''Eleotris sandwicensis'', the Sandwich Island sleeper, Hawaiian sleeper or oopu, is a species of fish in the family

Eleotridae Eleotridae is a family of fish commonly known as sleeper gobies, with about 34 genera and 180 species. Most species are found in the tropical Indo-Pacific region, but there are also species in subtropical and temperate regions, warmer parts of th ...

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to the

Hawaiian Islands The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost Kur ...

, where it can be found in marine, fresh, and brackish waters around the coast. Due to this capability of migrating between different marine environments, they are amphidromous. This fish can reach a length of . It is locally important to

commercial fisheries Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often ...

and is also used as bait by fishermen after larger fishes. In the

Hawaiian language Hawaiian (', ) is a Polynesian language of the Austronesian language family that takes its name from Hawaii, the largest island in the tropical North Pacific archipelago where it developed. Hawaiian, along with English, is an official language o ...

, the fish is also known as ''oopu'', ''oau'', ''owau'', and ''hiu kole''. The distribution of ''E. sandwicensis'' is limited as this species does not have the ability to travel upstream of steep waterfalls. This is due to their lack of pelvic fins.

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sandwicensis Freshwater fish of Hawaii Endemic fauna of Hawaii Fish described in 1875 Taxonomy articles created by Polbot {{Gobiiformes-stub