Gulf Corvina, Cynoscion orthonopterus

Gulf Corvina, Cynoscion orthonopterus. Fish caught from a kayak within coastal waters of the northern Sea of Cortez off Baja California, April 2018. Length: ca. 32 cm (13 inches). Catch, photograph and identification courtesy of Ben Cantrell, San Diego, California.

Gulf Corvina, Cynoscion orthonopterus. Fish caught from coastal waters off Puertecitos, Baja California, July 2012. Length: 34 cm (14 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

The Gulf Corvina, Cynoscion orthonopterus, is a member of the Croaker or Sciaenidae Family, that is also known as the Gulf Croaker and the Gulf Weakfish and in Mexico as corvina golfina and corvina del golfo. Globally, there are twenty-four species in the genus Cynoscion, of which thirteen are found in Mexican waters, three in the Atlantic and ten in the Pacific Ocean.

The Gulf Corvina has an elongated compressed fusiform body with an oval cross-section. They have a dusky silvery coloration that is blue-gray dorsally. The scales have dark spots, the tip of the chin is dusky and their fins are yellowish. Their head is long and pointed, extending to just before the end of the eyes. Their mouth is large, equipped with 1 pair of large canines, and an oblique projecting lower jaw. They do not have chin barbels. Their anal fin has 2 spines and 10 or 11 rays; their caudal fin is square; their first dorsal fin has 9 to 10 spines; their second dorsal fin has 1 spine and 23 to 27 rays with a long base; and, their pectoral fins are long, reaching past the pelvic fin tips. They have 13 to 16 gill rakers. They are covered with rough scales. Their lateral line is arched anteriorly and becomes straight near the second dorsal fin origin.

The Gulf Corvina is a demersal species that is found in shallow coastal waters at depths up to 30 m (100 feet). They reach a maximum of 70 cm (2 feet 3 inches) in length and 2.4 kg (5 lbs 4 oz) in weight. Adults mainly feed on large crabs and sardines, and juveniles feed on small fish and small benthic organisms, such as amphipods, shrimp, and crabs. The Gulf Corvina 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 Corvina is a resident of the Pacific Ocean but has a very limited distribution, being found only in the northern half of the Sea of Cortez. There is a report of a small population living in coastal waters off Culiacan, Sinaloa. They enter river basins, specifically the Colorado River Basin, in the early spring to spawn.

The Gulf Corvina can be confused with a series of other Croakers found in the northern Sea of Cortez including the Gulf Croaker, Micropogonias megalops (low first dorsal fin; brown, oblique bars pointing backwards; 7 or 8 anal rays; 27 to 29 second dorsal fin rays), the Slender Croaker, Micropogonias ectenes (high first dorsal fin; 23 to 26 second dorsal fin rays), the Sharpnose Corvina, Cynoscion phoxocephalus (short pectoral fins; 20 to 22 second dorsal fin rays), the Shortfin Corvina, Cynoscion parvipinnis (short pectoral fins; 7 and 8 first dorsal fin spines, 21 to 23 second dorsal fin rays), the Totoaba, Totoaba macdonaldi (lacks canine teeth, 7 to 8 anal fin rays) and the White Seabass, Atractoscion nobilis (lacks canine teeth; deep notch between the dorsal fins).

From a conservation perspective the Gulf Corvina is currently considered to be VULNERABLE facing extinction in the near future. They reside in a very limited area and although once considered abundant and formerly supporting an important commercial fishing industry and sport fishery, populations in the Sea of Cortez have been decimated since the 1940s due to loss of spawning habitat from conversion and degradation of the Colorado River Delta via the curtailment of water flow and intensive overfishing. They became commercially extinct in the 1960s. With an increase in the water flow, and the reduced salinities, that started in 1993, the commercial catches during the spring spawning runs quickly rebounded within three years, however the fish sizes were significantly reduced. The juveniles are caught in large quantities and killed by shrimp trawlers.