Mexican lookdown

Selene brevoortii is a fish of the family Carangidae, with a deep, strongly compressed body, living in coastal waters of the tropical eastern Pacific ^[1],[2]. In Peru it is recorded under the names radio and jorobado ^[2]. It has been reported from southern California to northern Chile, and one source places it between 2 and 165 m depth ^[3]. It is of minor fishery interest ^[2], and its global IUCN Red List category is Least Concern ^[4].

Gill described the species in 1863 as Argyriosus brevoortii; the current valid name is Selene brevoortii ^[1]. Selene is the Greek word for the moon, and the epithet commemorates James Carson Brevoort (1818–1887), an American collector of coins and rare books ^[2]. Unaccepted synonyms include Vomer brevoortii and Argyreiosus pacificus, the latter by Lockington, 1877 ^[1].

The body is short, deep and strongly compressed, and scaleless; the lateral-line scutes are very weak and poorly differentiated ^[2]. The dorsal fin has 8 isolated spines, 1 further spine and 20 to 23 soft rays, and the lower limb of the first gill arch carries 29 to 34 gill rakers ^[2]. In adults the front lobes of the second dorsal and the anal fin are very long, whereas in juveniles it is the front dorsal spines that are drawn out ^[2].

Adults are golden or silvery with metallic blue sheen; juveniles are yellowish with dark transverse bars that are faint and broken ^[2]. The maximum recorded length is 38 cm fork length, and a common size is 25 cm ^[2]; another source gives up to 42 cm total length ^[3]. In 57 fish bought from fishers in Mazatlán the mean total length was 23.5 cm ^[5].

It is a marine, benthopelagic species of the eastern Pacific. FishBase places it from the southern tip of Baja California, Mexico, to Ecuador, between 1 and 50 m depth ^[2]. A 2021 fish checklist extends the range from Seal Beach, southern California, to northern Chile, including the Gulf of California, with depths of 2 to 165 m, and lists it in coastal waters, bays and estuaries ^[3].

In Peru, during the 2017 coastal El Niño, it was observed at the landing sites of Pisco, at 13.5° S, an occurrence the authors regard as unusual; temperatures above 26 °C and a salinity above 35.1 were measured at that time ^[6]. The authors state that the species is frequent in northern Peru and propose that those warm and somewhat saltier waters would have favoured its displacement southward ^[6].

Adults form small schools close to the bottom in shallow coastal waters ^[2]. Its prey includes juvenile cephalopods, prawns, bristle worms and little fishes, and the estimated trophic level is 3.8 ^[2].

FishBase gives no length at maturity, and no reproduction study was found in the sources reviewed ^[2]. The length-weight relationship estimated there has an exponent of 2.81, with total length in centimetres ^[2].

A study of 874 fish of 10 carangid species from the southeastern Gulf of California found 8 metazoan parasite species in Selene brevoortii, and it was the first description of this species' parasite community ^[7]. The communities of the Selene species were very similar to each other, with a similarity above 65 %, which the authors link to similar ecological habits ^[7].

Among its parasites is a gill copepod, Caligus selenecola, described from fish bought from fishers in Mazatlán and examined between June and November 2021; it occurred in 9 of 57 fish examined, a prevalence of 15 % ^[5].

The global IUCN category is Least Concern, according to the 2008 assessment ^[4]. FishBase estimates high resilience and a vulnerability to fishing of 33 out of 100, and notes that its commercial fishery is minor ^[2].

It supports a minor commercial fishery, is sold fresh or salted, and is also appreciated as a sport fish ^[2]. In Pisco in 2017 it was landed from gillnets, known in the region as cortina agallera ^[6].

The Peruvian literature consulted documents it at the landing sites of Pisco province, in the Ica department, during 2017, as a gillnet catch in a coastal El Niño year ^[6]. The same authors note that the species is frequent in northern Peru ^[6].