females into the green pen, and males into 

 either the male pen or the ripe pen to conform 

 with the number of ripe females available . 



4. If necessary the brail of the male pen 

 is raised and the required number of males 

 transferred to the ripe pen . 



A similar routine is followed in the 

 downstream trapping systems with the exception 

 that males surplus to the daily requirement are 

 either held in the green pen or transferred to 

 the male pen in the adjacent upstream trapping 

 system . By raising the brails until the water 

 is only a foot in depth the sorters can get in 

 with the fish, catch, check, and place them in 

 any desired pen. 



We have found the practice of retaining 

 the mature females an additional day before 

 spawning to be a practical, efficient procedure. 

 All eggs are not freed from the follicles simul- 

 taneously but ripeness progresses from the 

 posterior portion of the ovary forward to the 

 anterior end. In large, heavy-walled fish in 

 particular, all external symptoms, even the 

 free flow of eggs from the genital pore, may in- 

 dicate ripeness, but when the fish are killed, a 

 portion of the eggs in the anterior end of the 

 ovary may not be free from the follicles . Under 

 normal conditions retention of the fish for an 

 additional 24 hours insures complete maturity. 

 With complete maturity the percentage survival 

 of the eggs is also increased. The time re- 

 quired for spawntaking is reduced because the 

 eggs fall freely from the follicles . Ripe pens 

 in the trapping system are considered essential 

 if unwarranted losses in both fish and eggs are 

 to be avoided. 



Abnormal situations : - -Normally the 

 combination of upstream and downstream traps 

 will remove all the fish from the holding pond 

 and seining of the stragglers is not required. 

 When exotic races are held in an abnormal en- 

 vironment, however, the spawning desire may 

 be submerged and seining required. This type 

 of situation occurs in the Entiat holding pond 

 where an exotic run of late -spawning summer 

 chinook salmon has been developed. These fish 

 normally spawn in the main Columbia River and 

 the lower reaches of large tributary streams 



from the first of October to the last of November 

 while water temperatures are still above 40° F . . 

 The Entiat River which supplies the water to the 

 holding pond usually drops abruptly to below 40° F . 

 the forepart of November. When this tempera- 

 ture drop occurs the female chinook apparently 

 lose the spawning urge. Although the process of 

 maturation continues, the fish are lethargic and 

 if left undisturbed will become overripe and 

 eventually die without making any attempt to en- 

 ter the traps or construct spawning redds in the 

 pond. Under such conditions repeated seining 

 is necessary in order to procure the ripe females. 

 Fortunately the cold water temperatures impede 

 disease development and if the fish are handled 

 carefully no mortality results. 



A similar effect has been noted when un- 

 seasonably warm water temperatures occur 

 during the spawning period. Trapping activity 

 practically ceases . However, a drop in water 

 temperature reactivates the migration tendency 

 and an abnormal influx of ripe and overripe fish 

 is the result. Seining should not be considered 

 under these conditions as catastrophic mortalities 

 could be the result. 



Installation of trapping facilities increases 

 the initial cost of the holding pond but also re- 

 duces operating costs. A two-man spawning 

 crew can operate two or three holding ponds. 

 By no other known method can the fish be removed 

 from holding ponds as efficiently . 



The trapping systems described above 

 offer the best method developed to date for the 

 procurement of the sexually mature salmon from 

 holding ponds . The method takes advantage of 

 the instinct of the fish to search for a spawning 

 site and thereby segregates the immature and 

 mature fish without excessive handling. Because 

 handling is avoided mortalities are reduced. The 

 trapping systems are a necessary and indispens- 

 able adjunct of the channel -type holding pond 

 because of their contribution to the reduction in 

 mortality of both fish and eggs. 



CONSTRUCTION 



The design drawings, figures 1-4, in- 

 dicate concrete construction of all permanent 

 facilities including the holding pond itself. 



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