Concrete is desirable but not necessary, par- 

 ticularly in temporary or experimental installa- 

 tions. The holding ponds themselves can be 

 roughed out of the material available. Prefer- 

 ably they should be brought to grade and lined 

 with clay. Gravel bottoms and sides are to be 

 avoided if possible. The conduits and walls of 

 the trapping systems and fishways may be made 

 of heavy planking. The Entiat traps and ladders 

 are of wooden construction and, surprisingly 

 enough, are still in fair condition after 10 years 

 of use. While substitutions may be made in the 

 materials of construction, alterations should 

 not be made in the design without previous ex- 

 perimentation to determine the reaction of the 

 fish. 



SUMMARY 



Holding ponds of the channel -type offer 

 a most efficient method for the retention of 

 adult salmon if the interval between the up- 

 stream and spawning migration is longer than 

 three or four weeks. The channel-type pond is 

 designed to minimize self-inflicted injuries by 

 means of a submerged, diffused water intake 

 and sloping pond banks . Disease inhibition and 

 recuperation are enhanced by means of a favor- 

 able environment in which an average current 

 velocity of . 2 fps is maintained at least during 

 periods of high water temperature . Rapid water 

 passage is demonstrated to be as effective as 

 cold water temperatures in disease inhibition. 

 In the Entiat holding pond no correlation exists 

 between holding survivals and the maximum 

 water temperatures encountered over a 10 -year 

 period. The average survival for chinook sal- 

 mon of 81 percent is much superior to that 

 encountered in other types of holding ponds . In 

 order to fully exploit the carrying capacity of 

 the water supply, it is suggested that the holding 

 ponds be operated in series . 



Upstream and downstream trapping sys- 

 tems are an essential and integral part of this 

 holding pond . Salmon on the spawning migration 

 move either upstream or downstream . If both 

 types of traps are available the mature fish may 

 be captured with a minimum of handling . Be - 

 cause injury to the fish is avoided, losses dur- 

 ing the spawning period are reduced. The trap- 

 ping systems employ holding pens for the 

 retention of the segregated ripe and green 



females. Ripe females are held for an addition- 

 al day after all symptoms of sexual maturity 

 are present to insure fully mature ovaries. More 

 eggs per female and increased egg survival are 

 the result of this procedure. 



LITERATURE CITED 



Atkins, Charles G. 



1884. Memorandum relative to inclosures 

 for the confinement of salmon drawn 

 from experience at Bucksport, Pen- 

 obscot River, Maine. Bulletin U. S. 

 Fish Commission, vol. 4, pp. 170- 

 174. 



Combs, Bobby D., Roger E. Burrows, and 



Richard G . Bigej 



1959 . The effect of controlled light on the 

 maturation of adult blueback salmon . 

 U.S. Department of the Interior, Fish 

 and Wildlife Service, Progressive 

 Fish-Culturist , vol. 21, No. 2, pp. 

 63-69. (April). 



Fish, Frederic F. 



1944 . The retention of adult salmon with 

 particular reference to the Grand 

 Coulee fish -salvage program. U.S. 

 Department of the Interior, Fish and 

 Wildlife Service Special Scientific 

 Report No. 27, 29 pp. 



Fish, Frederic F., and Robert R. Rucker 

 1943. Columnaris as a disease of cold- 

 water fishes. Transactions 

 American Fisheries Society, vol. 73, 

 pp. 32-36. 



Fry, F. E. J. 



1957. The aquatic respiration of fish. 

 The Physiology of Fishes, Vol. 1, 

 Metabolism, chap. 1, part 1, pp. 

 1-63. Margaret E. Brown, ed. 

 Academic Press, New York, 447 pp. 



Hume, R. D. 



1893. The salmon of the Pacific Coast. 



Private publication, 70 pp. Reprinted 

 Washington Department of Fisheries 

 Annual Report No . 68, pp. 117-140. 

 1958. 



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