FIG. 3 Assembled live cages in floats. Note extended frame of 

 raised intermittent-exposure cage in background. 



periods of 7 to 12 days, it was felt that tests of 

 10 days' duration would be practical. However, the 

 mortality rates of the first test were much lower 

 than originally anticipated, so the second and third 

 tests were lengthened to 20 days. 



Fish Used 



The juvenile chinook salmon used in these 

 tests were provided by the Washington Department 

 of Fisheries from its hatchery facilities at the Wells 

 Spawning Channel. Much of the success of these 

 tests can be attributed to the excellent condition of 

 these upper Columbia River summer run chinook 

 salmon. The fish were free of complicating 

 diseases and appeared very healthy when placed 

 in the live cages. The fish showed no signs of 

 smolting at the time they were placed in the live 

 cages. The fish had an average fork length of 

 97 mm in Test I, 105 mm in Test II, and 112 mm in 

 Test III. One hundred fish were placed in each of 

 the 1 m deep cages. Between 100 and 200 fish were 

 placed in the deeper volition cages, depending on 

 the number of fish provided. 



Feeding of Fish 



No food was given to the fish during Tests I 

 and III. The fish used in Test II were fed from the 



11th day to the end of the test period. It was decided 

 to begin feeding the Test II fish with Oregon Moist 

 Pellets® when some began to show signs of starva- 

 tion. They were fed at times when the cages were 

 brought to the surface to check mortalities. It was 

 hoped that feeding the fish only when the cages 

 were raised would prevent an artificial depth dis- 

 tribution in the volition cages that might occur with 

 surface feeding when the cages were at their 

 normal depth. Although feeding with the cages 

 near the surface was successful, it did appear to 

 cause at least some of the fish to spend more time 

 near the surface. For this reason no feeding was 

 attempted in Test III. 



Mortalities 



Each live cage was raised and checked for 

 mortalities between 0800 and 1100 daily for each 

 test. During this period the cage was held with its 

 bottom several inches below the water's surface 

 so that the fish could be observed for signs of gas 

 bubble disease (GBD) or any other problems that 

 might occur. This procedure permitted close obser- 

 vation of the fish each day without unduly stressing 

 the fish. The procedure also permitted cleaning 

 and inspection of the cage netting. Dead fish float- 

 ing in the cages that extended to the surface were 

 also removed at 1600, 2000, and 2400 hr when 

 the depth of the intermittent-exposure cages was 

 changed. All three of the intermittent-exposure 

 cages were lowered to a depth of 3 to 4 m at 0800 

 each day. One of the cages was then raised to the 

 surface position at 1600, 2000, and 2400 hr to pro- 

 vide the surface exposures of 16, 12 and 8 hr, 

 respectively. 



The mortalities were checked immediately 

 following their removal from the cages for external 

 signs of GBD. The locations of external emboli and 

 hemorrhages were recorded as well as the fish 

 length. The abdominal cavities of all mortalities 

 were checked for internal signs of GBD and the 

 presence of food in the digestive tract. 



Dissolved Gas Analysis 



During the morning inspection of the live 

 cages, the dissolved gas levels present in the fore- 

 bay were measured using a Weiss saturometer. The 

 measured saturations given in this report are most 

 likely lower than the levels actually present in the 

 forebay water. An on-site comparison of the satu- 

 rometer used in this study was made with several 

 other saturometers, indicating readings were 1% 

 to 3% low. Routine monitoring by the Chelan 

 County PUD indicated that supersaturation in the 

 study area ranged from 120% to 131% during the 

 test periods. The saturometer readings were also 

 taken at a time of day when river supersaturations 

 were near their lowest level. A 24-hr monitoring 



26 Weitkamp 



