Endangered and Threatened Species of Fish Slough
Photo of Owens Pubfish swimming in Fish Slough

There are only four native fish of the Owens Valley, and two live here at Fish Slough.

The Owens pupfish is a small fish with vast numbers reported throughout Owens Valley’s wetlands in 1859. They were still abundant in 1916 in many sloughs and swamps in the northern part of the valley. But their habitat declined rapidly. The wetlands shrank as creeks were diverted for farming, water was exported and dams were built. Non-native fish that prey on the pupfish were also introduced. By 1948, the species was believed extinct. In 1964, a small population of Owens pupfish was rediscovered in Fish Slough. They are now listed as endangered.

Pupfish feed on insect larvae and aquatic plants and can survive in warm or cool, fresh or salty water, and with low levels of oxygen. Pupfish are extremely territorial, and the males will fight aggressively to protect the area they claim. Male Owens pupfish flash blue and silver colors during the mating season, spring through autumn. Spot the two-inch pupfish by their distinctive "stop-start" swimming style.

Owens speckled dace haven’t yet been officially recognized as a subspecies of speckled dace, so they can’t yet be listed as endangered. But they survive in only a few sites within the Owens River drainage where they are able to hide from predatory non-native fish. More than 60 years since they’d last been seen in Fish Slough, they were rediscovered here in 2000.

The Owens tui chub is a minnow that disappeared from Fish Slough by the 1930s. The species is endangered, mainly because of interbreeding with non-native tui chubs brought to the Owens River drainage as bait fish. Pure Owens tui chubs are now very rare. Biologists hope to reintroduce them to Fish Slough soon.

The Owens sucker is also unknown in Fish Slough today, although suckers were seen here until the 1930s. The Owens sucker is not endangered. It grows big and reproduces rapidly, so can coexist with non-native fishes. Because of this, and because Fish Slough may not be ideal habitat for them, biologists haven’t decided if they will reintroduce them here.
 
Though not yet listed as endangered, the Fish Slough springsnail is a California Species of Special Concern. This tiny snail lives only in the waters of Fish Slough’s springs. Little is known about its biology. 

Non-native intruders to the delicately balanced aquatic environment include largemouth bass, carp and mosquitofish. We maintain two native fish refuges here at Fish Slough, with fish barriers to keep the larger fish away from small, vulnerable natives. Anglers enjoy sport fishing throughout the rest of the slough.

Alkali meadow is a rare plant community. You’ll find it at Fish Slough surrounding the edges of the wetland. The soil is seasonally damp and often coated with a white crust of evaporated alkali salts. Plants adapted to this challenging environment include Fish Slough milk-vetch, listed as threatened with designated critical habitat at Fish Slough – the only place it grows. Fish Slough milk-vetch is a low, sprawling plant in the pea family, with purple flowers and inflated, spotted seed pods.

What exactly does "endangered" mean?