Discharge line 



Vacuum gouge 

 Air exhaust X End plate a 



-N \. ^P Plastic window 



122 cm X 183cm 

 Fish holding tank 



9 



Aerator 



Water pump 



Chiller Cooling coils 



Figure 1. — Fish holding-recirculating system and pressure chamber vacuum system. 



All test fish were held in the laboratory hold- 

 ing facility for a minimum of 2 days and in the 

 pressure chamber for 1 hr before testing. After 

 exposure to negative pressure, the fish were held 

 in chambers for observation for as long as 1.5 hr, 

 then transferred to the holding facility for final 

 observation at the end of 24 hr. Water from 

 the holding facility was circulated through the 

 chamber at atmospheric pressure before and 

 after each test. 



Counts were taken of the numbers of fish par- 

 tially immobilized, completely immobilized, and 

 dead during the following periods after expos- 

 ure: 5, 10, 20, 30, 40, 50, 60, and 90 min and 

 24 hr. Partially immobilized fish were recog- 

 nized by their feeble eflforts to swim; completely 

 immobilized fish were identified by spasmodic 

 movements or absence of movement other than 

 respiratory. Those fish showing no evidence of 

 opercular movement were considered dead, sub- 

 ject to later verification. 



Each treatment was repeated three times on 

 different groups of each species, for a total of 

 six tests at each vacuum level. The number in 

 each test averaged 16 for wild chinook salmon 

 and 23 for the hatchery coho salmon for a total 

 of 151 chinook and 216 coho salmon. The re- 

 sponse of the test fish to decompression was com- 

 puted from the three tests at each negative pres- 

 sure and expressed as an average response. The 

 order in which the fish were tested was dictated 

 more by availability than by design. Generally 

 the testing proceeded from the highest vacuum 

 level to the next lower level. 



Ice Harbor Dam Study 



The coho salmon and rainbow trout tested in 

 the turbines at Ice Harbor Dam had been reared 

 in hatcheries to about 100-127 mm long. They 

 were transported to temporary holding tanks 

 near the dam a few days before the test to per- 

 mit them to acclimate to Snake River water. 

 Each fish was marked with a cryogenic brand 

 to identify it as to time and place of release. A 

 total of 5,408 coho salmon and 2,291 rainbow 

 trout were branded and released in the turbines 

 in 11 tests that began 11 October and ended 30 

 November 1966. 



The test equipment used for studies of finger- 

 ling mortality in turbines was described by Long 

 and Marquette (1967). It consisted of three 

 basic components — a release hose extending from 

 the deck of the dam to the turbine intake, a fun- 

 nel net attached to the draft tube exit, and a 

 recovery barge secured to the cod end of the 

 net. A trough with several screened compart- 

 ments was placed on the barge to hold immo- 

 bilized fish for observation. 



The test fish passed through a turbine that was 

 being operated at rated or overload capacity. 

 The first of the fish usually arrived at the barge 

 within 3 min and the majority within 20 min 

 after release. Those fish with characteristic 

 symptoms of immobilization associated with de- 

 compression, yet apparently free of net or tur- 

 bine injury, were immediately put into individual 

 holding compartments for further observation. 

 The times of release in the turbine intake, of 



