| Summary: | Between 1994 and 1996, life history and winter habitat characteristics were determined for a population of Arctic grayling (Thymallus arcticus) in an irrigation canal (Sunnyslope Canal, Teton County, Montana, USA) with seasonally intermittent flow: (1) approximate locations and times of spawning; (2) growth rates; (3) numbers present in the residual pools and their survival through winter; and (4) depths and dissolved oxygen (DO) beneath ice cover of inhabited pools. Water flowed for five months from late April-early May to late September, peaking at 46-48 m3/s and averaging 11.4 degrees C (range 4.7-16.0). Reproduction within the upper canal was confirmed by sightings of spawning fish and observations and collections of developing embryos and newly swimming young. Spawning occurred in May, within 1 or 2 weeks after flow started. During the seven months without flow, 8 to 13 residual pools within the uppermost 6 km provided potential fish habitat. Four pools with combined length of 342 m and volume of 1487 m3 provided the major wintering habitat during winter 1995-1996, and 76-100% of fish survived until spring in these pools. Under ice cover, mean DO ranged from 7.4 to 9.2 mg/l and mean depths from 0.26 to 0.82 m. These Arctic grayling had growth rates among the highest known among populations in Montana, but numbers of age-1 and older fish in the upper canal were estimated at less than 350 in spring 1995 and 1996. The persistence of this population, unlike their disappearance from all but one stream known to have been inhabited by the species in Montana, may be related to the failure of non-native fishes to become established in the canal, together with summer water volume and temperature and availability of wintering pools. Barndt and Kaya "Reproduction, growth, and winter habitat of Arctic grayling in an intermittent canal." Northwest Science. 2000; 74(4): 294-305
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