Effects of post-settlement mortality on size and parasite load in juvenile Diplodus vulgaris and D. sargus in the Mediterranean

Abstract

This study explored how mortality processes influence life history traits of recently set- tled juvenile fishes (Diplodus vulgaris and D. sargus) in the Mediterranean. Mortality was estimated by measuring the decrease in abundance of a cohort from settlement to 4 mo post-settlement. Growth and parasite load were simultaneously measured over time to determine those phenotypes more sus- ceptible to mortality. Diplodus spp. juvenile mortality was between 71 and 81% over the 4 mo period. A decrease in the coefficient of variation in size over time suggests that mortality may influence growth of both Diplodus species. A decrease in parasite abundance of both Diplodus species 60 d after settlement suggests that fish with higher parasite loads may have been more susceptible to mor- tality. Overall, mortality did not act randomly in D. vulgaris and D. sargus cohorts, as the variance in both size and parasite abundance of recently settled juveniles was not comparable to that of the adult population; only larger, parasite-free individuals survived.