234 BULLETIN OF THE BUREAU OF FISHERIES 



Records of E. norvegica along the slope westward and southward from the 

 eastern channel have all been from deeper than 100 meters, and this southward 

 extension of its range is probably only a narrow zone above the 500-meter level — 

 perhaps not more than 20 to 30 miles -wide — sandwiched in between the continental 

 slope on the one side and the high temperatures offshore on the other. The recent 

 discovery of this copepod living at 1,000 to 1,250 meters at two Michael Sars stations 

 in the Sargasso Sea west of the Azores, however, between the fortieth and fiftieth 

 meridians of longitude (Murray and Hjort, 1912, p. 657), makes it probable that it 

 will be found widely distributed over the whole Atlantic basin in the deeps^ like the 

 chffitognath Eukrohnia liamata, with which it is often taken. 



The presence of E. norvegica at six out of our seven deep stations off the slopes 

 of Georges Bank and off Shelburne, Nova Scotia, during the spring of 1920 (not 

 found at station 20109), but at only three of our five summer stations outside the 

 continental edge abreast the gulf, and at none of our July, August, or October stations 

 off Marthas Vineyard, indicates a distinct seasonal periodicity in this part of its 

 range, with its maximum abundance in the cold months; but one of these spring 

 stations (20069, March 12, 1920) yielded it in greater numbers per square meter 

 (about 7,750) than any vertical haul yet made within the Gulf of Maine. 



Actual numbers. — Although E. norvegica often gives character to the catches of 

 the deepest horizontal hauls because of the scarcity of other copepods, it has averaged 

 only about 930 per square meter for all seasons and at all the stations where it figures 

 in the lists for the vertical hauls, with maxima of 4,690 in the eastern basin on August 

 6, 1915 (station 10304), and 7,750 off the southeast slope of Georges Bank on March 

 12, 1920, as just noted (station 20069). The average for June to September within 

 the gulf (about 1,200 per square meter) has been slightly above the annual average, 

 and that for February to May slightly below it (about 800), but so small a difference 

 can not safely be interpreted as evidence of any notable seasonal fluctuation in the 

 numerical strength of the species. 



The density of aggregation, as measured by number per cubic meter, is like- 

 wise invariably small. Assuming that all the specimens taken in hauls deeper than 

 100 meters came from below that level, as most of them certainly did, the maximum 

 per cubic meter would be less than 50 and the average something like 10; but this is 

 probably an overstatement, because some few Euchreta were shoaler — that is, 

 scattered through a longer column of water. 



In terms of percentage E. norvegica has invariably ranked low in the vertical 

 hauls, its maximum being 20 per cent off the southwest slope of Georges Bank, Feb- 

 ruary 22, 1920 (station 20044), and 10 per cent on several occasions within the gulf 

 (tables, p. 297), where its average for all the verticals has been about 4 per cent. But 

 it occasionally dominates the catch in the deepest horizontal hauls at or below 150 

 meters (e.g., closing-net haul at 85 to 60 fathoms, August 29, 1912, station 10043), 

 and on several occasions it has amounted to 30 to 50 per cent of the copepods taken. 

 At times, however, we have found only 2 per cent or less of Euchreta in hauls as deep 

 as 175 to 250 meters (table, p. 304). 



Vertical distribution. — Perhaps the most interesting phase of the status of E. 

 norvegica in the gulf is its vertical distribution, for, unlike most of the other common 



