CHAPTER V 



GROWTH, MIGRATIONS, FOOD AND HABITS 



Growth. A considerable amount of evidence has been collected 

 bearing upon the question of the growth of fishes. When the 

 fish has passed through the two stages already considered, the 

 development in the egg and the transformation into the perfect 

 form, it enters upon the third stage of its life, its adolescence, 

 which extends to the time when it becomes sexually mature and 

 begins to breed. It is important to know how large and how old 

 each kind of fish is when it spawns for the first time, and some 

 of the fundamental facts bearing on these questions are not 

 difficult to ascertain. It is obvious and certain that if every 

 individual fish that survived began to breed when it was a year 

 old, in other words spawned the year after it was hatched, then 

 there would be no immature fish in the spawning season, all 

 would be spawning or about to spawn. We know, however, that 

 this is not the case. If we take the trouble to find out the 

 condition of a large number of any kind of fish at the beginning 

 of the spawning season, we find that many of the larger indi- 

 viduals are spawning, but a large number of smaller can be 

 and are caught which show no signs of becoming ripe, which arc 

 evidently immature. The youngest of these fish cannot be 

 much less than a year old, they must have been hatched 

 in a preceding spawning season, although some of them 

 may be more, than one year old. This first fact is therefore 

 firmly established, that all the fish of one kind do not spawn 

 when a year old. 



Before proceeding further with the subject of age it will be 

 convenient to consider that of size. A great deal of attention 

 has been drawn to the question of the sizes at which fishes of 

 different kinds begin to spawn, or, as it is usually expressed, 



