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. 



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