variability in impingement catch of most species changes considerably 

 because of plant operations, local changes in number and distribution, 

 and varying susceptibility to impingment due to changes in behavior or 

 response to physical environmental factors such as water temperature and 

 wind. Sampling effort should therefore change in proportion to the 

 variability in catch in order to obtain more precise impingement estimates. 

 The methodology of El-Shamy (1979) was applied to determine the precision 

 of the winter flounder impingement estimates for the current sampling 

 program and that for an optimum allocation of the same effort to reduce 

 sampling variability within months. In addition, the precision was 

 determined for various reductions in sampling effort. 



The data for winter flounder impingement at Millstone Units 1 and 2 

 from 1978 through 1981 were used to examine the variability of the 

 catch. The annual mean number of winter flounder per impingement collec- 

 tion during 1977-81 was 31.2 (Table 30). Largest and most variable 

 impingement catches occurred in January (72.4) and February (122.5) and 

 smallest and least variable from July through November (3.3-6.8). The 

 precision for the current program with uniform sampling effort (3 samples 

 per week, 156 per year) and with a standard error of 7.8 is 50% (Table 

 31 ). For optimum allocation, samples were redistributed among months 

 with more samples in months with greater variability in catch in order 

 to reduce the associated standard errors (Table 32 ) . The first redis- 

 tribution of effort was made without restriction to the number of samples 

 per month, thus February was allocated 80 samples. The excess sampling 

 days were then redistributed among the other months. The precision 

 improved from 50 to 10% (standard error of 1.6 for the same mean of 

 31.2) when the same number of samples as currently collected was allocated 



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