PLANKTON OF THE GULF OF MAINE 99 



was probably Calanus or otber copcpods. Unfortunately, little is known of tbe 

 babits of the Atlantic right whale, but it is well established that the pollock whale 

 (Balsenoptera borealis) feeds chiefly on copepods at certain times and places, for 

 Collett (1886, p. 26) found the stomachs of several, killed off East Finmark in July, 

 "filled with a fine gritty mass, which consisted entirely of Calanus finmarchicus," 

 with the Calanus occurring "in great numbers and in a tolerable state of preserva- 

 tion" among the hairs of the baleen plates; and since he gives excellent figures of 

 these copepods, their specific identification is assured. In West Finmark, however, 

 this same whale has been reported as subsisting chiefly on euphausiids (Collett, 

 1886). Kukenthal (1900) likewise states that it feeds on these shrimps, and 

 Andrews (1916) writes that most of the specimens which he opened in Japanese 

 waters contained euphausiids only, while a few had eaten fish. G. M. Allen (1916) 

 and Millais (1906) are therefore fully justified in crediting it with a mixed copepod 

 (Calanus and Temora) and euphausiid diet. 



The fact that only two of the species of whalebone whales known to occur in 

 the Gulf of Maine eat copepods, while all feed on euphausiids, seems not to have 

 been appreciated, though established past cavil by the analyses of stomach contents 

 just mentioned. 



It is, I think, impossible to explain this preference for shrimps on the ground 

 of voluntary selection, for while it is not unreasonable to suppose that whales follow 

 the schools of Crustacea rather than the soft-bodied Sagitte, ccelenterates, or 

 mollusks, copepods (and particularly Calanus) usually abound in northern seas 

 wherever euphausiids are plentiful, and finback, pollock whale, and right whale must 

 gather them all, the large with the small, into their open and expectant mouths as 

 they swim. With whales, however, just as with tow nets of different mesh, the 

 fineness of the straining apparatus determines what part of the total planktonic 

 population is retained to serve as food. If the whalebone be coarse or comblike, as 

 it is in the finback whale (fig. 40), the blue whale, and the humpback, objects as 

 small as copepods are driven out through the sieve with the outrush of water when 

 the mouth is closed, while the much larger euphausiids are retained. The pollock 

 whale, however, possesses, in the "unusually fine and curly, almost wooly bristles" on 

 the inner side of the baleen plates (fig. 41), so well described by Collett (1886, p. 263), 

 a straining apparatus so much more efficient as to sift out the copepods as well as 

 the larger crustaceans. This is true also of the right whale, with its silky-fine 

 baleen (Collett, 1909, p. 95) and ability to strain large volumes of water with little 

 effort. 46 However, the finer the strainer and the better adapted for the capture of 

 the smaller animals, the less effective it is for capturing fish, as witness the depend- 

 ence of the pollock whale on plankton contrasted with the piscivorous habit of the 

 finback. 



The fertility of the gulf as a feeding ground for whales depends, then, not only 

 on the total amount and local concentration of the plankton or on its nature — whether 

 or not crustacean — but equally on the size of the units of which it is composed. 

 Thus, the abundance of Calanus in Massachusetts Bay and off northern Cape Cod 



" For a general account of its feeding habits see Beddard, 1900. 



