Meeting Abstract
Many species of freshwater and marine fish experience high levels of mortality during early ontogeny. While few experimental studies have identified why larval fish perish, recent research suggests that the hydrodynamic regime restricts their ability to acquire prey, and possibly leads to starvation. In this study, gilthead seabream (Sparus aurata) larvae were reared under increasing water viscosities to test the hypotheses that (1) the hydrodynamic regime affects survival through the critical period, and that (2) phenotypic differences among larvae predict survival. Seabream were reared individually, and phenotypic traits of survivors and mortalities were assessed on each rearing day. Survivorship was negatively correlated with viscosity and age, and positively correlated with body size. Additionally, individuals reared under high viscosity exhibited the greatest measures of body depth. Other morphological characteristics that are linked to foraging and locomotion were weak predictors of survivorship, but there was higher morphological variance among mortalities. These data suggest that larger body sizes may be beneficial for overcoming the viscous effects of the hydrodynamic regime during the earliest stages of ontogeny, and that functional, external morphological traits may have a secondary role in determining survival of larval fish.
