Atlantic moonfish - Selene setapinnis

 

Atlantic moonfish

 

Diagnostic characters: Body short, very deep (at sizes greater than 10 cm fork length, body depth 46.0to 51.5% fork length), and extremely compressed, with ventral profile more convex than dorsal; headprofile rounded at top and sharply sloping through a slight concavity in front of eye to a blunt snoutwith lower jaw protruding.Eye moderately small (diameter contained 3.4 to 3.7 times in head length). Upperjaw short, expanded at posterior end, and ending far below and about under anterior margin of eye.Teeth relativelysmall; upper jaw with a narrow irregular band; lower jaw with a narrow irregular band tapering to an irregularrow posteriorly. Gill rakers 7 to 10 upper, 27 to 35 lower, and 34 to 44 total. Dorsal fin with 8 spines,followed by 1 spine and 21 to 24 soft rays; anal fin with 2 spines (resorbed into body at about 13 cm fork length)separated from rest of fin, followed by 1 spine and 16 to 19 soft rays; first 4 dorsal-fin spines elongated infish shorter than 6 cmfork length, with the longest (second) spine about equal in length to body depth, thesespines becoming very short and nearly resorbed by 30 cm fork length; second dorsal-fin lobe only slightlyelongated, shorter than head, contained 7.5 to 11.4 times in fork length; pelvic fins relatively short at allsizes, becoming nearly rudimentary (contained 7.2 to 9.8 times in pectoral fin length).Scutes in straight part oflateral line weak, scarcely differentiated, numbering from 7 to 17 over caudal peduncle; body superficiallynaked, scales small and embedded, covering most of lower half of body but absent anteriorly on most ofarea from pelvic-fin base to junction of curved and straight portions of lateral line.Vertebrae 10 precaudal and14 caudal. Colour: in fresh fish, body and head silvery, sometimes with a metallic bluish cast, more pronouncedon upper body, head, and snout; a faint dark spot on edge of opercle near upper margin; a narrowblack area on top of caudal peduncle; fins clear or hyaline, with dusky or olive yellow tints on second dorsalandcaudal-fin lobes in some. Juveniles generally silvery with an oval black spot over straight portion oflateral line, persistent on some individuals to 9 cmfork length but disappearing on others at 7 cmforklength.

Size: Maximum to 33 cm fork length; 39 cm total length; common to 24 cm fork length.

Habitat, biology, and fisheries: A schoolingspecies, usually near the bottom from inshorewaters to at least 54 m depth. Young occur nearthe surface, as far as 180 km offshore. Juvenilesmay occur in bays and river mouths. Sexual maturityis reached by about 13 cm fork length.Feeds on small fishes and crustaceans. Caughtwith trawls or seines. Edibility rated poor to good.

Distribution: In the Western Atlantic apparentlyrestricted to continental margins from Nova Scotiato Mar del Plata, Argentina. Two closely relatedspecies occur in other areas, Selenedorsalis (Gill) in the eastern Atlantic, and Seleneperuviana (Guichenot) in the eastern Pacific.