286 BULLETIN OF THE BUREAU OF FISHERIES 



Gulf of Maine. — This species has not been reported previously from the gulf, 

 nor for that matter from off the American seaboard south of Nova Scotia, but it 

 appeared in one vertical haul off Yarmouth, Nova Scotia, and one off Shelburne, 

 Nova Scotia, in 1915 (stations 10272 and 10313), off Boothbay Harbor on March 4 

 and again on April 10, 1920 (stations 20058 and 20096), and in one horizontal haul 

 near the mouth of the Merrimac Eiver on the 20th of the following December (sta- 

 tion 10492), in each case for odd specimens only (tables, pp. 297 and 299). 



This copepod is typically warm oceanic, though tolerance for low temperature is 

 evidenced by its more northerly distribution in the Arctic-Atlantic area. In the Gulf 

 of Maine it occurs only as one of the rarest of strays from outside the continental 

 edge. The localization of the records of capture (fig. 72), in which it agrees with 

 Khincalanus, points to the upper 100 meters as the stratum in which it most often 

 enters the gulf, where, like other immigrants, it circles first north, then west, then 

 south around the periphery, drifting in the great anticlockwise eddy. If it were 

 swept in with the deeper lying water along the bottom of the eastern channel it would 

 be more apt to be found along the two branches of the basin; and since it has been 

 taken over a wide range of depth elsewhere, from the surface downward, in low lati- 

 tudes as well as high, and most often from 20 to 400 meters (With, 1915), odd captures 

 of it may be expected in the deepest strata of the gulf. So far it has not been detected 

 in any surface haul in the Gulf of Maine. 



The present records, with those of the Canadian fisheries expedition off Nova 

 Scotia and in the Gulf of St. Lawrence (Willey, 1919), cover so many different months 

 that this copepod may be expected in the Gulf of Maine at any season, a fact instruc- 

 tive for its bearing on the question of the periodicity of oceanic circulation in the 

 region. 



The biology of this species must be understood better before the relationship 

 of its distribution to temperature and salinity can be stated. The records of capture 

 locate it over a wide range of each — that is, in temperatures as low as —1.6° to 

 - 1.8° along East Greenland to upward of 24° in the Gulf of Guinea, while in the 

 Greenland Sea the Belgica (Damas and Koefoed, 1907) found it nearly universal in 

 salinities ranging from about 32 per mille on the Greenland side to nearly 35 per mille 

 about Spitsbergen. 



So far as temperatures and salinities per se are concerned, the Gulf of Maine is 

 thus wide open to it, and its presence there in any particular temperature and salinity 

 is simply the result of the particular drift which the specimens in question have taken 

 and of its ability to survive wide fluctuations, something which is true of most 

 copepods. 



Scolecithricella is never sufficiently numerous in the Gulf of Maine to figure in 

 the natural economy of the local plankton, but its immigrant nature being beyond 

 dispute, with the Atlantic Basin as the source, it is among the most instructive of 

 natural floats when it appears there, as showing the course followed by the indraft. 



