Prey-Dependent and Size-Selective Mortality Obscures the Importance of Larval Traits to Recruitment Variability in Pink Snapper

In fishes, the growth-mortality hypothesis has received broad acceptance as a driver of recruitment variability, with food-limitation and selective mortality resulting in the removal of slow-growing, small individuals from the population. Based on long-term monitoring in Port Phillip Bay, Australia, pink snapper, Chrysophrys auratus (Sparidae), experience high recruitment variation. Lower recruitment years were characterised by low larval prey availability and slow larval growth, and the risks of starvation and predation are likely to be greater in these years. To test this, we considered both intra- and inter-annual variation in mortality, using a five-year (2005, 2007, 2008, 2010, 2011) data set of larval and juvenile snapper abundances and their daily growth histories, based on otolith microstructure. An index of daily mortality within and among years was related to per capita prey availability, providing support for the match-mismatch hypothesis. Selective mortality acted on larval size at five days post hatch in four low and average recruitment years. The highest recruitment year (2005) was characterised by no size-selective mortality. Variability in the magnitude and occurrence of mortality in species with complex life cycles can obscure relationships between larval traits and population replenishment, leading to an underestimation of their importance in recruitment studies.