the water in the dirt pond are given in Appen- 

 dix tables A-1— A-7. Because of its cooler 

 temperature, it is customary to utilize Tyee 

 Springs water for most of the holding period, 

 and to introduce warmer Wind River water to 

 hasten maturation in late summer. Water from 

 both sources is mixed before being introduced 

 through a submerged diffusion chamber at the 

 upper end of the pond. A trap to capture fish 

 for collection of eggs is installed upstream 

 from the diffusion chamber. As the spawning 

 season approaches, additional water is intro- 

 duced for attraction into the trap. Most of the 

 salmon move into the trapping facility of their 

 own accord; however, each year, near the end 

 of the egg-taking operations, it has been 

 found necessary to capture, by seining, those 

 fish that try to spawn in the pond. In earlier 

 years, when seining was not done, some of the 

 fish spawned in the pond, with a subsequent 

 loss of eggs. No deleterious effects have been 

 observed from such seining operations. Data 

 pertaining to fish that have spawned in the 

 pond are given in table 3. 



Length measurements are taken of all fish 

 handled. In addition, data are recorded regard- 

 ing disease, injuries, and condition of eggs. 



fish (Ptychocheilus oregonensis), transported in 

 the loads of fish from Bonneville Dam or 

 young fish resulting from their spawning in 

 the pond. At the close of the salmon spawning 

 operation, the pond is drained and all scrap 

 fish present are removed and destroyed. 



In 1954, a few summer chinook salmon were 

 hauled from Bonneville Dam and placed in 

 the dirt holding pond at the Carson hatchery 

 to determine optimum flows required and 

 proper method of introducing Wind River 

 water into the facility. Data collected have 

 formed the basis for present operations. 



Flows of water in the pond have varied 

 from 11 to 19 cubic feet per second (c.f.s.). It 

 has been determined by studying the reactions 

 of the fish that a flow of about 14-15 c.f.s. is 

 most desirable for holding the adult spring 

 Chinook salmon at Carson hatchery. In intro- 

 ducing Wind River water into the pond to hasten 

 maturation, it was found necessary to make 

 gradual additions of the warmer water. When 

 Wind River water was introduced too quickly, 

 the fish became very agitated, and in some 

 instances swam out of the water and up on the 

 banks. Considerable jumping also occurred. 



An inclined-plane screen trap located at the 

 pond outlet has been provided to capture 

 any adult scrap fish, largescale suckers 

 (Catostomus macrocheilus) and Northern squaw- 



To date, fish held in the dirt holding pond 

 have not developed fungus to any serious 

 degree. This has not been the case, however, 

 with adults held in the concrete holding ponds. 



Table 3. — Records of adult spring Chinook salmon held in dirt holding pond, 

 Carson National Fish Hatchery, 1955-61. 



^ Includes jacks. 



^ Does not include 3 fish which died in truck. 



' Does not include 4 fish which died in truck. 



