YELLOWTAIL FLOUNDER OFF NEW ENGLAND 



207 



lOO-i 

 75- 

 50- 

 25- 



- 



1942- 1ST Q 



N-25 



1942 



-3D Q 



N'74 



1942 



4THQ 



N'256 



3D Q. 



N-668 



30 Q 



N-499 



NUMBER OF ANNULI 



Fioube 20. — Age composition of yellowtail from the 

 southern New England stock during each quarter, 1942- 

 47. (N=number of fish.) 



An interruption in the sequence of summer and 

 winter populations occurred in 1945. Here we 

 find a close resemblance in the age distributions 

 of the third and fourth quarters which persisted 

 somewhat less clearly in the third and fourth 

 quarters of 1946 and 1947. The change may be 

 reflected also in the total landings, which were 

 markedly greater in the fall months of 1945 



through 1947 than in 1943 and 1944 (table 7). 

 The first and second quarters in 1945, 1946, and 

 1947 have age distributions which appear to differ 

 from those of the third and fourth quarters and 

 also among themselves. 



When we seek evidence of dominant year classes, 

 these changes in age distributions within the 

 southern New England stock emphasize the neces- 

 sity of comparing each quarter only with the same 

 period in other years and that with caution. 

 When we do so for the first quarter (fig. 21) by 

 plotting the deviations from the average age-fre- 

 quency curve for the 6 years, 1942-47, we find one 

 series of small modes as indicated by the dashed 

 line. The series runs from the mode at the second 

 annulus in 1943 to the mode at the fifth annulus 

 in 1946. Recalling that the second annulus in the 

 first quarter of 1943 was completed March 31, 

 1942, we identify this series of modes as repre- 

 senting a more abundant year class from the 1940 

 spawning. However, the age distribution during 

 the first quarter was remarkably uniform, and 

 this year class was only slightly more abundant 

 than the others — its maximum deviation above 

 the average being less than 9 percent. 



Turning to the second quarter (fig. 21), we find 

 little indication of a dominant year class passing 

 through the fishery. Only two pairs of modes sug- 

 gesting this appear — one from the 1941 year class 

 in 1944 and 1945 and the other from the 1942 year 

 class in 1946 and 1947. Since these modes are 

 neither preceded nor followed by peaks, their in- 

 terpretation as dominant year classes is dubious. 



Much clearer is the succession of modes from 

 the 1941 year class which appear as peaks from 

 1944 to 1947 in both the third and fourth quarters 

 (fig. 21). Why both of these quarters in 1943 

 produced fewer fish from this year class, which 

 was subsequently abundant, is of interest. Clearly 

 the 1941 year class was not as available as other 

 year classes at the 2-annuli stage during these 

 quarters, nor was it more available during other 

 quarters in 1943. 



Other features of these curves are significant. 

 The proportion of 2-annuli fish increased abruptly 

 in 1945 in both the third and fourth quarters, and 

 since no decrease occurred in the cull size (see 

 length frequency data, p. 245) they must have be- 

 come more available to the fishery. Significant, 

 too, is the fact that they either did not remain 



