172 



BULLETIN OF THE BUREAU OF FISHEBIES 



February, and Dr. C. B. Wilson contributes the statement that in and around 

 Chesapeake Bay A. clausi is more abundant than A. longiremis. 



The earlier cruises in the Gulf of Maine gave no grounds for supposing that A 

 clausi was ever plentiful there, Esterly having detected it at one station only (Glou- 

 cester Harbor) in the towings taken during the summer of 1912, and not at all for 

 July and August, 1913 or 1914, nor for the winter of 1912-13 (Bigelow, 1914, 1914a, 

 1915, and 1917). Willey (1919), however, reported it from Passamaquoddy Bay in 

 August, 1915, and on January 16, 1920, he found that adults and juveniles of A. 

 clausi formed 68 per cent of the total catch of copepods there (Willey, 1921). Dr. 

 C. B. Wilson has detected it in so many of the Gulf of Maine towings made during the 

 summer of 1915 (fig. 59), the spring of 1920 (fig. 58), and the winter of 1920-21, that 

 it was certainly widespread and locally abundant in the gulf during those years at 

 least. 



The counts tabulated here may be considered from two aspects — a, the relative 

 importance of A. clausi in the copepod community, and I, its absolute abundance. 

 It constituted 0-15 per cent of a comparatively scanty copepod plankton during 

 December, 1920, and January, 1921, but was so nearly universal in the inner parts 

 of the gulf that it occurred at 85 per cent of the stations. In February, 1920, how- 

 ever, it was not taken at all, either in the surface or in the vertical hauls, at the few 

 stations occupied in the southwest deep and on Georges Bank during that month. 

 It is probably at its minimum in early spring, because it averaged only 41 specimens 

 per square meter inshore of the 100-meter contour, and 47 in the deeper parts of the 

 gulf, in March, 1920, occurring in 15 of the 35 hauls. In April, however, it was 

 detected in 25 of the 30 vertical hauls, having risen, on the average, to 10 per cent 

 of the total catches of copepods and in absolute abundance to an average of 2,390 

 individuals per square meter within the 100-meter contour, 180 in the deeps. In 

 May it occurred in all the vertical hauls, both in 1915 and in 1920, averaging 6 to 9 

 per cent of the total copepods, with an average of 2,787 per square meter in shoal 

 water in 1920, and 7,857 in shoal and 8,469 in deep water in 1915. The augmenta- 

 tion which takes place in its numbers during the spring is further illustrated by 

 counts of the numbers taken at pairs of stations in the western part of the gulf in 

 February and March and again in May of 1920, as follows: 



Locality 



Southwest part of Georges Bank 



Southwest corner o( basin 



Oil Gloucester 



Date 



Feb. 22 

 May 17 

 Feb. 23 

 May 17 

 Mar. 1 

 May 4 



Station 



20046 

 20128 

 20048 

 20127 

 20050 

 20120 



Number of 



specimens 



in surface 



tow 







60 







162 



115 



1,750 



Number of 



specimens 



per square 



meter in 



vertical 



tow 





 1,425 



8 

 1,437 





 5,500 



In 1915 it continued universal in June, averaging 14 per cent of the total copepods 

 in the vertical hauls and 45 to 50 per cent at two of the stations, but its absolute 

 abundance was somewhat less (averaging about 4,000 per square meter in shoal water 



