Predation risk mediates cognitive constraints following physical exertion in schoolmaster snapper

Abstract

A large body of literature suggests that physically exhausted fish, including those that are released following fisheries interactions, experience behavioural and cognitive constraints and are at elevated risk of predation during homeostatic recovery. However, previous studies have focused on exhausted fish subsequently encountering predators, and not on fish that had been exposed to elevated predation risk prior to exhaustive exercise. Here, we exercised individual schoolmaster snapper (Lutjanus apodus) for 0, 1, or 4 min via hand chases following exposure to conspecific chemical alarm cues or seawater controls. The snapper were then introduced into one end of a rectangular arena supplied with mangrove prop roots as a refuge at the opposite end. Snapper exposed to the seawater control treatment demonstrated graded responses in mean times to move one body length and latency to enter the refuge, with unchased fish taking the least time and fish chased for 4 mins taking the longest. Amongst the snapper pre-exposed to alarm cues, the graded response did not occur and mean responses did not differ between chase treatments. Consistent with increased antipredator vigilance, alarm cue-exposed snapper were more likely to subsequently exit the refuge and to do so more times than fish exposed to seawater controls, independent of chase time. These observations suggest that perception of elevated predation risk may induce a conditional response offseting the behavioural and cognitive constraints associated with physical exhaustion through an unknown physiological mechanism to prioritize immediate survival-oriented behaviours over recovery.