METHODS 



Water temperatures were collected with three 30-day record- 

 ing thermographs at Sylvan and Lightning lakes during 1973 and 

 1975. Surface to bottom water temperatures were measured over 

 deep portions of these lakes with a thermistor and probe. 

 Instantaneous temperatures v/ere read with a pocket thermometer in 

 association with all investigative actions. 



Substrate composition of artificial and natural spawning 

 sites was taken with the aid of a 2-pound coffee tin. Grain-size 

 analysis followed the procedures of Welch (1948) . A Price-type 

 current meter and a staff gauge was employed in the outlets of 

 Sylvan and Lightning lakes, and flows were converted to cubic 

 feet per second. Redd sites were measured to the nearest inch. 



Fish were collected in nylon 5xl25-foot gill nets (graduated 

 mesh 3/4 to 2 inches square) set overnight in each lake. All 

 representative samples were photographed and coloration was noted 

 and sketched. Lengths, weights, sex, fat content and body condi- 

 tion were recorded on each fish. Stomachs were removed, sorted 

 to length groups and preserved in formalin. Contents of stomachs 

 were sorted, counted and weighed. Only contents anterior to the 

 pyloric caece were considered. Food types were cataloged in 

 relation to where it was consumed: terrestrial, water column or 

 benthic zones. 



Scales and otoliths were removed from each fish for aging. 

 Eggs were counted in each morbid female of various size groups. 



Protocol for collection of fish health inspections followed 

 the format of the U. S. Department of the Interior, Fish and 

 Wildlife Service, Fish Disease Control Center. Attempts were 

 made to have at least a 30-fish sample of each feral population 

 of golden trout. Samples collected included fecal material in 

 10% formalin, fecal smears trypticase soy agar, (TSA) cultures, 

 saline preserved kidney/spleen samples and gill arches in 10% 

 formalin. Genetic samples involved collecting one eye, a slice 

 of kidney and muscle tissue from each fish. Genetic variation 

 was determined by Steve Phelps, Population Genetics Laboratory, 

 University of Montana, using horizontal starch gel electro- 

 phoresis according to method of Utter, Hodgins and Allendorf 

 (1974) . 



FINDINGS 



Locations 



As of 1981, the State of Montana had 17 lakes harboring 

 golden trout (Table 1) . Because of the close proximity of cer- 

 tain waters and interchange of fish between waters as in Light- 

 ning and Little Lightning and three Hidden lakes in the Gallatin, 

 only 14 real populations existed in 1981. 



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