Redside Blenny

Redside Blenny, Malacoctenus hubbsi

Redside Blenny, Malacoctenus hubbsi. Fish provided by the commercial fishermen of Puerto Los Cabos, Baja California Sur, January 2008. Length: 2.5 cm 1.0 inch). Fish identification courtesy of H.J. Walker, Jr., Scripps Institution of Oceanography, La Jolla, California.

Redside Blenny, Malacoctenus hubbsiUnderwater photographs taken in coastal waters of the greater Los Cabos area, Baja California Sur, May 2018 and October 2019. Photographs courtesy of Bob Hillis, Ivins, Utah.

The Redside Blenny, Malacoctenu hubbsi, is a member of the Labrisomid Blenny or Labrisomidae Family, and is known in Mexico as trambollo rojo. Globally, there are eighteen species in the genus Malacoctenus, of which fourteen are found in Mexican waters, six in the Atlantic Ocean and eight in the Pacific Ocean.

The Redside Blenny has a shortened elongated body with a uniform depth throughout that tapers gradually at the rear into the tail. The sexes have different colorations. Males are light green to reddish-brown dorsally and reddish to pinkish ventrally with 5 or 6 irregular shaped dark brown bars on their sides and narrow stripes below. Females are similarly colored but lack the reddish and pink colorations ventrally and have spotted caudal and dorsal fins. Both sexes have bars and spotting in their throat area and a dark spot in front of their pectoral fin base. Their head is slender with a pointed snout, large eyes, and a pair of closely set and heavily branched cirri. They have a branched cirrus over each eye. Their mouth is small, opens at the front, and is equipped with one row of large teeth on the upper jaw. Their anal fin has 2 spines and 18 to 23 rays; their caudal fin is square; and, their dorsal fin has 19 to 21 spines and 9 to 13 rays with a slight notch in between. They have 11 or 12 gill rakers. They are covered with a limited number of scales. A key to identification is the lack of scales on the mid-line in front of the dorsal fin.

The Redside Blenny is a shallow water coastal species found in intertidal shallows, bays, and estuaries in rocky areas at depths up to 20 m (65 feet). They reach a maximum of 9.0 cm (3.5 inches) in length. They are diurnal highly territorial predators that feed mostly on benthic crustaceans including small crabs. Reproduction is oviparous with females depositing eggs in protected areas. The Redside Blenny 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 Redside Blenny is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found from Guerrero Negro, Baja California, southward along the southwest coast of Baja and throughout the Sea of Cortez; they are absent from along the coast of the mainland south to Guatemala.

The Redside Blenny can be confused with the Fishgod Blenny, Malacoctenus ebisui (numerous white spots on throat), the Mexican Blenny, Malacoctenus mexianus (dark oval with white margins on gill cover), the Sonora Blenny, Malacoctenus gigas (red lines on lower body), the Throatspotted Blenny, Malacoctenus tetranemus (many dark spots on throat) and the Zaca Blenny, Malacoctenus zacae (brown lines on lower body).

From a conservation perspective the Redside Blenny is currently considered to be of Least Concern with stable, widely distributed populations. They are small in stature and of limited interest to most.