THE SEA FISHERIES OF EASTERN NORTH AMERICA. 63 



to sustain life, as they feed not merely for subsistence but for material 

 to keep up the animal heat. 



The cetaceans of various species are, of course, the most destructive 

 by their much greater bulk, the larger of the porpoises being most no- 

 table in this respect. It is not [infrequently with feelings of satisfaction 

 that the human spectator observes schools of* bluefish that have de- 

 voured and driven on shore schools of mackerel and menhaden, them- 

 selves attacked and subjected to a similar treatment by troops of por- 

 poises, forming a line outside of them and devouring them with ex- 

 traordinary rapidity, frequently forcing them on the beach in large 

 numbers. Whales, too, take their part in this conflict, but probably con- 

 line themselves to smaller fishes, especially the herring, and possibly 

 mackerel, capelin, or other species, of which large numbers, while 

 schooling can be taken at a gulp. 



The method of feeding of the whale is, of course, only appreciable 

 when the operation is conducted at the surface. Here they may be 

 often seen (the finback whales especially), with the mouth wide open 

 and swimming with great velocity against large bodies of herring and 

 floating invertebrates, such as pteropods, jelly-fishes, &c. The greater 

 the development of whalebone in the mouth, the less do the whales ap- 

 parently feed on fish and the more on invertebrates. The finback is 

 characterized by the small amount of whalebone. To what extent the 

 sperm whale, which is essentially a large porpoise, feeds upon fish is not 

 known ; its principal food, however, is believed to be the giant cuttle- 

 fish, which inhabits the depths of the ocean, with the largest of which 

 it appears able to cope. It is very seldom that a sperm whale is cap- 

 tured without having in its stomach some fragments of this large ceph- 

 alopod, the beaks being almost always found in their intestines and 

 excrement. AuibergrLs almost always contains such remains. 



Seals come next to the cetaceans in voracity and destructiveness, and 

 occupy only a second place, in view of their more limited distribution 

 and their confinement to a certain proximity to the land. The numbers 

 of fishes, especially of the Gadidw, doubtless also of salmon, devoured 

 by the seals in the Xorth Atlantic must be something almost beyond 

 calculation, and the destruction on the part of the much larger seals, 

 sea-lions, fur-seals, &c, of the Pacific is probably still greater. 



How far the walrus is a destroyer of fish I am unable to say, although 

 it is generally believed to depend, to a considerable extent at least, upon 

 mollusca for food. 



Otters are also worthy of mention in this connection, the sea- otter of 

 the Pacific Ocean being very destructive in proportion to its size and 

 numbers. The common otter also devours large numbers of fish in 

 fresh water, levyiug tribute on many a fine salmon, shad, and other val- 

 uable fish. 



Although at first sight we may not be inclined to attach much im- 

 portance to birds as destroyers of fish, yet it is found that they repre- 



