GRAYLING SPAWNING REPORT 



this portion of the draxnage indicated that their irrigation 

 diversions were 'shut off either in July prior to haying (and not 

 turned back on again) or around Labor Day in S3ptsfr;ber, prior to 

 the initiation of down river movement by grayliiig. 



Direct habitat enhancement would depend upon better defining 

 habitat requirements of this population and determining if 

 physical habitat was limiting populations. If this was the 

 case, a habitat improvement program could be initiated. This 

 optiion would rely on the collection of more information. 



Direct enhancement of riverine grayling populations in the 

 Big Hole River could be accomplished by supplementing ths 

 existing population with other riverine stock or with frv hatched 

 from eggs taken from Big Hole grayling. There is a risk in the 

 first option in that it could potentially introduce undesirable 

 genetic material into the present population and alter the 

 genetic makeup of the existing native population. The second 

 option is the more preferable, however, one problem with this 

 option 15 that the availability of eggs to supplement the 

 population is presently limited due to the low numbers of mature 

 females in the population and the difficulty in obtaining eggs 

 during the extremely short spawning period. During tiie 1983 

 spawning season approximately 5 , OOO fertilized eggs were ootaired 

 from the Big Hole grayling population for fry behavior research 

 conducted by Dr. C. Kaya (Montana State University, Bozeman ) . 

 After Dr, Kaya hatd completed his experiments and these fry had 

 suffered some mortality due to disease, approximately 3,000 fry 

 remainea. These fry were released into a lake which was 

 previously barren of fish. This lake has an inlet which should 

 provide suitable spawning habitat for these grayling. This 

 release should provide additional fry for the Big Hole system. 

 Our plan is to return to the lake vjhen these fry mature (m two 

 to three years) to obtain fertilized eggs by trapping the inl3t 

 stream. It is hoped that during the course of maturing these 

 released fry do not lose too much of the genetic component that 

 makes them riverine Big Hole River stock due to adaption to the 

 lake environment. The objectives of this release were two-fold. 

 One was to provide a source of fry to stock back into the Big 

 Hole system so that we could enhance thie Big Hole population 

 while we were investigating how to enhance survival within the 

 Big Hole system. The other objective was to preserve some 

 genetic material from the Big Hole grayling population in an 

 isolated location so that if the Big Hole population suffered a 

 catastrophic decline to extinction we would have a source -or re- 

 introducing grayling back into the Big hole. Since the 3 , 0'. O fry 

 which were stocked into the lake m 1983 were the progeny of only 

 SIX feiviales, we plan to spawn some additional females during 1939 

 to increase the genetic variabilLt/ within this lake population. 



Page - 



