GRAYLING SPAWNING REPORT 



the course of the spawning run in an Alberta tributary from 3.0 

 males: 1.0 female early in the run to 5.0 malesii.O female late 

 in the run . 



The grayling in the Big Hole River system became sexually 

 mature at age II. Hubert et al.'s (1985) reviev-^ of riverine 

 grayling studies found that age at sexually maturity varied, 

 dependent upon latitude and population density. In general, the 

 above authors reported that grayling populations with low to 

 moderate densities at lower latitudes attained sexual maturity at 

 ago II to III, while in northern latitudes or high population 

 densities fish matured at age IV and older, not reaching sexual 

 maturity until age VI in many Alaskan waters. Tack (1974) 

 concluded that angler harvest may have been responsible for 

 grayling r.iaturing at a smaller size (earlier age) in the Chena 

 River than in ijther waters of Alaska. 



The growth curve for grayling in the Big Hole system 

 illustrates that the majority of growth is put on during their 

 first two years (Figure 5). The presence of some juveniles in 

 tributaries to the river and the interpretation of early growth 

 from a few scales suggests that a small segment of the juvenile 

 population may rear for up to two years in river tributaries. In 

 Hubert et al.'s review (1935) of riveririe populations they 

 reported that grayling m Hon tana and Wyoming reach 7.2 to 9.8 

 inches in 2 years and -from 11.2 to 14.7 in 4 years. Growth for 

 the Big Hole grayling population appears to be toward the upp^r 

 end of this range through age II (9.6 inches), while the average 

 length of age IV grayling (12.7 inches) lies in the middle of the 

 range reported by Hubert et ai. (1965). 



DISTRIBUTION OF SPAWNING WITHIN THE DRAINAGE 



The distribution of spawning grayling within the Big Hole 

 drainage shows that areas above the North Fork of the Big Hole 

 River were more intensively used for spawning. Precise reasons 

 for this distribution of spawning Are unknown at this time, 

 however, the following speculation may encourage further 

 investigation. One possible explanation for the spawning 

 distribution could be the high fine sediment load contributed to 

 the Big Hole from the North Fork watershed. This drainage is 

 underlain by highly erosive granitic batholithic material and lias 

 recently experienced more intensive land-use. Previous streambed 

 sampling by the senior author in 19S7 found that a riffle a.reA 

 within the ri^er near Wisdom contained only 16X fine material 

 (material less than 0.25 inch), whiile a riffle located aiova the 

 Highway 43 bridge near Squaw Creek (An Ar^a below the North Fork) 

 contained 297. fine material, and a riffle near Sportsmen's Park 



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