112 BULLETIN OF THE BUREAU OF FISHERIES 



in the stocks of herring, mackerel, haddock, etc., which are reared in the gulf, 

 depend more on the abundance of the rapacious members of the planktonic com- 

 munity (and especially on the abundance of Sagittse, medusae, Pleurobrachia, and 

 Euthemisto) than on any other one factor. If plankton studies need any defense 

 from the standpoint of the fisheries we need look no further. 



THE MORE IMPORTANT GROUPS OF PLANKTONIC ANIMALS 



MOLLUSKS 



In coastal and estuarine waters generally the larval stages of mollusks are 

 abundant in the plankton, but in the open gulf they hardly figure in the catches, 

 leaving the pteropods as the only molluscan group that is a regular factor in the 

 planktonic community. The cephalopods are also considered briefly because of 

 their importance in the natural economy of the sea, although so large and such 

 active swimmers that they are not properly "plankton." 



Cephalopods 



Only two of the considerable list of cephalopods recorded at one time or another 

 from the coasts of New England (for a complete list see Johnson, 1915) play a role 

 of any importance in the pelagic life of the Gulf of Maine, but these two — Loligo 

 pealii Lesueur and TUex iUecebrosa (Lesueur) — are extremely abundant locally in 

 their proper season, when they form one of the principal sources of bait for fisher- 

 men. While, on the one hand, their young provide an important element in the diet 

 of various larger fishes, the adult squids devour innumerable fish fry. 



So active are these cephalopods and so easily do they avoid small or slow- 

 moving gear that we have never taken a single specimen in our tow nets. Indeed, 

 I can, from my own experience, verify Verrill's (1882, p. 306) statement that it 

 is hard to capture them with a dip net, even when confined in a fish pond or weir. 

 Hence I can offer the reader only a brief summary of accounts published pre- 

 viously, with such notes as have been gleaned from personal observation on the 

 beaches, and from accounts given me by fishermen and other observers. 



Loligo is the common squid south of Cape Cod, Illex north of Cape Ann, with 

 the ranges of the two overlapping in Massachusetts Bay. Illex also occurs, if less 

 commonly, as far south and west as the Woods Hole region (Sumner, Osburn, and 

 Cole, 1913a). Loligo, on the other hand, has long been known occasionally as far 

 north as Penobscot Bay, and Dr. A. G. Huntsman and Dr. A. H. Leim write me 

 that it has recently been found to be quite common in summer in various estuaries 

 of the Bay of Fundy; for instance, Passamaquoddy Bay, Scotsman Bay, and Cobe- 

 quid Bay. 



Since more is known of the life history of Loligo than of Illex, it may be con- 

 sidered first. Loligo is common in the Woods Hole region from April or May until 

 November but disappears during the winter. During the 10-year period, 1900 to 

 1909, the earliest captures ranged from April 16 to May 7 (Sumner, Osburn, and 

 Cole, 1913a), which probably applies to Massachusetts Bay, though, taking one 

 year with another, this squid appears there later in spring and disappears earlier in 

 autumn than it does along the southern coast of New England. During the late 



