Spring 



The catch per tow (total and by ages) and the percentage age composition by 

 subarea for 1950 (spring is shown in figure 8 and table A-2). The total catch per tow 

 was greatest in subarea N, showing a shift from the summer distribution. Two-year- 

 old fish dominated the catch as in the summer of 1950. 



Because these subdivisions of the bank are based on commercial fishing concen- 

 trations and thus purely artificial boundaries, discussion of the distribution of 

 different age fish will now be considered in the light of certain ecological conditions . 



Abundance and Age Composition as Related to Depth 



As stated in the introduction, sampling at census stations was stratified by 3 

 depth zones: 0-30, 31-60, and 61-150 fathoms. A preliminary analysis, however^ 

 revealed that the catch per tow dropped markedly in depths between 60 and 90 fathoms. 

 For this reason the third depth zone was further divided into 2 zones. Thus, there 

 are four zones used in the study of the relation of the distribution of haddock with 

 depth. They are as follows: 



Depth zones Depth range in fathoms 

 I 0-30 



n 31-60 



III 61-90 



IV 91-150 



Summer 



Figure 9 and table A -3 show the total and relative abundance of the different ages 

 in the four depth zones for the years 1948, 1949, and 1950, as well as the 1949-1950 

 means. In all three years depth zone II yielded the most haddock followed in descend- 

 ing order by depth zones I, IV, and III The only exception was in 1948 when depth 

 zone rv yielded a slightly greater catch per tow than depth zone I . In every year of 

 the survey the zone between 61 and 90 fathoms showed a very much lower concentra- 

 tion of haddock than depths either above or below it. 



The age composition of the catch also varies with depth. This is evident from 

 figure 9, but is brought out more clearly in figure 10 where the catch per tow of each 

 age is expressed as a percentage rather than numerically. It is clearly seen that the 

 percentage of older fish increases with increasing depth from zone 1 and IV. This is 

 best illustrated by the 1949-1950 means. 



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