Reproduction 



Ice covered about half of Sylvan and Lightning lakes' sur- 

 face when Age III and older fish started assembling near warmer 

 outlet waters. In Sylvan Lake this occurred June 20, 1981; June 

 27, 1973 and July 12, 1975. Spawning began 15- days later m 

 Lightning Lake with less exposure and 187 additional feet of 

 elevation than Sylvan Lake. 



Fish moved into outlet traps and shoal area near the outlet 

 when water temperatures were near 40° F and began spawning in 

 temperatures from 44 to 58° F. No eggs could be artifically 

 taken at temperatures less than 44°^ F. The peak spawning 

 activity in Sylvan Lake occurred July 6, 1981; July 9^^1973 and 

 July 20, 1975 when temperatures ranged between 48 and 54 F. 



During 3 years of studying reproductive activities of golden 

 trout, the 3 and 4-year-old fish were the most numerous age 

 aroups in the spawning run (Table 5) in Sylvan Lake. Age II fish 

 were predominately precocious males. A few 2-year-old females 

 yielded 50 to 150 eggs. Ages III and IV females, usually 9-11 

 inches in length, produced 350-700 eggs. One 19-inch female had 

 1,750 eggs (Fig. 1). 



Pedds were generally small, often occupying small gravel 

 deposits between rocks. A typical redd covered a 3x6-inch area, 

 3-4 inches deep and from 8-12.5 inches under water. Redd sites 

 in pea gravel along lake shoals were mostly high and dry before 

 emergence. 



The spawning substrate at each successful artifical redd 

 site as we] 1 as numerous selected natural redds was composed of 

 2-inch and smaller rock. All successful hatching was in material 

 with less than 1% fines and with less than 10% of the material 

 smaller than .5 mm. 



Incubation period ranged from 46-50 days at a mean tempera- 

 ture of 52° F in Sylvan Lake. In Lightning Lake, emergence took 

 52 days at a mean temperature of 46° F. Fish were 1.2 inches 

 when their yolk sacs were absorbed in September. Eggs incubated 

 at 52° F at the Yellowstone River Trout Hatchery took 31 days to 

 hatch. Hatching time was 28 days at 46° F at Daniel Hatchery, 

 Wyoming (Hudelson, pers. comm.) and 24 days at 60° F at the Mount 

 Whitney Hatchery in California (Toth, pers. comm.). 



Examination of other Montana waters with golden trout 

 revealed a similar preference for outlets as primary spawning 

 sites. Evidence of some inlet spawning was apparent at Hidden 

 Lake #2 which had a lake upstream; some at Golden Trout Lake, 

 also with lotic waters upstream, and Sawtooth Lake. No evidence 

 of outlet utilization by goldens was apparent at Sawtooth Lake. 

 Water temperatures < = 40° F during the physiological stage 

 goldens were ready to spawn apparently determined whether a 

 population became self-sufficient. Most alpine lakes, unless 

 part of a chain or a wide spot in the stream, did not have one 



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