FISHES OF THE GULF OF MAINE 



185 



the empty shells of which are often found neatly 

 nested in cod stomachs : cockles (Polynices) ; and 

 sea mussels (Modiolus) are staples, all of which 

 they swallow whole. Cod also eat crabs, hermit 

 crabs, lobsters (large and small), shrimps, brittle 

 stars (of which they are sometimes crammed full) , 

 sea urchins, sea cucumbers, and sea worms 

 (Nereis). Brittle stars and small crabs, for 

 example, had been the chief diet of the cod 

 examined by Welsh on the Isles of Shoals-Boon 

 Island ground in April 1913, while Wilcox 67 states 

 that a number of 17-pound fish caught in Ipswich 

 Bay were full of large red prawns 2 to 4 inches 

 long (evidently the northern edible shrimp 

 Pandalus). And we have found crabs (Cancer; 

 Libinia) the chief food of the cod on Nantucket 

 shoals. 



Tunicates (sea squirts) also bulk large in then- 

 diet. Occasionally they eat hydroids, bryozoans, 

 and algae, perhaps taking these for the amphipods 

 that are hidden among them. And in late summer 

 cod frequently feed on ctenophores (Pleurobrachia 

 fileus). But while its diet list would probably 

 prove almost as extensive as that of the haddock 

 (p. 202), the cod shows so decided a preference for 

 large shells rather than for small ones that the 

 stomach contents of cod and haddock taken side 

 by side differ noticeably. Nor is it likely that 

 cod root the bottom as haddock do (p. 202), for 

 worms. 



Cod pursue and gorge on squid at every oppor- 

 tunity, and on various small fish, particularly on 

 herring, on launce, and (in the north) on capelin; 

 also on shad, mackerel, menhaden, silversides, 

 alewives, silver hake, young haddock, and even 

 on their own young, rising into the upper waters 

 for this purpose when necessary (p. 184). They 

 also pick up flounders, cunners, rock eels (Pholis) , 

 blennies, sculpins, sea ravens, small hake and 

 skates from the bottom. In fact, they take any 

 fish small enough to swallow, including the hard 

 slim alligatorfish (p. 457) and even the sea horse 

 (p. 315). And Welsh noted that many cod taken 

 near the Isles of Shoals on May 1, 1913 spat up 

 small rosefish from 4 to 6 inches long. The eggs 

 of the longhorn sculpin M and of the eelpout 

 (Macro zoarces) 69 also have been found in cod 



" Bull. U. S. Fish. Comm., vol. 6, 1887, p. 95. 

 ■ Warfel and Merrinmn, Copeia, 1944, p. 198. 



•' Olsen and Merrlman, Bull. Bingham Oeeanogr. Coll., vol. 9, art. 4, 

 1946, p. 77. 



210941—53 13 



stomachs. Adult cod as well as small are also 

 known to feed on pelagic shrimps in the waters 

 around Iceland, 70 but we have never heard of 

 them doing so in the Gulf of Maine. 



Even a wild duck does not escape from a 

 large cod now and then. Thus we have heard of 

 several scoters found in the stomachs of large fish 

 caught off Muskeget Island in 1897; and though 

 sea fowl are not a normal article in their diet, the 

 flesh of the greater shearwater (hagdon) has long 

 been considered excellent cod bait. Objects as 

 indigestible as pieces of wood and rope, fragments 

 of clothing, old boots, jewelry, and other odds and 

 ends have repeatedly been found in cod stomachs. 

 And they often swallow stones; but probably for 

 the anemones, hydroids, and other animals growing 

 thereon, and not to take on ballast for a journey 

 as the old story has it. 



Although cod are so rapacious they fast gener- 

 ally while they are spawning; the stomachs of 

 nearly all the ripe fish examined by Earll, and 

 recently by Welsh, were empty. 



Experiments performed on the cod in captiv- 

 ity, 71 combined with the general experience of 

 fishermen, suggest that they capture moving 

 objects by sight. But apparently cod (and for 

 that matter other fish), can see clearly only for a 

 few feet, and their greediness in snapping up the 

 naked meat of clams and cockles (foods which 

 they never find in that condition in nature) , added 

 to the fact that they bite as readily by night as 

 by day, seems sufficient evidence that they 

 depend largely on smell. 



Enemies. — In the Gulf of Maine, large sharks 

 and the spiny dogfish are the worst enemy of the 

 adult cod. Formidable enemies of young cod 

 fry are the small pollock which infest our harbors. 

 These are so fierce that a single pollock 7 or 8 

 inches long will disperse a school of hundreds of 

 cod fry, driving them to shelter among the weeds 

 and rocks, while Earll remarks that in the aquar- 

 ium a cod so fears a pollock of equal size that it 

 will invariably hide if possible. Young cod, up to 

 7 to 8 inches, are also devoured in large numbers 

 by the larger cod. 



n Schmidt (Skrift. Komm. Havunderstfgelser, No. 1, 1904, p. 70) and 

 Paulsen (Meddelel. Kommls. Havunderstfgelser, Serie Plankton, vol. 1, 

 No. 8, 1909, p. 39). 



« Bateson, Jour. Mar. Biol. Assoc. United Kingdom, N. Ser., vol. 1, 

 1889-90, p. 241. 



