436 MIGRATORY MOVEMENT OF SEA FISH. 



of a good glass, the desired intelligence may gener- 

 ally be acquired. 



Another all-important point is to have an accurate 

 knowledge of the times when the shoals of fish may be 

 expected to arrive upon the coasts. Many kinds of sea- 

 fish are very migratory in their habits, periodically ap- 

 pearing and disappearing from the banks at regular inter- 

 vals and in fact only visiting the fishing grounds in any 

 considerable numbers at certain seasons of the year. 



In this respect again the habits of fish resemble 

 very much those of the wild animals and birds inhabit- 

 ing the great hunting grounds throughout the world. 

 Most of these animals and birds, as we have already 

 pointed out, are well known to migrate with the 

 changes of the seasons, sometimes to great distances ; so 

 that a country which at one time is literally swarming 

 with game of all kinds, at another contains little or 

 nothing the game having then deserted it. This 

 is a matter which is of course more fully considered 

 in the sections on hunting and shooting. But had 

 we the means of accurately determining the causes of 

 these fish migrations, we should probably find that 

 the same causes which govern the migrations of 

 animals on land, govern those of the deep sea also 

 namely, variations in temperature, and the periodical 

 abundance and scarcity of food in the various localities, 

 according to the changes in the seasons. But our 

 knowledge of the habits of the finny tribe is practi- 

 cally almost nil, everything being still very much a 

 matter of conjecture, and possibly may always to a 

 certain extent remain so. 



It is, however, a matter of ascertained fact that 

 " Temperature is the supreme condition which determines 



