Figure 5.-Length frequencies of coastrange sculpin col- 

 lected in the Elokomin River after releases of salmon 

 in 1962 and 1963. Salmon predators are shaded, and 

 nonpredators are unshaded. N = total number of 

 sculpins in sample of which P = number of predators. 

 Total number of sculpins is smaller than in Table 2 

 because Table 2 includes some sculpins taken prior 

 to the release of hatchery reared salmon. 



Estimation of loss of salmon. — The per- 

 centage of salmon lost from hatchery releases 

 is the prime criterion in evaluating- the gross 

 effect of predation by sculpins in the Elokomin 

 River — the smaller number of predators were 

 not able to eat a significant number of salmon 

 the one night they were available in Herman 

 Creek. To compute the loss of salmon requires 

 knowledge of number of predators, incidence 

 and rate of predation, and duration of ex- 

 posure to predation. The data available met 



_Prickly: HG = -S Mil -1 

 03I0BL N= 1 17 



Torrent: G ;- I 1 045+ 0.2947 L 

 N=I52 



Reticulate G = 8613 ♦ 0.2490 L N = 76 



Coastrange G = 8874 ♦ 2024 L N = 248 



50 



100 150 



LENGTH (MM) 



200 



Figure 6.-Relation of length to mouth gape of sculpins 

 from Elokomin River (G) and Herman Creek (HG). 

 Regression lines show length range of sample. 



