Butter Hamlet, Hypoplectrus unicolor

Butter Hamlet, Hypoplectrus unicolor. Fish caught from coastal waters off Ft. Lauderdale, Florida, February 2022. Length: 8.5 cm (3.3 inches). Catch, photograph and  identification courtesy of Dominick Porcelli, Lighthouse Point, Florida.

Butter Hamlet, Hypoplectrus unicolor. Fish caught from coastal waters off Ft. Lauderdale, Florida, February 2022. Length: 12 cm (4.7 inches). Catch, photograph and identification courtesy of George Brinkman, Guelph, Ontario, Canada.

Butter Hamlet, Hypoplectrus unicolor. Fish caught from coastal waters off Islamorada, Florida, July 2022. Length: 13.1 cm (5.2 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Butter Hamlet, Hypoplectrus unicolor. Underwater photograph taken in coastal waters off Bonaire, December 2019. Photograph courtesy of Bob Hillis, Ivins, Utah.

The Butter Hamlet, Hypoplectrus unicolor, is a member of the Sea Bass or Serranidae Family, and is known in Mexico as mero mantequilla. Globally, there are eighteen species in the genus Hypoplectrus, of which fourteen are found in Mexican waters, all in the Atlantic Ocean.

The Butter Hamlet has a deep and strongly compressed body. The head has a straight profile with a relatively short snout, a protrusible top jaw, fixed teeth, and several small forward pointing spines on the lower margin of the gill covers. The adults are pale yellow being darker dorsally transitioning to grayish yellow ventrally. Their head has iridescent blue lines on the head that extend to the leading edge of the pelvic fins and one blue line around the eye that extends ventrally. Some fish have two black pigment spots around the nostrils. They have a large black saddle on the caudal peduncle that extends below the lateral line. The pectoral fins are clear and the pelvic fins are yellow. Their anal fin has 3 spines and 7 rays; their caudal fin is slightly forked; their dorsal fin is continuous with 10 spines and 14 to 17 rays; the pelvic fins are long reaching past the anus. They have 17 to 23 gill rakers. They are covered with small scales.

The Butter Hamlet is a non-migratory, solitary, species that is found in shallow water reefs at depths up to 25 m (82 feet). Juveniles are found within mangroves. They reach a maximum of 12.7 cm (5.0 inches) in lengTh. They feed on crustaceans and smaller fishes. In turn they are preyed upon by a variety of larger fishes and the juveniles are consumed by the invasive Red Lionfish, Pterois volitans. Reproduction is as synchronous hermaphrodites with individuals alternating male and female “roles” during spawning. The Butter Hamlet is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Butter Hamlet is most likely confused with the Tan Hamlet, Hypoplectrus randallorium (dark blue dorsally) and the Veracruz Hamlet, Hypoplectrus castroaguirrei (dark bar thru the eye that extends ventrally).

The Butter Hamlet is a resident of Mexican waters of the Atlantic but has a limited range being found only along the southern coast of the Gulf of Mexico from Tuxpan, Veracruz eastward and along the east coast of the Yucatán Peninsula in the Caribbean.

From a conservation perspective the Butter Hamlet is currently considered of Least Concern with stable and widely distributed populations. They are small in stature and of limited interest to most. They are utilized by the aquarium trade on a limited basis.