314 BULLETIN OF THE BUREAU OF FISHERIES 



ebb offshore, having proved sufficiently plentiful in April and May for the vertical 

 net to pick up at least a few specimens at almost every station. Similarly, Hunts- 

 man and Reid (1921) record considerable numbers of Sagittse in the open Bay of 

 Fundy in March and May, though McMurrich found few or none at St. Andrews 

 at that season. 



We have no definite evidence, of vernal impoverishment in the numerical strength 

 of S. elegans on Georges Bank, having, on the contrary, made rich catches there in 

 March, April, and May 65 as well as in midsummer. 



In the Massachusetts Bay region S. elegans increases in numbers after the first 

 few days of May coincident with the multiplication of copepods, which is so nota- 

 ble an event in the planktonic cycle (p. 41), and may do so rapidly. In 1920, for 

 example, the S. elegans population had risen to the respectable number of about 

 100 per square meter at two stations in the bay and at its mouth on the 16th (sta- 

 tions 20123 and 20124). Unfortunately we have no data on this subject for this 

 part of the gulf for June, but it is probable that S. elegans usually reaches its max- 

 imum abundance there during the last half of that month, because in the very cold 

 summer of 1916, when the seasonal cycle lagged several weeks behind more normal 

 summers, vertical hauls at two stations within the bay on July 19 yielded an extra- 

 ordinary abundance of this Sagitta — 2,500 and 1,750 per square meter (stations 

 10341 and 10342) — numbers far in excess of its usual summer frequency there, and 

 which may reflect the status of this chsetognath during late June of warmer sum- 

 mers. This tremendous Sagitta population had dwindled, however, to perhaps not 

 more than 50 individuals per square meter by the 29th of the month following; 60 

 and this may be an annual event, for although we have taken S. elegans in every 

 subsurface haul which we have made in the Massachusetts Bay region in summer, 

 it has usually been only a minor element in the local plankton in July or August, as 

 reflected in catches of only 10, 50, and 15 individuals per square meter, respectively, 

 on August 9, 1913, August 22, 1914, and August 31, 1915. 



Apparently S. elegans may be expected to increase again in numbers in the 

 western side of the gulf during the early autumn, because our vertical net yielded 

 it at the rates of 130 and 145 per square meter in Massachusetts Bay on Septem- 

 ber 29, 1915 (stations 10320 and 10321), and of 100 and 385 per square meter at 

 neighboring localities on October 27 (stations 10338 and 10339). By the evidence 

 of horizontal hauls it was perhaps as abundant as this near the Isles of Shoals on 

 November 1, 1916 (station 10400), and formed about one-fifth to one-fourth of the 

 volume of the catch in Massachusetts Bay, off Gloucester, on December 4, 1912 

 (Bigelow, 1914a, p. 404). But S. elegans proved scarce throughout the northern 

 half of the gulf generally on the December to January cruise of the Halcyon in 

 1920-1921, none of the hauls yielding more than a scattering among the copepod 

 plankton, and at one station (10493) we missed it altogether — an unusual event. 

 Our data on the status of S. elegans during the later winter are confined to the 



81 On the eastern part of the bank S. elegans dominated the horizontal catch on March 11, 1920 (station 20066), though the 

 vertical haul indicated only about 50 per square meter, which illustrates the unreliability of the latter method when dealing 

 with animals so large and so active. There were 490 per square meter at a neighboring location on April 16 (station 20110), 

 and on the southwest part of the bank 1,000 per square meter on May 17 (station 20128). 



M Judging from the scanty yield of the horizontal haul at station 10298. No vertical haul was made. 



