Number of 

 fieh 



GRAYLING OF GREBE LAKE 



325 



Males 

 (154) 

 Females 

 (80) 



8 9 10 11 12 13 U 

 Total length in inches 



15 16 17 



Number of 

 fish 



1954 



Males 



(164) 



Females 



(141) 



8 9 10 11 12 13 

 Total length in inches 



15 16 



Figure 13. — Length-frequency diagrams of Grebe Lake hybrid trout captured during the 1953 and 1954 spawning 



migrations. 



selection by males. Some were in water so shallow 

 that their backs and those of the females were out 

 of water while spawning. Tryon (1947) published 

 a picture of a grayling on its spawning location 

 in water so shallow its dorsal fin was emerging 

 from the water. Other territories used for spawn- 

 ing were in the Gibbon River between 4 and 5 

 feet deep. Because of the large number of spawn- 

 ing fish, nearly every available location was pre- 

 empted by males. 



Fish on the spawning grounds became uneasy 

 at sudden movements and shadows, but within a 

 matter of minutes returned to spawning activities. 

 Brown (1938) also observed that spawning gray- 

 ling, though wary, were without apparent fear. 



When fighting in defense of a spawning site, 



the mouth of the guardian male was open slightly 

 so that the white lining inside the jaw could be 

 seen. The dorsal fin was erect and the fish usually 

 threatened the intruder with slightly rigid body 

 movements, then, attacked him. After a few 

 such passes by the aggressive guardian, the intruder 

 would leave the area with the victor in close pur- 

 suit. Some unwanted fish were chased as far as 

 15 feet, after which the defending male would re- 

 turn to the particular part of his territory where 

 he consistently lay. 



Often two or three grayling of mixed sexes con- 

 gregated below a spawning pair and appeared to 

 be consuming eggs that drifted downstream before 

 settling to the bottom. On one occasion a drift 

 net (described later, figs. 17 and 18) was set below 



