Bay Blenny, Hyposoblennius gentilis

Bay Blenny, Hyposoblennius gentilis, Juvenile. Fish caught in the Del Mar Lagoon, San Diego, California, December 2019. Length: 5.0 cm (2.0 inches). Catch, photography and identification courtesy of Ben Cantrell, San Diego, California.

Bay Blenny, Hyposoblennius gentilis, Juvenile. Fish caught from a tidal pool in coastal waters of Puerto Peñasco, Sonora, June 2021. Length: 5.9 cm (2.3 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Bay Blenny, Hyposoblennius gentilis, Female. Fish provided by the commercial bait salesmen of Puerto Los Cabos Marina, March 2014. Length: 5.2 cm (2.0 inches). Identification courtesy of Dr. Phil Hastings, Scripps Institution of Oceanography, La Jolla, California.

Bay Blenny, Hyposoblennius gentilis, Male. Fish caught from coastal waters off San Diego California, March 2012. Length: 7.6 cm (3.0 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

Bay Blenny, Hyposoblennius gentilis, Male. Fish caught in the Del Mar Lagoon, San Diego, California, December 2019. Length: 9.6 cm (3.8 inches). Catch, photography and identification courtesy of Ben Cantrell, San Diego, California.

Bay Blenny, Hyposoblennius gentilis, Male. Underwater photograph of a fish caught in the Del Mar Lagoon, San Diego, California, December 2019. Length: 9.6 cm (3.8 inches). Catch, photography and identification courtesy of Ben Cantrell, San Diego, California.

Bay Blenny, Hyposoblennius gentilis, Male. Underwater photographs taken in coastal waters with Mission Bay, San Diego, California, September 2017. Length: 12.7 cm (5.0 inches). Photographs courtesy of Bob Hillis, Ivins, Utah.

The Bay Blenny, Hyposoblennius gentilis, is a member of the Combtooth Blenny or Blennidae Family, and is known in Mexico as borracho de bahia. 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 Bay Blenny has an elongated body that are deepest under the front part of the dorsal fin and taper gradually to the tail. They are overall dark brown with green tints and are white on their throat and belly regions. Their upper back has a series of dark brown saddle-like marks and their sides have a row of off-white blotches along the mid-body. Their dorsal fin has a red spot at the front. They are dimorphic with adult males having a red bar across their throat that becomes more pronounced during breeding season. Adult females have a large metallic blue spot between their first and third dorsal spines. Their head is short and robust with a very steep forehead profile and small cirri above the posterior nostril; the cirri in males are exceedingly long. 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 16 to 19 rays; their caudal fin is rounded; their first dorsal fin has 11 or 12 spines; and, their second dorsal fin has 16 to 18 rays.

The Bay Blenny is a coastal species found in the intertidal shallows, bays, and estuaries at depths up to 24 m (80 feet). They reach a maximum of 14.7 cm (5.8 inches) in length. 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 two to three weeks until they hatch. Each female will spawn three or four times per year. They are eurythermal and thus able to tolerate extreme winter and summer temperatures.  They have lifespans of up to seven years. The Bay 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 Bay Blenny is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found along the west coast of Baja and throughout the Sea of Cortez. They are absent from along the coast of the mainland south to Guatemala. The Bay Blenny is the most common Combtooth Blenny in the upper Sea of Cortez.

The Bay Blenny is easily confused with three other blennies, the Barnaclebill Blenny, Hypsoblennius brevipinnis (white and black spots on throat), the Mussel Blenny, Hypsoblennius jenkinsi (mottled brown and white body color), and the Notchfin Blenny, Entomacrodus chiostictus (deep notch between dorsal fins).

From a conservation perspective the Bay 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, however, they are used on a limited basis in the aquarium trade and thrive in captivity.