Razor surgeonfish

Prionurus laticlavius is a surgeonfish of the family Acanthuridae, order Acanthuriformes ^[1]. In Peru it is called «pez viringo» ^[2]. It is a herbivore of shallow rocky bottoms in the eastern Pacific that moves in large schools and grazes the algae growing on rock ^[3],[4]. The IUCN Red List rates it Least Concern ^[5], but taking it is banned in three sectors of the Reserva Nacional Mar Tropical de Grau ^[2],[2],[2].

A study that examined 66 museum specimens of this species and 103 of the spotted form gave these counts for both: 7 to 8 spines and 24 to 28 soft rays in the dorsal fin, 2 to 3 spines and 22 to 24 rays in the anal fin, and 15 to 17 rays in each pectoral fin; body depth goes 1.6 to 2.1 times into standard length ^[6].

What has traditionally set it apart from Prionurus punctatus is the lack of dark spots on the body, but 8 of the specimens examined had faint spots, mostly from Costa Rica, where the two forms meet ^[6]. Neither the mitochondrial COI gene nor more than 800 nuclear loci grouped the two forms apart, and their genetic differentiation proved low, so that study treated Prionurus punctatus as a synonym of Prionurus laticlavius ^[6]. WoRMS, however, does not list Prionurus punctatus among the synonyms of this species ^[1].

Similar species

• Prionurus punctatus: Its body is sprinkled with dark spots, which Prionurus laticlavius lacks; since fish with faint spots exist and the fin counts of the two forms coincide, colour is not always enough to tell them apart ^[6].

It belongs to the fauna of the tropical eastern Pacific, a region spanning about 29° of latitude from Magdalena Bay, Mexico, to the Gulf of Guayaquil, Ecuador ^[6]. The unspotted form was linked with the stretch from Costa Rica to Ecuador and the oceanic islands, and the spotted one with the coast from the Gulf of California to Costa Rica ^[6]. A later study describes the species from the northern Gulf of California to Ecuador, including the Revillagigedo and Galápagos islands ^[7]. In Peru, the management plan of the Reserva Nacional Mar Tropical de Grau lists it among the rocky-reef fishes of the Arrecifes de Punta Sal, Cabo Blanco – El Ñuro and Isla Foca sectors ^[2],[2],[2].

It lives close to the bottom, generally over rock, between 3 and 30 m deep ^[3]. In the southeastern Galápagos it was the most counted species in visual surveys, making up 17.9 % of all fish recorded, and one of the most abundant in coral habitats and on artificial substrate; it is more abundant in structurally complex coastal habitats ^[8]. The species of its genus occur only in cooler waters on either side of the tropics and in equatorial areas with cold-water upwelling, such as the Galápagos ^[4].

It reaches about 60 cm in length ^[4]. In the southwest of the Gulf of California, 379 fish were measured, from 3 to 45.6 cm total length and up to 1904.8 g ^[7]. With all fish pooled, growth was isometric (b = 3.01), with positive allometry in juveniles (b = 3.14) and negative allometry in adults (b = 2.75); any fish of 20 cm or more with a developed gonad was treated as an adult ^[7].

In monthly sampling over one year in the Gulf of California, most adults were females, and females mature at a larger size: half of the females are mature at 35.1 cm and half of the males at 33.3 cm ^[9]. Males invest most in their gonads from August to October, with a gonadosomatic index near 3.4 %; from November to July both sexes remain mature, with indices below 1 % and females predominating ^[9]. To judge maturity by eye, a scale of 5 gonad stages was proposed and checked by histology in 271 fish, in which colour helps to tell the stages apart ^[10].

It belongs to a group of surgeonfishes that crop algal turf: the spatula shape of their multi-cusped teeth, their way of feeding and what is found in their stomachs indicate that its genus feeds mainly on short algae forming mats on rock ^[4]. The management plan of the Reserva Nacional Mar Tropical de Grau highlights surgeonfishes, or viringos, together with the green parrotfish, as herbivores that clean the rocks and stop algae from multiplying in excess ^[2].

In a comparison of 38 ecoregions worldwide, the eastern Galápagos showed the highest herbivorous fish productivity measured so far, averaging 67.15 g of new biomass per 250 square metres per day, more than 2.6 times that of the second ecoregion, the Gulf of Papua; this species produced more than 94 % of it ^[4]. The productivity of its genus peaked at around 25 °C, whereas that of the other herbivore groups peaked in warmer water ^[4].

In the Galápagos it is attacked by the blenny Plagiotremus azalea, a false cleaner that bites off pieces of skin and mucus; such wounds can let pathogens in ^[11]. In January 2016, during El Niño, it was one of 18 fish species, out of 93 recorded in the central archipelago, showing signs of an ulcerative skin disease ^[11].

The IUCN Red List classifies it as Least Concern, based on a 2010 assessment ^[5].

In Peru, the 2026-2031 management plan of the Reserva Nacional Mar Tropical de Grau names it, along with the mero ojo chiquito and the green parrotfish, among the rocky-reef species regarded as highly threatened as a result of poor spearfishing practices and other fishing gear ^[2]. The plan bans taking it throughout the Arrecifes de Punta Sal sector, throughout the Cabo Blanco – El Ñuro sector and throughout the Isla Foca sector ^[2],[2],[2]. Within 300 m of Isla Foca and its islets, catching fish with a speargun is not allowed either ^[2].

It is in high demand for aquariums and aquaculture, and is sometimes eaten locally ^[7]. FishBase lists it as commercially used both in fisheries and in the aquarium trade ^[3].

The management plan of the Reserva Nacional Mar Tropical de Grau states that the worst-affected reef fishes and invertebrates are often speared or taken above sustainable levels to be sold, and counts the «pez viringo» among the species highly threatened by these practices ^[2].

The 2026 management plan of the Reserva Nacional Mar Tropical de Grau places the «pez viringo» on the rocky reefs of the Arrecifes de Punta Sal, Cabo Blanco – El Ñuro and Isla Foca sectors ^[2],[2],[2]. In the Arrecifes de Punta Sal sector, to which the plan attributes the highest coastal diversity in the Peruvian sea, the recovery zone receives occasional recreational diving tourists ^[2]. Taking it is banned in all three sectors ^[2],[2],[2].