King angelfish

Holacanthus passer is an angelfish of the family Pomacanthidae, described by Valenciennes in 1846 ^[1]. In Peru it is called «pez ángel», and the country's marine fish catalogue gives its range as Cabo San Lucas, Mexico, to Talara, including the Galápagos Islands ^[2]. The adult is dark blue crossed by a vertical white bar behind the pectoral fin, while the juvenile is yellow or orange with blue bars ^[3]. The IUCN Red List classifies it as Least Concern ^[4].

The adult has a dark blue body with a single white vertical bar behind the pectoral fin ^[3]. The juvenile looks very different: yellow or orange, with bright blue vertical bars and blue edges on the dorsal and anal fins, and its colours shift as it grows ^[3].

Males and females look alike except for the pelvic fins, white in males and yellow in females ^[3]. That white pelvic fin is the mark by which an adult male is recognised ^[5].

In a DNA barcoding study of reef fishes from northern Peru, Holacanthus passer sequences did not differ from one another (0 %), and the nearest species in the study, the angelfish Pomacanthus zonipectus, lay at a distance of 18.2 % ^[6].

It lives in the tropical eastern Pacific, from Cabo Tepoca and Bahía de los Ángeles in the northern Gulf of California (29° N) to the coast of Peru (5° S), and also around the oceanic islands of Revillagigedo, Galápagos, Malpelo and Cocos ^[7]. The Peruvian catalogue puts its southern limit at Talara ^[2].

It is found from the intertidal zone down to 80 m, though mostly between 0 and 30 m, on rocky and coral reefs and also in black coral gardens ^[7]. The Peruvian catalogue describes it as a coastal fish of sandy and rocky bottoms that also enters mangrove lagoons ^[2].

According to a 2025 study, the tropical eastern Pacific reaches south as far as Cabo Blanco, in Piura, and rocky reefs have been described between Cabo Blanco and Punta Sal ^[6].

It can reach 36 cm in total length ^[7]. In Bahía de Loreto National Park, in the Gulf of California, 794 fish were measured in May 2009, 659 of them juveniles, ranging from 3 to 29 cm and from 2 to 797 g ^[7].

From those data, the von Bertalanffy growth curve gave an asymptotic length of 37.9 cm and a growth coefficient of 0.127 per year; the estimated maximum age was about 20 years, and length at first maturity was 21.8 cm, reached at around 6.1 years ^[7]. An earlier study had put that length at 17 cm ^[7].

It spawns in batches, its ovaries maturing eggs asynchronously, and it is mature and active from April to November ^[3]. Of 45 adults caught in July and August 2014 at El Dátil, near Kino Bay (Sonora), 66.7 % were females, smaller than the males, and most gonads of both sexes had already released their gametes, so spawning seemed to have begun earlier, perhaps in spring ^[3].

In the genus Holacanthus females turn into males as they grow; in these angelfishes social organisation ranges from solitary individuals to harems, and they may divide their habitat by sex and size ^[5]. Its assembled genome is 583 Mb, and it had been estimated to have split from its Atlantic twin species, Holacanthus ciliaris, between 1.7 and 1.4 million years ago ^[5].

In the Gulf of California it feeds on the bottom, on algae and sessile invertebrates, and also in the water column, mainly on the faeces of the fish Chromis atrilobata ^[7]. In Mazatlán and Banderas bays, on the Mexican Pacific coast, only 2 of 13 fish species examined had sponges in their stomachs, Holacanthus passer and Pomacanthus zonipectus; Holacanthus passer had eaten 23 sponge species, 10 of them of the order Hadromerida, the broader diet of the two, and the authors conclude that, of the fishes studied, the two angelfishes were the main sponge eaters ^[8].

In the Pacific it was already known to clean marine megafauna, and at Los Órganos, on 22 February 2023, at 5 m depth, one individual ate organisms attached to a green turtle, the first record of Chelonia mydas as a client of this species ^[9].

During the 2015 to 2016 El Niño, an ulcerating skin disease struck 18 fish species in Galápagos; in January 2016 it showed on 18.7 % of 318 king angelfish checked ^[10]. At Cuatro Hermanos East island their abundance fell by 86 %, from 14.83 to 2.07 fish on average per video, and recovered quickly in November 2016 with the cold waters of La Niña ^[10].

The IUCN Red List classifies it as Least Concern ^[4].

Mexico declared it a species under special protection over concern that uncontrolled catches of juveniles would harm its populations, and its fishery is regulated ^[7]. Overfishing reduced its populations, and in the Gulf of California it was added to the Mexican protected-species standard NOM-059-SEMARNAT-2001 ^[3].

At Loreto Bay the estimated exploitation rate was 0.74, with fishing mortality of 0.88 per year against natural mortality of 0.315 per year, and most fish measured had not reached maturity length; the authors propose different catch rates for juveniles and adults ^[7].

It is one of the main species caught in the Gulf of California for the aquarium trade, which has taken it since the 1970s, and a single fish can sell on the beach for up to 200 US dollars ^[7]. Its juveniles are caught mainly in Mexico and Costa Rica for export to the United States and other countries ^[3].

According to a 2024 study, a fish cost between 150 and 900 dollars in the trade ^[5]. Breeding marine fishes in captivity reduces fishing pressure on wild populations, and analysis of this species' gonads aims to help formulate a diet for its broodstock and to develop its culture ^[3].

The 2001 catalogue of Peru's marine fishes places its southern limit at Talara ^[2]. A study published in 2025 included the species among the rocky reef fishes of northern Peru that it sequenced, collected by diving at places including the coast between Cabo Blanco and Los Órganos and Punta Sal (Tumbes), and notes that sampling and reaching those reefs is difficult ^[6].

In February 2023 it was seen cleaning a green turtle at Los Órganos, at the dive site known as La Vuelta or Arrecifes de Punta Veleros, a rocky reef covered mostly by red and green algae, soft corals and sponges, between 5 and 10 m deep ^[9].