An accumulated sample of 419 stomachs were collected season- 



^ ally from six Absaroka-Beartooth lakes between 1972 and 1981 and 



■^ another 401 stomach samples in Sylvan and Lightning lakes. 



Differences were more evident among diets of fish in small lakes 



than those larger fish typical of large lakes (Table 7). 



Larger fish in large lakes fed heavily on benthic organisms, 

 larva forms of Diptera, Plecoptera, Tricoptera and Ephemoptera. 

 Water column foods were next most popular; Diptera pupa and, when 

 available, Gammarus dominated the choice. Zooplankton were found 

 incidental to other foods in only six fish in larger lakes. 

 During, before and after spawning, some surface feeding was 

 observed. The total weight and numbers of terrestrial organisms 

 in golden trout diets was usually small, even though the fre- 

 quency of terrestrial-originated foods was common, especially 

 during the spring. 



Most of the food consumed in small oligotrophic lakes origi- 

 nated in the water column followed by the benthic and lastly from 

 the terrestrial environment. Dipteran pupa again were the most 

 heavily utilized feed. During winter, larval Dipterans from the 

 benthic zone dominated the menu. Cladoceran zooplankters were 

 utilized under ice conditions by some of Sylvan lakes' younger 

 golden trout, a food source rarely utilized in the lakes studied. 

 The dominant terrestrial food organisms in both small and large 

 oligotrophic lakes were flying ants. 



>% Of 820 stomachs analyzed, there was never an incidence of 



'"^ fish or fish eggs. This held true throughout the spawning and 

 emergence periods. Golden trout occupying Lightning Lake were 

 rarely seen after spawning season. This disappearing act was in 

 harmony with resumption of benthic feeding activity, often in the 

 deepest water near the outlet. 



Competition 



The demise of Montana's 50 plus populations of golden trout 

 were largely due to introductions of other spring spawning 

 species of fish. Hybridization was commonplace; species were 

 replaced. Seventeen lakes in Montana are still known for these 

 colorful crosses (Table 8). 



Golden trout are eventually eliminated when cohabiting a 

 lake with brook trout. Golden trout in Fourmile Basin Lake #3 

 never sustained in the presence of brook trout. One golden trout 

 and 42 brook trout were gillnetted in 1962 (Whitney and Domrose 

 1964); 2 goldens, 40 brook trout were netted in 1973 (Marcoux 

 1973)' and no goldens were found and 32 brook trout netted in 

 1981. Density of trout in Fourmile #3 was dependent on an 

 occasional escape from Fourmile #4 upstream, escaping predation 

 and finding food in an already crowded environment of brook 

 trout. 



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