Coherent growth and diet patterns in juvenile spot ( Leiostomus xanthurus Lacepéde) reflect effects of hydrology on access to shoreline habitat

Abstract

A previous study of hydrological effects on early recruitment of estuary-dependent spot ( Leiostomus xanthurus Lacepéde) underscored the importance of fluctuations in temperature and salinity on early growth; however, considerable variability in early growth remained unexplained. Hydrology might also influence early growth by mediating access to emergent shoreline vegetation (ESV). In this study, access to ESV was mediated by hydrology over the 38-day study period. Furthermore, otolith microstructure inferred that standard deviation (S.D.) and mean growth decreased with access to ESV. Diets of fish during onshore and offshore frontal passages were consistent with the growth patterns. Less access to ESV corresponded with more variable and greater amounts of food; whereas more access to ESV coincided with the opposite diet pattern. Ontogenetic diet relationships were well defined during ESV access, whereas they were undefined during ESV restriction. This study illustrates how physical forcing can indirectly affect early growth through complex interactions between abiotic and biotic variables.