inodorus) species at any test temperature. However, several specimens of both species failed to recover physiologically and physically after 10 hours, thereby indicating C&R-related impairment and potential for mortality. Given the predator-rich environment of coastal waters in Namibia, best C&R practices are needed to minimise post-release mortality.