Gulf Opaleye, Girella simplicidens

Gulf Opaleye, Girella simplicidens, Juvenile. Fish caught from coastal waters off Puerto Peñasco, Sonora, November 2020. Length: 5.4 cm (2.1 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Gulf Opaleye, Girella simplicidens, Juvenile. Fish caught from coastal waters off Puerto Peñasco, Sonora, November 2020. Length: 10.2 cm (4.0 inches). Catch, photograph and identification courtesy of Chris Moore, Peoria, Arizona.

Gulf Opaleye, Girella simplicidens. Fish caught from a kayak within coastal waters of the northern Sea of Cortez off Baja California, April 2018. Length: 25 cm (10 inches). Catch, photograph and identification courtesy of Ben Cantrell, San Diego, California.

Gulf Opaleye, Girella simplicidens. Fish caught from coastal waters off Puertecitos, Baja California, July 2012. Length: 33 cm (13 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

The Gulf Opaleye, Girella simplicidens, is a member of the Sea Chub or Kyphosidae Family, and is known in Mexico as chopa ojo azul. Globally, there are eighteen species in the genus Girella, of which two are found in Mexican waters, both in the Pacific Ocean.

The Gulf Opaleye has an oval moderately compressed body. They are dark brownish gray in color with the head a breast being slightly lighter and 3 or 4 diffuse white spots in the upper back below the dorsal fin. They have bright blue eyes. Their head has a short blunt head and a small mouth with thick lips opening at the front that is equipped with small incisiform teeth set horizontally in the mouth with flattened three-pointed tips and a curved hockey-stick shape. Their anal fin has 3 spines and 12 rays; their caudal fin is straight; their dorsal fin is continuous with 14 spines folding down into a scaly grove and 14 rays; and, their pectoral and pelvic fins are relatively short. Their anal, caudal and dorsal fins have angular tips. Their body is covered with small, thick, and rough scales.

The Gulf Opaleye is found in large schools, within rocky areas with an abundance of algae growth at depths up to 15 m (49 feet). They reach a maximum of 46 cm (18 inches) in length. They are diurnal omnivores grazing on algae and preying on invertebrates. The Gulf Opaleye 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 Gulf Opaleye is a resident of Mexican waters of the Pacific but has a limited range being found throughout the Sea of Cortez and are more abundant in the northern portions of the Gulf.

The Gulf Opaleye is most likely confused with the Halfmoon, Medialuna californiensis (black blotch at top of gill cover), the Opaleye, Girella simplicidens (blunt anal, caudal and dorsal fins; 1 to 2 white spots; blue-green eyes), and the Zebraperch, Hermosilla azurea (8 faint bars on sides; black spot at pectoral fin base).

From a conservation perspective the Gulf Opaleye is currently considered to be of Least Concern with stable, widely distributed populations. They are considered to be marginal table fare and only retained by subsistence fishermen.