PLANKTON OF THE GULF OF MAINE 



187 



There is no positive evidence that Anomalocera ever sinks more than a few 

 meters in the Gulf of Maine in summer, and most of the Gulf of St. Lawrence records 

 listed by Willey (1919) are likewise from the surface or from trivial depths. In 

 winter and spring it seems to live slightly deeper, for it was not taken in any of the 

 surface hauls from November, 1912, to April, 1913, or February to May, 1920; 

 but it descends to only a moderate depth — probably to escape the most severe 

 winter chilling — the vertical records for December, March, and April all being from 

 hauls shoaler than 75 meters. 



Anomalocera is similarly an inhabitant of the upper strata of water in north 

 European seas. Sars (1903) always found it swimming close to the surface off the 

 west and south coasts of Norway, and T. Scott (1911) describes it as most generally 

 met with at or near the surface, very rarely in deep water, though he gives its vertical 

 range as extending down to 700 meters. 



This copepod occurs only in water of tolerably high salinity, and its preference 

 for the surface makes it easy to establish the precise conditions under which it is 

 living at any given station. In the Gulf of St. Lawrence it occurred regularly in 

 water as little saline as about 30 per mille (Willey, 1919; Bjerkan, 1919). In the 

 Gulf of Maine most of the records are from salinities of 31.55 to 33.06 per mille, and 

 south and west of Cape Cod it occurs in water salter than 35 per mille, which is a 

 usual salinity for it in the eastern North Atlantic. It is certainly able to survive 

 a wide range of temperature, but in the Gulf of Maine it is most abundant when the 

 surface water in which it lives is warmer than 10°, which may prove about the lower 

 limit for its successful reproduction. Temperatures as high as 21° to 25°, even, seem 

 not unfavorable for it. 



Anomalocera is an inhabitant of the open sea, never yet recorded from harbors 

 or from estuarine situations except when brought in by heavy winds or by surface 

 currents, as occurs at times in Norway (Sars, 1903) and at Woods Hole (Wheeler, 

 1901). In its relationship to the North American littoral it may be described as 

 intermediate between neritic and oceanic, maintaining itself in the Gulf of Maine 

 and in the Atlantic basin alike. 



Asterocheres boecki (Brady) 



Doctor Wilson contributes the following note on this copepod, which is only 

 accidental in the plankton: 



This species occurred in the form of two partially mutilated specimens taken in one of the 

 surface tows early in March, 1920. As far as could be determined, these specimens were identical 

 with those described by Brady in his monograph on British Copepoda as Artotragus bcecki, but 



