64 LIFE-HISTORY AND DEVELOPMENT OF 



certain regions during the spawning season, as pointed out 

 for instance by Sars, off Lofoten, where they occur in vast 

 numbers from January to March. In our own country, again, 

 the appearance of shoals of haddocks and whiting in certain 

 localities is another example. How far such multitudes, 

 however, are influenced by the abundance of food is still an 

 open question. In British seas the herring is the main cause 

 of these congregations of cod and haddock ; the former chiefly 

 pursuing the fishes, the latter their eggs. In the same way, 

 the abundance of Norway lobsters and similar food on the 

 grounds called banks exercises considerable influence on the 

 presence of cod. 



It has already been pointed out, however, that in their 

 young stages certain migrations do occur. Thus the post-larval 

 cod by-and-by seeks the laminarian region, while the older 

 forms for the most part tend to go seaward. The haddock 

 keeps to the deeper water in its post-larval and very young 

 state. The same occurs even in a more pronounced manner 

 with the ling, the adults of which as a rule are found in deep 

 water. The pelagic post-larval ling seeks downwards as it 

 grows, and is seldom found near the shore till it attains the 

 length of six or seven inches, in short, until it is barred with 

 pigment. As it increases in size it migrates seaward. Similar 

 features are noticed in the plaice. As observed in the trawling 

 expeditions of 1884, only large plaice as a rule are procured in 

 deep water off the east coast, while the sandy bays abound 

 with those ranging from 11 inches downward, and none of 

 the females of which appear to be mature. Multitudes of 

 little plaice haunt the margins of these sandy beaches, but 

 it cannot be said that forms which have the length, for 

 example, of 3 inches, are confined to any particular line 

 drawn across a bay, for small forms (2-4 in.) occur in hauls 

 all over such a bay as that of St Andrews. Small turbot and 

 halibut in the same way are often found in the shallow bays, 

 while the large adults are inhabitants of the deeper water. 

 Such would not, however, seem to be the case with certain 

 skate, very large adults of which occur in the shallow water 

 of the sandy voes in Shetland. 



