HUGHES and HIRSCHHORN: BIOLOGY OF WALLEYE POLLOCK 



Table 2.— Mean length (centimeters) at age of western Gulf of Alaska Theraga chalcogramma by survey and sex; growth 

 parameters (L^, A', <„) for original and "selected" data sets, with standard deviation (a-) of departures from fit; departures of 

 1967 and 1970 year class mean lengths at age, from fit (A67YC, A70YC). 



'Age, increment (AT) for sample date 



'Extreme frequencies eliminated in computing mean length at age 7. 



es to see whether differences agree, in direction, 

 with those generated by use of synthetic cohort 

 growth curves. In this comparison, only early 

 season samples were considered. Both year classes 

 indicated lower mean lengths than other year 

 classes sampled at like ages. 



Growth completion rates (A') were 0,34 in males 

 and 0.28 in females, from surveys indicating 

 prominence of the 1967 or 1970 year classes (Fig- 

 ure 3). A similar averaging of length-at-age in all 

 remaining data gave higher A'-values (0,40 and 



0,35, respectively), possibly reflecting lower rela- 

 tive year class strengths. We also ranked relative 

 percent frequency at each age within range 2-8 yr, 

 then fitting lengths of ages within ranks, thus 

 replacing the original time-area classifications. 

 Extreme A'-values (males 0,25, 0.38; females 0,24, 

 0,40) were associated with extreme ranks; how- 

 ever, at intermediate ranks fluctuations were con- 

 siderable. The A'-ranges from this rearrangement 

 of the data are similar to those shown in Table 2 for 

 the original data configurations by survey (males, 



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