PLANKTON OF THE GULF OF MAINE 221 



Nantucket, and 7 per cent of the total catch of copepods; but it was much more plenti- 

 ful, relatively as well as absolutely, in the shoal water south of Marthas Vineyard on 

 October 21 and 22 (stations 10331 to 10333), with 12,240 to 58,500 per square meter 

 (constituting 6 to 25 per cent of the total copepods), and was most numerous at the 

 station closest to the land. 



Numerical data as to the occurrence of C. hamatus are not available for the early 

 winter, but it formed about the same proportion of tho catches in the inner parts of the 

 gulf (2 to 16 per cent, averaging 6 to 7 per cent), at the stations where it occurred in 

 December, 1920, and January, 1921, as in autumn. It has never amounted to more 

 than 1 to 2 per cent of the copepods at any station from February to the middle of 

 September, nor has it been more numerous than about 4,000 per square meter. 

 Obviously this suggests that C. hamatus is definitely seasonal in the gulf, occurring 

 with some regularity from September until January but only very sparsely from 

 February until August. Thus, even at the season and in the zone of its greatest 

 abundance, C. hamatus is but a minor element in the copepod population of the gulf. 



The regional distribution of the captures (fig. 70) is interesting, nearly all being 

 near shore and the majority within a few miles of land, with not a single record 

 anywhere in the central and southern parts of the basin or on Georges or Browns 

 Banks. Although C. hamatus occurs across the whole breadth of the continental 

 shelf off southern New England, on the one hand, and from Cape Sable eastward, 

 on the other, its geographic range within the Gulf of Maine 22 has so far proved neritic, 

 as contrasted with oceanic, and closely parallels that of the neritic medusae (p. 33). 



No observations have been made on the breeding of C. hamatus in the gulf, 



but the abundance of developmental stages of copepods of some sort during August 



and the first half of September, preceding the increase that takes place in the number 



of adults of this species and of its ally, C. typicus, during the last half of September, 



suggest that both of these species are regularly endemic in the gulf. If this be the 



case it breeds in comparatively high temperatures, stated tentatively as upwards 



of 7° in the gulf because of its neritic distribution, chiefly in salinities lower than 



32.5 per mille. 



Centropages typicus Kr0yer 



This species is described by T. Scott (1911) as a true Atlantic form, estuarine 

 as well as oceanic. In the eastern Atlantic it occurs from the Mediterranean to 

 northern Norway, being one of the common species in the North Sea region generally, 

 where it often occurs side by side with C. hamatus; but it has not been reported from 

 Arctic seas. In the western North Atlantic it has been found on the Louisiana coast 

 of the Gulf of Mexico (Foster, 1904) and occurred commonly over the continental 

 shelf as far south as the mouth of Chesapeake Bay during the summers of 1913 and 

 1916 — was, in fact, the commonest copepod at many of the stations but chiefly in the 

 uppermost stratum of water, as I have described in earlier reports (Bigelow, 1915, 

 p. 293, and 1922, p. 146). 



In July, 1913, the Grampus took it abundantly off New York, and although 

 Williams (1906) does not list it from Narragansett Bay, Wheeler (1901, p. 173) 



" Also plentiful in the eastern side of the basin on August 20, 1926. 



