276 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



significant difference between the means of the 

 years; therefore the years were averaged without 

 weighting. 



From the analysis of the variance of the loga- 

 rithms of the ratios, the least significant mean 

 difference {P=.05) between ratios was calculated 

 for the mean ratios of the species in the shallow 

 zone and in the deep zone (Snedecor 1940, p. 344) ; 

 these are shown in table 2. Examination of 

 table 2 reveals that the difference in availability 

 is usually statistically significant for any two 

 species at the same depth. 



The relative abundance (availability) at each 

 depth is shown in figure 6. In interpreting this 

 figure it must be borne in mind that the chief 



object of this otter-trawl fishery by large vessels 

 has been haddock. Thus, the sample of data 

 used in this table comprises a total of 5,437 cor- 

 rected days of fishing with a catch of 92,201,000 

 pounds. Of this total, 43.4 percent, or 39,955,000 

 pounds was large haddock, and 29.2 percent, or 

 26,914,000 pounds was scrod haddock, making 

 a total of 72.6 percent haddock. 



Since haddock was the principal object of this 

 fishery, the fleet concentrated where haddock 

 could be taken in greatest abundance. Thus, 

 the fact that the fleet spent most of its time in 

 water of medium depth would indicate that the 

 haddock is most often found at that depth. 

 When the haddock move into shallow water for a 



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Figure 6. — Relative abundance of each species of groundflsh in each depth zone in Area XXII South, from otter-trawl 



catches. 



