Selective mortality during the larval and juvenile stages of snappers (Lutjanidae) and great barracuda Sphyraena barracuda

Abstract

Selective mortality during the early life stages in marine organisms can affect the magnitude and composition of recruitment, yet these processes have not been examined in economically important predatory coral reef fishes. Utilizing 3 different stage-specific sampling techniques (shipboard plankton tows, larval light traps, juvenile surveys/seines), we repeatedly sampled multiple cohorts of 3 lutjanid (Ocyurus chrysurus, Lutjanus synagris, and L. griseus) and 1 sphyraenid (Sphyraena barracuda) species through time in the Florida Keys (USA). Comparisons of daily growth and size-at-age (from otolith microstructure analysis) for early- and late-stage larvae and young and older juveniles revealed that size- and growth-selective processes operate during the larval stage, while after settlement, growth-selective mortality occurred in the absence of significant size differences. In all 3 lutjanid species, larvae and juveniles that were larger at hatch preferentially survived. In O. chrysurus and L. synagris, selective mortality of smaller, slowergrowing individuals during the larval stage reduced variability in these traits such that larvae were of similar sizes at settlement. Following settlement, patterns of growth-selective mortality were initially opposite (favoring faster juvenile growth in L. synagris, and slower growth in O. chrysurus), but ultimately survivors of both species grew faster, leading eventually to a size advantage. In contrast, patterns of selective mortality were not evident until settlement in L. griseus and S. barracuda, and favored larger and smaller sizes-at-settlement, respectively. Overall, our results reveal important patterns of selective mortality and variability between even closely related species. © Inter-Research 2013.