Equivalent Adult Estimates for Losses of Fish Eggs, Larvae, and Juveniles at Seabrook Station with Use of Fuzzy Logic to Represent Parametric Uncertainty

Abstract

Regulatory agencies continue to direct their attention to the impact of coastal power generating stations on fishery resources. We analyzed 6 years of entrainment and 2 years of impingement data for selected species at the Seabrook Station, Seabrook, New Hampshire, in combination with selected life history parameters to provide equivalent adult estimates of fish losses at the station. The species examined were the winter flounder Pleuronectes americanus pollock Pollachius virens, and red hake Urophycis chuss. The standard equivalent adult method involves estimates of numbers of fish entrained and impinged, survival from egg to impacted life history stage, and the average lifetime fecundity of a newly recruited female. However, this method does not account for the uncertainty in model parameters. The method was extended by applying fuzzy arithmetic to fuzzy numbers constructed from empirical data to provide upper and lower bounds on the estimated losses as equivalent adults. The analyses indicated that impingement losses were not ecologically significant for any of the three species. The largest equivalent adult losses were attributed to the entrainment of winter flounder larvae. However, even these represented an ecologically insignificant fraction of any sustainable stock. The offshore location of the intakes at middepth and the use of velocity caps were believed to account for the relatively small losses compared to similar coastal facilities. A specific comparison of equivalent adult estimates for winter flounder from another coastal power station (Pilgrim Station) indicated losses due to entrainment that were generally higher than for Seabrook Station.