290 BULLETIN OF THE BUREAU OF FISHERIES 



Vineyard onOctober21, 1915 (station 10331). But perhaps less reliance can be placed 

 on quantitative calculations based on vertical tows for this species than for any of 

 the other copepods of frequent occurrence in the gulf, because, as Farran (1910, 

 p. 72) has remarked (which our own experience corroborates), it "has the habit, 

 more marked than in most copepoda, of forming swarms of great density but of 

 limited extent.'' For this reason conclusions as to its abundance in any region 

 may be entirely misleading unless a great number of hauls are made close together, 

 both in time and in location. 



On two occasions we have encountered such swarms (fig. 20) within the geographic 

 limits covered by this report — first over Nantucket shoals on July 9, 1913 (station 

 10060), when Temora dominated the tow at 40 meters (Bigelow, 1915", p. 287), 57 and 

 second on the surface off Gloucester on October 31, 1916 (station 10399), as recorded 

 elsewhere (Bigelow, 1922, p. 135). Had a vertical net chanced to pass through either 

 of these swarms, we would have obtained very much larger numbers per square 

 meter than have ever resulted from the vertical hauls actually made. But were 

 Temora as abundant in the Gulf of Maine (relative to other copepods) as Brady 

 (1878-1880) describes it about the British Isles, along the Norwegian coast, at the 

 mouth of the Baltic, or in the Gulf of St. Lawrence (where Willey (1919) found it 

 locally constituting up to 62 and 70 per cent of the copepod catches of the surface 

 nets), surely our many towings would more often have yielded it in comparative 

 abundance instead of with monotonous scarcity. 



Because the distribution of Temora is so often streaky and its frequency of occur- 

 rence varies so much in the gulf from year to year, numerical calculations based on 

 vertical hauls scattered through different years, and often too far apart in miles, 

 can not be depended upon to reflect its seasonal cycle correctly. But whereas the 

 frequency of occurrence has been as high for March and April as for summer or 

 autumn, the numbers of specimens actually taken per station have ranged smaller, 

 averaging only about 200 per square meter for March and 300 for April at the stations 

 where it was taken, with maxima of 1,075 (station 20068) and 1,300 (station 20105), 

 respectively; and if the stations where the species failed were included in the calcula- 

 tion the averages would fall below 100 per square meter for both these months. 



In summer Temora has usually been much more plentiful than this, if taken 

 at all, the August catches for 1913 ranging from 600 to 18,000 per square meter 

 (average 5,362), with 800 to 3,300 (average 1,484) for September, 1915. 58 In 

 October, 1915, there were from 980 to 5,700 per square meter at the stations within 

 the gulf (average 2,755), with 32,760 and 8,160 at two stations off Marthas Vineyard. 

 No vertical hauls were made in November, December, or January, but the small 

 percentages of Temora in the uniformly scanty catches of copepods in the horizontal 

 hauls for December, 1920, and January, 1921 (table, p. 304), and ourfadure to take 

 it at all off Gloucester during the winter of 1912-13 (Bigelow, 1914a, table, p. 409), 

 point to this as a season of local scarcity. 



Thus, there is some evidence, if not entirely conclusive, that while Temora is 

 widespread in the open gulf in early spring it is usually very sparsely represented 



•' In the published account this and the preceding station are confused. 

 « Also 18,760 per square meter od Shelburne, Nova Scotia, station 10313. 



