ESTIMATING ABUNDANCE OF GROUNDFISH ON GEORGES BANK 

 Table 2. — Dialribution of species of groundfish according to depth zones on Georges Rank. 1932-38 



277 



short time, tlic fleet follows them. Because we 

 get catches from shallow water only for the 

 period that the fleet is there (when haddock are 

 abundant), it appears as thougli haddock are 

 equally abundant in shallow and in medium-depth 

 water, but such is not the case. 



According to figure 6, the smaller sizes of had- 

 dock tend to be less abundant in deep water, but 

 the true difference between the depth zones for 

 this species may be more pronounced than the 

 data indicate. 



In the case of pollock, the data are somewiiat 

 misleading. The otter trawlers make a few large 

 catches of pollock in deep water in the fall and 

 winter months, when the pollock are concentrated 

 in dense schools, but these fish are caught only 

 incidentally to the pursuit of haddock during the 

 remainder of the year. Thus, although the data 

 indicate that the pollock is chiefly a deep-water 

 species, pollock are known to frequent all depths. 

 For example, along the Maine coast the pollock 

 school at the surface and are captured by small 

 purse-seine boats. 



SUMMARY 



1. The fishing intensity, by areas and depths, 

 by otter trawlers during a period of 10 years 

 (1928 to 1937, except 1931) was determined for 

 Georges Bank, Subareas XXII, G, H, J, M, \, 

 and O. The information was obtained from i)lo(s 

 of more than 32,000 days of fishing by otter 

 trawlers of more tlian 50 gross tons. 



2. During the 10-year period, the otter trawlers 



fished 23.4 percent of their time in water of to 30 

 fathoms in depth, 53.0 percent in water of 31 to 60 

 fathoms in depth, and 23.6 percent in waters of 

 more than 60 fathoms. 



3. During the 10-year period, the productive 

 areas amounted to 54.3 percent of 6,531 square 

 miles of shallow area (0-30 fathoms), 51.3 percent 

 of the medium-depth area (31-60 fathoms) of 

 9,121.5 square miles, and 37 percent of the area 

 of 6,501 square miles of deep area (61 to 125 

 fathoms). 



4. The relative abundance of each species of 

 groundfisli in each depth zone was determined from 

 5,437 standard otter trawler days of fishing, land- 

 ing 92,201,000 pounds of groundfish from 1932 to 

 1938 inclusive. 



5. The shallow zone was the center of abundance 

 for blackback, lemon sole, and yellowtail flounders. 

 The medium zone was the center of abundance 

 for scrod cod (1}^ to 2K pounds). The deep zone 

 was the center of abundance for ocean perch, cusk, 

 gray sole, pollock, hake, and dabs. Halibut, 

 wolffish, haddock, and cod of more than 2)i pounds 

 did not differ widely in abundance between depth 

 zones. 



6. Because of the differences in relative popula- 

 tion densities between depth zones, the catch per 

 unit of fisliing effort cannot be used as a measure 

 of ahundance for most of the species, unless it is 

 tabulated by depth zones. 



7. In order to obtain usable indexes of abund- 

 ance for certain of the species, it may first be 



