Food Habits of Mangrove Fishes: A Comparison along Estuarine Gradients in Northeastern Florida Bay
Abstract:Gut analyses were performed on 1,081 fishes from four species resident in mangrove habitats in northeastern Florida Bay to determine: (1) if the diets varied systematically along a complex salinity gradient; and (2) if diets in the upstream areas were of lower overall quality than those from portions of the gradient with less salinity variability. Fishes commonly consumed amphipods, isopods, shrimp, nematodes, eggs of unknown origin, fish, insects, and algae. Diets of two of the four species differed significantly along the estuarine gradient. This systematic variation in diet along the longitudinal gradient may distinguish locations in terms of habitat quality. The tidewater mojarra (Eucinostomus harengulus) and goldspotted killifish (Floridichthys carpio) ingested more algae, a relatively low quality food, upstream in areas of high salinity variability. These same species ingested more benthic invertebrates, relatively high quality foods, downstream in areas of lesser salinity variability. If we accept the premise that gut contents of fishes are a good indicator of habitat quality, then these upstream locations afford fishes a relatively poor quality habitat. We propose that highly variable amounts of submerged aquatic vegetation in upstream locations provide reduced (and variable) abundances of benthic invertebrates for fishes at these sites. Our results, combined with those of others cited herein, provide support for the hypothesis that water management practices in the catchment of northeastern Florida Bay may be, at least in part, responsible for lowered productivity there. We suggest that gut contents of resident fishes can be used as one measure of habitat quality as part of a comprehensive monitoring and restoration program for the region.
Document Type: Research Article
Publication date: May 1, 1994
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