Effects of Urbanization on Brown Trout Salmo Trutta, Other Fishes and Macroinvertebrates in Valley Creek, Valley Forge, Pennsylvania

Abstract

We determined the effects of urbanization on fish and benthic macroinvertebrate communities of Valley Creek and its tributary, Little Valley Creek, in southeastern Pennsylvania. Brown trout (Salmo trutta) were a major component of the fish community except in the urbanized upstream portions of the watershed. Growth rates and condition factors of brown trout were within the upper range of reported values, indicating high productivity in the nonurbanized portions of the Valley Creek system. In the urbanized portion of the watershed, fish communities and benthic macroinvertebrate communities consisted of pollution-tolerant species (e.g., Semotilus atromaculatus, Lepomis cyanellus, Isopoda) and brown trout were absent. In nonurbanized areas, pollution-tolerant fish and benthos declined while less tolerant species (Salmo trutta, longnose dace; Rhinichthys cataractae, darters; Etheostoma olmstedi, cutlip shiners; Exoglossum maxillingua, and invertebrates such as Amphipoda, Ephemeroptera, and Trichoptera) increased. Regressions of community-level patterns (species richness, diversity, evenness, number of trout, number of age-0) trout) vs. watershed physical characteristics (stream order, distance from source, stream discharge, water temperature) differed between the two main branches of the stream (Valley Creek, Little Valley Creek). This indicated that localized factors related to urbanization differentially affected these areas. Dramatic changes in the fish and benthic communities in the most urbanized sections of Valley Creek demonstrated the deleterious impacts associated with increasing urbanization of file watershed.