Image source: catta | inaturalist.org
Eleotris sandwicensis, commonly known as the Sandwich Island sleeper, the Hawaiian sleeper, or oʻopu, is a species of fish in the family Eleotridae.
Endemic to the Hawaiian Islands, it can be found in marine, fresh, and brackish waters around the coast. Due to this capability of migrating between different marine environments, it is considered amphidromous.
Eleotris sandwicensis is a dorso-ventrally flattened fish, almost like a smaller catfish. It varies in color, but is most commonly darker black/gray or brown with green/yellow spots surrounding its body.
This fish can reach a length of 33 cm (13 in).
It is locally important to commercial fisheries and is also used as bait by fishermen after larger fishes.
In the Hawaiian language, the fish is also known as ʻoau, ʻowau, and hiʻu kole.
Eleotris sandwicensis is an ambush predator that uses suction to hunt its prey. Like other species that rely on suction to capture prey, Eleotris sandwicensis has enhanced cranial muscles and level mechanism that controls its highly kinetic feeding apparatus.
The distribution of E. sandwicensis is limited as this species does not have the ability to travel upstream of steep waterfalls due to their lack of pelvic fins. Distribution Eleotris sandwicensis is an endemic species of Hawaii that inhabits estuarine regions.
This species can be found in the lower parts of streams and in the ocean as hatchlings, proceeding into the lower part of streams soon after. Within the streams Eleotris sandwicensis is most commonly found in pools, runs, and fast riffles.
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