Cortez Halibut, Paralichthys aestuarius

Cortez Halibut, Paralichthys aestuarius, Right Eyed. Fish provided by the commercial fishermen of Bahía Kino, Sonora, March 2015. Length: 31 cm (12 inches). Photograph courtesy of Maria Johnson, Prescott College Kino Bay Center, Kino Bay, Sonora.

Cortez Halibut, Paralichthys aestuarius, Left Eyed. Fish caught from within the Morgan Estuary, Puerto Peñasco, Sonora, April 2021. Length: 33 cm (13 inches). Catch, photograph and identification courtesy of Chris Moore, Peoria, Arizona.

The Cortez Halibut, Paralichthys aestuarius, is a member of the Sand Flounder or Paralichthyidae Family, and is known in Mexico as llenguado de Cortés. Globally, there are twenty-one species in the genus Paralichthys, of which six are found in Mexican waters, three in the Atlantic and three in the Pacific Ocean.

The Cortez Halibut has an elongated oval deep body with a depth that is 42% to 45% of standard length. They are left-eyed flatfish with a small percentage being right-eyed fish. Their eye-side is pale chocolate brown with mixed light and dark spotting that is more predominant at the margins of their disk. Their fins have the same color as the body. Their blind side is off-white to tan. They have a short pointed head and the majority of fish have eyes found on the left side and set parallel with a flat space in between. They have one row of teeth on both jaws with large canines in the front. Their anal fin has 57 to 67 rays; their caudal fin is small, short, and wide with straight margins; and their dorsal fin has 82 to 85 rays and begins over the upper eye. They have 24 to 31 gill rakers. Both sides of their body are covered with smooth scales. Ttheir lateral line is arched and extends onto their head and branches toward their top eye and below their lower eye.

The Cortez Halibut is a demersal species that is found near structures over and within sandy and muddy bottoms at depths up to 55 m (180 feet). They are also known to enter brackish waters. They reach a maximum of 58 cm (23 inches) in length. They are opportunistic and well-camouflaged ambush predators that lie in wait half-submerged on the ocean floor. They consume crustaceans, anchovies, grunions, sardines, and other small fish. The Cortez Halibut 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 Cortez Halibut is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being found from Guerrero Negro, Baja California southward along the central and southwest coasts of Baja, throughout the Sea of Cortez, and along the coast of the mainland south to Acapulco, Guerrero. They are most abundant in the northern portions of the Sea of Cortez.

The Cortez Halibut is most likely confused with the California Halibut, Paralichthys californicus (doubly concave caudal fin) and the Dappled Flounder, Paralichthys woolmani (less than 20 gill rakers).

From a conservation perspective the Cortez Halibut is currently considered to be Data Deficient. They are considered to be a quality food fish but they are not abundant. They are caught primarily as a by-catch of deep water shrimp trawlers.