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We developed an estuarine index of biotic integrity to assess habitat quality in Narragansett Bay, Rhode Island. Fish were collected at 18 fixed stations with a 61-m × 3.05-m beach seine once per month in July and August from 1988 to 1999. Stations were designated high or low quality depending on the total nitrogen concentration, number of low dissolved oxygen events, extent of human disturbance, abundance of macroalgae, and presence or absence of eelgrass Zostera marina. We used stepwise discriminant analysis on 13 candidate metrics based on fish community data to determine those most important in distinguishing between high and low habitat categories. We then used discriminant analysis and canonical discriminant analysis with the resulting significant metrics. The six metrics that were able to discriminate between sites were the number of estuarine spawner species, proportion of killifish, number of individuals, proportion of flounder, Shannon's diversity index, and proportion of benthic-associ...