GRAYLING SPAWNING REPORT 



DISCUSSION 



TIMING OF SPAWNING 



Grayling spawning in the Big Hole appeared to be triggered 

 by a combination of water temperature and river discharge (Figure 

 2). Daily maximum water temperatures at Wisdom rose above 50 F 

 on April 16 for the first time (reaching 52 F) and remained 

 above 50 F from then until April 18, however, river flows also 

 rose rapidly during this time period from 1,900 cfs to 2,110 cfs 

 and continued to rise to 2,530 cfs by April 22. Daily naximum 

 water temperatures again rose higher than 50 F on April 27 (52 F) 

 ana remained over 50 F for the remainder of April. River flows, 

 meanwhile, dropped from the early peak of 2,530 cfs down to l,6t0 

 on April 25 and stabilized at around 1,300 cfs between April 26 

 to Mf>y 13. This suggests that grayling initiatec spawning in 

 response to the combined cues of daily maximum water temperatures 

 rising above 50 F in conjunction with the falling limb of the 

 initial spring sub-peak flow event that is characteristic of the 

 upper Big Hole River nydrograph. Spawning then occurred during 

 a relatively stable flow period between the initial spring sub- 

 peak flow and the mam higher spring peak flow that occurred 

 during late-May and early-June- Mean daily water temperatures 

 during the peak of spawning activity (April 27 to day 10) 

 averaged 47 F, but during the last five days of April (when 

 spawning was initiated) mean daily water temperatures av^r^ged 

 48 F. 



A review of previous studies found t j me of spawning w^5 

 variable. Environmental factors that cued spawning activity 

 were suggested to be water temperature and flow changes. Brown 

 (1938) stated that 'The actual period of spawning for the Montana 

 grayling has been found to vary greatly between different years 

 and between different localities in the same year." Previous 

 studies of grayling in Montana found that spawning occurred from 

 mid-March through July. Specifically spawning occurred, mid- 

 March to April 24 in Odell Creek, a Madison River tributary, 

 peaking around April 16 (Brown 1938); from mid-May to early June 

 in Narrows Creek, a tributary to Elk Lake in the Centennial 

 Valley of southwest Montana (Lund 1974); from early May through 

 May in an inlet of Rogers Lake in the northwest portion of the 

 state (Tryon 1947); through early July with the time of initial 

 spawning unknown in three high mcuntain lake inlets within the 

 Wise River drainage, a tributary to the Big Hole River (Erik sen 

 1975) ; f rcTi mid-May to l^.te June in tributaries to G(-ate Lake in 

 Yellowstone National Park ( Kruse 1959); from May 19 to June 6 in 

 Red Rock Creek and from May 23 to June 1 in Antelope Creek, both 

 tributaries to Upper Red Rock Lake in the Centennial Valley of 



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