Barberfish

Johnrandallia nigrirostris, the «barberfish» ^[1], is a butterflyfish of the family Chaetodontidae and the only accepted species in its genus ^[1]. It lives on rocky and coral reefs of the tropical eastern Pacific, usually between 6 and 12 m deep though it reaches 40 m, and grows to about 20 cm at most ^[2]. It is best known as a cleaner: at oceanic islands such as Cocos it forms stationary schools that hammerhead sharks visit to have their parasites removed ^[3]. In northern Peru it has been seen at Los Órganos, Piura, where in 2023 one individual fed on the epibionts of a green turtle ^[4].

Gill described it in 1862 as Sarothrodus nigrirostris; it was later placed in Chaetodon, Heniochus and Pseudochaetodon, and today belongs to the genus Johnrandallia, erected by Nalbant in 1974 ^[1]. The genus name honours John Randall, a marine biologist at the Bishop Museum in Hawaii whose work centred on the systematics of Indo-Pacific fishes ^[2].

Its body is tall, strongly flattened from side to side and disc-like, with a steep, concave head profile and a protruding snout; the teeth are minute and arranged in a comb-like band ^[2]. The lateral line is complete and runs on to the tail stalk. The dorsal fin carries 11 or 12 spines and 24 or 25 soft rays, and the anal fin 3 spines and 18 to 20 rays ^[2].

The ground colour is yellowish. The snout bears a dark patch and the eye is ringed in black; the nape, a strip along the base of the dorsal fin, the rear margin of the gill cover and the base of the pectoral fins are black as well ^[2].

Similar species

• Chaetodon humeralis: This is the three-banded butterflyfish, which at Los Órganos gathers with the barberfish on the same rock wall ^[4]. The barberfish has no bands crossing the body: it is yellowish, with black limited to the snout, the ring around the eye, the nape, the base of the dorsal fin, the edge of the gill cover and the base of the pectorals ^[2].

FishBase gives its range as the Gulf of California south to Panama, counting Cocos, Malpelo and the Galápagos, between 40° N and 10° S ^[2]. Further south, the Peruvian literature records it on the coast of Piura ^[4], and a paper on new records of tropical coastal fishes for Peru lists in its bibliography a 1990 work giving the first record of the species in the country ^[5].

It is a fish of coral and rocky reefs, from 6 to 40 m deep and most often between 6 and 12 m ^[2]. At Los Órganos it was seen on a rocky reef 5 to 10 m deep covered mainly by red and green algae, soft corals and sponges ^[4].

It reaches about 20 cm in total length, though about 14 cm is the usual size, and it often swims in large schools ^[2]. It eats algae, snails and small crustaceans, and also picks parasites off larger fishes such as Paranthias colonus and Mulloides dentatus ^[2].

It lays eggs, and adults pair up in the breeding season ^[2].

At Cocos Island, Costa Rica, there are permanent cleaning stations at the sites Alcyone, Manuelita and Roca Sucia: there, scalloped hammerheads Sphyrna lewini are regularly seen swimming through motionless schools of barberfish, which feed on their ectoparasites ^[3]. Similar stations exist at Darwin and Wolf islands in the Galápagos ^[3].

At Cuatro Hermanos East, in the Galápagos, one of the largest and busiest cleaning stations in the study area is dominated by this species ^[6]. It was there, in January 2016, that an outbreak of ulcerative skin disease tied to the 2015-2016 El Niño was discovered; during the outbreak, researchers several times saw Myripristis leiognathus, a nocturnal and secretive fish that is never seen being cleaned, come to that station in broad daylight with damaged skin to seek cleaning. For that reason they suggest the barberfish could act as a carrier of the disease ^[6].

Its list of clients keeps growing. In December 2025 the species was documented for the first time cleaning Haemulon maculicauda on a coastal coral formation in Golfo Dulce, Costa Rica ^[7]. In Peru, on 22 February 2023, at 5 m depth, 1 individual fed on epibionts of a green turtle together with a Bodianus diplotaenia and a Holacanthus passer, the first time this butterflyfish has been recorded cleaning Chelonia mydas ^[4].

The IUCN Red List classifies it globally as Least Concern (LC), according to its 2009 assessment ^[8]. The Punta Veleros reef where it was documented in Peru lay, according to the 2023 study, inside the proposed Mar Tropical de Grau reserve ^[4].

Not medical advice. For a sting, a poisoning or an allergy, seek medical care.

FishBase considers it harmless to people ^[2].

According to FishBase, the species is of commercial interest to fisheries and to the aquarium fish trade ^[2].

The Peruvian coast north of 4° 15' S holds fauna of the Panamic biogeographic province: about 70 % of the species of Peru's rocky reefs are found there, and butterflyfishes are well represented ^[5].

Between October 2022 and March 2023, over 50 non-consecutive days of diving, it was observed in the southern part of Punta Veleros beach, Los Órganos district, Talara province, Piura, beside a rock wall dominated by butterflyfishes, where green turtles swam slowly and held neutral buoyancy ^[4]. Local divers call the places where these cleanings happened the butterfly wall and the passageways, both in the dive spot La Vuelta or Los Arrecifes de Punta Veleros; the cleaning by this species was seen at 5 m depth ^[4].