270 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



15-20 



25-30 



35-40 



45-50 55-60 65-70 75-60 85-90 

 DEPTHS BY 5-FATHOM INTERVALS 



95-100 105-110 115-120 125-130 



Figure 2. — Number of days fished at hailed depths in Area XXII (solid line) and number of days of fishing that falls 

 into the three depth zones in [our] analysis for group B of large otter trawlers during 1033 (dotted and dashed lines). 



two portions; and (3) tiie hailing of a depth not 

 in accordance with the depth of water available 

 at the indicated position (for instance, a vessel 

 may hail 50 to 75 fathoms at a position where 

 maximum depth is 60 fathoms). 



The 60-fathom contour affords a well-defined 

 breaking point between medium- and deep-water 

 fishing, but the 30-fathom break between shallow 

 and medium water is not so well defined. This is 

 partly due to the fact that the 30-fathom contour 

 in Area XXII South occurs chiefly on gradually 

 shelving bottom, whereas the banks tend to drop 

 off steeply at 60 fathoms. In spite of the diffi- 

 culty of accurate determination, the shallow- 

 water depth zone has been retained because some 

 species, especially the yellowtail flounder, the 



blackback, and the lemon sole, are much more 

 abundant in these shallow waters. 



The depth zones also help in isolating the fishing 

 efTort directed toward the catching of ocean perch 

 because the bulk of them are taken at depths of 

 more than 70 fathoms. 



AMOUNT OF FISHING BY OTTER TRAWLERS IN 

 EACH DEPTH ZONE 



The amount of fishing effort expended in each 

 depth zone was determinetl from more than 32,000 

 days of fishing by otter trawlers of more than 50 

 gross tons, covering the period from 1928 to 1937, 

 inclusive (except 1931). These days of fishing 

 were plotted on the chart by unit areas (10' of 



