194 BULLETIN OF THE BUREAU OF FISHERIES 



of the vertical hauls, and three-fold on Browns, but decreased by about that same 

 proportion in the eastern channel, a change probably too small to be significant. 

 In the western basin the average number of C. finmarchicus at all the stations was 

 practically the same in April (about 13,000 per square meter) as in February and 

 March (about 12,000), but an equalization of the species had taken place. 



The augmentation of the stock of C. finmarchicus that takes place during the 

 later spring is the most notable event in the seasonal history of the animal plankton 

 of the gulf. In 1920 this multiplication of Calanus began in the Massachusetts 

 Bay-Cape Cod region by the middle of April, as I have just pointed out (p. 41), 

 and by the first week in May it had progressed sufficiently to raise the numbers per 

 square meter to an average of 19,000 for all the stations from near Cape Ann out 

 across the western end of Georges Bank. 



In 1913 no notable increase of Calanus was observed in Massachusetts Bay 

 until the first week in May; this was first evidenced in Gloucester Harbor, where on 

 the 3d Welsh found the water "reddened for areas of about a square yard, several 

 yards apart, with what proved to be swarms of copepod nauplii and young copepods. 

 And on the 17th, hauls off Magnolia, Mass., yielded great numbers of small copepods, 

 chiefly C. finmarchicus." (Bigelow, 1914a, p. 407.) 



In the spring of 1915 the vernal augmentation of Calanus either commenced earlier 

 in the season than in 1913 or 1920, or proceeded more rapidly, for on May 4 the 

 vertical net took it at the rate of 459,900 per square meter off Gloucester (station 

 10266), this being the greatest number ever counted in the gulf. It was only slightly 

 less numerous in the eastern basin off German Bank on the 6th, and the average 

 number per square meter for a belt right across from the Massachusetts Bay region 

 in the west to German Bank and Lurcher Shoal in the east was about 150,000. It 

 is probable that the multiplication of Calanus does not proceed so rapidly in the 

 northern parts of the gulf, though it may commence there as early as mid-April (p. 

 41), the June counts off Penobscot Bay and eastward 9S ranging from only 7,500 to 

 21,000 per square meter for 1915. Probably a fairer concept of the late spring status 

 of the species, both numerically and regionally, would result from the union of the 

 May with the June counts despite the disparity in date, which gives an average of 

 about 96,000 per square meter for the whole gulf north of a line Cape Cod- Cape 

 Sable, or about 63,000 if the vertical hauls for May, 1920, be included. Although 

 this calculation may very well be 100 per cent out of the way, due to faidts inherent 

 in the process of estimation and to the paucity of stations, at least it shows that the 

 stock is many times as great in late spring and early summer as it is in winter or 

 during March and April. 



It is not possible to follow the seasonal fluctuations of C. finmarchicus at close 

 intervals through the summer for want of sufficient data for late June and July, nor 

 have the percentages in which the species occurred been determined for the vertical 

 hauls for August, 1912 or 1914. This was done for the vertical hauls for August, 

 1913 (Bigelow, 1915, p. 286), and for most of the horizontal hauls at various depths 

 for stations for 1912 and 1914, when the total numbers of copepods were calculated 

 from verticals. With Calanus so greatly preponderating over all other copepods 



» No vertical hauls were made in this part of the gulf in May. 



