Fat Sleeper, Dormitator maculatus

Fat Sleeper, Dormitator maculatus, Juvenile. Fish caught from an irrigation canal in the greater Melbourne, Florida area, April 2019. Length: 7.8 cm (3.1 inches). Catch and photograph courtesy of Ryan Crutchfield, Tampa, Florida.

Fat Sleeper, Dormitator maculatus. Fish caught from an irrigation canal in the greater Palm Bay, Florida area, August 2019. Length: 7.8 cm (3.1 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Fat Sleeper, Dormitator maculatus. Fish caught in coastal waters off Gulf Shores, Alabama, September 2023. Length: 10.0 cm (3.9 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Fat Sleeper, Dormitator maculatus. Fish caught from an irrigation canal in the greater Micco, Florida area, June 2023. Length: 11 cm (4.3 inches). Catch and photograph courtesy of Chris Moore, Peoria, Arizona.

Fat Sleeper, Dormitator maculatus. Fish caught from an irrigation canal in the greater Micco, Florida area, November 2020. Length: 11 cm (4.3 inches). Catch and photograph courtesy of Ben Cantrell, San Diego, California.

The Fat Sleeper, Dormitator maculatus, is a member of the Sleeper or Eleotridae Family, that is also known as the Storm Minnow and in Mexico as naca. Their common name Storm Minnow stems from their observed behavior of congregating in large schools on the surface in late fall, referred to as a nuptial wedding parade, when storms are approaching. Globally, there are five species in the genus Dormitator, of which two are found in Mexican waters, one in the Atlantic and one in the Pacific Ocean.

The Fat Sleeper has a short stubby flattened relatively deep body. They are an overall dark brown to black in color with dark lines radiating from the eyes and the rear of the body having oblique, forward-pointing, dark bars and a large electric blue blotch immediately behind the head and above the pectoral fins. Their anal and dorsal fins have a reddish margin. They become darker with maturity. Their head has a blunt snout, with a large strongly oblique mouth that reaches the small eyes set on the side, and is equipped with two rows of slender teeth on each jaw. Their anal fin has 1 spine and 9 or 10 rays; their caudal fin is rounded; their first dorsal fin is large and has 1 to 7 spines; their second dorsal fin is large and has 9 to 15 rays; their pectoral fins have 14 rays and long and rounded; the pelvic fins have 1 spine and 5 rays and are long. They have 40 to 65 gill rakers. They are covered with large scales. They do not have a lateral line.

The Fat Sleeper is a demersal species that is found in both freshwater and marine shallow water coastal environments that have an abundance of aquatic vegetation and organic detritus over muddy substrate, such as estuaries and marshes with water temperatures between 25oC and 36oC salinities between 0 and 21 ppt at depths up to 5 m (15 feet). They reach a maximum of 70 cm (2 feet 4 inches) in length. They have the ability to survive in low oxygen environments and out of water for extended periods of time. They are aggressive ambush predators that are omnivores that will consume almost anything living or dead including animals, invertebrates and plants. They utilize their cryptic coloration and an ability to submerge within the substrate to avoid predation. Their reproduction has been poorly studied but they are believed to be catadromous requiring access to brackish mangrove areas for reproduction. They are sexually dimorphic with males developing enlarged anal and caudal fins and an extended second dorsal fin while breeding. There are laid in nests and the eggs attach to vegetation. Males are known to vigorously guard nests on the bottom and hatching normally occurs within 24 hours.

The Fat Sleeper is most likely confused with the Emerald Sleeper, Erotelis smaragdus (prominent, ventrally pointed spine on the gill cover; slender, elongated body), and the Largescales Spinycheek Sleeper, Eleotris ambyopsis (prominent, ventrally pointed spin on the gill cover; moderately deep body).

The Fat Sleeper is found in all coastal lagoons and freshwater systems of Mexico’s Atlantic Ocean.

From a conservation perspective the Fat Sleeper is currently considered to be of Least Concern with stable, widely distributed populations. Their long-term viability is threatened by the loss of mangrove and marsh habitats caused by human development. They can be caught in abundance with cast nets. They are a popular aquarium fish. They are also a valued food fish for human consumption and can be found as live fish in Asian Markets in New York City. There roe is considered to be a regional delicacy in the greater Veracruz area of Southeast Mexico. They are also considered to be an excellent hardy and durable live bait utilized for targeting Red Drum or Redfish, Sclaenops ocellatus, and Spotted Seatrout or Specked Trout, Cynoscion nebulosus.