COMPARISON OF FISH ASSEMBLAGES ASSOCIATED WITH SEAGRASS AND ADJACENT UNVEGETATED HABITATS OF PORT-PHILLIP BAY AND CORNER INLET, VICTORIA, AUSTRALIA, WITH EMPHASIS ON COMMERCIAL SPECIES

Species richness, abundance and biomass of fishes from seagrass and un vegetated habitats were analysed for sites in the Swan Bay region of P ort Phillip Bay, and Corner Inlet, Victoria, Australia. Fish assemblag es from intertidal Zostera muelleri sites showed greater similarity wi th a number of shallower unvegetated sites than to subtidal Heterozost era tasmanica. Similarly, subtidal, unvegetated sites in Swan Bay were more similar to subtidal Heterozostera sites than to other, generally shallower, unvegetated sites. Species richness was significantly high er in seagrass beds and showed an increase over the warmer months of t he year. Differences in abundance and biomass of fishes between vegeta ted and unvegetated habitats depended on the location of sampling. In general, abundance and biomass of fish in the deeper subtidal seagrass were significantly higher than in unvegetated habitats of the same de pth. In contrast, abundance and biomass were not significantly differe nt between seagrass and unvegetated habitats of the intertidal and sha llow subtidal zones when significant abundances of the long-finned gob y, Favonigobius lateralis, occurred on unvegetated habitats. As a cons equence, species richness would be expected to decrease with any seagr ass loss; however, decreases in abundance and biomass of fishes would be greatest with loss of deeper subtidal Heterozostera habitats. Altho ugh juveniles of a number of commercially important species were assoc iated with subtidal Heterozostera habitats, juveniles of other species of commercial significance were found on shallow, unvegetated habitat s. Newly settled juveniles of the King George whiting, Sillaginodes pu nctata, were associated with unvegetated patches amongst subtidal seag rass in Swan Bay, in contrast with a direct association with seagrass reported from other areas. (C) 1997 Academic Press Limited.