Monitoring at Unit 1 ceased with the installation of a fish return system in 1983. A gill-net program was 

 established in 1971 to monitor pelagic fishes that were not caught in the trawl or seine programs, but it 

 was discontinued in 1982 after an evaluation concluded that the gill-net program did not provide qualitative 

 data, was not cost effective, and did not sample potentially impacted fish (see Appendices la and lb and 

 NUSCo 1982c). 



The monitoring studies were supplemented over the years by several entrainment survival and fish 

 diversion studies, and by an evaluation of the Unit 1 fish return (sluiceway) system. Special studies of 

 mortality experienced by fish larvae during entrainment and the thermal tolerance of selected species were 

 conducted (Carpenter 1975; NUSCo 1975). Mortality of larvae entrained through Unit 1 was estimated 

 to range from 20 to 50%. I^arvae were captured at the intake, discharge and quarry cut and held for 24 

 hr at intake water temperatures. Laboratory thermal tolerance studies, conducted on larvae of the silverside 

 (Menidia spp.) mummichog (Fundulm spp.) and winter flounder {Pseudopkuronectes americanm) to assess 

 thermal effects of power plant entrainment, indicated that mortality was low for silversides and mummichogs. 

 The application of several devices (electric screens, noise generator, underwater lights, surface and bottom 

 barriers and barrier nets) was investigated in an attempt to divert fish from the intakes and reduce 

 impingement. Of the different devices tested, none reduced impingeftient (NUSCo 1976b). In 1980, 

 NUSCo (1981b) demonstrated that it was practical and cost-effective to backfit a fish return system at 

 Unit 1. A sluiceway was fabricated and installed there in December 1983, and results from a subsequent 

 study indicated that survival of demersal fish and non-molting crustaceans exceeded 70% (NUSCo 1986b). 

 Because the Unit 1 sluiceway has worked as designed and has successfully returned most organisms to 

 LIS, it has mitigated the impact of impingement. 



This report summarizes the monitoring data gathered by the ichthyoplankton, trawl, seine, and 

 impingement programs during the period of two-unit operation, 1976 through 1985. Accounts of the 

 evolution of these programs are also provided. In addition, the monitoring data and life history of eight 

 potentially impacted fish species are presented and evaluated to determine if two-unit operation of MNPS 

 has had any detrimental effect on them. Finally, it is noted that the monitoring data summarized in this 

 report consitute the baseline against which three-unit operational data will be compared after 1986. 



