THE SCHOOLING OF TI1K CODFISH. 207 



occurrence is accidental and the young will not follow the old in tbeir migrations until they reach 

 maturity, though after this point is reached they seem to mingle freely without regard to age. 



"Codfish are probably governed in their movements by the abundance and migrations of 

 food, the spawning instinct, and the temperature of the water, though the last named seems to 

 exert but little influence. It is generally acknowledged by the fishermen that during the feeding 

 season fish are plenty only where food exists in considerable quantity, and that after 'cleaning up" 

 one part of the bank they go to another. They also follow schools of bait for long distances, living 

 upon them until they are broken up or entirely destroyed. Thus they often follow the capolin 

 (Mallotus villosus) into the shoal water, and even drive immense numbers of them upon the shore. 



"The spawning instinct seems to exert a decided influence upon the movements of the fish, 

 for we find them visiting the same locality year after year during the spawning season, often 

 remaining for several months at a time. The fish that visit the waters of Cape Ann during the 

 winter, doubtless come in for the purpose of spawning rather than for food. This seems clear from 

 tlie fact that they do not arrive when bait is most plenty, nor do they follow any species to the 

 shore. On the contrary, the pasture-school usually arrives about three weeks after the large 

 herring have left the coast, and remains on the south side of Cape Ann, while Sperling are abundant 

 in Ipswich Bay. The Ipswich school is also the largest after the sperliug have been driven away 

 by the cold weather, and remains on the sand -flats, which supply almost no food. From these 

 facts we are led to believe that food has little influence upon the movements of the fish during the 

 spawning season. 



"The instinct that leads the spawning fish to seek the shoal water in such great numbers is 

 certainly a wise one, for they generally select spawning-grounds where the tide runs strong and 

 the water is rough, and the large number of individuals is absolutely necessary, that the water 

 may be filled with germs for their successful impregnation. If, instead of schooling in such 

 numbers during this period, they remained scattered over a large area, almost no eggs would be 

 fertilized. 



"Again, while food is not essential to the spawning fish, it is of vital importance to the young, 

 and it seems a wise provision that these should be brought into being where food is abundant, 

 rather than that they should be hatched in mid-ocean, where almost no suitable food exists." 



MIGRATIONS AND MOVEMENTS OF THE SCHOOLS. The causes which influence Codfish to 

 assemble together in schools also influence their movements from place to place. It seems most 

 probable that while great numbers of these fish may remain together in the same locality, feeding 

 upon the same kind of food without it being said that they are schooling, a movement from place 

 to place is, however, usual, in obedience to some tangible law, and is made simultaneously by 

 numerous individuals. 



The migrations of the Codfish are usually of the class which I have described under the name 

 "bathic." 1 



The Cod, like most of the other species which migrate to and from the shore instead of 

 northward and southward, is, doubtless, more or less dependent upon temperature conditions than 

 fishes like the menhaden and the blue-fish, and, as Mr. Earll has suggested, 2 the abundance of food 

 doubtless has much more influence upon its movements. We cannot doubt, however, that the Cod 

 moves periodically to and from the shore as a direct result of the seasonal changes of temperature. 

 The Cod prefers a temperature of from '.ft to 42 F., approximately, and this it secures in a 

 temperate climate, such as that of Southern New England, by remaining on the off-shore banks in 



1 Report of United States Commissioner of Fish and Fisheries, pt. v, 1879, p. 51. 

 ! Op. cit., p. 707. 



