At water temperatures below 60° F . the 

 virulence of the major disease organisms is 

 reduced and a lower rate of inflow is possible. 

 Under such conditions a single holding pond of 

 this type has been operated successfully on 12 

 cfs of inflow . Only rarely, however, will such 

 conditions be encountered in salmon holding 

 ponds and, even then, a higher inflow would be 

 more desirable to provide adequate attraction 

 water for the trapping systems. 



Results of experimental holding -- This 

 type of holding pond has been under observation 

 at the Entiat Station for ten years. Maximum 

 water temperatures during August varied from 

 62 . 5 ° F . to 72 . 5 ° F . . Adult chinook salmon, 

 (O . tshawytscha) have been held from the mid- 

 dle of May until the last of November with an 

 average holding period for individual races of 

 three months. Blueback salmon (O. nerka ) have 

 been held in significant numbers only since 1954. 

 This species has a holding period of about two 

 months. During this testing period the condi- 

 tion of the salmon entering the ponds has varied 

 tremendously due to the changing conditions en- 

 countered on the upstream migration. The 

 survivals of chinook and blueback salmon, in- 

 cluding both the holding and spawning period, 

 are shown in tables 1 and 2 . The maximum 

 water temperatures encountered during each 

 holding period are included in the tables. Statis- 

 tical analyses of these data showed no signif- 

 icant correlation between either the water 

 temperature and survival or the number of fish 

 held and survival . Close surveillance of the 

 fish during the holding period indicated that, in 

 both species, the degree of debilitation at the 

 time the fish entered the holding pond was the 

 principal factor influencing survival. Fish 

 which had deteriorated to the point where a 

 fungus infection was apparent rarely recovered. 



The survival records of the Leavenworth 

 holding ponds are in marked contrast to those at 

 Entiat. The same race of summer chinook sal- 

 mon held in the Leavenworth holding ponds dur- 

 ing the years 1940 through 1943, as reported by 

 Fish (1944), showed survivals as follows: 1940- 

 62 percent, 1941-18 percent, 1942-44 percent, 

 and 1943-14 percent. Blueback salmon survivals 

 for the same years were: 59, 5, 37, and 14 

 percent respectively. Comparing these data 

 with the survivals in the Entiat holding pond, 



the worst survivals experienced at Entiat were 

 comparable to the best at Leavenworth. With 

 water temperatures similar, the difference in 

 survival may be attributed, at least in part, to 

 the difference in holding pond design. In fact, 

 an experiment conducted at Leavenworth in 1943 

 was the basis for the present holding pond de- 

 sign . Blueback and chinook salmon held in a 

 narrow, shallow, experimental pond with a per- 

 ceptible current velocity showed marked recovery 

 from injuries and resistance to disease when 

 compared with similar fish held in the Leaven- 

 worth holding ponds . This difference in mortality 

 was the first indication that adequate current 

 velocities could improve the environment suffic- 

 iently to compensate for unfavorable water 

 temperatures . 



The Leavenworth holding ponds were 

 dammed sections of the Icicle River stream bed. 

 Three stoplog type dams each three feet high 

 created three holding sections each approximately 

 one -quarter mile in length. Although 75 cfs of 

 water was diverted through these sections, there 

 was no perceptible current. Water depths ranged 

 from 2 to 10 feet and the width approximated 150 

 feet. Fish concentrated in the deep stagnant areas 

 and losses due to disease were high. The Leaven- 

 worth type of holding pond is essentially a true 

 pond with slight current velocity and a high degree 

 of stratification while the Entiat type could be 

 better described as a channel with a high current 

 velocity and limited stratification . 



Unlike the experience encountered in the 

 Leavenworth ponds, fish which entered the Entiat 

 pond with open wounds usually recovered rapidly . 

 Only those fish which had massive injuries or 

 were seriously debilitated before entering the 

 ponds, as indicated by even a slight fungus condi- 

 tion, failed to recover during the holding period. 

 The numbers of these fish increased during low 

 water years and certain periods of dam construc- 

 tion on the Columbia River. Columnaris disease, 

 while present and a significant factor in the mor- 

 tality, did not reach truly epidemic proportions . 



Carrying capacity 



The capacity of the channel-type of hold- 

 ing pond is not known . The Entiat pond has held 

 1,700 fish, chinook and blueback, of varying 

 sizes and an estimated weight of 17,500 pounds, 



