184 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



many small cod are caught about the rocks only a 

 fathom or two deep even in summer. But it is 

 certain that many cod fry take to bottom on the 

 offshore banks also, for we have trawled young fry 

 at many localities between Nantucket Shoals and 

 Browns Bank. As a rule, the large cod lie deeper 

 than 7 or 8 fathoms in summer in our latitudes. 

 But the fishing is often good in only 3 to 5 fathoms 

 of water in wintertime, especially in Ipswich 

 Bay. At the other extreme, comparatively few 

 cod are caught much deeper than 100 fathoms 

 within the Gulf of Maine. And although fisher- 

 men sometimes do well at much greater depths on 

 the slopes of the offshore banks, the 5- and 75- 

 fathom contours probably include the great 

 majority of all the cod living in the Gulf, summer 

 or winter. 



The largest catches of cod are made on rocky 

 and pebbly grounds; on gravel; on sand, and on 

 a particularly gritty type of clay with broken 

 shells. They also frequent the deeper slopes of 

 ledges along shore, where they forage among the 

 Irish moss (Chondrus crispus) and among sea- 

 weeds of other kinds. Young red ones are espe- 

 cially common in these situations, while one some- 

 times catches a large rock cod as these dark brown 

 or red fish are called. And the bottoms where 

 cod and hake are found are so distinct that a long 

 line set from a hard patch out over the soft sur- 

 rounding ground will often catch cod at the one 

 end, hake at the other. But fair catches are 

 sometimes taken on mud, as off Mount Desert, 

 where large- and medium-sized cod are regularly 

 caught on soft ground in winter. And a few very 

 large cod (35-60 lb.) have also been brought in 

 from the mud bottom of the deep basin to the 

 westward of Jeffreys Ledge (about 90 fathoms). 



The cod, as appears from the foregoing, is typi- 

 cally a ground fish; except on some journey (a 

 subject to be discussed later) or when following 

 its prey, it usually lies within a fathom or so of the 

 bottom. And large ones keep closer to the ground 

 than small ones as a rule, so that the closer one 

 fishes to bottom the larger the cod are likely to 

 run. But even the large ones sometimes follow 

 herring up to the surface; we have known of 

 large cod gaffed from a vessel's side in Northeast 

 Harbor, Mount Desert Island, in September, 

 while they were chasing sardines. And they come 

 to the surface more commonly on the Grand 

 Banks and along the eastern coast of Labrador, 



when they are following capelin. Cod even 

 strand on the Labrador beaches while harrying 

 schools of capelin, but we have never known cod 

 to strand anywhere around the coasts of the 

 Gulf of Maine, as silver hake so often do (p. 175). 



The adult cod is at home in any temperature 

 from 32° to 50°-55° F. ; in all but the superficial 

 layers of the Gulf of Maine, that is, at all seasons. 

 But experience at the Woods Hole hatchery, 

 proves that freezing may be fatal by the forma- 

 tion of anchor ice. On the other hand, while 

 large cod tend to avoid water warmer than about 

 50° F., except that they are abundant at times 

 in temperatures as high as 58°-59° F. on Nan- 

 tucket Shoals (the most southerly year-round 

 cod-ground in the Atlantic). Small cod are 

 somewhat less sensitive to heat than large, a fact 

 reflected in the presence of greater numbers of 

 them in shoal water in summer than of larger 

 fish. The relationship of the spawning of the cod 

 to temperature is discussed below (p. 194). 



Food. — When the larval cod first breaks from 

 the egg it subsists on the yolk with which its 

 abdomen is distended (fig. 88), as do most other 

 sea fishes. But this source of nutriment is com- 

 pletely absorbed by the sixth day after hatching, 

 and the future existence of the little fish depends 

 as much on finding a plentiful supply of food as 

 on escaping the enemies by which it is encom- 

 passed. So far as known, the larval and post- 

 larval cod subsist almost exclusively on copepods 

 and on other minute Crustacea, during the several 

 months while they are drifting in the upper layers 

 of water. 65 And this same diet, varied with 

 amphipods, barnacle larvae, and other small 

 crustaceans, as well as with small worms, is the 

 chief dependence of the little cod when they first 

 seek the bottom 68 but as they grow larger they 

 consume invertebrates in great variety and in 

 enormous amount. 



Mollusks, collectively, are probably the largest 

 item in the cod's diet in the Gulf of Maine; any 

 shellfish that a cod encounters is gobbled up, so 

 that their stomachs are mines of information for 

 students of mollusks. Large sea clams (Mactra), 



•» Bumpus, Science., N. Ser„ vol. 7, 1898, p. 485. 



•* For further details on the diet of cod larvae and fry, see Brook (5 ann. 

 Rept., Fish. Board Scotland (1SS6) 1887, p. 327), Mcintosh and Masterman 

 (British Marine food flsbes, 1897, p. 242), Kendall (Rept. U. S. Comm. Fish. 

 (1896) 1898. p. 179), Bumpus (Science, N. Ser., vol. 7, 1898 p. 485), and Good- 

 child, Graham and Carruthers (British Mlnist. Agric. Fish., Fish. Inv., 

 Ser. 2, vol. 8, No. 6, [1925) 1926. 



