necessarily compresbed into a few miles. Over Georges Bank, which cdn be 

 considered as an extension of the continental shelf, the regional distribution is 

 similar to that of other sections of the shelf, having a like arrangement of bottom 



sediments in which depth is the controlling factor . Althou^ the zonation over the 

 bank has a similar sequence and depth limitations, the width of certain zones is 

 greatly extended. 



Figure 15 represents diagramatically typical profiles across various sections 

 of the continental shelf and Georges Bank . 



Apparently then the main factor differentiating the 61-90 fathom depth zone 

 from the others is the lack of silt in the bottom sediments . Although obviously the 

 silt in itself is not the direct cause for the scarcity of haddock, it is an indication of 

 stronger current action . Such current action not only prevents the deposition of fine 

 bottom sediments, but would also prevent the accumulation of detritus which serves 

 directly or indirectly as food for the haddock Considering that the search for food , 

 other than at periods of spawning, is the primary cause for the movements of bottom 

 living fish, this could be a possible explanation for the scarcity of haddock in depth 

 zone III during the summer months . 



Spring 



From figure 14 it is seen that during the spring of 1950 only 1 -year-old fish 

 were caught over mud bottom . The catch per tow and weight per tow data when 

 grouped into unmarketable, scrod, marketable, and large haddock as shown m table 16 

 is again comparable to the depth distribution during this season (see table 12). The 

 majority of the fish were concentrated in shoaler water and were consequently found 

 over sand bottom . 



A relatively high concentration of older haddock were found in depth zone 111 

 during tJhe spring while in summer there was a scarcity of haddock in this region, 

 theoretically accounted for by the lack of food at this depth. This reasoning still 

 appears valid for there exists good evidence that haddock cease feeding during the 

 spawning season. (Vladykov and Homans, 1935; Bigelow and Welsh, 1925; Needier 

 1930) 



Comparison of Census and Commercial Data 



In order to verify the age distribution of haddock as determined from the census 

 data, a comparison was made with the catch of the commercial fleet on Georges Bank 

 during July and August, 1949 and 1950, and April 1950. The method used in analyzing 

 the commercial catch was as follows: 



39 



