recorded for a species exceeded 100 were randomly chosen to form the 

 data base. Fifty individuals per sample date (600 total) for each 

 species were then randomly removed from this base (with replacement) and 

 the length distributions derived from each were compared. Of the five 

 species considered (winter flounder, Atlantic silverside, threespine 

 stickleback and grubby, Atlantic long-finned squid), all demonstrated 

 extreme closeness of fit (P > .98, Table 6). Therefore, subsamples of 

 50 individuals per species are adaquate to represent length information. 



Estimating Monthly Impingement 



The third change concerns the technique used to estimate species 

 impingement totals. Beginning with the 1979-80 annual report (NUSCo 

 1981a) monthly impingement estimates were based on actual counts (3 

 days/week) extrapolated using a volumetric ratio. Previously counts 

 were multiplied by a real time to sample time ratio. The volumetric 

 method estimates impingement by multiplying the actual monthly count for 

 each species by a ratio of the cooling water flow during the days 

 sampled in the month to the total cooling water flow for that month. 

 The volumetric method is considered more accurate in that impingement 

 levels have been found to be influenced by cooling water flow (Con Ed. 

 1977; PSE&G 1980; NUSCo 1982; WPLC 1976). A comparison of estimates 

 based on each method showed that differences are only a matter of a few 

 percentage points. 



Despite efforts to control precision and accuracy of impingement 

 data there were factors known to introduce sample bias resulting in 

 underestimates of impingement totals and overestimates of mean lengths. 

 For example, at Units 1 and 2, specimens have been lost for a variety of 



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