Rainbow Chub, Kyphosus ocyurus

Rainbow Chub, Kyphosus ocyurus, Juvenile. Fish caught from shore off the beach at Palmilla, Baja California Sur, January 2009. Length: 20 cm (7.9 inches).

Rainbow Chub, Kyphosus ocyurus. Fish caught from coastal waters off  Mazatlán, Sinaloa, October 2016. Length: 43 cm (17 inches). Catch and photograph courtesy of George Brinkman, Guelph, Ontario, Canada.

Rainbow Chub, Kyphosus ocyurus. Fish caught from coastal waters off  Puerto Los Cabos, Baja California Sur, February 2004. Length: 48 cm (19 inches).

Rainbow Chub, Kyphosus ocyurus. Fish caught from coastal waters off  Point Palmilla, Baja California Sur, October 2020. Length: 56 cm (22 inches).

Rainbow Chub, Kyphosus ocyurus. Underwater photographs taken in Zihuantanejo Bay, Guerrero, December 2019 and September 2023. Photographs courtesy of Maude Jette, Dive Zihuantanejo,  www.Divezihuatanejo.com.

Rainbow Chub, Kyphosus ocyurus. Underwater photographs taken in Zihuantanejo Bay, Guerrero, February 2022. Photographs courtesy of Ron Woheau, Zihuantanejo.

The Rainbow Chub, Kyphosus ocyurus, is a member of the Sea Chub or Kyphosidae Family, and is known in Mexico as chopa salema. Globally, there are eighteen species in the genus Kyphosus, of which six are found in Mexican waters, one in the Atlantic, three in the Pacific and two in the Atlantic and Pacific Oceans.

The Rainbow Chub has an elongated compressed oval body that has a depth that is 33% to 37% of standard length. They are silvery-olive dorsally transitioning to white ventrally. They have a broad bright blue mid-lateral stripe and a yellow stripe immediately below. Their caudal fin is yellow. There is a blue band along the base of their dorsal fin. They have a small pointed head with convex upper and lower profiles. They have a short snout and a very short horizontal mouth that opens at the front with small incisiform flattened teeth. Their anal fin has 3 spines and 14 rays and is low and of uniform height; their caudal fin is forked; their dorsal fin is low and continuous with 11 spines folding down into a scaly grove and 13 rays; and, their pectoral and pelvic fins are relatively short. Their body is covered with small, thick, and rough scales.

The Rainbow Chub is a schooling fish found near floating logs far out at sea from the surface to depths up to 30 m (100 feet). They reach a maximum of 70 cm (2 feet 4 inches) in length. They are omnivores feeding on benthic algae, plankton, and small invertebrates. The Rainbow Chub 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 Rainbow Chub is a resident of Mexican waters of the Pacific Ocean but has a limited distribution being are found along the entire west coast of Baja, in the southern extreme of the Sea of Cortez (documented by a fish that I caught), and along the coast of the mainland from Mazatlán, Sinaloa to Guatemala. They are a far-ranging pelagic species that are also found in the waters of Hawaii, the Marquesas Islands of Polynesia, and Tahiti.

The Rainbow Chub is most likely confused with the Rainbow Runner, Elagatis bipinnulata (more aerodynamic; body width 20% to 24% of standard length).

From a conservation perspective the Rainbow Chub has not been formally evaluated. They are not abundant and are of little interest to most.