PLANKTON OF THE GULF OF MAINE 207 



of nauplii such as that just mentioned does actually presage the great augmentation 

 of C. finmarchicus that takes place in that side of the gulf during the late spring and 

 early summer. In other words, the Massachusetts Bay region and neighboring 

 waters are actually important centers of reproduction for the species, and of growth, 

 leading to a dominance of adults in July. Willey (1921) has remarked that this 

 part of the Gulf of Maine would seem to be the southern headquarters for the pro- 

 duction of C. finmarchicus in the northwestern Atlantic, and it is not unlikely that 

 the Calanus population of the gulf as a whole originates chiefly in the area bounded 

 by Cape Elizabeth on the north, Cape Cod on the south, and the western basin 

 offshore. 



Judging from the data for 1915 and 1920, the production in this region must 

 be very large to account for the local abundance of this copepod in May and July, 

 but it is probably not to be compared with the tremendous production that takes 

 place in the Norwegian sea, for Calanus eggs have not occurred in notable numbers 

 in any of the samples in question, 7 whereas Damas (1905, p. 12) describes them as 

 locally so abundant between Norway and Iceland that in certain regions they are 

 one of the principal elements in the plankton, even to the exclusion of everything else. 



No attempt has yet been made to determine the presence or absence of the early 

 stages of C. finmarchicus in the samples from other parts of the gulf. Probably it 

 breeds to some extent over the whole of it (Willey (1921) mentions juveniles in 

 Passamaquoddy Bay in April), but the preliminary study of the tow nettings points 

 to the region just outlined as by far the most productive center of local production. 

 It is also safe to say that spring, from late April on, is the chief breeding season for 

 Calanus in the gulf, and that breeding probably continues actively through June to 

 account for the abundance of juveniles in various stages which we found off Cape Cod 

 on July 9, 1913 (station 10057; Bigelow, 1915, p. 291), 8 and in Provincetown Harbor 

 on July 20, 1916 (station 10343). It is certain that no production comparable with 

 the vernal wave takes place later in the summer, though positive evidence (in the 

 form of eggs and juveniles) as to whether Calanus spawns at all in the gulf during 

 July, August, or September is yet to be sought among the masses of copepods collected 

 on our cruises. Doctor Esterly's 9 report of many juveniles at two stations off 

 southern Nova Scotia on July 29 and August 6, 1914 (stations 10235 and 10237), 

 shows that Calanus breeds well into the summer east of Cape Sable. 



In 1915 the increase in the numbers of C. finmarchicus in the gulf during early 

 autumn was preceded during the first half of September by an abundance of develop- 

 ment stages of copepods in the tow. (See table, p. 298.) If these larval stages actually 

 were C. finmarchicus, as seems probable from the constant dominance of the copepod 

 fauna by that species, this points to a second but less productive breeding season in 

 autumn, an interpretation corroborated by the presence of a large proportion of 

 juveniles of this species in the surface tows near the Isles of Shoals and in the western 

 basin on November 1, 1916 (stations 10400 and 10401). Development stages of 

 some copepod were likewise recorded in comparative abundance for January, 1921, 



7 N'o special attention has yet been paid to the eggs in the Gulf of Maine tow nettings — a task for the future. 

 1 These were identified by Dr. C. O. Esterly. 

 1 In a letter. 



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