The cod (Gadus callarias) leads a partly bottom-dwelling life. It is a fine strong fish with 

 a heavy appearance. The fins are made of soft rays, the dorsal fin being divided into three 

 parts and the anal fin into two. The jaws are strong, being armed with teeth powerful enough 

 to crush shell-fishes. A small barbel hangs from the chin. The colouration blends with the 

 nature of the bottom and is most often a clear light-brown or grey with round dark spots and 

 yellowish mottlings. But in some regions, as in Norwegian fjords, reddish colours predo- 

 ininate. The lateral line is brilliantly white and stands out like a silver ribbon against the dark 

 skin. The belly is white. 



Over the Newfoundland Banks the cod move around near sea bottoms made of sand, gravel 

 or mud. The attached fauna is rich. There are big greyish sea-anemones • hydroids of a fine 

 clear green colour; small flattened sea-urchins. "Basque-berets " ( Echinarnchniiis parma) ; 

 brown holothurians blown out like balloons, " melons " (Cucninaria frondosa) ; and 

 sac-like sea-squirts, Boltenias sway at the end of long, flexible stalks. Other flattened, orange- 

 coloured sea-squirts are sufficiently thick on the ground in places to give the bottom a glazed 

 appearance (icy bottoms). Half-covered by the sand are pitots (Cyrlodnria slUqiia), which 

 look like mussels with a very small shell covering only a part of the body. Sizeable patches of 

 big whelks with extended proboscises gather around the bodies of dead fishes or the guts thrown 

 out of the fishing vessels. The cod-fishermen call them " bulots " and in the time of sailing-ships 

 used them to bait their lines. The bulky orange spawn of these whelks sticks to the gravel like 

 big sponges. Pitots and whelks are among the preferred food organisms of the cod, but these 

 are voracious fishes and go after many other kinds of animals. In the spring they take capelan 

 (Malloliis villosus), marine salmonids which travel in dense shoals, drawn by their partly anadro- 

 nious habits to seek their spawning grounds on coastal banks, but they never enter fresh waters. 

 In summer cod eat cuttle-fishes which swim in the surface layers, and at all seasons take herrings 

 and other fishes, including the young of their own species. 



These gadids have a prodigious fecundity, for big females carry from '.) to (J million eggs. 

 They move up to shallow grounds in order to spawn and soon afterwards the larvae form part 

 of the plankton populations of northern regions. Growth is rapid, a length of about 11 inches 

 being reached after 2 years, 2 Vi feet after 5 years, 3 feet or more towards lU years and about 

 5 feet towards 20 years. But much older cod measuring 6 Yz feet are known. 



Cod are clearly stenothermal fishes. They liv'e in waters of a definite temperature and 

 follow the movements of the water layers they require. So their habitat is hydrological rather 

 than geographical. The Scandinavian fishermen successfully track them down with the aid of 

 special reversing thermometers, a method that has never found a place in the practices of French 

 cod-fishermen. Consequently, one should not talk of cod-grounds, but rather of " cod waters ". 

 The optimum living temperatures in these waters vary according to each race. 



The cod ranges over a wide geographical area, comprising the whole of the North Atlantic 

 — from the Arctic Ocean down to the English Channel and the Irish Sea on the European 

 side and as far as Cape Hatteras along the American coasts. In this immense sector, the 

 researches of the Danish oceanographer Johannes Schmidt have enabled us to recognise different 

 local races, which are distinguished by the number of their vertebrae. For numerous fishes it 

 is possible to frame a biological rule, for the number of vertebrae increases with latitude. In other 

 words, given the same species, the northern animals have more vertebrae than those living more 

 to the south. Concerning the cod, the following races may be recognised ; the American race 

 (I^abrador, Newfoundland and Nova Scotia) with 54 or 55 vertebrae and an optimum temper- 

 ature from to 2°C. The Arctic race (Newfoundland Banks, Greenland, Iceland, Scandinavia 

 and the Barents Sea) with 52 to 54 vertebrae and an optimum temperature from 4 to 6°C. ; the 

 North Sea race (Faroes, eastern English Channel) with 52 vertebrae and an optimum temperature 

 from 6-7°C. ; and the Atlantic race (west of the British Isles) with 51 or 52 vertebrae and an 

 optimum temperature from 6 to 9°C. 



The Arctic race is that most directly concerned in the great French fishery of the New- 

 foundland Banks. Through varying fortunes the cod-fishers have experienced real crises, for 

 there have been times when cod were lacking on the Banks. As early as 1922-23 I showed 

 that these crises arise from hydrological conditions. In years when the Labrador Current 



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