224 BULLETIN OF THE BUREAU OP FISHERIES 



There are only two records of C. typicus in the gulf in July — one off Cape Elizabeth 

 on the 29th (station 10019) and the other in Casco Bay on the 31st (station 10020) — 

 both in 1912. The records point to a notable increase in August, when it occurred at 

 23 percent of the stations (7 out of 31) in 1912, 40 per cent (8 out of 20) in 1913, 

 and at 2 out of 11 in 1914. It is most regularly distributed in the gulf during autumn 

 and early winter, occurring at 60 per cent of the September stations and 66 per cent 

 of the October stations in 1915 and at about 60 per cent of the stations for December, 

 1920, and January, 1921. The local abundance of the species, as well as the generality 

 of its distribution, likewise increases during late summer and autumn, mounting 

 to an average of about 1,000 per square meter for August, 1913 (counting only the 

 stations where it is actually recorded east and north of Nantucket), about 5,300 for 

 September, 1915 (maximum 18,200 in Massachusetts Bay on the 29th), and to about 

 8,637 during that October (maximum 24,450 in Massachusetts Bay on the 27th). 

 Off Marthas Vineyard on October 22, 1915, the numbers per square meter ranged 

 from about 58,400 near shore (station 10331) to slightly more than 12,000 on the 

 outer part of the continental shelf (station 10333). Even at its season of maxi- 

 mum abundance, C. typicus is usually a minor element in the plankton of the gulf, 

 averaging only 7 to 9 per cent of the total copepod population at the stations where it 

 occurred in September and October, 1915 (table, p. 298). Occasionally, however, it 

 may dominate locally near shore — witness 40 per cent of this species in Massachusetts 

 Bay on September 21 of that year (station 10321) — but probably this never happens 

 out at sea in the gulf. 



C. typicus constituted so small a percentage (1 to 8 per cent) of the scanty 

 catches of copepods made during the December and January cruise of 1920 and 1921 

 as to suggest a shrinkage in its numbers during the late autumn. 



The numbers of C. typicus present per square meter are further interesting as 

 proving the Massachusetts Bay region generally and the waters off Cape Cod its 

 chief centers of abundance in the gulf during the late summer and autumn. In late 

 winter and spring the largest catches have been made in the western and eastern sides 

 of the basin — 2,600 per square meter at the former locality on February 23, 1920 

 (station 20049), and 41,100 per square meter near German Bank on May 6, 1915 

 (station 10270). It is also worth noting that this last was the richest catch of C. 

 typicus that has ever been recorded east of Nantucket, though at a time of year when 

 the species occurs only irregularly in the gulf and usually in very small numbers. 



Breeding. — No observations have been made on the breeding of this species in the 

 gulf, but the fact that its chief center of local abundance lies off Massachusetts Bay, 

 whereas summer immigrants, whether of northern or of Tropic origin, enter chiefly 

 via the eastern side, is strong evidence that the stock is maintained by local reproduc- 

 tion, aided little, if at all, by immigration. The presence of this species within the 

 gulf throughout the year tends to corroborate this. Seasonal fluctuations point to 

 summer as the chief breeding season, as does the fact that in 1915 the autumnal 

 multiplication of C. typicus and C. hamatus was preceded by an abundance of larval 

 copepods of some sort (see table, p. 298). With only one period of abundance 

 annually, and that well-marked in contrast to the scarcity of the species during the 

 other months, it is safe to assume one chief breeding period for it yearly. 



