GRAYLING SPAWNING REPORT 



vulnerable to angling (Fal.k and Gillman 1974; Tack 1974; Graback" 

 1981) and recent regulation restrictions have attempted to remove 

 that component of mortality from the riverine Big Hole population 

 (Table 1). The other three potential avenues for preservmc 

 and/or enhancing this population B.rs: 1) habitat enhancemant, 

 either through the enhancement of river flows or direct habitat 

 enhancement by creating more preferred habitats; 2) population 

 enhancement through releases of riverine stock grayling fry into 

 the system; and 3) control of competitors and predators, if 

 further research finds these tv-jo types of interactions contribute 

 significantly to overall mortality. We will discuss each of 

 these options in detail. 



One of the most likely candidates for preserving and /or 

 enhancing populations is to provide more stable river flows and 

 reduce potential loss of grayling in irrigarion ditches. By 

 providing more stable flows, particularly during the relative 

 short spawning and incubation period, survival from eggs through 

 the first summer of life should be enhanced. More work is needed 

 to confirm our observations from 1988 and further refine the 

 relationship between the timing of spawning and river flows and 

 water temperatures. If we can accurately predict when spawning 

 will occur, we can work with local irrigators to provide for more 

 stable river flows from the initiation of spawning through the 

 time fry emerge (a two to three week time period). The senior 

 author has already approached irrigators in the upper Big Hole 

 vallev near Wisdom and received a very positive response to this 

 concept. There appears to be a very real possibility of 

 initiating this type of management. 



Another potential source of mortal itv is the loss of 

 grayling, particularly fry and juveniles, into irrigation 

 ditches. One way to limit this loss would be to attempt to 

 return any grayling fry or juveniles back to the river from 

 irrigation ditches before these ditches Brs shut down for haying 

 or at the end of the season. Work done in the Gallatin River 

 system found that an incremental shut-down of ditches o^er a two 

 to three day period triggered trout to move up the ditch and 

 return to the river (Clothier 1953 1954; Kraft 1972). Orienta- 

 tion of irrigation diversions relative to the river channel can 

 also reduce loss of fish into ditches (Spindler 1955). Again, 

 the senior author approached the irrigators of the upper Big Hole 

 drainage and these irrigators agreed to begin implementing the 

 incremental shut-down of ditches immediately, and were wiUmq •-- 

 discuss orientation and operation of diversion structures to 

 minimize fish loss. The loss of grayling migrating down river 

 during the fall to seek overwjnter habitat into irrigation 

 ditches does not appear to be a concern in the upper Big Hol° 

 drainage (from Jackson down to Squaw Creek). The irrigators m 



Page - 30 



