Monitoring the marine environment of Long Island Sound at Millstone Nuclear Power Station, Waterford, Connecticut : summary of studies prior to Unit 3 operation / [prepared by the Environmental Laboratory staff of Northeast Utilities Service Company].

Abstract

Several programs were established to provide baseline data for assessing impacts of MNPS on fish assemblages. These include studies of planktonic, demersal, pelagic and shore-zone fish assemblages, and estimates of the number offish impinged and entrained. Plankton studies conducted since 1973 included collections of fish larvae at various stations, and entrainment mortality and thermal tolerance research on selected larval fish taxa. The trawl sampling program was established in 1973 to monitor spatial and temporal fluctuations of demersal fish. The gill net program, started in 1971 to provide qualitative estimates of local pelagic fish assemblages, was dropped at the end of 1982 because catches were generally low and none of the species collected were adversely affected by MNPS. The seine sampling program was established in 1969 to monitor shore-zone fish. Impingement monitoring began at MNPS Unit 1 in 1972 and at Unit 2 in September 1975 and was supplemented by several fish diversion and survival studies. These programs, which provide the data necessary for assessing the effects of two-unit operation also provide the baseline for three-unit impact assessment.Over 100 taxa of fish have been collected in the various Fish Ecology monitoring programs at MNPS from .January 1976 through December 1985. Composition of the fish assemblages studied during that period remained relatively stable and were typical of those reported for LIS by other researchers. Eight taxa were selected for detailed analyses based on their susceptibility to impact from impingement and entrainment: anchovies, sand lance, sticklebacks, silversides, tomcod, grubby, cunner and tautog.The abundance of these taxa varied both seasonally and annually in all programs and to separate fluctuations representing natural variability from those resulting from the construction and operation of MNPS, a time-series approach was developed and applied to the monitoring data. This approach, which combined several statistical techniques (harmonic regression, analysis of variance and time-series analysis) to summarize catch fluctuations in the long-term data series, provided confidence intervals that were narrower than those associated with annual or monthly means or medians and was, therefore, more sensitive to unusual abundance fluctuations.The abundances of potentially impacted taxa remained relatively stable throughout the 10-year period, except for larval and juvenile sand lance, and larval anchovy, cunner and tautog. Except for larval sand lance, these abundance changes were short-term. Larval sand lance abundance decreased during 1982 and has remained low since then. A mass impingement (390,000) of sand lance juveniles occurred in a one week period in .luly 1984 but was an uncommon event and is not expected to recur. 10In 1984, there was a marked decrease in the abundance of larval anchovy, cunner and tautog but this decrease was also observed in other parts of LIS. The reasons for this decline were not known but during this time ctenophores, a plankton pre...