Washington State Status Report for the Olympic Mudminnow

The Olympic mudminnow is one of five species worldwide in the family Umbridae and is the only member of the genus Novumbra. Three other species are found in North America and one in eastern Europe. Olympic mudminnows are found only in Washington State. No other members of the family Umbridae are found in Washington.

The current distribution of the Olympic mudminnow includes the southern and western lowlands of the Olympic Peninsula, the Chehalis and lower Deschutes River drainages, and south Puget Sound, west of the Nisqually River. They are usually found in slow-moving streams, wetlands and ponds. Within these habitats, mudminnows require a muddy bottom, little or no water flow and abundant aquatic vegetation.

Spawning occurs over an extended period from late November to the following June. Mature mudminnows are about 50 mm (2 in) to 75 mm (3 in) long. Males become brightly colored and aggressive during spawning. Females deposit eggs in vegetation and they hatch in approximately ten days.

Little is known about mudminnow mortality. However, they are less abundant when associated with both native and exotic species of fish. It is not known whether this is a result of competition or predation, but some combination is likely. Mudminnows are carnivorous and they eat a various assortment of invertebrates.

Wetland loss in Washington since settlement is estimated to range from 20 to 50 percent. In one part of the mudminnow's range an estimated 55 percent of wetlands have been destroyed. There were likely many more mudminnow populations before settlement of Washington because much more wetland habitat was available. There are now a myriad of federal, state, county and city wetland regulations. The rate of loss has been reduced, but despite the regulations there are still losses of 280 to 800 ha (700 to 2000 ac) each year.

Nearly 90 percent of the mudminnow populations monitored in this study seem to be stable. However, mudminnows are completely dependent on healthy wetland habitat for their survival. Because of this, and the Olympic mudminnow's very restricted range and the continuing loss of wetlands, we believe they are vulnerable and likely to become threatened or endangered in a significant portion of its range without cooperative management. The Department of Fish and Wildlife recommends that the Olympic mudminnow be designated as a sensitive species in Washington.