Common names

Types of sleeper

5 species carry sleeper in an English common name. They sit in 1 family, so the group is a name, not a scientific rank.

About sleeper

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 the Americas and near the Atlantic coast in Africa. Many eleotrids pass through a planktonic stage in the sea; the majority live as adults in freshwater streams and brackish water, although some spend their entire lives in the sea. One of its genera, Caecieleotris, is troglobitic. They are especially important as predators in the freshwater stream ecosystems on oceanic islands such as New Zealand and Hawaii that otherwise lack the predatory fish families typical of nearby continents, such as catfish. Anatomically, they are similar to the gobies (Gobiidae), though unlike the majority of gobies, they do not have a pelvic sucker.

Like the true gobies, they are generally small fish that live on the substrate, often amongst vegetation, in burrows, or in crevices within rocks and coral reefs. Although goby-like in many ways, sleeper gobies lack the pelvic fin sucker and that, together with other morphological differences, is used to distinguish the two families. The Gobiidae and Eleotridae likely share a common ancestor and they are both placed in the order Gobiiformes, along with a few other small families containing goby-like fishes.

Dormitator and Eleotris, two of the most widespread and typical genera, include a variety of species that inhabit marine, estuarine and freshwater habitats. Among the largest members of the family are predatory species such as the bigmouth sleeper (Gobiomorus dormitor) at up to 90 cm (3.0 ft) from freshwater near the West Atlantic region. However, most are much smaller, such as the fresh- and brackish-water species from Australia and New Guinea, including Hypseleotris, known locally as gudgeons (not to be confused with the Eurasian freshwater cyprinid Gobio gobio, also known as the gudgeon and after which the Australian sleeper gobies were likely named). A few of these, such as the empire gudgeon (H. compressa) and peacock gudgeon (Tateurndina ocellicauda), are sometimes kept in aquariums. The smallest in the family are the Amazonian Leptophilypnion with a standard length of less than 1 cm (0.4 in).

Fossil remains of the extinct freshwater eleotrid Mataichthys have been identified from the Early Miocene of New Zealand. The extinct Oligocene -aged genus Pirskenius from Europe has sometimes been placed in the Eleotridae, which would make it the earliest known member of the family, but more recent analyses have disputed this and support placing it in its own family.

Taxonomy

The family has been divided into three subfamilies: Butinae, Eleotrinae and Milyeringinae. However, because of the deep divergence between the three, some authorities have recommended splitting them into separate families: Butidae, Eleotridae and Milyeringidae. The 5th edition of Fishes of the World follows this classification and this means that the following genera are currently included within the Eleotridae. However, the family Xenisthmidae is regarded as a synonym of the Eleotridae, according to the 5th Edition of Fishes of the World.

Sleeper species in focus

These species profiles show how members of the group differ. Their biology describes each named species, rather than every fish in the group.

Fat Sleeper

The fat sleeper (Dormitator maculatus) is a species of fish belonging to the family Eleotridae, known for their flat heads; they are generally found in fresh water, usually found in lakes, ponds and rivers.

Description

Fat sleepers are small fish that have two distinct dorsal fins and scaled, flat heads. Their tails are rounded. They are fully scaled, and their fins are higher up on the body than other species. Their bodies are a darker brown, whereas their dorsal and anal fins are redder in color. They have a dark blue spot around their gill covers.

Distribution and habitat

The fat sleeper is found from the Bahamas and North Carolina to Brazil. It lives in intertidal areas on muddy bottoms, and is more frequent in brackish water. It can be found commonly in freshwater or saline coastal pools and river mouths.

Read the full species guide.

Akupa Sleeper

Eleotris sandwicensis, commonly known as the Sandwich Island sleeper, the Hawaiian sleeper, or o ʻ opu, 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 ʻ oau, ʻ owau, and hi ʻ u kole.

Anatomy and morphology

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.

Habitat

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.

Read the full species guide.

Range