Yellowfin Surgeonfish, Acanthurus xanthopterus

Yellowfin Surgeonfish, Acanthurus xanthopterus. Fish caught from coastal waters off Kona, Hawaii, March 2021. Length: 20 cm (7.9 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.

Yellowfin Surgeonfish, Acanthurus xanthopterus. Fish caught from coastal waters off Kapa’a, Kauai, Hawaii, July 2023. Length: 25 cm (10 inches). Catch, photograph and identification courtesy of Chris Moore, Peoria, Arizona.

Yellowfin Surgeonfish, Acanthurus xanthopterus. Fish caught off Point Palmilla, Baja California Sur, November 2017. Length: 39 cm (16 inches).

Yellowfin Surgeonfish, Acanthurus xanthopterus. Fish caught off Point Palmilla, Baja California Sur, April 2013. Length: 40 cm (16 inches). Note: this fish is a very difficult photography subject whose coloration fades very quickly from being truly gorgeous to an ugly pale tan upon collection.

Yellowfin Surgeonfish, Acanthurus xanthopterus. Underwater photographs taken in coastal waters of the greater Los Cabos area, Baja California Sur, May 2018. Photograph courtesy of Bob Hillis, Ivins, Utah. Note: the fish immediately above has a white bar on the caudal peduncle which I have observed in about 10% of the population.

Yellowfin Surgeonfish, Acanthurus xanthopterus. Underwater photograph taken in Zihuantanejo Bay, Guerrero, January 2019. Photograph courtesy of Maude Jette, Dive Zihuantanejo,   www.Divezihuantanejo.com.

Yellowfin Surgeonfish, Acanthurus xanthopterus. Underwater photograph taken in Zihuantanejo Bay, Guerrero, January 2019. Photograph courtesy of Ron Woheau, Zihuantanejo.

The Yellowfin Surgeonfish, Acanthurus xanthopterus, is a member of the Surgeonfish or Acanthuridae Family, and is known in Mexico as cirujano aleta amarilla. Globally, there are forty-two species in the genus Acanthurus, of which seven are found in Mexican waters, three in the Atlantic and four in the Pacific Ocean.

The Yellowfin Surgeonfish are the largest of the Surgeonfish. They have elongated oval compressed bodies, which are gray-blue and change to light blue ventrally. They have numerous irregular dark lines covering their sides. The outer third of their pectoral fins are yellow. The area around and in front of their eyes is yellow and their caudal fin base often has a white bar. Their anal and dorsal fins feature alternating dark and light blue bars with dark margins and a pink tinge. Their caudal fin is strongly concave with an abundance of horizontal dark lines. They have a steep profile with eyes set high on their head and a small protrusible mouth placed low on their head with large flattened close-set teeth. Their anal fin has 3 spines and 23 to 25 soft rays; their dorsal fin is continuous with 9 spines and 25 or 27 rays; and, their pelvic fins have 1 spine and 5 soft rays. A key to identification is the tail base, which has a large depressed spine that fits into a groove on the side of their caudal base. Their body is covered with rough scales. They have a complete lateral line.

The Yellowfin Surgeonfish is a coastal schooling species normally found in shallow waters over sandy substrate adjacent to coral and rocky areas at depths up to 120 m (400 feet). They reach a maximum of 70 cm (2 feet 4 inches) in length. As of January 1, 2023, the International Game Fish Association world record stood at 3.42 kg (7 lbs 8 oz) with the fish caught in coastal waters off Panama in November 2015. They feed diurnally and primarily on benthic algae. The Yellowfin Surgeonfish 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 Yellowfin Surgeonfish have a wide global distribution being found in the Indian and Pacific Oceans. In Mexican waters, however, they have a limited distribution being found only in the extreme southern portion of the Sea of Cortez between La Paz and Cabo San Lucas, Baja California Sur, and along the coast of the mainland from Acapulco, Guerrero, south to Guatemala.

The Yellowfin Surgeonfish is an easy fish to identify due to its coloration and thus cannot be confused with any other species.

From a conservation perspective the Yellowfin Surgeonfish is currently considered to be of Least Concern with stable, widely distributed populations. They are fairly abundant in the southern extreme of the Sea of Cortez and can often be seen in schools of up to 20 individuals in a chum line slowly moving toward the surface. They are very difficult to catch by hook and line requiring significant downsizing of hooks as they are very finicky nibblers. If hooked they become a fierce foe on light tackle. Upon collection they quickly changes from a gorgeous blue to an ugly dark blue-gray. They are considered good food fish, and are pursued commercially with hook and line and spears by certain cultures, however, there is a concern that they may contain ciguatoxin, which is present in Surgeonfish outside the Eastern Pacific Ocean. They are also utilized by the aquarium trade and can be purchased on-line. Caution: The spines found at their tail base provide these fish with a unique defense mechanism rendering them exceedingly “dangerous” to handle as these spines can inflict major slashing wounds. In addition, the base of their caudal fin has a truly lethal scalpel.