1990 Grayling Spawning Report 



INTRODUCTION 



The last riverine (fluvial) native population of Montana 

 Arctic grayling ( Thymallus arcticus montanus [Milner]) in the 

 contiguous 4 8 United States exists in the upper Big Hole River of 

 southwestern Montana (Liknes and Gould 1987). Shepard and Oswald 

 (1989) reported the historic distribution and status of Arctic g- 

 rayling in the lower 48 United States and discussed the evidence 

 for a unique Big Hole River fluvial stock. They documented the 

 past investigations of the Big Hole River grayling population and 

 the recent declines observed in grayling numbers. They also 

 reviewed the literature regarding spawning cues and habitat 

 requirements . 



STUDY SITE DESCRIPTION 



The study area included the upper Big Hole River drainage up 

 river from Divide, Montana (Figure 1). Sampling was concentrated 

 within the main stem Big Hole River from the towns of Wise River 

 upstream to approximately 5.0 miles above Wisdom and in the lower 

 portions of its tributaries including Big Lake Creek, Deep Creek, 

 Sand Hollow Creek, Steel Creek, and Swamp Creek. Unfortunately, 

 the USGS river flow gauge and water temperature gauge at Wisdom did 

 not begin operation until May 1, 1989. Consequently, river flow 

 and water temperature data were unavailable during the entire 

 sampling of the spawning run. During May, Big Hole River flows and 

 water temperatures ranged from 36 to 648 cfs and 41 to 61 F, 

 respectively, using preliminary data supplied by the USGS from a 

 gauge located at the Highway 43 bridge near Wisdom (Figure 2). 



METHODS 



FISH COLLECTION 



Grayling were captured using either boat mounted electro- 

 fishing gear (either a Buffalo Drift boat or Coleman Crawdad 

 outfitted with a 240 watt gas powered generator connected to a 

 Harvey Leach constructed variable voltage pulsator with mobile 

 anodes) or a backpack electrof isher (Coeffelt BP-IC) electrof ished 

 in a downstream direction. Sampling began on April 18 and 

 continued through May 18 (Table 1). Two crews operated during the 

 peak of the spawning run. A total of approximately 4 9 miles of 

 river and 8 miles of tributaries were surveyed during the spawning 

 season. We restricted our sampling during 1989 to those areas 

 where we captured grayling during 1988. We placed red plastic 

 survey flags at most locations where ripe or mature grayling were 



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