spillways. A popular belief is that 

 if fish ladders or fishways are pro- 

 vided in a structure for the up- 

 stream passage of adult salmon, the 

 problem is solved. This is far from 

 the truth. A salmon, as jDreviously 

 stated, has stored energy which is 

 sufficient only to maintain himself 

 and develop reproductive products 

 during the diffcult journey from the 

 ocean to the spawning area. Fur- 

 thermore, he follows a time sched- 

 ule and must arrive at the 

 spawning area during the brief 

 period when water temperatures 

 are suitable for successful spawn- 

 ing. His time schedule does not 

 take into consideration one or more 

 dams at each of which he may be 

 delayed several days before finding 

 and ascending the fish-passage fa- 

 cility. 



Losses of young salmon when 

 passing a dam while on their way 

 to the ocean are substantial. Stud- 

 ies at 62-foot Bonneville Dam on 

 the Columbia River indicate sub- 

 stantial loss among young salmon, 

 and current investigations of the 

 Washington Department of Fish- 

 eries and of the International Pa- 

 cific Salmon Fisheries Commission 

 at 3 dams over 100 feet high reveal 

 losses of 35 percent or more among 

 downstream migrant salmon. 



It is apparent from the foregoing 

 that fish ladders alone will not pre- 

 serve salmon runs. The adults must 

 quickly find and easily ascend the 

 ladders, and the young salmon must 

 be led to safe passageways by some 

 as-yet-undeveloped device. 



There are still other undesirable 

 features that develop upon the con- 

 struction of many dams. Species of 



fish that prey upon young salmon 

 and are not themselves desirable for 

 sport or food find reservoirs behind 

 some dams conducive to their exist- 

 ence and increase. In a single 

 reservoir, and particularly in a 

 series of impoundments such as is 

 planned for the Columbia River, 

 predatory species will cause major 

 losses among young salmon. Also, 

 reservoirs often inundate spawning 

 areas, making them unattractive to 

 spawning salmon because of water 

 depth and absence of quite rapid 

 flow over and through the gravel. 



Hatchery propagation is not ex- 

 pected to be able to compensate for 

 or to mitigate satisfactorily the 

 losses caused by dams and pollu- 

 tion, but hatchery-reared salmon 

 can help maintain populations at 

 the highest possible level of abun- 

 dance by supplementing natural 

 reproduction. 



Methods 



The salmon hatcheries operated 

 by the fishery agencies of Califor- 

 nia, Oregon, and Washington, and 

 by the United States Fish and Wild- 

 life Service in the three States, 

 propagate, collectively, chinook, 

 red, silver, chum, and pink salmon, 

 and steelhead trout. There are dif- 

 ferences in techniques and proce- 

 dures employed by different hatch- 

 eries, usually because of the species 

 propagated and the physical char- 

 acteristics of the watershed and the 

 fish-cultural station, but generally 

 the methods of salmon propagation 

 at hatcheries on the Pacific coast 

 are quite similar. 



The species of salmon differ con- 

 siderably in characteristics, and 



22 



