r-gsn.- 



Figure 3. — Floating trap used to capture juvenile salmon moving near the shore. Salmon were diverted 

 to the trap by a lead extending from the shoreline. 



A combination of length-frequency ranges and 

 the above marks identified specific populations and 

 individual fish and, thus, yielded data on direction 

 and rat« of movement, spatial distribution, gro^vth, 

 and survival of the populations of salmon that 

 entered the reservoir. 



Upon capture, the fish were anesthetized, meas- 

 ured (fork length) to the nearest millimeter, ex- 

 amined for marks, and tagged if not previously 

 marked. Scales for age determination were taken 

 each month from a sample of up to 10 fish in each 

 5-mm. length group in the catches. All fisli were 

 released near the capture site. 



THE ENVIRONMENT OF THE RESERVOIR 



Apparently, the conditions 

 effect on the environment of 

 were the size and timing of 

 drawdown and fillui> and 

 through the impoundment, 

 reservoir, filling, spillway 



exerting the greatest 

 Brownlee Reservoir 



the annual reservoir 



the volume of flow 

 Water level of the 



discharge, and flow 



varied consideraibly during the 4-year study (fig. 

 4). The drawdown was least (6.4 m.) in 1963 and 

 greatest (28.3 m.) in 1965. Drawdown typically 

 began in December or January. Filling began 

 each year in early April except in 1965 when it was 

 delayed until mid-May. Filling was nearly com- 

 plete by late June 1962, mid-April 1963, mid-Juno 

 1964, and mid-June 1965. The extent of drawdown 

 or fill determined the length of the reservoii-, and 

 the time of filling determined tlie quality of thn 

 water through which the fish migrated. 



SURFACE CURRENTS 



The volume of inflow and outflow, together with 

 the water level of the reservoir, determined the 

 orientation and stability of currents and the ve- 

 locity of flow. Figure 5 shows typical currents 

 under different reservoir conditions. 



The stability, velocity, and orientation of the 

 reservoir surface cui'rents varied considerably over 

 the study yeai-s (1962-65). Surface currents near 



222 



U.S. FISH AND WILDLIFE SERVICE 



