INTRODUCTION 



The continued decline of the only known population of 

 fluvial Arctic grayling ( Thymallus arcticus) in the lower 48 

 states has caused increasing concern. Liknes (1981) cited 

 dewatering, overharvest, and competition with brook trout 

 (Salvelinus fontinalis ) as the principle factors that may be 

 contributing to the decline of the Arctic grayling in the Big 

 Hole River. The severe drought conditions (low water and very 

 high water temperatures) in the Wisdom, Montana section of the 

 Big Hole River during the summers of 1987 and 1988 appear to have 

 seriously impacted the grayling population there. From Fall 1986 

 to Fall 1989 the linear density of age I and older grayling in 

 the Big Hole River declined from about 35 per mile to 

 approximately 18 per mile (R. Oswald, pers. comm.). 



The Montana Natural Heritage Program, the Montana 

 Cooperative Fisheries Unit, the Montana Department of Fish, 

 Wildlife and Parks (MDFWP) , and the U.S. Forest Service, through 

 a cooperative effort, provided funding, equipment, and logistical 

 support for a study of the Big Hole River grayling. This study, 

 which began in the Spring of 1988, emphasizes the early-life 

 history requirements and habitat preferences of young-of-the- 

 year (YOY) Arctic grayling in the upper Big Hole River and its 

 tributaries near the town of Wisdom, Montana. 



The first portion of this study was conducted through the 

 summer of 1988 and provided information on the distribution and 

 habitat utilization of YOY Arctic grayling (Skaar 1989) . This 

 report presents the results of the continuation of the 1988 study 

 and focuses again on the distribution and habitat preferences of 

 YOY grayling as well as the possibility of interspecific 

 competition for food between Arctic grayling and the non-native 

 brook trout. 



