FISHERY BULLETIN: VOL. 74, NO. 1 



-3 3 6 9 12 15 18 



DISTANCE FROM HIGH TIDE MARK (0) IN HUNDREDS OF METERS 



Figure 4. — Relative distribution of subyearling and older 

 (1 + ) sculpins in Lymn Creek during the period August- 

 December. 



sculpins made at the head of tide in December 

 suggest the return upstream of individuals which 

 made the downstream migration in the previous 

 spring. 



In general, size of fish increased with distance 

 upstream, the largest individuals of both species 

 living at the upstream border of their respective 

 ranges (Figures 5-7); however, subyearling and 

 yearling sculpins of both species tended to be 

 larger both upstream and downstream from the 

 head of tide. 



Age Structure 



Age structure of populations of both species in 

 Lymn, Chef, and Waterloo creeks was determined 

 by reading the otoliths. Only the first two age- 

 classes could be identified from length frequency 

 histograms (Figures 5-7), and these modes agreed 

 with the otolith readings. The Lymn Creek popu- 

 lations were aged from three successive monthly 

 samples (August-October) that indicated similar 

 lengths within age-groups for this time interval 

 (Tables 2, 3). Slight length increases for a given 

 age-group reflected detectable growth. 



oleul'Cus^78a 

 N 

 ospef =421 



METERS 

 - 1212 



-— ^■•'1 I 



>^»fl<F^' 



— -24010-303 



I •■ ^T'' 



5 6 7 8 9 



TOTAL LENGTH (cm) 



Figure 5. — Length-frequency histograms for sculpin popu- 

 lations in Lymn Creek from collections made in September 

 and October. Sampling stations are identified as distances 

 upstream or downstream (-) from high tide mark (0) in meters. 



5£.' 5 



^0 



O 5 

 CO 



(T 15 



^.0 

 2 5 



Z 

 5 

 

 5 



oieuttcus:2G7 

 osper ' 140 



• ^f""" — "i»w— 



250 

 159 



70 

 24 



-ALEUTICUS 



8 



-38 



5 6 7 8 9 10 M 



TOTAL LENGTH (cm) 



Figure 6. — Length-frequency histograms for sculpin popu- 

 lations in Cabin Creek from collections made in September 

 and October. Sampling stations are identified as distances 

 upstream or downstream (-) from high tide mark (0) in meters. 



Both sculpins showed differences in age struc- 

 ture in the three streams (Tables 2, 3). There 

 were eight age-classes of C. aleuticus in Lymn 

 Creek but only five in Chef and Waterloo creeks. 

 For C. asper there were six age-classes in Lymn 

 and Waterloo creeks but only four in Chef Creek. 



136 



