Changes in Impingement and Entrainment Characteristics As a Function of Changes in the Fish Aggregation of Black Rock Pool of the Schuylkill River from 1970 to 2007

Following the a massive de-siltation of the Schuylkill River and implementation of various management practices, most notably those required by the Clean Water Act of 1972 and the banning of phosphate detergents, great improvements in water quality of the Schuylkill River were observed.  These improvements were evident during almost 40 years of fish collection data (non-continuous) from studies in the vicinity of Cromby Generating Station (CGS) on Black Rock Pool of the Schuylkill River, PA.  

CGS operated throughout a multi-decade period of time during which a pollution tolerant fish community, dominated by pumpkinseed, brown bullhead, redbreast sunfish and goldfish, was present in the river.  When continuing improvements in water quality in the Schuylkill River occurred, the relative abundance of these fish species declined.  The decline of these four fish species was so great that they moved from predominance to minor components of the fish community.  Despite frequent predictions throughout the United States that improving water quality would result in increased levels of impingement and entrainment, levels at CGS did not increase due to increased competition and predation facilitated by improving water quality.