The U. S. Fish and Wildlife Service today announced the withdrawal of the fluvial Arctic grayling of the upper Missouri River from the list of species being considered for protection under the Endangered Species Act (ESA). The Service has determined that listing this population of Arctic grayling at this time is not warranted because it does not constitute a distinct population segment as defined by the ESA.
Under the ESA, 'species' is defined broadly to include species, subspecies, and also to include distinct population segments of vertebrate species. A distinct population segment (DPS) is a portion of a vertebrate species or subspecies population that is geographically discrete from the rest of its kind and also is significant to its survival.
Discreteness refers to the isolation of a population from other members of the species and is evaluated based on specific criteria. If the population is determined to be discrete, the Service evaluates its significance based on available scientific information to determine its importance to the taxon to which it belongs. If the population is determined to be discrete and significant, the Service evaluates it for endangered or threatened status based on ESA standards.
The Service's 1994 status review identified the fluvial (river dwelling) form the Arctic grayling in the upper Missouri River drainage as a DPS based on geographical isolation and behavioral distinctiveness. The Service continues to conclude that this population is discrete from other populations of the same taxon based on physical and behavioral factors.
However, currently available genetic information indicates the fluvial Arctic grayling of the upper Missouri River drainage do not differ markedly in their genetic characteristics from adfluvial (lake and reservoir dwelling) Arctic grayling native to the Missouri River system. The fluvial Arctic grayling, therefore, is not considered biologically or ecologically significant based simply on genetics.
The 2005 candidate assessment also asserted that the loss of the fluvial Arctic grayling of the upper Missouri River would result in a significant gap in the range of the taxon because these fish are the only existing fluvial graying population in the contiguous United States and represent the southernmost extent of the species. However, a federal court recently ruled in an unrelated case that in designating a DPS, the Service must find that a discrete population is significant to the taxon as a whole, not to the United States. Therefore, the Service has determined, based on current available information, the loss of the Montana population of fluvial Arctic grayling would not result in a significant gap in the range of the species.
Because the Service is unable to conclude at this time that the fluvial Arctic grayling population of the upper Missouri River is significant, it does not qualify as a distinct population segment and is not a listable entity under the Act.
The Service continues to encourage cooperative conservation and restoration of fluvial Arctic grayling in the upper Missouri River and supports the efforts of Montana, Fish, Wildlife and Parks in cooperation with the USDA Natural Resources Conservation Service, Montana Department of Natural Resources and Conservation, and the Service to work with local landowners to protect the Big Hole River population.
In 1994, the Service published a petition finding and 12-month status review concluding that listing the fluvial Arctic grayling indigenous to the upper Missouri River was warranted but precluded by higher listing actions. In May 2003, the Center for Biological Diversity and Western Watersheds Project filed a complaint challenging the Service's continuing warranted-but-precluded determination. In a settlement agreement, the Service agreed to send a final determination to the Federal Register on or before April 16, 2007. This revised 12-month finding is being published as a final listing determination per the settlement agreement.
The Arctic grayling (Thymallus arcticus) is a freshwater fish in the same family (Salmonidae) as salmon, trout, and whitefish. A distinctive morphological characteristic of this fish is its large, sail-like dorsal fin. Arctic grayling is an obligate cool- or cold-water species. Individual fish can range widely, moving tens of miles on a seasonal or annual basis between spawning, rearing, and sheltering habitats. Arctic grayling are native to drainages of the Arctic Ocean, Hudson Bay and northern Pacific Ocean in North America and Asia. Two distinct populations historically inhabited waters in Michigan and Montana.
Although no further action will result from this finding, the Service will accept additional information and comments from all interested parties concerning this finding and will reconsider this determination if appropriate. New information concerning the taxonomy, biology, ecology, and status of the Arctic grayling of the Upper Missouri River can be sent to the U.S. Fish and Wildlife Service, Montana Field Office, Attention: Arctic Grayling Coordinator, 585 Shepard Way, Helena, Montana 59601.
his finding will be published in the Federal Register on April 24, 2007. This finding and other information concerning Arctic grayling will be available on the Service's web site at:
http://mountain-prairie.fws.gov/species/fish/grayling/grayling.htm
