100 BULLETIN OF THE BUREAU OF FISHERIES 



provided an ideal pasture for the Atlantic right whale, of which it once fully availed 

 itself, as early records show, but not for the finback, for which the bay is a desert 

 except when herring or other fish are schooling there or during the brief local swarm- 

 ings of euphausiids. It is common knowledge among fishermen that finbacks 

 seldom appear in any numbers anywhere in the gulf except when in pursuit of fish. 

 It is also probable, that the volumetric preponderance of copepods over euphausiids 

 in most parts of the gulf explains the comparative rarity there of the shrimp-eating 

 blue whale with its very coarse whalebone. 



Before leaving this subject I should emphasize that the large, easily recog- 

 nized, pelagic amphipod Euthemisto, locally and temporarily so abundant, has 

 never been recognized in the stomachs of any of the whalebone whales. Is it not 

 eaten? And if not, why not? 



It is probable that copepods are the main dependence of the basking shark 

 (Cetorliinus maximus), whose gillrakers perform the same service in filtering its 

 crustacean food from the water taken into the mouth as do the baleen plates of the 

 whalebone whales. I need merely point out that the alimentary canal of a speci- 

 men taken at West Hampton Beach, Long Island, on June 29, 1915, contained a 

 large quantity of minute Crustacea, "whose reddish bodies lent color to the entire 

 mass" (Hussakof, 1915, p. 26). 



When we turn to the dependence of the smaller fishes on crustacean plankton, 

 we are confronted by a published record so embarrassing for its wealth (mostly, 

 however, based on experiences in European seas) that I shall lay only a few of the 

 more typical examples before the reader, and those most applicable to the Gulf of 

 Maine. 



The unicellular plants have been described repeatedly in zoological literature as 

 the chief food supply of the youngest larval fishes, and a long list of diatom and peri- 

 dinean species has, at one time or another, been recorded as having been eaten by 

 them; but recent studies of the stomach contents of large series of various common 

 fishes in the English Channel (Lebour, 1919, 1920, 1924) have proved that although 

 many fish do take more or less diatoms, peridinians, etc., few depend on these uni- 

 cellular forms to the extent that has been generally supposed, even during their 

 earliest larval stage (cf. also Hjort, 1914, p. 205), but begin to take larval copepods 

 and other microscopic animals by the time the yolk sac is absorbed, if not sooner. 

 However, Lebour found the young European flounder (Pleuronectes flesus) subsisting 

 chiefly on the green flagellate genus Phseocystis up to the time of its metamorphosis, 

 with other flatfish taking a considerable proportion of peridinians and diatoms, and 

 this proved true of young herring less than 10 millimeters long, which also take Halo- 

 sphsera. 



Outside of the littoral zone, where the mummichogs (Fundulus Tieteroclitus) 

 consume diatoms as well as other small organisms indiscriminately, the menhaden 

 is the oidy important Gulf of Maine fish that continues throughout life to subsist 

 chiefly on diatoms and peridinians, with the most minute of Crustacea and other 

 animals. These it is enabled to sift out of the water by its fine branchial sieve, as 

 Peck (1894) long ago described. 47 



" On the feeding habits of the menhaden see also Bigelow and Welsh, 1925, p. 123. 



