Seasonal variability in antipredator performance of red drum larvae

Variability in environmental conditions during early life-history stages can have important consequences for recruitment and population success. The red drum Sciaenops ocellatus spawns between September and November, a period of seasonal temperature decline overlain by quick and rather unpredictable change brought by frequent meteorological fronts. During 3 consecutive spawning seasons (2005 to 2007), we assessed behavioral performance of wild-caught red drum larvae in response to simulated predator attacks. Responsiveness and reactive distance of postsettlement red drum larvae decreased towards the end of the season. Several factors could explain the observed seasonal trends in escape performance, including variability in egg quality, changes in the intensity of predation, and declining temperatures (which may act on performance through a developmental mechanism). Our data suggest that long-term thermal experience (10 to 14 d) is more important than short-term thermal acclimation in determining escape performance. These results imply that late season larvae are less likely to survive to the juvenile stage and recruit to the fishery.