En<rainiticnt estimates. Annual entrainment estimates for selected species of larvae were calculated 

 from 1976 through 1985 and for eggs from 1979 through 1985. These estimates were obtained by 

 multiplying the median density at FN during the period when 95% of the annual cumulative abundance 

 occurred times the total volume of water passed through MNPS during the same period. A nonparametric 

 method (Snedecor and Cochran 1967) was used to construct a 95% confidence interval around each 

 median density and corresponding entrainment estimate. 



Impingement estimates. Historically, several methods were used to estimate impingement when counts 

 were no longer made daily after April 1977. The first method used the real-time to sample-time ratio to 

 obtain estimates. Beginning in 1979, monthly impingement estimates were based on the extrapolation of 

 actual counts using a volumetric ratio. The daily cooling-water volume was calculated based on 15 min 

 flow rates from 0000 to 2345 for the date on which the impingement sample was taken during the morning. 

 This flow rate was then lagged back one day before it was used in the estimation procedure. The present 

 estimation procedure was developed in 1985 to account for the fact that impingement rates are directly 

 influenced by cooling water flow (Con Ed and PASNY 1977; lawler, Matusky and Skelly Engineers 1980). 

 Cooling-water volume estimates corresponding to the actual 24-h impingement period (0800 to 0745) of 

 each sample were used in order to improve accuracy. Within each monfh, an estimate for every day not 

 sampled was calculated by multiplying the average impingement density (number of fish per m of cooling 

 water) based on the days sampled in that month times the volume of cooling water on each day not 

 sampled. All of these daily estimates were then added to the sum of the actual sample counts to arrive 

 at the monthly totals for each species. Annual impingement estimates were calculated by summing the 

 monthly estimates. 



Fish length frequency data. As indicated previously, sampling effort was stratified by season for seine 

 sampling and by month for impingement sampling during some periods of the study. Therefore, whenever 

 appropriate, the length-frequency data were weighted to account for unequal effort during the year. Because 

 seine sampling effort from April through October was twice that during the remainder of the year, data 

 collected from November through March were weighted by a factor of two. For impingement collections, 

 monthly weight factors of 4 (.January), 2 (February and March, 6 (April), 7 (May through November), 

 and 3 (December) were used to standardize monthly effort close to 30 (range of 28 to 32). 



17 



