Figure 2. — Scoop traps in operation in the turbine tailrace. 



EQUIPMENT 



Three scoop traps (fig. 2) were used to collect 

 juvenile migrants.^ Each trap was 3.0 m. wide 

 by 3.2 m. long and fished at a depth of 1.2 m. A 

 pontoon-type barge, 5.5 m. by 7.5 m., supported 

 the individual traps and winch equipment. In the 

 turbine tailrace, the traps were close to the right 

 (Idaho) bank. At the Interstate Bridge, one trap 

 was in the center of the channel and the other two 

 were about 30 m. from the right and left banks. 



PROCEDURES 



The traps were emptied of fish and cleared of 

 debris at 8 a.m. and 4 p.m. Additional checks 

 were made at noon and at midnight during peak 

 outmigration and at any time that excessive debris 

 accumulated. During special studies, the traps 

 were emptied of fish and debris at intervals of 1, 

 4, and 6 hours. 



> Bell, Robert. 1969. Time, slje, and estimated numbers of seaward migra- 

 tions of Chinook salmon and steelhead trout in the BrownleeOibow section 

 of the middle Snake River. Idaho Department of Fish and Game, Boise, 

 Idaho, 34 pp. (Processed.) 



All salmon and trout were identified, examined 

 for marks or tags, and measured for fork and 

 standard length. All live salmon and trout were 

 anesthetized before examination and then were 

 released unless needed for special studies. Scale 

 samples were taken from dead and injured fish 

 when possible. 



TESTS OF TRAP EFFICIENCIES 



Fish marked by partial fin clip, tattoo, or ther- 

 mal biand were used to evaluate the efficiency of 

 the scoop traps at both sampling sites. Hatchery- 

 reared juveniles were used for marking in all 

 years, except in 1964 when a few tests were made 

 with native age-group I spring and fall chinook 

 salmon from scoop trap catches. Hatchery-reared 

 age-group chinook salmon were used in 1964 and 

 1965, age-group I coho salmon in 1964, and 

 sockeye salmon in 1965. 



Tests at the Interstate Bridge required that 

 test fish be released into the spUlway and into the 

 turbine penstocks; tests at the turbine tailrace site 

 required releases only into the penstocks. Pen- 



JUVBNILE SALMON AND TROUT EMIGRATION FROM BROWNLEB RBSEHIVOIR 



247 



