ANADROMY: GENERAL CONSIDERATIONS. 37 



time occasionally excited by objects of the nature of food or having that appearance, 

 and that this excitability grows weaker as the breeding time and place is approached. 

 This seems to be in accord with the facts as indicated by the observations mentioned 

 and by general experience, and would account for the fact that salmon occasionally eat 

 a fish, or insect, swallow a leaf, or piece of bark, or take a bait or artificial fly. It would 

 also perhaps account for what have been regarded as peculiar idiosyncracies of the 

 salmon. It also may suggest the reason why the best angling season is in the spring 

 or early summer. It appears also from observations cited and from general experience, 

 statements to the contrary notwithstanding, that salmon kelts do not abruptly begin 

 to feed in ravenous manner, and those kelts most commonly found with food within their 

 stomachs are males. This latter fact possibly is connected with what appears to be a 

 fact that at least some males linger longer than females in fresh water after spawning. 



Anadromy. 

 General Considerations. 



The habit of ascending fresh-water streams from the sea for the purpose of procrea- 

 tion is common to a considerable number of fishes which pass the adult stages feeding 

 and maturing in the sea. This habit may be regarded merely as an elaboration of the 

 movements of other fishes in the sea for the same purpose. Doubtless all such movements 

 are in conformity to 'natural laws.' The so-called spawning migration, however, is not 

 always sharply defined from movements of other kinds or 'purposes.' In fact, the 

 spawning migration may apparently begin as one distinctly of another kind, as, for 

 instance, pursuit of food. Yet both are doubtless correlated, the latter in many instances 

 being a necessary preliminary and preparatory stage of the other. Various spring 

 'migratory' fish, as mackerel, menhaden, etc., are poor when they first appear, and their 

 vernal movements are plainly influenced by the food supply. The mackerel, it is known, 

 gorge themselves with food, bj^ which they are nourished, and the reproductive organs 

 rapidly develop. 



Some 'migratory' species spawn at sea, either at the surface or at some varying depths. 

 Others require shoals or 'banks;' others approach the shore and spawn m the shoal 

 water of bays; others spawn upon the open shore or beaches; others ascend estuaries 

 into brackish water; others spawn just above the influence of tide water; and still others 

 ascend to fresh-water streams, in some instances even to their headwaters. All are 

 impelled to attain certain requisite conditions. These must be attained, for no other 

 conditions will avail and, the requisite conditions failing, the species 'perishes from the 

 earth' or, rather, from the waters. 



The anadromous habit is not restricted to marine fishes. Among fresh-water fishes 

 there appear to be similar movements, of Uke variabihty, except that there are no sur- 

 face or pelagic spawners, or, rather, no species producing floating eggs. 



Meek (1916, p. 18) says that aU degrees of anadromous migration from mid-ocean to 



