Age-1 Red Snapper Lutjanus Campechanus Exclude Age-0 Red Snapper From High-Quality Recruitment Habitat

Current evidence suggests that juvenile mortality rates of red snapper Lutjanus campechanus are density dependent, with year-class mortality varying inversely with year-class strength in both age-0 and age-1 fish.  Such compensatory effects often arise in early post-settlement reef fishes as a result of high levels of predation when refuge space is limiting.  Here we present results of an observational study which suggests that (1) high-quality settlement habitat is a limiting resource for early post-settlement age-0 red snapper, and (2) age-1 red snapper displace age-0 red snapper from high-quality refuge habitat.  Visual surveys of fish communities on small artificial reefs off the coast of Alabama during the red snapper recruitment season (August 2012) demonstrated that abundance of age-0 red snapper was 6.7 times greater (95% C.I. from 3.0 to 15.2) on recently deployed reefs lacking potential competitors, compared to one-year-old reefs with high densities of potential intra- and interspecific refuge competitors (p < 0.0001).  After accounting for this reef-age effect, the abundance of age-0 snapper was negatively correlated with the abundance of age-1 snapper (p = 0.036).  Reductions in age-0 snapper abundance of 29.8% (95% C.I. from 2.4 to 49.6%) were associated with every doubling in the abundance of age-1 red snapper.  This study suggests a potential mechanism by which early post-settlement mortality in red snapper may be a function of predation, habitat availability, and the density of the previous snapper year class.  These results have important implications for constructing accurate fisheries models for this important Gulf of Mexico fishery species.