entrainment. F.ggs of cunner and tautog were the two most abundant egg taxa entrained; cunner was also 

 often caught in other sampling programs. Silversides ranked fifth in impingement. The grubby ranked 

 fourth among both impinged and entrained larval taxa. Sticklebacks and Atlantic tomcod each contributed 

 over 3% to the total impingement. 



Results for the two-unit operational period (1976-1985) are summarized separately for the 

 ichthyoplankton, impingement, trawl, and seine sampling programs, and are followed by a discussion for 

 each of the eight selected taxa. Although the analytical techniques previously described were applied to 

 the data of all eight taxa, not all of the analytical results provided useful interpretations for impact 

 assessments. Therefore, the results and conclusions that follow may be based on different techniques 

 depending on the sampling program and taxon. 



Ichthyoplankton 



Because natural ichthyoplankton mortality rates are one of the most important controlling factors of 

 adult fish stock abundance (Gushing and Harris 1973; Bannister et al. 1974; Gushing 1974; May 1974; 

 DcAngelis et al. 1977), additional mortality due to entrainment could affect local fish populations. Thus, 

 the plankton studies conducted at Millstone since 1973 have included ichthyoplankton entrainment esti- 

 mates, density indices, and species composition. The data summarized in this section arc from the period 

 1976 through 1985 and restricted to stations EN and NB. 



Annual entrainment estimates (based on medians) for the most common larval and egg taxa are 

 presented in Table 9. Anchovies were the most abundant fish larva entrained; annual estimates ranged 

 from a minimum of 1.5x10*' in 1984 to a maximum of 1,284x10^ in 1981, and the 10-yr total was 4,056x10^ 

 larvae. The numbers of larval sand lance and grubby entrained during 1976-1985, totaled 359 and 313x10*' 

 respectively and were an order of magnitude lower than the estimates for anchovies. During the past 7 

 yr, more cunner eggs were entrained than any other taxon (13,480x10 ). Median densities were relatively 

 constant and entrainment estimates ranged from 1,610 (1981) to 2,589 (1983) xlO^ eggs (Table 9). The 

 total entrainment estimates of tautog and anchovy eggs were about one-half and one-fifth, respectively, of 

 that for cunner. 



21 



