Loosetooth parrotfish

Nicholsina denticulata is a small parrotfish of the tropical eastern Pacific; the current taxonomic register places it in the family Labridae ^[1]. It lives at depths of 1 to 11 m, mostly on rocky coasts with macroalgae, and reaches about 32.0 cm in total length ^[2]. In Peru it is known from Lobos de Afuera, Lobos de Tierra, Don Martín and North Chincha islands ^[3]. The IUCN lists it as Least Concern ^[4].

The genus name honours J.T. Nichols, a curator of ichthyology at the American Museum of Natural History ^[2].

Nicholsina was established in 1915 as a subgenus of Cryptotomus, and was later treated as a genus by Schultz (1958) ^[3]. The species was described in 1917 under the name Xenoscarus denticulatus ^[3].

A fresh specimen caught in northern Chile was very dark brown, with red at the rear base of the pectoral fin; the branchiostegal membrane, the underside of the chin and the isthmus were reddish brown ^[3]. The membrane of the tail fin was red and its rays a dark brown that contrasted with it; no conspicuous stripes or borders were seen, nor radial lines around the eyes ^[3].

The same specimen had IX dorsal spines and 10 soft rays, III anal spines and 9 anal rays, 12 pectoral rays, 27 pored scales on the lateral line and 22 large cycloid scales in a lengthwise series ^[3]. A narrow free fold crosses the isthmus; the teeth of the lower jaw form a fused plate, while those of the upper jaw are conical, free and in a single row ^[3]. That individual measured 282 mm in total length ^[3], and the largest size recorded for the species is 32.0 cm ^[2].

Similar species

• Nicholsina usta: It lives in the Atlantic, not the eastern Pacific; Nicholsina denticulata is told apart from it by its typically dark colour pattern ^[3].

The species belongs to the eastern Pacific, from the Gulf of California to Ecuador and northern Peru, and it includes the Galápagos Islands ^[2]. Its northern limit in the Gulf of California is Guaymas, where its juvenile phase was described under another name, Xenoscarus hubbsii ^[3]. A specimen caught near Iquique, at 20°12'S, pushed the known southern limit into northern Chile and was the first record of the family Scaridae for the continental Chilean coast ^[3].

It is a marine reef-associated fish that lives at 1 to 11 m and is abundant in shallow coastal areas, above all on rocky coasts with macroalgae ^[2]. The Iquique specimen was speared at 10 m over a rocky bottom ^[3].

It scrapes or breaks off pieces of reef to digest the algae growing in them, or feeds directly on algae; it can be solitary or form loose schools ^[2]. FishBase gives it a trophic level of 2.0, estimated from its food items ^[2].

FishBase estimates a medium resilience for the species, with a minimum population doubling time of 1.4 to 4.4 years ^[2].

The global IUCN category for Nicholsina denticulata is Least Concern, according to the current assessment ^[4].

FishBase assigns it a low to moderate vulnerability to fishing, 33 out of 100 ^[2].

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

FishBase rates it as harmless to humans ^[2].

FishBase classes it as a minor commercial fishery species and gives it a high price category ^[2].

The literature records it in Peru at Lobos de Afuera, Lobos de Tierra, Don Martín and North Chincha islands; the data date from 1917 and 1946 ^[3].