84 



BULLETIN OP THE BUREAU OF FISHERIES 



found swarming there in 1912, 1913, and 1914 (p. 19) . 40 While 1914 is the only 

 summer for which we have quantitative data from the offshore banks, all the most 

 productive (100 + cubic centimeters) of the summer hauls of 1913, 1914, 1915, and 

 1916 41 were hkewise similarly concentrated in the Cape Cod-Bay of Fundy belt 

 just outlined (fig. 38). So uniformly productive has this "rich zone" proved in 

 summer that only 3 of the 25 vertical hauls, which we have made there in June, 

 July, and August, have failed to yield upwards of 100 cubic centimeters of animal 

 plankton per square meter, although the waters both immediately to the north and 

 to the south of it have often proved decidedly barren, as the chart illustrates. 

 The average volume of plankton for aU the vertical summer hauls in this rich zone 

 has been nearly 170 cubic centimeters per square meter including those for 1916 

 (an exceptionally rich year), and more than 150 cubic centimeters if the 1916 hauls 

 are omitted. 



Approximate volume of plankton per square meter of sea surface. July and August hauls, 1912 to 1916 



1 For a list of the hauls for other months of this year see Bigelow, 1917, p. 314. 



Contrasting with the rich belt, the entire coastal zone of the gulf, from Cape 

 Ann on the south and west to Grand Manan Island at the mouth of the Bay of 

 Fundy on the east and north, has invariably proved far less productive of zooplankton 

 in midsummer — never with more than 90 cubic centimeters per square meter, usually 



*> These ctenophores had shrunk in the preservative to only a fraction of their natural bulk before the vertical hauls were 

 measured. 



" In 1916 the zooplankton was unusually abundant in the waters off Cape Cod and in the southwest corner of the gulf in 

 July, a fact discussed on p. 97. 



