PLANKTON OF THE GULF OF MAINE 237 



32 to 33 per mille are an effective bar to its wanderings, and its distribution in tbe 

 Gulf of Maine is consistent with this. 



Economic importance. — E. norvegica has been considered as of comparatively little 

 economic importance in the northeastern Atlantic because of the considerable depth 

 of its habitat. But it occurs regularly within reach of at least one of the important 

 plankton-eating fishes in the Gulf of Maine, for Willey (1921) found the stomach of 

 an American pollock (Pollachius wrens) densely packed with a mass of Euchreta and 

 euphausiid remnants in about equal amounts, the percentages of different copepods 

 which he tabulates — 84 per cent Euchseta, 3 per cent Calanus finmarchicus, 2 per 

 cent C. hyperboreus, and 1 per cent Metrldia longa — suggesting that the fish had 

 voluntarily selected the Euchasta? in preference to the smaller C. finmarchicus, which 

 was probably far the more plentiful of the two. Another pollock opened by him 

 had also eaten Euchreta. To what extent mackerel and the several species of her- 

 ring feed upon it in the gulf is not known, but it is likely to be an important article 

 in their diet when it rises toward the surface. 



Euchseta spinosa Giesbrech.1 



This species, known from locahties in the North Atlantic, Mediterranean, 

 Indian Ocean, and Pacific (Giesbrecht, 1892; van Breemen, 190S; Thompson and 

 Scott, 1903; Esterly, 1905), has been reported from surface collections off Nausett 

 Beach, Cape Cod, and off the northern extremity of the cape by Sharpe (1911, 

 p. 410), but it has not appeared in any of the more recent to wings in the gulf or in 

 Canadian Atlantic waters. 



Euch.eirella rostrata (Clans) 



This is an oceanic species, widespread in the temperate Atlantic (Cleve, 1900; 

 T. Scott, 1911) and common on the Pacific coast of the United States at San Diego, 

 Cahf. (Esterly, 1905 and 1911). It has been recorded at several stations along and 

 outside of the continental edge off Chesapeake and Delaware Bays and off New 

 York (Bigelow, 1915, p. 296; 1922, p. 147), abreast of Georges Bank (stations 10218 

 and 10219), and thence eastward and northward along the slope of the Nova Scotian 

 shelf and in the Laurentian channel (Willey, 1919, p. 189, fig. 9) . Although this cope- 

 pod is not typically tropical, it enters the Gulf of Maine as a visitor from the mid- 

 depths along the inner edge of the "Gulf Stream," and its locality records, like 

 those for other planktonic organisms of that category, are localized in the eastern 

 side of the gulf and around its periphery (fig. 71). The station records number 13, 

 all but 4 of them being for July and August — 2 for May, 1 for June, and 1 for 

 September. Evidently the species is most apt to enter the gulf during the warm 

 months, and apparently it does not do so at all in the low temperatures of late 

 autumn, winter, and early spring. 



All records of the species off the east coast of America have been from depths of 

 50 meters or deeper, and the Gulf of Maine records are all based on occasional 

 specimens. 



