Silvergray Grunt

Silvergray Grunt, Anisotremus caesius

Silvergray Grunt, Anisotremus caesius, Juvenile. Fish provided by the commercial fishermen of the greater Los Cabos area, October 2011. Length: 6.0 cm (2.4 inches). Identification courtesy of H.J. Walker, Jr., Scripps Institution of Oceanography, La Jolla, California, who believes there is a remote possibility that this might be a Blackbarred Grunt, Anisotremus dovii, also known only to the coast of the mainland which has similar “counts” noting that the adult Black Barred Grunt has a very different body shape than the Silvergray Grunt.

Silvergray Grunt, Anisotremus caesius.  Fish caught from coastal waters off Mazatlán, Sinaloa, March 2016.  Lengths:  15 cm (5.9 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

Silvergray Grunt, Anisotremus caesius. Fish caught from coastal waters off Mazatlán, Sinaloa, October 2021. Length: 18 cm (7.1 inches). Catch, photograph and identification courtesy of Bart, The Netherlands  (worldangler.eu).

Silvergray Grunt, Anisotremus caesius. Fish caught from coastal waters off Mazatlán, Sinaloa, October 2017.  Lengths:  19 cm (7.5 inches). Catch, photograph and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.

Silvergray Grunt, Anisotremus caesius. Underwater photograph taken in Zihuantanejo Bay, Guerrero, March 2018. Photograph courtesy of Ron Woheau, Zihuantanejo.

The Silvergray Grunt, Anisotremus caesius, is a member of the Grunt or Haemulidae Family, and is known in Mexico as burro mojarro. Globally, there are ten species in the genus Anisotremus, of which six are found in Mexican waters, two in the Atlantic and two in the Pacific Ocean.

The Silvergray Grunt has a deep compressed body with a depth that is 38% to 40% of standard length. They have an overall golden or yellowish color becoming white on their lower sides and have a broad horizontal black bar immediately behind their head. All their fins have a yellow tint. They have a high back, a short head, a blunt snout and a small mouth with fleshy lips. Their anal fin has 3 spines, with the second being long and thick, and 9 or 10 rays; their caudal fin is forked; their dorsal fin is continuous but deeply notched and has 12 spines, the fourth spine being the longest, and 15 or 16 rays; and, their pectoral fins that reach the anal fin origin or beyond. They are covered with large rough scales.

The Silvergray Grunt is a demersal species that is found inshore over coral reefs, in rocky and rubble substrate, and in rocky habitats in estuaries at depths up to 24 m (80 feet). They reach a maximum of 30 cm (12 inches) in length. The Silvergray Grunt 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 Silvergray Grunt is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found from Mazatlán, Sinaloa, southward along the west coast of the mainland to Guatemala. The fish photographed above extends this known range to the extreme southern portions of Baja.

The Silvergray Grunt cannot be confused with any other species as their anal and dorsal fin counts are unique.

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