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Volume 2, Pages 169-189
Research Article

Indicators of AEI Applied to the Delaware Estuary

1LWB Environmental Services, Inc.,105 Wesley Lane, Oak Ridge, TN 37830, USA
2PBSJ, 12101 Indian Creek Court, Beltsville, MD 20705, USA
3P.O. Box 459, Gaecklin Rd., Boothbay, ME 04537, USA
4University of Washington, School of Fisheries, Box 355020, Seattle, WA 98195, USA
55Dalhousie University, Department of Biology, Halifax Nova Scotia, B3H 4J1, Canada

Received 15 November 2001; Revised 8 April 2002; Accepted 17 April 2002

Academic Editor: Joe Wisniewski

Copyright © 2002 Lawrence W. Barnthouse et al.


We evaluated the impacts of entrainment and impingement at the Salem Generating Station on fish populations and communities in the Delaware Estuary. In the absence of an agreed-upon regulatory definition of “adverse environmental impact” (AEI), we developed three independent benchmarks of AEI based on observed or predicted changes that could threaten the sustainability of a population or the integrity of a community.

Our benchmarks of AEI included: (1) disruption of the balanced indigenous community of fish in the vicinity of Salem (the “BIC” analysis); (2) a continued downward trend in the abundance of one or more susceptible fish species (the “Trends” analysis); and (3) occurrence of entrainment/impingement mortality sufficient, in combination with fishing mortality, to jeopardize the future sustainability of one or more populations (the “Stock Jeopardy” analysis).

The BIC analysis utilized nearly 30 years of species presence/absence data collected in the immediate vicinity of Salem. The Trends analysis examined three independent data sets that document trends in the abundance of juvenile fish throughout the estuary over the past 20 years. The Stock Jeopardy analysis used two different assessment models to quantify potential long-term impacts of entrainment and impingement on susceptible fish populations. For one of these models, the compensatory capacities of the modeled species were quantified through meta-analysis of spawner-recruit data available for several hundred fish stocks.

All three analyses indicated that the fish populations and communities of the Delaware Estuary are healthy and show no evidence of an adverse impact due to Salem. Although the specific models and analyses used at Salem are not applicable to every facility, we believe that a weight of evidence approach that evaluates multiple benchmarks of AEI using both retrospective and predictive methods is the best approach for assessing entrainment and impingement impacts at existing facilities.