The Sleeper Family – Eleotridae
Pacific Sleeper, Gobiomorus maculatus. A representative member of the Sleeper or Eleotridae Family.
The Sleepers or Eleotridae Family are known as guavinas in Mexico. They are small to medium-sized fish that reach a maximum length of 60 cm (24 inches). There are 164 global species in the Eleotridae Family that have been placed in 36 genera with the majority belonging to the genus Eleotris (31) and Mogurnda (26). Ten members of the family are found in Mexican waters, six in the Atlantic and four in the Pacific. They are close relatives of the gobies (Gobiidae Family) but lack the fused pelvic fins that form the sucker in gobies. They have elongated, stout, and cylindrical bodies that are deepest before the second dorsal fin. Most are drab in color, however, during mating the males of some species exhibit vibrant breeding colorations. They have a short broad head with a blunt snout and a large oblique mouth that opens at the front and is equipped with small conical teeth set in several rows on the jaws. Their gill membranes are joined to the throat with six rays. Their anal fin originates behind the second dorsal fin and has one spine and 6 to 12 rays. They have two separated dorsal fins with short bases, the first with 6 or 7 weak spines and the second with one spine and 6 to 12 rays. Their pelvic fins are long with bases either close together or united with one spine and five rays. They have no lateral line but have canals and pores on their head. They are covered with large scales that are smooth or rough. Most have relatively long lifespans in excess of 10 years.
Members of the Sleeper Family are found primarily in fresh and brackish water systems among vegetation over sandy and muddy substrates. They are abundant in tidelands and within river mouths and generally found in waters that are less than 10 feet deep at elevations of less than 100 feet. They prefer water temperatures between 25oC (77oF) and 33oC (91oF). A few spend their entire lives in the sea and a few migrate back and forth from brackish water to the ocean. Most can tolerate dramatic changes in the salinity of their habitat and some can survive out of water for extended periods of time. They are distinguished from each other by their teeth, gill rakers, and scales. They are benthic and lead lethargic lifestyles. They are strong ambush predators that consume detritus, plankton, and small fish playing an important role in freshwater steam ecosystems. Reproduction is oviparous with small adhesive eggs released by the females that are fertilized externally and then attach themselves to the substrate where they are maintained by both parents. They are scientifically interesting as they are believed to have evolved in the ocean and then moved to freshwater systems.
A few of the Sleepers are sold commercially and raised by aquaculture. Within some cultures they are an important food fish. In general, they have a long shelf-live without refrigeration. A limited number of Sleepers are a component of the aquarium trade. From a conservation perspective, most have not been evaluated but those that have are considered of Least Concern, being widespread and common with stable populations.
There are three members of the Sleeper or Eleotridae Family, all from the Pacific, presented in this website: