GRAYLING OF GREBE LAKE 



341 



categories of hybrids based on the number of 

 circuli from the focus to the first year mark. In 

 one of these fish, which had more than 15 circuli 

 within this area, an extra annulus was assigned 

 (fig. 20). The first circulus from the focus was 

 used as the first year mark. In the other category, 

 trout with fewer than 15 circuli on the scale be- 

 tween the focus and the first annulus were judged 

 to have their first year mark. 



Eroded and broken scales 



Many trout scales in 1953 and 1954 had broken 

 edges, clear hyaline spots, and eroded or re- 

 Total 

 length 

 (inches) 



17.0 

 16.0 

 15.0 

 U.0 

 13.0 

 12.0 

 11.0 

 10.0 



9.0 



8.0 



7.0 



6.0 



5.0 



4.0 



I II III IV 



absorbed margins. Such scales were discarded as 

 undependable for age-and-growth analyses. They 

 made up 14.3 percent (22 fish) of the sample in 

 1953 and 2.5 percent (5 fish) in 1954. Some 

 bias may have been incurred bj* removing these 

 fish from the sample, because most of the individ- 

 uals were more than 14 inches in total length. 



Age and Growth of Hybrid Trout in Grebe Lake 



Averages of calculated total lengths (inches) at 

 various annuli for hybrid trout based on combined 

 samples taken in Grebe Lake, 1953 and 1954, 

 were: I, 3.7; II, 7.2; III, 10.5; IV, 12.8; V, 14.9; 



VI VII VIII IX 



Annulus 



Figure 26. — Comparative growth rates of grayling from United States (Nelson 1954, and Kruse, present study) 

 and Canada (Miller 1946). Fork lengths converted to total lengths. 



