GENERAL FACTS ABOUT SEA FISH 27 



were things otherwise. Beyond assuming, however, that the 

 majority of fishes wander considerable distances, either along 

 our coasts or to and from the deeper water outside, we know 

 comparatively little that is certain of the precise season, object, 

 and direction of these journeys. The mackerel, for instance, and 

 the herring were formerly thought to travel round our islands 

 and off to Arctic seas with a most complicated itinerary. Later 

 observers, with far more statistical material at their disposal, 

 have come to the conclusion that these migrations are by no 

 means so extensive as was then supposed, and that the fish 

 merely move into deep or shallow water for spawning 

 purposes. Something will be said later on the subject ot 

 the kinds which prefer deep water for the purpose and, on 

 the other hand, those which repair to the shallows. There 

 are other reasons for migration than spawning. A change 

 in the temperature of the water, sudden or normal at given 

 seasons, will cause the shoals to move from one part of the sea 

 to another. Food, too, may be the motive of these journeys. 

 An instance of this is on record, in which numbers of hake 

 appeared suddenly off^ the Cornish coast in pursuit of a small 

 and rare species of gadoid, and will be duly related in the 

 chapter on the cod family. All shoaling fishes must be 

 continually on the move, on account of this same food problem, 

 for only solitary kinds, like the weever and angler-fish, could 

 possibly find supplies for a long period in one place. Fish do 

 not consume a great quantity of food during the spawning 

 season, so that the shoals are then less restless. 



A good deal of unnecessary mystery has been allowed to 

 invest this shoaling habit in some fishes. So far as we have 

 any reason to suppose, it is not materially different from the 

 parallel habit of flocking in some birds. Suitable conditions ot 

 food and temperature take the members of each species to 

 certain neighbourhoods, and those of the same size, being 

 unable to devour each other, swim in company. This is 

 why we find the broods of one " class " — that is to say, hatched 



