320 FISHES AND FISHING 



of capture are known), and as throwing light upon the 

 life-histories of allied but less known species. 



Often the young of a fish are found in localities widely 

 different from those ordinarily inhabited by the adult, 

 and, especially in the case of fishes of commercial 

 importance, records of the places in which the young 

 are found at various sizes, their comparative abun- 

 dance, and their seasonal movements, may have a very 

 great practical value. 



Certain differences in form and proportions between 

 the young and adults of fishes are so constant and well 

 known as to deserve mention. For instance, the eye 

 of a young fish is, as a rule (and with the known excep- 

 tion of a few oceanic fishes), proportionately larger 

 than that of the adult, and consequently bears a larger 

 ratio to the length of the head and snout and to the 

 interorbital width. The form of the young is not infre- 

 quently slighter, and the serrations of the operculum and 

 preoperculum (if present) may be more strongly marked. 



Such characters as an elongated beak, prolonged 

 fin rays, or a characteristic colour pattern, cannot be 

 safely looked for in the young, nor can the elongated 

 fin rays of some larvae be expected to persist. On the 

 other hand, the number of fin rays and scales is nor- 

 mally very constant throughout life, and, once the 

 larval phase is passed, the positions of the insertions 

 of the paired fins seem to change but little, however 

 subject to modification their shape and the relative 

 lengths of their rays may be. 



Oceanic Fishes. 



We advisedly combine under the above heading all 

 the fishes of the open ocean, whether inhabitants of 

 the bottom, the surface, or the intervening waters, 



