Slender fusilier (Gymnocaesio gymnoptera)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Chordata · Class: Teleostei · Order: Eupercaria incertae sedis · Family: Caesionidae · Genus: Gymnocaesio.

Accepted name: Gymnocaesio gymnoptera · Authority: (Bleeker, 1856) · Taxonomic status: accepted · AphiaID: 219998.

Synonyms and superseded combinations recorded for this taxon: Caesio gymnopterus Bleeker, 1856; Gymnocaesio gymnopterus (Bleeker, 1856).

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=219998 (CC BY 4.0). Accessed 2026-09-23.

Biology and life history (FishBase)

Measured values published by FishBase for Gymnocaesio gymnoptera. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Maximum length: 18 cm · Depth range: 0–500 m · Habitat zone: reef-associated · Body shape: fusiform / normal · Vulnerability index: 10 of 100 · Fishery importance: minor commercial · Aquarium trade: never/rarely.

FishBase notes: Inhabits coastal areas around coral reefs (Ref. 30573). Feeds on zooplankton in large midwater aggregations. Forms schools with members of the genus Pterocaesio . Oviparous, with numerous, small pelagic eggs (Ref. 402). Often mistaken for juveniles and easily overlooked because of small size (Ref. 48636). Also caught with drive-in nets. Utilized as tuna bait fish (Ref. 30573).

Source: FishBase species summary (SpecCode 929) — https://www.fishbase.se/summary/Gymnocaesio-gymnoptera.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-23.

Distribution and occurrence records (GBIF)

194 georeferenced occurrence records for Gymnocaesio gymnoptera are published through GBIF from 20 countries or marine areas. The map above plots 51 distinct locations from a sample of 194 records, omitting 7 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: Mayotte (97); Fiji (17); Philippines (16); South Africa (8); Mozambique (7); Indonesia (6); Papua New Guinea (6); New Caledonia (5); Maldives (4); Réunion (4); Thailand (4); Madagascar (3); Solomon Islands (3); Seychelles (3); Egypt (2).

Marine regions with a valid WoRMS distribution record: Kenyan Exclusive Economic Zone; Tanzanian Exclusive Economic Zone; Somali Exclusive Economic Zone; Seychellois Exclusive Economic Zone; Mauritian Exclusive Economic Zone; Eritrean Exclusive Economic Zone; Red Sea; Réunion Exclusive Economic Zone; Madagascar; Djiboutian Exclusive Economic Zone.

Source: GBIF Occurrence Search (taxonKey 2374814) — https://www.gbif.org/occurrence/search?taxon_key=2374814&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=219998 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-23.

Conservation status (IUCN Red List)

The IUCN Red List assesses Gymnocaesio gymnoptera (Bleeker, 1856) as Least Concern (code LC). No trend, population estimate or threat analysis is given here, because none is available from this source without the Red List API; follow the source link for the full assessment, including its date.

Source: IUCN Red List of Threatened Species (taxon 20251174) — https://www.iucnredlist.org/species/20251174/0; GBIF IUCN Red List category endpoint (taxonKey 2374814) — https://api.gbif.org/v1/species/2374814/iucnRedListCategory. Accessed 2026-09-23.

Description and natural history (Wikipedia)

The slender fusilier was first formally described in 1856 as Caesio gymnopterus by the Dutch ichthyologist Pieter Bleeker with the type locality being given as Ternate. In 1876, Bleeker described a new genus, Gymnocaesio with C. gymnopterus as its type species by montypy, it is still the only species in that genus. The genus name is a compound of gymno meaning "naked" and caesio as in the related genus Caesio in which this species was originally placed. The specific name also uses gymno as a prefix for pterus which means fin, a reference to the lack of scales on the dorsal and anal fins, these are scaled in Caesio.

The slender fusilier has a slender, fusiform, elongated and moderately laterally compressed body. There are small conical teeth on the maxillae and the vomer while the premaxilla and palatines lack any teeth. The dorsal fin has 10–11 spines and 14–16 soft rays while the anal fin has 3 spines and 11–13 soft rays. There are 20–22 pectoral fin rays. The back and upper flanks are bluish green in colour, with centres of scales paler, creating a striped appearance. There is a yellow or brown stripe its widtrgh being roughly equal to a single scale over the lateral line, running for much of the later line's length but running above the lateral line on the caudal peduncle. There is frequently a vivid blue horizontal band directly underneath the lateral line stripe taking up as much as one third of the flanks. The rest of the body is silvery white. The axil of pectoral fin is black and there are black tips to the lobes of the otherwise dusky caudal fin, the rest of the fins are white. This species attains a maximum total length of 18 cm.

The slender fusilier is found in the Indian Ocean from the southern Red Sea to South Africa, eastwards through the Seychelles and Mascarenes to the Maldives and Laccadives, Sri Lanka and southern India eastwards as far as Fiji in the Pacific Ocean. It extends as far north as Japan and as far south as Papua New Guinea and New Caledonia. It occurs in coastal waters in the vicinity of coral reefs at depths down to 500 m.

The slender fusilier has a diet of zooplankton which it forages for in large midwater aggregations. It frequently joins in mixed species schools with members of the genus Pterocaesio. It is an oviparous species which lays large numbers of small, pelagic eggs.

The slender fusilier has minor importance as a target species for fisheries. It is sometimes caught using fish traps and drive-in nets. In the Philippines the fish landed are sold as fresh fish while in the Maldives, Laccadives and the Western Pacific it is caught to be used as bait for tuna fishing. In some parts of its range it is overfished.

Source: Wikipedia: Slender fusilier — https://en.wikipedia.org/wiki/Slender_fusilier (CC BY-SA 4.0). Accessed 2026-09-23.