标题：The Impact of Above Grade Sewerline Crossings on the Distribution and Abundance of Fishes in Recovering Small Urban Streams of the Upper Ohio River Valley
摘要：The distribution and abundance of fishes along four small urban streams in western Pennsylvania and northern West Virginia were examined. The water quality of three of these streams was moderately to severely degraded along various reaches. While resident fish communities in the degraded streams were depauperate, reaches with access were nonetheless routinely used by transient species from the nearby navigation system. Species richness and biomass of the fish communities dropped abruptly upstream of above grade, concrete-encased sewerline crossings. Similar abrupt declines in diversity and biomass were also apparent upstream of a sewerline crossing in a nondegraded stream with a high quality fishery. Where access for transient fishes from larger downstream waters was denied, index of biotic integrity scores declined by 26% to 43%, and species diversity declined by 39% to 69%. Also, partly because of the tendency for the transients to be larger than resident fishes of small streams, there was a biomass reduction between downstream and upstream sites of 81% to 87%.
