of a series of ponds of the dimensions shown in 

 figure 2 in preference to a single long pond is 

 recommended. One advantage is that the fish 

 are segregated according to time of appearance 

 which rather grossly separates races and spec- 

 ies and tends to shorten the spawntaking period 

 within an individual pond. A second advantage 

 is that the capacity of the trapping facilities 

 within a pond is not exceeded with the smaller 

 concentrations of fish. 



The retention of the adult fish until sex- 

 ual maturity is one problem for which the chan- 

 nel type of holding pond offers an effective 

 solution. The design prevents self-inflicted 

 injury, and rapid passage aids in disease inhib- 

 ition . A second problem, that of the capture 

 of the sexually mature fish for spawntaking, is 

 of equal importance to the holding problem. If 

 proper methods of capture are not employed, the 

 effectiveness of successful retention can be null- 

 ified by the mortality incurred during the spawn - 

 taking period. 



HOLDING POND TRAPS 



Capture of the sexually-mature salmon 

 for egg-taking operations is complicated by sev- 

 eral characteristic environmental and physiolog- 

 ical reactions of the maturing fish. The spawn- 

 ing migration of salmon may be either upstream 

 or downstream and consists of a movement of 

 but a few feet or several miles. A species or a 

 race within a species may move predominately 

 upstream or downstream in its migration but 

 this does not preclude the possibility of individ- 

 uals within a group differing from the majority. 

 Sexual maturation is influenced by both light and 

 temperature. Combs et jd.(1959) have demon- 

 strated that light is the dominant factor but 

 temperature has a definite effect. Unseason- 

 ably warm or cold temperatures may delay the 

 spawning migration but not necessarily sexual 

 maturity. Sexual maturity does not occur simul- 

 taneously in all fish within a race or species of 

 salmon . Usually within a race the spawning 

 period is confined to a single month but where 

 several races and species are involved it is 

 possible to have sexually -mature fish occurring 

 over a six -month period. These factors affect 

 the capture of mature fish for egg-taking opera- 

 tions . 



During the spawning period, salmon 

 are still susceptible to injury and disease. At 

 this time mortalities as high or higher than 

 those during the holding period can be induced 

 by improper handling. Regardless of the race 

 involved, if the temperatures are high and the 

 fish are repeatedly handled to check for ripeness, 

 few of the late -spawning females will survive to 

 maturity . At water temperatures in the sixties 

 the losses can be disastrous. At low water tempera- 

 tures, in the forties, losses may be light enough 

 to be tolerated. Any method of capture which 

 will reduce handling to a minimum is to be pre- 

 ferred. 



Holding pond trap design 



Trapping has proved to be a most effective 

 method of capture of sexually mature salmon in 

 holding ponds . Certain characteristic reactions 

 of the confined fish make trapping particularly 

 feasible. For the first week or ten days of con- 

 finement in holding ponds the salmon are extremely 

 restless, cruising the pond, seeking an avenue of 

 escape. After this initial period the fish settle 

 down in the deeper areas . As sexual maturity 

 approaches, the female followed by one or several 

 males begins the spawning migration. It is on 

 this migration that the fish may be successfully 

 trapped. 



The extent and persistance of the desire 

 of certain individuals to move downstream on the 

 spawning migration was not realized when the 

 Entiat holding pond was designed and constructed. 

 Only a single upstream trap was included in the 

 original installation. As a result, some fish re- 

 fused to enter the upstream trap and natural 

 spawning in the pond occurred. The pond has 

 since been altered to include two downstream 

 traps in the positions shown in figure 1 . After 

 their installation approximately 60 percent of the 

 summer chinook and 35 percent of the blueback 

 salmon have been taken in the downstream traps 

 and natural spawning within the pond has been 

 virtually eliminated. 



Both upstream and downstream traps are 

 considered advisable in any holding pond installa- 

 tion. Figure 3 shows the recommended design 

 for the upstream trap and figure 4 the design for 

 the downstream traps. In both designs holding 



