HINCKLEY: REPRODUCTIVE BIOLOGY OF WALLEYE POLLOCK 

  I — 



/ 



\ 



\ 





N \. 



X.N 



Northwest / I 



"> slope 



Northwest 

 shelf 



\ 



N 

 I 



Southeast 

 shelf 



sr% 



"200 mile 



imit 





^ 



/'Y 



Southeast 

 slope 



Aleutian Basin 







<5^ 



. 200 nV 



^ 



^ 



^ 



61 OON 



- 56 OON 



i;'9 OOE 176 OOW 171 OOW 166 OOW 



Figure 1.— Sampling areas within the Bering Sea. Shaded areas are buffer zones. 



61 



 51 OON 

 OOW 



The cells were then classified for each sex and 

 quarter using an index of similarity, Pris ). This 

 index was based on the ratio of the sum of squared 

 deviations of the observed mean length at age 

 from the 6-yr fitted average for the southern re- 

 gion, to the sum of the squared deviations of the 

 observed mean length at age from the southern 

 and northern regions combined: 



Pr{s) = 1 -[SS{s)/SSis) + SSin)] 



where SS(s)^ Sum [X(i) - ES(i)f and 



SS(n) = Sum [X(i) - EN(i)]^. 

 (=1 



SS(s) = the sum of squared deviations for 



the southern regions, 

 SSin ) = the sum of squared deviations for 



the northern regions, 

 ES (i) = the 6-yr fitted average from the 



southern region, 

 End) = the 6-yr fitted average from the 



northern region, 



I = age, 

 X(i) = the observed mean length at age 

 ii), 

 k = the maximum age observed. 



Thus, Pris) is the likelihood of the cell being a 

 southern cell. Arbitrary cut-off values of 0.75 and 

 0.25 were imposed to classify the southern and 

 northern cells, respectively. Any value >0.25 and 

 <0.75 defined an unknown cell. 



New 6-yr average growth curves were fitted for 

 each region by quarter and sex using only those 

 estimates of mean length at age from cells that 

 were classified as northern or southern (i.e., ex- 

 cluding all unknown cells). Partial F-tests 

 showed (P < 0.001) that there are significant re- 

 gional differences in growth between the "south- 

 ern" (southeast shelf and slope) and the "north- 

 ern" (Aleutian Basin and northwest slope) areas. 



Using the new 6-yr average growth curves, the 

 1984 data were divided into cells, compared to 

 Francis and Hollowed's (unpubl. data) growth 

 curve, and were classified as northern, southern, 

 or unknown, based on the index of similarity 

 [Pris)] for both sexes combined: 



483 



