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.
Males become brightly colored and aggressive during spawning.
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.