Variations in structure of estuarine fish communities in relation to abundance of submersed vascular plants

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Abstract
Fish communities and other ecological variables were sampled for 6 mo (May to October) in successive years (1979, 1980) at vegetated and non-vegetated areas in 2 distinctively different littoral zones (an open bay and a protected cove) of mid-salinity Chesapeake Bay, USA. Fish abundance, biomass and species richness were higher in vegetated areas at both sites, and were significantly correlated with macrophyte biomass. Diel patterns of fish abundance varied, but highest catches generally occurred at dusk or at night. At one sampling site fish assemblages were dominated by smaller individuals in the vegetated area, suggesting an attraction of juveniles to macrophyte beds for food or refuge from predation. Larger piscivorous fish, which were also caught in greater numbers in vegetated areas, may have been attracted there by high densities of forage fish. At the cove site the biomass of Paleomonetes sp. was comparable to that of the fish community towards the end of the plant growing season. Benthic infauna were also more abundant in vegetated areas at both sites, and stomach analyses indicated these organisms to be the dominant food resources for common fishes. Diets were generally non-selective in non-vegetated areas while highly selective for epiphytic fauna in macrophyte beds. Fish stomachs were also significantly fuller in vegetated areas, indicating generally greater feeding success. Fish production varied among major species but was higher overall at vegetated areas, following the seasonal patterns of primary production. Most of the differences in fish production between areas were attributable to higher instantaneous growth rates rather than higher biomass. It appears that the greater abundance and species richness of fish assemblages in vegetated areas of this region of Chesapeake Bay resulted from the attractiveness of these habitats as rich sources of preferred foods.