ICHTHYOPLANKTON ASSEMBLAGE STRUCTURE IN MISSISSIPPI SOUND AS REVEALEDBY CANONICAL CORRESPONDENCE ANALYSIS

The spatiotemporal dynamics of the ichthyoplankton assemblage structur e were investigated in Mississippi Sound, a northern Gulf of Mexico es tuary. The study was based on a comprehensive survey constituting 528 collections from 22 stations over 12 months at two tow depths. Importa nt environmental correlates of assemblage structure were identified us ing canonical correspondence analysis (CCA). A wide taxonomic diversit y was encountered during the ichthyoplankton survey, including 152 tax a distributed among 48 families. Strong physical gradients in water te mperature, dissolved oxygen and salinity correlated predominantly with ichthyoplankton assemblage structure, and reflected substantial spati otemporal variation. The CCA results were interpreted in light of adul t life-style characteristics. Ecological groups of larvae, as defined by adult life-style characteristics for respective taxa, showed distin ctive dispersion patterns in 2-dimensional canonical space. A diverse group of offshore demersal taxa clustered as larvae in a region of CCA space corresponding spatiotemporally with stations located in passes and outside of the Sound during late summer and autumn. Other ecologic al groups, such as the inshore nektonic and offshore pelagic fishes, w ere widely dispersed as larvae in canonical space, with member taxa oc curring under dissimilar physical conditions. Estuarine embayments in the north-central Gulf of Mexico, like Mississippi Sound, might: be vi ewed appropriately as landwardmost sections of the wider, highly produ ctive nursery grounds of this region. (C) 1996 Academic Press Limited