Largemouth Blenny, Labrisomus xanti

Largemouth Blenny, Labrisomus xanti, Juvenile. Fish caught from coastal waters off Puerto Vallarta, Jalisco, February 2023. Length: 12 cm (4.7 inches). Catch and photograh courtesy of Allyn Toth, Peoria, Illinois. Identification should be considered to be tentative.

Largemouth Blenny, Labrisomus xanti. Fish caught from coastal waters off Puerto Vallarta, Jalisco, February 2023. Length: 12 cm (4.7 inches). Catch and photograph courtesy of Allyn Toth, Peoria, Illinois. Identification should be considered to be tentative.

Largemouth Blenny, Labrisomus xanti. Fish caught within the coastal waters of Magdalena Bay, Baja California Sur, March 2017. Length: 13 cm (5.2 inches).

Largemouth Blenny, Labrisomus xanti. Fish caught from coastal waters off Puerto Vallarta, Jalisco, February 2023. Length: 13 cm (5.2 inches). Catch and photographs courtesy of Ben Cantrell, Peoria, Illinois. Identification should be considered to be tentative.

Largemouth Blenny, Labrisomus xanti, Breeding Male. Fish caught from shore at Playa Los Zacatitos, Baja California Sur, February 2020. Length: 15.3 cm (6.0 inches).

Largemouth Blenny, Labrisomus xanti, Breeding Male. Fish caught from shore at Cero Colorado, Baja California Sur, March 2015. Length: 15.3 cm (6.0 inches). Fish identification courtesy of Dr. Phil Hastings, Scripps Institution of Oceanography, La Jolla, California.

Largemouth Blenny, Labrisomus xanti, Breeding Male. Fish caught from coastal waters within Magdalena Bay, Baja California Sur, May 2018. Length: 19.7 cm (7.8 inches) which establishes a new maximum length for this species.

Largemouth Blenny, Labrisomus xanti, Breeding Males. Underwater photographs taken in coastal waters off La Jolla, California, August 2016. Photographs and identification courtesy of Bob Hillis, Ivins, Utah.

Largemouth Blenny, Labrisomus xanti.Underwater photograph taken in coastal waters off Loreto, Baja California Sur, October 2024. Photograph courtesy of Bob Hillis, Ivins, Utah.

Largemouth Blenny, Labrisomus xanti. Underwater photographs taken in Zihuantanejo Bay, Guerrero, March 2018. Photographs courtesy of Ron Woheau, Zihuantanejo. Productive discussions with Dr. Phil Hastings, Scripps Institution of Oceanography, La Jolla, California, related to the first three photographs noted.  For these three Phil indicated that the fish are from the Labrisomus Genus. Looking at range maps and numerous photographs it is clear to me that these are Largemouth Blennies. I would give my call a greater than 98% probability of correctness. The identification of the fourth photo has been reconfirmed by Dr. Ross Robertson, Smithsonian Institute, Panama City, Panama.

The Largemouth Blenny, Labrisomus xanti, is a member of the Labrisomid Blenny or Labrisomidae Family, and is known in Mexico as chalapo. Globally, there are twenty-seven species in the genus Labrisomus, of which thirteen are found in Mexican waters, nine in the Atlantic and four in the Pacific Ocean.

The Largemouth Blenny has a shortened elongated robust bodies with a uniform depth throughout that tapers gradually at the rear into the tail. They are greenish-brown in color with 8 dark bars along their sides and two thin dark stripes bordering a pale area behind and a little below their eyes. They have a black blotch at the front of their dorsal fin and numerous small white spots on the lower parts of their head and body. Breeding males are red with a large black spot between the second and fourth dorsal spines (pictured below). Their head is broad with a blunt snout, large eyes, a branched cirrus over each eye, and several branched cirri on each side of the nape. Their mouth is large, opens at the front, and is slightly oblique; it is equipped with one row of small teeth on the upper and lower jaws and includes teeth on the roof of the mouth. Their anal fin has 2 spines and 17 to 19 rays; their caudal fin is square; and, their dorsal fin has 17 to 19 spines and 10 to 12 rays with a deep notch in between. They are covered with small smooth scales.

The Largemouth Blenny is a shallow water coastal species found within weed-covered rocky shores at depths up to 11 m (35 feet). They reach a maximum length of 19.7 cm (7.8 inches), with this maximum length established by the photo that I caught below. 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 Largemouth 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 Largemouth Blenny is a resident of all Mexican waters of the Pacific Ocean with the exception that they are absent from Acapulco, Guerrero, southward along the coast of the mainland to Guatemala.  A friend of mine Ben Cantrell, has recently caught one as far north as Carlsbad, California establishing the northerly range for this species. This catch was documented in the following publication indicative of global warming: “The Largemouth Blenny, Labrisomus xanti, New to the California Marine Fauna with a List of and Key to the Species of Labrisomidae, Clinidae and Chaenopsidae found in California Waters,” Milton S. Love, Julianne Passarelli, Ben Cantrell and Philip Hastings, Bulletin Southern California Academy of Sciences, 115, 191-197 (2016).

The Largemouth Blenny can be easily confused with a series of Blennies including the Green Blenny, Labrisomus striatus (brown coloration; brown spots and thin stripes; two oblique bars on cheeks; front dorsal spines are shortest; dark spots on base of anal, caudal, and dorsal fins) and the Porehead Blenny, Labrisomus multiporosus (2 oblique bars on cheeks; rows of spots on fins).

From a conservation perspective the Largemouth Blenny is currently considered to be of Least Concern with stable, widely distributed populations. Although plentiful, they are seldom seen by humans and are of limited interest to most due to their small size.