The US Fish & Wildlife Service (FWS) is currently re-evaluating the Distinct Population Segment (DPS) status for fluvial populations of Arctic grayling (Thymallus arcticus) in Montana. Up until now, the agency has judged fluvial Arctic grayling to be a DPS. The DPS status of fluvial Arctic grayling has been the crucial criterion for considering the fish as a candidate species under the Endangered Species Act (ESA). DPS status hinged largely on studies showing that Age 0 fluvial grayling would hold their position in a stream, whereas lacustrine Age 0 grayling from the same watershed would move downstream with the current. (Kaya and Jeanes, 1995). 

In a recent review, the FWS points to available genetic data in concluding that that "fluvial and lacustrine populations of Arctic grayling in Montana do not appear to satisfy the discreteness criterion of the DPS policy (Fed. Reg. 1996) and, thus, do not represent two distinct population segments under the ESA." (Campton 2006) Since lacustrine grayling are plentiful in the Big Hole River watershed (Mussigbrod, Agnes, Miner, Bobcat lakes, etc.), withdrawing DPS status for fluvial grayling will remove Montana fluvial grayling from ESA candidacy. 

The FWS realizes that additional genetic information could change its opinion regarding DPS status. To better address the uncertainties, FWS has proposed a study (Ardren, Campton, and Peterson 2005) to further elucidate genetic differences among grayling populations in Montana. To date, this proposal has not been funded. 

In lieu of additional information supporting DPS status for fluvial grayling in Montana, it is likely that the FWS will remove Montana fluvial grayling from ESA candidacy. Under a legal agreement reached with the Center for Biological Diversity, the FWS has until April 2007 to decide whether the Montana fluvial Arctic grayling should be placed on the endangered species list. 

It is unclear how removing Montana fluvial Arctic grayling from ESA consideration would affect the Conservation Candidate with Assurances Agreements now being implemented by the agency. 

Ardren, W.A., D.E. Campton, and D.P. Peterson. 2005. “A Genetic Evaluation of Arctic Grayling in Montana with special emphasis on the remnant fluvial population in the Big Hole River.” Study Proposal for the U.S. Fish and Wildlife Service, Conservation Genetics Laboratory, Abernathy Fish Technology Center, Longview, Washington. 

Campton, D.E. 2006. “Should Arctic grayling in the Big Hole River, Montana be considered a Distinct Population Segment (DPS) under the U.S. Endangered Species Act? An Evaluation of Existing Genetic Information.” Report for the U.S. Fish and Wildlife Service, Abernathy Fish Technology Center, Longview, Washington. 

Kaya, C.M. and E.D. Jeanes. 1995. “Retention of adaptive rheotactic behavior by F1 fluvial Arctic grayling.” Transactions of the American Fisheries Society 124: 453-457. 

Professor Pat Munday, PhD
Technical Communication Dept
Montana Tech
Butte Montana  59701
Voice mail 406.496.4461
Email pmunday@mtech.edu