Refuge-Seeking Impairments Mirror Metabolic Recovery Following Fisheries-Related Stressors in the Spanish Flag Snapper (Lutjanus carponotatus) on the Great Barrier Reef

Abstract

Fisheries and marine park management strategies for large predatory reef fish can mean that a large proportion of captured fish are released. Despite being released, these fish may experience high mortality while they traverse the water column to locate suitable refuge to avoid predators, all the while recovering from the stress of capture. The predatory reef fish Spanish flag snapper (Lutjanus carponotatus) is frequently released because of a minimum-size or bag limit or by fishers targeting more desirable species. Using L. carponotatus as a model, we tested whether simulated fishing stress (exercise and air exposure) resulted in impairments in reflexes (e.g., response to stimuli) and the ability to identify and use refuge in a laboratory arena and whether any impairments were associated with blood physiology or metabolic recovery. Control fish were consistently responsive to reflex tests and rapidly located and entered refugia in the arena within seconds. Conversely, treatment fish (exhausted and air exposed) were unresponsive to stimuli, took longer to search for refugia, and were more apprehensive to enter the refuge once it was located. Consequently, treatment fish took more than 70 times longer than control fish to enter the coral refuge (26.12 vs. 0.36 min, respectively). The finding that fish exposed to stress were hesitant to use refugia suggests that there was likely cognitive, visual, and/or physiological impairment. Blood lactate, glucose, and hematocrit measures were perturbed at 15 and 30 min after the stressor, relative to controls. However, measurements of oxygen consumption rate revealed that about 50% of metabolic recovery occurred within 30 min after the stressor, coinciding with apparent cognitive/visual/physiological recovery. Recovering the treatment fish in aerated, flow-through chambers for 30 min before introduction to the behavioral arena restored reflexes, and "recovered" fish behaved more similarly to controls. Therefore, we suggest that temporarily holding coral reef fish that have undergone an exhaustive fishing interaction and an air exposure episode should enable significant recovery of cognitive and metabolic attributes that would enable fish to more rapidly locate and utilize refugia to avoid postrelease predation. However, after nonexhaustive fishing interactions (i.e., minimal reflex impairment), it is likely that immediate release would be most beneficial.