Deepwater Serrano, Serranus aequidens

Deepwater Serrano, Serranus aequidens, Juveniles. Both fish caught from coastal waters off Point Palmilla, Baja California Sur, June 2016. Length: each 8.5 cm (3.3 inches). This is a highly colored fish which was caught in atypical relatively shallow water perhaps indicative the juveniles settles out in shallower waters and then move to deeper waters. Identification courtesy of H.J. Walker, Jr., Scripps Institution of Oceanography, La Jolla, California.

Deepwater Serrano, Serranus aequidens. Fish caught from coastal waters off  Point Palmilla, March 2008. Length: 18 cm (7.0 inches). Identification courtesy of H.J. Walker, Jr., Scripps Institution of Oceanography, La Jolla, California.

Deepwater Serrano, Serranus aequidens. Fish caught from coastal waters off Point Palmilla, Baja California Sur, May 2015. Length: 16 cm (6.3 inches).

The Deepwater Serrano, Serranus aequidens, is a member of the Sea Bass or Serranidae Family, that is known in Mexico as serrano de agua profunda. Globally, there are twenty-seven species in the genus Serranus, of which thirteen are found in Mexican waters, ten in the Atlantic and three in the Pacific Ocean.

The Deepwater Serrano has an elongated body. They have an overall tan coloration and a white belly. Their head is long with a short snout, their disproportionately large eyes, a large mouth with a lower projecting jaw. They have a narrow tail base and a series of characteristic markings that include a large blue-gray spot on their gill covers and 6 irregular bars on their upper body; the second of these bars has a large blotch on the lateral line. Their anal and caudal fins are transparent. Their first dorsal fin has a yellow margin with spines 1 to 4 increasing in size and spines 4 to 9 decreasing in size; their second dorsal fin has a black margin and a black stripe along its base. The pectoral and pelvic fins are yellow. Their anal fin has 3 spines and 7 rays and the third anal spine and the first anal ray are the longest; their caudal fin is blunt with a straight margin; their dorsal fin has 9 to 11 spines and 11 to 13 rays; their pectoral fins have 17 rays and are short and do not extend to the anus. They have 10 to 12 gill rakers on the lower arch. They are covered with large rough scales.

The Deepwater Serrano is found over sandy bottoms at depths between 69 m (225 feet) and 243 m (800 feet). They reach a maximum of 24.5 cm (9.6 inches) in length and are virtually weightless. The Deepwater Serrano 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 Deepwater Serrano is a resident of all Mexican waters of the Pacific Ocean with the exception that they are absent from the east coast of the mainland within the Sea of Cortez.

The Deepwater Serrano is similar in size, shape, and habitat to the Flag Serrano, Serranus huascarii (large yellow blotch behind pectoral fins; tail with black margin) but the markings and colors of the two species are very different making them easy to differentiate.

 From a conservation perspective the Deepwater Serrano is currently considered to be of Least Concern with stable widely distributed populations. They are too small and too rare to be of interest to most.