Table 8. — Annual average density indices (ADIs; in metric tons per hour trawled) and relative ADIs (as percentage of I97S ADD 

 for walleye pollock in the eastern Bering Sea by area-time cells (see Figure 2 and text) and vessel-gear categories, 1973-76. 



'GRT is gross registered tons. 



'Standardized to mothership pair trawler ADl units. 



Tables— Overall average density indices (ADIs; as percent of 1976 metric tons per hour 

 trawled) for walleye pollock in the eastern Bering Sea computed from ADIs in area-time 

 cells which were weighted by catches, 1973-76. 



^jiT^t-srs- ,00 Q 



Variances about the monthly and annual means of 

 catch, effort, and catch per unit effort (CPUE) calcu- 

 lated from the daily records were small for most years. 

 In 1964 and 1965 when the number of daily records was 

 small, the coefficients of variation were 19% and 9%. As 

 the annual sample size of daily records approached 300, 

 coefficients of variation for CPUE generally declined to 

 below 4'^c, which was about the level for the data from 

 1966 to 1969. As the fishery expanded after 1969 and the 

 number of daily fishing records approached 5,000; coef- 

 ficients of variation were reduced to between 1% and 

 2%. 



Figure 3.— Trends in catch per unit effort (CPUE) and average den- 

 sity index (ADl) for walleye pollock in the eastern Bering Sea, 1964- 

 78. 



10 



