1990 Grayling Spawning Report 



age II fish experienced poor survival, while age fish experienced 

 good survival, from the spring of 1988 to the spring of 1989. This 

 differential survival between age and age II fish warrants 

 further investigation. We found the numbers of fish age two and 

 older were very low and it appears that once the age 4 and older 

 fish die, there will be few mature fish to spawn during 1990 and 

 1991. 



DISTRIBUTION OF SPAWNING WITHIN THE DRAINAGE 



The distribution of grayling spawning within the Big Hole 

 drainage was similar in 1988 and 1989. Areas in the main stem 

 above the North Fork of the Big Hole River and lower Swamp Creek 

 were used for spawning. Sample electrof ishing in the portion of 

 the Big Hole River between Fishtrap Creek and the East Bench BLM 

 access indicated that rainbow trout were utilizing spawning 

 habitats where grayling were typically found in the Wisdom portion 

 of the river. We speculate that rainbow spawners may compete with 

 grayling spawners and have successfully excluded them from spawning 

 sites in the lower portion of their range within the Big Hole. 



MOVEMENT 



The movement patterns observed through recaptures of tagged 

 fish in the Big Hole suggests that a segment of the riverine Big 

 Hole grayling population spends the winter in deep pools in the 

 portion of the river down river from the Wisdom area as far as the 

 Divide dam and perhaps in some tributaries with deep pools or areas 

 of groundwater recharge. During the spring, some of the mature 

 grayling from the lower river move up river and spawn in the 

 portion of the river from the mouth of the North Fork up to 

 immediately above Wisdom, and in the lower portions of Swamp, 

 Steel, Big Lake, Rock, and Sand Hollow creeks. 



From tag return data it is difficult to determine if the gray- 

 ling population within the upper Big Hole River consists of one or 

 more discrete stocks. It is apparent that some grayling in the Big 

 Hole system move between the lower and upper river seasonally for 

 spawning and, perhaps, to seek over winter habitat. Seasonal 

 movement patterns indicate that some grayling adults move into 

 spawning areas located in the upper river above the North Fork from 

 the lower river near Fishtrap Creek. We are unsure if these fish 

 move immediately down river after spawning, or if they remain in 

 the upper river over the summer before moving back down during the 

 fall. Past information indicated mature-sized grayling spent the 

 entire summer within the upper portion of the drainage in the 

 Wisdom area as documented by summer and fall electrof ishing (Liknes 

 1978; Oswald 1984; Oswald 1986). There may be two discrete life- 

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