relatively lower reaches of the rivers 

 and often close to tidewater. The 

 spring chinook is in prime condition 

 when it enters the rivers, having 

 stored fats for sustenance on a long 

 journey inland; and usually the 

 female contains immature or green 

 eggs that will not be developed for 

 spawning for many weeks or per- 

 haps several months. The fall chi- 

 nook, on the other hand, usually 

 is not in prime^condition when it 

 enters the river; the flesh deterio- 

 rates rapidly, as the spawning time 

 is often a matter of only days or 

 possibly 2 or 3 weeks. 



It is evident that to trap the 

 spring chinooks for spawning at the 

 mouth of a long river would require 

 that these fish be held for many 

 weeks or several months before the 

 sexual products would be "ripe" 

 and suitable for artificial spawning. 

 Successful holding of adult spring 

 chinook, even in carefully con- 

 structed "natural" ponds or streams 

 sections, has proved very difficult. 

 Experience at several hatcheries has 

 revealed the difficulties to be en- 

 countered in such holding. At a 

 few points spring chinook adults 

 have been retained successfully 

 until mature; the success appeared 

 to be due to the Avater supply. 

 There may be also a psychological 

 as well as a physiological effect upon 

 the fish because they are in foreign 

 waters and not en route to their 

 home streams. Theoretically, it 

 would be possible to trap these 

 spring-run fish immediately below 

 their spawning areas, but the cost 

 in relation to the relatively few fish 

 that w^ould be taken in the small 

 tributaries would be excessive. 



Even here, too, many quite green 

 fish would be taken. 



The fall chinook adults are quite 

 readily trapped and spawned in the 

 tributaries of the lower reaches of 

 the various watersheds. There the 

 fish are almost ripe and usually need 

 be held for only a few days before 

 spawning. The fall fish do not 

 "resent" being held in ponds or be- 

 tween racks as do the springs. The 

 fall fish are much more docile and 

 are quite readily "herded" or led 

 where most convenient for accom- 

 plishment of spawning. 



After the eggs of spring or fall 

 fish are taken and placed in the 

 hatchery, there is no appreciable 

 difference in the incubation. Maxi- 

 mum returns to the fishery are se- 

 cured by rearing the young spring 

 chinooks for about 1 year before re- 

 leasing them into the streams. Such 

 rearing should be wnth as nearly 

 natural water temperatures as pos- 

 sible. Experience has shown that 

 when the spring chinook fingerlings 

 attain a size of 3 to 5 inches they ex- 

 hibit a decided desire to migrate 

 downstream. In hatcheries where 

 warm spring water is available, the 

 tendency is to provide warmer than 

 natural waters for rearing, resulting 

 in unnaturally great food intake 

 and growth of the fish. Thus, the 

 migration urge may come upon the 

 young fish, requiring their release 

 during periods of severe cold when 

 there is anchor ice in the sti-eams or 

 other factors unfavorable for stream 

 survival. The fall chinook finger- 

 lings do not generally exhibit such 

 migration urges. 



The adults of silver and red sal- 

 mon trapped long before their 



24 



