of the commonly variable isozyme loci found in rainbow trout 

 strains, i.e., Idh-3,4; Mdh-3,4; Pam-2, were not present in these 

 Montana golden trout populations. It is unlikely that this low 

 amount of genetic variation would be present if there had been 

 introgression from rainbow trout. 



Genetic variation occurred at only a single locus, Sod-1 

 (Table 10). The variation consisted of a fast migrating allele, 

 Sod-l(152). This variation is common in both rainbow trout 

 (Allendorf and Utter 1979) and golden trout (Gall et al. 1976). 

 Aat-3,4 appeared to be variable, but inadequate resolution and 

 lack of inheritance data prevented a confirmation of the genetic 

 basis. There were statistically significant differences at Sod-1 

 between the golden trout populations started from the Surprise 

 Lake, Wyoming source and those sources from Montana: P <.01, = 

 10.9, Idf. The golden trout populations started from the Sur- 

 prise Lake stock had a low occurrence of the variant allele. 



DISCUSSION 



Present Status 



Of the 14 lake systems in Montana with golden trout in 1981, 

 only Lightning, Sylvan, Sawtooth, Island, Hidden #5, 6 and 7 and 

 Golden Trout lakes appear relatively secure. Among these six 

 populations, Lightning, Sylvan and Island had the greatest safe- 

 guards, due to their locations within a wilderness area. The 

 Hidden lakes and Golden Trout Lake were becoming increasingly 

 close to large timber sales. Both lake systems are influenced by 

 easy, close access and show deteriorating shorelines and water 

 quality. Sawtooth Lake also bordered considerable commercial- 

 sized timber. No logging was apparent in Sawtooth basin or along 

 Clarks Creek, its immediate drainage. Clear-cuts and roading 

 v/ere, however, common in the Pioneer Mountains. 



The status of Cave, Shrimp and Duck lakes had not been 

 adequately confirmed, nor had the populations been around long 

 enough to test sustainability. Blue Danube had historic longev- 

 ity and produced good yield to previous experimental netting. 

 Its present low population status may rally; however, its future 

 looks bleak. 



Heart and Crescent lakes in the Mission Mountains will 

 probably continue to produce erratic population densities, due in 

 part to their reliance on recruitment from Island Lake upstream. 

 Sylvan Lake endures; its only threat would be an unauthorized 

 transplant of brook trout from nearby Crow Lake or an aerial 

 stocking error. 



Ranking of Lakes 



A ranking of golden trout habitats (Table 11) lists Light- 

 ning lake best in Montana. Its fisheries status excels others 

 because of its size, outlet condition, flow and nursery area 200 



- 32 - 



