PLANKTON OF THE GULF OF MAINE 235 



local copepods, it is most characteristic of the deepest water there. As just pointed 

 out, it has been taken in the great majority of the horizontal hauls below 100 meters, 

 and as a general rule it may be stated that the deeper the haul the more certain it is 

 to yield Euchceta, and in the greatest numbers, both absolutely and relative to other 

 copepods. During the July and August cruises of 1913, for example, it was taken 

 more abundantly at "90-0 fathoms at station 10100, 80-0 fathoms at stations 

 10088 and 10097, 75-0 fathoms at station 10090, 70-0 fathoms at station 10061 " 

 (Bigelow, 1915, p. 292) than in any of the shoaler tows. The use of closing nets is 

 requisite for more definite information on this point, because the open tow T nets often 

 pick up such large amounts of Calanus and other copepods in their journeys up and 

 down that it is impossible to estimate the relative abundance of Eucha?ta and Calanus 

 at the towing level. 



In contrast with the frequency with which E. norvegica occurs in the deepest 

 Gulf of Maine hauls, it is usually w-anting in tows shoaler than 100 meters, which 

 establishes that level as roughly the upper limit to its regular range. Among the 

 several hundred hauls at lesser depths with various nets it has been detected in only 

 20 of the horizontals 30 and 7 verticals (tables, pp. 297 and 299) and only twice shoaler 

 than 40 meters; and the fact that on at least two of these occasions it was about 

 equally abundant at 60 meters and in considerably deeper hauls is evidence that E. 

 norvegica reaches the upper strata of water as the result of temporary dispersals and 

 not by a general ascent on the part of the whole local stock. On six occasions it has 

 been taken on the surface in various parts of the gulf, as follows: (1) 12 nodes off 

 Mount Desert Rock, August 16, 1912, at 3 a. m. (station 10032) ; (2) in the northeastern 

 part of the basin off the mouth of the Bay of Fundy, August 13, 1913, 2 a.m. (station 

 10097); (3) near the same locality, August 12, 1914, 10 p.m. (station 10247); (4) west- 

 ern basin, August 22, 1914, 8 p. m. (station 10254); (5) in the southwestern part of 

 the basin, the following night, 11 p. m. (station 10256); and (6) Fundy Deep, March 

 22, 1920, 2 p. m. (station 20079). It will be noted that these localities extend right 

 across the gulf from northeast to southwest — that is, they do not suggest thatEuchasta 

 comes more often to the surface in the northeastern corner of the gulf, where vertical 

 mixing by tidal currents is most active, than in the more stagnant and stratified and 

 vertically stable waters off Massachusetts Bay and Cape Cod. More extensive data 

 may prove that a local difference of this sort does actually obtain; indeed, it is to be 

 expected. Neither does the evidence available suggest that Euchseta rises to the 

 surface more frequently during the winter or spring than in summer, for it appeared 

 in only one of the 55 surface tow r s for February-May, 1920 (table, p. 303). The times 

 of day for the several surface captures of E. norvegica, if corroborated, would indicate 

 that in summer it makes its rare visits to the surface only at night, but that in 

 early spring (probably also in winter) it may do so at any hour. 



Damas and Koefoed's (1907) characterization of E. norvegica as a form living 

 mostly in midwater but occasionally appearing at the surface applies as well to it in 

 the Gulf of Maine as in the Greenland seas. E. norvegica has been found in small 

 numbers at the surface in most other regions where it occurs regularly. This, for 



30 Willey (1921) also reports Euchseta at about 20 meters oS Eastport and near the surface at St. Andrews. 



