Fish distribution patterns in Pennsylvania: Anthropogenic influences and the status of rare fishes

To document long-term changes among Pennsylvania's fish communities, I assembled a fishes database using a geographic information system. Using these data I investigated historical and extant indigenous fish distribution patterns, assessed the influence of introduced fishes on native fish communities, examined the relationship between landscape alterations and fish community stability, and assessed the current status of rare and endangered fishes. Over the last 100 years, 11 fishes have been extirpated from Pennsylvania rivers and streams, and seven fishes, previously considered extirpated are present in contemporary collections. Eighty-percent of 104-delineated watersheds experienced declines in fish species richness. Cluster analysis revealed that several unique community groupings exist among Pennsylvania's native fishes, but the presence of exotic and introduced fishes appears to be eroding the uniqueness of these fish communities. Among 200 small watersheds, 400 historical and contemporary fish collections were analyzed in conjunction with land use and land cover data. Significant relationships were found between forested and agricultural land use percentages and the Jaccard coefficient of similarity. Relationships among urbanized watersheds were not so clearly determined. Agricultural and developed watersheds experienced greater species declines than did those with increased forested land amounts. Declines in distribution were greatest among insectivores and benthic insectivores, while increases were greatest within the insectivore-piscivore fish guild. Land use alterations have exerted some influence on Pennsylvania's fish community structure and certain species occur in small enough numbers to warrant protection. I evaluated current species' designations using a species' overall distribution and abundance over a 32-year period. My results indicate that 54 Pennsylvania fishes could be considered rare: 28 endangered, 15 threatened, and 11 candidate; representing nearly 35% of Pennsylvania's native fish fauna. Testing a 30% rarity expectation among each fish Family revealed no over or under prediction among species designations. The Ohio River drainage, which contains over 60% of these rare fishes, constitutes 30% of Pennsylvania's total land area. Less than 10% of the land in the Ohio River Drainage is publicly owned, and little of that supports rare fishes. These results suggest that conservation efforts, particularly on private lands, need to be implemented to preserve Pennsylvania's fishes.