342 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Total 



length 



(Inches) 



20.0 



15.0 



10.0 



5.0 



0.0 



a— « West Gallatin River, Montana 

 O— — O Grebe lake, Wyoming 



—r- 

 II 



III 



IV 



VI 



VII 



Annulua 



Figure 27. — Calculated growth rates of hybrid trout from the West Gallatin River, Mont, (data from three elevations 



combined, Purkett 1951) and from Grebe Lake, Wyo. 



VI, 17.3; VII, 17.5 (tables 23 and 24). This was 

 not maximal. It was slightly less than that in the 

 West Gallatin River through the third year and 

 markedly less than that in the fourth and fifth 

 years (fig. 27). 



Some male hybrid trout were mature in Grebe 

 Lake at the start of their third growing season 

 (annulus II). All female hybrids captured during 

 the spawning season were at least 3-year-olds. 

 Trout reached the legal size limit of 6 inches in 

 their second or third year of life. 



Female hybrid trout in Grebe Lake grew faster 

 than did the males (table 25), and by the third 

 year females were approximately 1.3 inches longer 

 than the males. 



Table 23. — Average calculated total lengths of fish in inches 

 at various annuli of Grebe Lake trout, 1953 



Table 24. — Average calculated total fish lengths in inches 

 at various annuli of Grebe Lake trout, 1954 



Table 25. — Empirical average total lengths of fish in 

 inches in successive years of life for 1953 and 1954 collec- 

 tions of male and female trout in Grebe Lake 



Length-Weight Relation 



Length-weight relation for both the grayling 

 and the hybrid trout were used in computing 

 pounds of fish in Grebe Lake from length meas- 

 urements. According to Hile (1936) this relation 



