FISHERY BULLETIN; VOL, 74, NO. 4 



Table 13.-Cumulative deaths of echo salmon fry taken from the inner bay of Little Port 

 Walter, the weir trap at the mouth of Sashin Creek, and Sashin Creek and held in waters of 

 various salinities, July 1964. 



'Accidentally discontinued before 72 h, 



^Of seven survivors in 17 6°/oo at 96 h, three were transferred to 31 °/oo for 48 h, and one 

 survived; four were transferred to 23.5*^/00, and three survived for 48 h. 

 'Period from 96 to 144 h at 31°/oo salinity. 



ended (Table 13). Otto (1971) found that salinity 

 tolerance of juvenile coho salmon was increased by 

 a 35-day exposure to water of lower salinity. 



The inner bay has horizontal and vertical salin- 

 ity gradients (Powers 1963), which are excellent 

 for acclimation of young salmon to salt water. 

 Much of the surface of the inner bay is usually less 

 than 10-15'/iKi salinity. Our bioassays show that fry 

 able to survive 48 h in 2Z"/w salinity should be able 

 to acclimate fully to salinities encountered in the 

 inner bay if they have access to the low salinity 

 refuge. Our observation of coho salmon fry in 

 live-boxes confirms this ability. 



Juveniles in the Stream 



Age Determination 



Because length frequencies of different age- 

 groups can overlap broadly at some times of the 

 year (Figures 5-7), scales of juvenile coho salmon 

 were analyzed to assign age-groups. Analysis of 

 scale samples indicated that an average of 11% of 

 all fingerlings (age I and older) collected from the 

 stream were age II. Sizes of the various age- 

 groups sampled by month for 1964-67 are shown in 

 Figure 5. 



10 



  



50 



60 



_l_ 



70 



-1- 



100 



Figure 5. -Length frequencies and 

 ages of coho salmon juveniles from 

 Sashin Creek grouped by month of 

 collection, June to September 1964-67. 

 Ages were determined by analysis of 

 scale samples, and lengths were mea- 

 sured on preserved fish. Arrows in- 

 dicate location of mean lengths for each 

 age class. 



FORK LENGTH (mm) 



910 



