Mussel Blenny, Hyposoblennius jenkinsi

Mussel Blenny, Hyposoblennius jenkinsi. Fish caught coastal waters off San Diego, California, February 2020. Length: 7.5 cm (3.0 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Mussel Blenny, Hyposoblennius jenkinsi. Fish caught coastal waters off San Diego, California, February 2020. Length: 12.7 cm (5.0 inches). Photographs courtesy of Ben Cantrell, San Diego, California.

Mussel Blenny, Hyposoblennius jenkinsi. Fish caught within the Ventura Harbor, Ventura, California, July 2021. Length: 13.0 cm (5.1 inches). Photographs courtesy of Chris Moore, Peoria, Arizona.

The Mussel Blenny, Hyposoblennius jenkinsi, is a member of the Combtooth Blenny or Blennidae Family, and is known in Mexico as borracho mejillonero. Globally, there are sixteen species in the genus Hyposoblennius, of which four are found in Mexican waters, one in the Atlantic and three in the Pacific Ocean.

The Mussel Blenny has an elongated body. They are tan in color and covered with numerous brown bars of varies widths and lengths with a series of 9 wider bars under the dorsal fin. Their head has two thin dark bars under the eyes, has a crescent behind the eye and is covered with small round spots. All of the fins are lightly speckled and the pectoral base is dark. Their head is short and robust with a very steep forehead profile and one pair of heavily branched cirri above the eyes. Their mouth is small, opens at the front, and is equipped with 1 row of teeth with blunt flattened tips on each jaw. Their anal fin has 2 spines and 15 to 20 rays; their caudal fin is rounded; and, their dorsal fin has 11 to 13 spines and 15 to 18 rays with a slight notch in between.

The Mussel Blenny is a coastal species found in the intertidal shallows, bays, and estuaries at depths up to 21 m (70 feet). They inhabit boring clam burrows, serpulorbis tubes and mussel beds. Their growth is limit to the size of the tubes in which they reside. They are sedentary and highly territorial rarely wandering more than a meter from its home refuge. They reach a maximum length of 13.0 cm (5.1 inches). They feed on algae and small benthic invertebrates. Reproduction is oviparous in distinct pairs with the females depositing eggs in protected areas. The eggs are sticky and adhere to the walls of the shelter; they are then fertilized by the males who guard them for 1 to 2 weeks until they hatch. The Mussel Blenny is a small shallow-water species and 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 Mussel Blenny is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found from Punta Marquez, Baja California Sur, northward along the central and north coastal areas of Baja California Sur and in the northern half of the Sea of Cortez.

The Mussel Blenny is most likely confused with the Barnaclebill Blenny, Hypsoblennius brevipinnis (pale oblique bar behind the eye), the Bay Blenny, Hypsoblennius gentilis (row of white blotches on the sides), and the Notchfin Blenny, Entomacrodus chiostictus (deep notch between dorsal fins).

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