GRAYLING SPAWNING REPORT 



RESULTS 



TIMING OF SPAWNING 



The first ripe male grayling was captured on April 20 in 

 the Big Hole River above the Highway 43 bridge near Wisdom 

 (Figures 1 and 3). The first female grayling identified as ripe 

 was captured in the Big Hole River on April 27 near the Wisdom 

 Cemetery an the east channel. The nurrbers of ripe females peaked 

 during the period between April 29 and May 11. The numbers of 

 ripe males peaked during the period between April 22 to May 17. 

 The first spent female was captured on May 4. 



CHARACTERISTICS OF THE SPAWNING RUN 



The sex ratio of ail fish identified as mature, ripe, or 

 spent was 2.0 malesil.O female (Table 3). Length and age 

 frequency information for mature fish illustrated that a large 

 portion of the age II fish were sexually mature (Table 3 and 

 Figure 4). The fact that the sex ratios change betv-^een age 

 classes suggests that not ail female grayling were maturing at 

 age II and that female grayling may be suffering higher mortality 

 than males after age iV (Table 3). The average length and weight 

 of ripe males i. n = 158) was 10.9 inches and 0.42 pounds, 

 respectively. The average length and weight of ripe females (n = 

 34) was 11.3 inches and 0.51 pounds, respectively. The majority 

 of growth in length was attained at by age III with the fastest 

 growth occurring during the first and second years of life 

 (Figure 5) . 



DISTRIBUTION OF SPAWNING igiTHIN THE DRAINAGE 



The majority of grayling spawning during 1988 occurred 

 within the main stem Big Hole River between the North Fork of the 

 Big Hole River upstream to approximately 3.0 miles above the 

 Highway 43 bridge near the town of Wisdom and in the lower 

 portions (generally from their mouth upstream one to two miles) 

 of Swamp, Big Lake, and Rock creeks (Figure 1). Isolated 

 spawning areas were observed in side channels within the main 

 stem Big Hole River above the Highway 43 bridge near Squaw Crnek 

 and between Sawlog and Fishtrap creeks. 



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