198 



BULLETIN OF THE BUREAU OP FISHERIES 



would contain at least one and sometimes two or three large oily adult Calanus, 

 even without the voluntary selection of such morsels which these fishes regularly 

 practice, and the fish may be expected to be (and often are) packed full of this "red 

 feed." 



At any time from early May until midsummer there exists a sufficient stock of 

 Calanus, which is dense enough in some part of the gulf to afford a bountiful food 

 supply. Our hauls point to the outer part of Massachusetts Bay, with the neighbor- 

 ing waters along Cape Cod to the south, offshore to the east, and probably north- 

 ward to Cape Elizabeth, as on the whole the subdivision of the guff where it appears 

 most abundantly during the spring and early summer, both absolutely and per cubic 

 meter of water. Secondary centers of abundance have been recorded in the eastern 

 basin, the northern channel, and off the southeast slope of Georges Bank, but the 

 last of these was certainly transitory, (p. 193) and the others may have been equally so. 



In warm summers, when the peak of abundance for Calanus finmarchicus has 

 passed before July, fewer are to be expected per cubic meter. In August, 1913, when 

 the percentage of Calanus in the vertical hauls was determined by Dr. C. 0. Esterly 

 (Bigelow, 1915, p. 286), this copepod averaged only 244 per cubic meter at 14 stations 

 generally distributed over the northern half of the gulf, even assuming that all of 

 them were taken above 175 meters, the figures being as follows: 



- The average at the Gulf of Maine stations inside the continental edge for July 

 and August, 1914, 100 was about 600 Calanus per cubic meter, varying from less than 

 100 to upward of 2,000. These calculations show that in late summer most parts of 

 the gulf offer by no means as fertile a feeding ground for the fishes that eat Calanus 

 as it does two or three months earlier in the season. 



In the offshore parts of the gulf there is less variation in the number of Calanus 

 per cubic meter of water, from station to station, in August than in May, with no 

 definite contrast between "rich" and "poor" regions; but in the coastal belt the 

 extremes, represented by very barren hauls between Mount Desert Island and the 

 mouth of the Bay of Fundy and by upward of 2,000 at one station close to Cape Sable 

 (station 10243), are perhaps as far apart as at any season. The fact that Calanus 

 about tripled in number at the locality last mentioned during the interval from July 

 25 (station 10230) to August 11, in 1914, shows that rapid changes take place. 



Nine vertical hauls for September, 1915, distributed over the eastern half of the 

 gulf along the coast of Maine and in Massachusetts Bay give an average of approxi- 



>°» A table of the number of copepods and large Calanus per square and per cubic meter for that year is given in an earlier report 

 (Bigelow, 1917, p. 315) . The present calculation for 1914 is based on an estimated average of 70 per cent Calanus, which is probably 

 below the true figure. 



