128 BULLETIN OF THE BUREAU OF FISHERIES 



observations have been made on the occurrence of larval Clione that might or might 

 not survive to maturity. Even in European seas, where the plankton has been 

 much more intensively studied, little is known of the conditions of temperature and 

 salinity under which its reproduction normally takes place (Paulsen, 1910). 



Granting that Clione does reproduce itself to some extent in the Gulf of Maine, 

 it follows that its presence at any particular time and place is not necessarily to be 

 taken as evidence of a northern current; but in the last analysis Clione is essentially 

 of northern origin in the gulf, and it is probable that a considerable proportion of the 

 stock existing there at any given time are actual immigrants via the Nova Scotian 

 current, some indirect evidence of which is yielded by the details of the records of its 

 occurrence in the gulf. Thus, although the data yet at hand do not indicate any 

 connection between the winter increase in the numbers of Clione and the fluctuations 

 of the cold current (the latter is then at a low ebb), and although Clione shows no 

 definite tendency toward concentration in the side of the gulf where this water is 

 most in evidence, the spring maximum for Clione corresponds to the maximum 

 annual intrusion of the latter into the gulf. 



West and south of Cape Cod Clione may safely be classed as primarily an immi- 

 grant. As such it was long ago recorded as far south as the coast of Virginia (Rath- 

 bun, 1889), and probably it is a more or less regular if usually uncommon visitor 

 along this part of the continental shelf in winter and spring, for the Albatross towed 

 it off Delaware Bay on February 20, 1920 (station 20042), and Rathbun (1889) 

 recorded it from localities on the outer part of the shelf between the latitudes of 

 New York and Chesapeake Bay in April and May of 1887. Occasionally large 

 numbers of them may drift south, De Kay (1843, p. 66) describing them as very 

 abundant in the bays near New York in April, 1823, but only for a few days, after 

 which they vanished. In warm summers, such as that of 1913, it vanishes beyond 

 Cape Cod by July, but in the cool summer of 1916 its presence off Chesapeake Bay, 

 off Delaware Bay, and off New York in August suggested temporary breeding activ- 

 ity under rarely favorable local conditions, a view supported by the fact that at 

 one of these stations (10386) Clione larvae were taken with the adults (Bigelow, 1922, 

 pp. 156, 174). Evidently, however, Clione did not succeed in maintaining itself 

 there much later into the season, because it was not taken in these southern waters 

 at any of the November stations for that year. The high temperatures of the tropical 

 "Gulf Stream" water are a fatal barrier to the offshore dispersal of Clione a few 

 miles outside the continental edge, from abreast of southern Nova Scotia southward. 



Probably Clione is never numerous enough, or locally numerous, in the Gulf of 

 Maine for a long enough period to be of any importance in its natural economy. 

 In more northern seas its great swarms afford a bounteous food supply for whales, 

 and it is an important article of diet for both mackerel and herring in Irish waters, 

 according to Paulsen (1910). 67 



•' Station records of Clione in the Gulf of Maine have been published as follows: For July and August, 1912, in Bigelow, 1914, 

 p. 118; for the winter of 1912-1913 and the spring of 1913, in Bigelow, 1914, pp. 403, 406, and 407; for the summer of 1913, in Bigelow, 

 1915, p. 302. In July and August, 1914, it was detected at stations 10213, 10243, 10249, and 10255; in the season of 1915 at stations 

 10276, 10277, 10278, 10280, 10281, 10282, 10286, 10287, and 10306; in July, 1916, station 10346; in October and November, 1916, not at all; 

 in the spring of 1920, stations 20046, 20048, 20049, 20053, 20055, 20056, 20057, 20058, 20068, 2O074, 20079, 20081, 20086, 20087, 20091, 20094, 

 20095, 20097, 20100, 20101, 20103, 20105, 20106, 20109, 20110, 20112, 20113, 20114, 20115, 20119, 20122, 20124, and 20126; in December, 1920, 

 and January, 1921, stations 10489, 10491, 10493, 10495, 10496, and 10497. 



