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Movements of Young-of-the Year Arctic Grayling in their first 

 summer 



Information about the movements of YOY Arctic grayling in 

 their first summer is largely circumstantial. Brad Shepard 

 (MDFWP) surveyed sample sections H and J during April and May 

 1988 for spawning grayling. Ripe or spent fish were found in 

 many locations that were in close proximity to areas where 

 concentrations of YOY fish were found in July and August (Figure 

 21) . This suggests that many fish stayed close to the spawning 

 areas in which they were born, but it is not possible to say if 

 or how many fish moved out of these streams. 



The fidelity of the YOY fish to riffle areas was seen when 

 five areas (one on Swamp Creek and four on the Big Hole River) 

 were electrof ished for a second time, from 14-29 days after the 

 initial survey. Forty-five YOY Arctic grayling were captured in 

 these areas during the initial survey, while 33 were captured 

 during the second survey. These fish were not marked, so it was 

 not known if they were the same fish that were captured the first 

 time. However, it is significant to note that the fidelity of 

 the fish for these areas continued through a time interval when 

 the streamflow discharge dropped by about 20% on the Big Hole 

 River and 33% on Swamp Creek. 



Interactions between Arctic grayling and brook trout 



Brook trout have been in the Big Hole River since about 

 1929, and it has been speculated that their presence has 

 contributed to the decline of the Arctic grayling as a result of 

 predation or competition (Liknes 1981) . If interspecific 

 competition for food or space is occurring, spacial segregation 

 might be expected. In this study, distinct differences in 

 habitat use by age 1+ and older fish were seen. Brook trout were 

 most abundant in the higher gradient, upper sample sections of 

 the Study Area, but were present throughout the Study Area. In 

 the sample sections where both species occured, there was a 

 tendency for brook trout to occupy faster water, often in 

 association with undercut banks or overhanging terrestrial 

 vegetation. The brook trout were not restricted to this type of 

 water, however, and were found in lesser numbers in typical 

 Arctic grayling habitat, which was slow runs or pools with depths 

 typically at least 2-3 ft. Often, the pools could be 

 characterized as backwater areas with foam on the water surface. 

 Nelson (1954) studied these two species in Red Rock Creek, 

 Montana, and found an inverse relationship in the distribution of 

 the two species, suggesting some sort of spatial segregation. In 

 this study, age 1+ and older Arctic grayling were usually in such 

 low densities that it was not possible to statistically compare 

 their densities with those of brook trout. 



