Review of the Status and Distribution of Olympic Mudminnow, An Endemic Species in Western Washington

The Olympic mudminnow is a small fish that is endemic to western Washington.  It is a Washington State Sensitive Species and is classified as a Priority Species under the Washington Department of Fish and Wildlife (WDFW) Priority Species and Habitat Program.  Olympic mudminnow prefer marshy, wetland type habitat with a muddy bottom, low water velocities, and abundant aquatic vegetation.  They are tolerant of a wide range of environmental conditions, but typically they are absent or in low abundance as the number of associated fish species increases, suggesting sensitivity to competition/predation from other fish species.  Over the past few years, little work has been done on Olympic mudminnow distribution and population status.  Some of the original systematic sampling of Olympic mudminnow was in the early 1970’s.  Sites were resurveyed from 1993-98 by WDFW and used to assess population trends.  In 2010 and 2011, sites were resurveyed again.  At most sites, Olympic mudminnow were still present; however, changes in land-use practices appear to limit the availability of preferred habitat.  Olympic mudminnow occur in four general areas of western Washington: Chehalis River basin, coastal drainages of the Olympic Peninsula, south Puget Sound, and east Puget Sound.  Presently, we are collecting tissue samples to examine the amount of genetic variation within Olympic mudminnow populations to determine the amount of gene flow and to determine the major evolutionary groupings for the species.