The Olympic mudminnow is a fish native to the western lowlands of Washington state: the Chehalis River basin, Deschutes R. basin, and some Olympic Peninsula

Olympic Peninsula

The Olympic Peninsula is the large arm of land in western Washington state of the USA, that lies across Puget Sound from Seattle. It is bounded on the west by the Pacific Ocean, the north by the Strait of Juan de Fuca, and the east by Puget Sound. Cape Alava, the westernmost point in the contiguous...

 basins. It grows to 8 cm (ca 3 inches) in length, and is Washington's only known endemic freshwater fish species. Although they strongly resemble killifish

Killifish

A killifish is any of various oviparous cyprinodontiform fish . Altogether, there are some 1270 different species of killifish, the biggest family being Rivulidae, containing more than 320 species...

, mudminnows are more closely related to pikes and mukellunge.

Taxonomy

The Olympic mudminnow is the only species in genus Novumbra, and one of five species worldwide in the family Umbridae

Umbridae

Umbridae are a family of Actinopterygii, ray-finned fish, that inhabit freshwater environments in temperate regions across the northern hemisphere...

.

Biology

The Olympic mudminnow resides in dark areas in the bottom of the river, living on fish larvae, egg

Egg (biology)

An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

s and small invertebrates. It prefers areas with mudbeds and dense vegetation, and has a remarkable tolerance of low oxygen levels.

Conservation status

The Olympic mudminnow is listed as a sensitive species by the state of Washington. Although there are many populations, the range is limited, and suitable habitat is easily lost to development