alevins or fry, live in the gravel of 

 the redd, where they are somewhat 

 protected from their larger enemies. 

 They gradually absorb the food in 

 the attached abdominal yolk or 

 umbilical sac. Upon almost com- 

 plete absorption of the yolk sac, the 

 young fish emerge from the gravel, 

 usually in late winter or early 

 spring, and seek food. The young 

 of some species almost immediately 

 start downstream toward the ocean, 

 but others remain in fresh water for 

 a year or more. The young of pink 

 and chum salmon usually enter salt 

 water soon after emerging from the 

 gravel. The young of the fall 

 chinook salmon may also start down 

 very soon after emergence. The 

 fingerlings of spring chinook, red, 

 and especially silver salmon may 

 remain in fresh water a year or 

 longer. 



Why some species of salmon enter 

 salt water soon after emergence 

 from the gravel and why other 

 species remain in fresh water for 

 extended periods, is imperfectly 

 known. Clemens (1952) believes 

 that the behavior of the fish at all 

 ages is the result of a series of inter- 

 actions between the fish and the en- 

 vironment. Seaward migration of 

 red (sockeye) salmon fingerlings 

 from the Fraser River (British Co- 

 lumbia) is described from this view- 

 point. Then, too, there must be 

 some physiological changes in the 

 organism. According to Black 

 (1951), "Young salmon entering 

 the sea must have adequately de- 

 veloped chloride-secreting cells in 

 the gills to survive." 



Studies indicate the heavy mor- 

 tality among young salmon during 



their periods in stream and ocean. 

 Neave (1953) shows that, of young 

 pink salmon spawned, 13.1 to l.G 

 percent enter the ocean, and of 

 those entering the ocean about 2 

 percent survive to return as adults 

 to their home stream. The mortal- 

 ity of other species seems to be about 

 the same. Under completely bal- 

 anced conditions, two fish of each 

 brood, a male and a female, would 

 have to survive to spawn^ — repre- 

 senting 100-percent effective main- 

 tenance of the species. 



There are years of too few fish and 

 years of too many fish for the 

 spawning areas available, but with- 

 out outside influence, the runs 

 would tend to stabilize themselves. 

 As in the maintenance of all living 

 things, one species lives upon, and 

 is controlled by, other species to pro- 

 vide a balance throughout the natu- 

 ral environment. 



It is well that in nature's scheme 

 of survival the salmon produces so 

 many eggs and resulting offspring, 

 for through the stages of its life 

 the salmon is preyed upon by in- 

 sects, birds, reptiles, mammals, and 

 fishes. The eggs in the nest provide 

 food for bottom organisms such as 

 crayfish and the water forms of 

 some insects. The fry are taken by 

 birds, other fishes, crayfish, flies, 

 and even by snakes. The young fin- 

 gerling on its way to the ocean runs 

 a gantlet of larger fish and birds. 

 In the ocean, other fishes and mam- 

 mals such as seals and sea lions prey 

 upon the salmon. When returning 

 to the river, the adult fish is sub- 

 jected to attacks by birds and bears 

 in the shallow rapids and on the 



6 



