Pacific mutton hamlet

Alphestes immaculatus is a fish of the family Epinephelidae, the groupers, described by Breder in 1936 ^[1]. In English it is called the Pacific mutton hamlet, and in Spanish WoRMS gives it the name guaseta del Pacífico ^[1]. It lives in the eastern Pacific, from the northern Gulf of California to Peru, and is a small fish that does not exceed about 30 cm ^[2]. By day it hides in crevices or among seaweed, and at night it hunts ^[2]. Its global category on the IUCN Red List is Least Concern ^[3].

The genus name, Alphestes, derives from a Greek word for a kind of fish ^[2]. Breder described the species in 1936, and its name is the one now accepted in WoRMS ^[1].

It is a grouper with a fusiform body, bearing 11 spines and 17 to 19 soft rays in the dorsal fin, and 3 spines and 9 soft rays in the anal fin ^[2]. The rear edge of the preopercle is rounded and serrated, and at its angle there is a large spine, usually covered by skin ^[2].

In life, the body is marbled reddish brown, with indistinct bars and small dark and pale spots on the head, body and median fins ^[2]. Each pectoral fin has 7 or 8 irregular rows of small dark spots ^[2]. Body depth is less than or equal to head length, and the eye diameter is similar to the snout length ^[2].

It occurs in the eastern Pacific, from the northern Gulf of California to Peru, including the Galapagos Islands ^[2]. The tropical limits given by FishBase run from 32° north to 13° south latitude ^[2]. WoRMS treats it as a strictly marine species ^[1].

It is a demersal, non-migratory fish, recorded between 1 and 50 m deep ^[2]. It lives in seagrass beds and also on rocky reefs ^[2]. A 2025 Peruvian study of DNA tools for authenticating seafood included Alphestes immaculatus among 10 commercially important Peruvian marine species ^[4].

FishBase describes it as a cryptically coloured, secretive fish: by day it shelters in crevices or among seaweed, sometimes partly covering itself with sand; at night it hunts, feeding mainly on benthic crustaceans ^[2]. The largest recorded size is 30 cm in total length, and the usual size is around 18 cm ^[2].

Part of its molecular biology is known from a study of the hepcidin gene, a peptide whose expression in muscle the authors consider possibly relevant to the immune response ^[5]. In that work, the species' HAMP1 gene turned out to have 3 exons and 2 introns, and to encode a molecule of 90 amino acids ^[5]. Baseline expression was high in the liver and muscle; in fish stimulated with bacterial lipopolysaccharide, the highest levels shifted to the spleen and head kidney ^[5].

It is a nocturnal predator of benthic crustaceans that spends the day hidden, and its cryptic colouring is part of that strategy ^[2]. It is associated with seagrass beds as well as shallow rocky bottoms, between 1 and 50 m ^[2].

Its global category on the IUCN Red List is Least Concern ^[3]. FishBase, for its part, rates the fishery for this species as of no interest ^[2].

In Peru, many groupers of the family Epinephelidae (for example species of Alphestes, Epinephelus and Mycteroperca) are sold under one generic commercial label, and groupers in general are fish of high economic value and a frequent target of substitution ^[4].