Mottled spinefoot (Siganus fuscescens)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Chordata · Class: Teleostei · Order: Acanthuriformes · Family: Siganidae · Genus: Siganus.

Accepted name: Siganus fuscescens · Authority: (Houttuyn, 1782) · Taxonomic status: accepted · AphiaID: 273912.

Synonyms and superseded combinations recorded for this taxon: Amphacanthus albopunctatus Temminck & Schlegel, 1845; Amphacanthus aurantiacus Temminck & Schlegel, 1845; Amphacanthus concavocephalus (Paradice, 1927); Amphacanthus fuscescens (Houttuyn, 1782); Amphacanthus gymnopareius Richardson, 1843; Amphacanthus kopsii Bleeker, 1851; Amphacanthus maculosus Quoy & Gaimard, 1825; Amphacanthus margaritiferus Valenciennes, 1835; Amphacanthus nebulosus Quoy & Gaimard, 1825; Amphacanthus ovatus Marion de Procé, 1822; Amphacanthus tumifrons Valenciennes, 1835; Centrogaster fuscescens Houttuyn, 1782; Siganus albopunctatus (Temminck & Schlegel, 1845); Siganus concavocephalus Paradice, 1927; Siganus consobrinus Ogilby, 1912; Siganus fuscenaus (Houttuyn, 1782); Siganus kopsii (Bleeker, 1851); Siganus margaritiferus (Valenciennes, 1835); Siganus nebulosus (Quoy & Gaimard, 1825); Teuthis albopunctata (Temminck & Schlegel, 1845); Teuthis fuscescens (Houttuyn, 1782); Teuthis gibbosus De Vis, 1884; Teuthis kopsii (Bleeker, 1851); Teuthis nebulosa (Quoy & Gaimard, 1825); Teuthis tumifrons (Valenciennes, 1835).

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=273912 (CC BY 4.0). Accessed 2026-09-23.

Biology and life history (FishBase)

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

Maximum length: 40 cm · Common length: 25 cm · Depth range: 1–50 m · Habitat zone: reef-associated · Body shape: short and / or deep · Vulnerability index: 20.9 of 100 · Fishery importance: commercial · Aquarium trade: never/rarely.

FishBase notes: Inhabits algal and seagrass flats and shallow lagoon and coastal reefs (Ref. 9710, 11230). Forms schools. Mainly diurnal. Juveniles feed on filamentous algae, adults feed on leafy algae and seagrasses (Ref. 9710). Commercially cultured in Japan. Commonly found in large estuaries (Ref. 9002). Anterolateral glandular groove with venom gland (Ref. 57406).

Source: FishBase species summary (SpecCode 4616) — https://www.fishbase.se/summary/Siganus-fuscescens.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-23.

Distribution and occurrence records (GBIF)

6,411 georeferenced occurrence records for Siganus fuscescens are published through GBIF from 36 countries or marine areas. The map above plots 185 distinct locations from a sample of 3,000 records, omitting 64 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: Australia (4,621); Philippines (552); Japan (258); Chinese Taipei (205); Hong Kong (160).

The full country table, WoRMS marine regions and the sampling notes are on this species' Distribution page.

Source: GBIF Occurrence Search (taxonKey 2390191) — https://www.gbif.org/occurrence/search?taxon_key=2390191&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=273912 (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 Siganus fuscescens (Houttuyn, 1782) 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 69689554) — https://www.iucnredlist.org/species/69689554/0; GBIF IUCN Red List category endpoint (taxonKey 2390191) — https://api.gbif.org/v1/species/2390191/iucnRedListCategory. Accessed 2026-09-23.

Description and natural history (Wikipedia)

Siganus fuscescens was first formally described in 1782 as Centrogaster fuscescens by the Dutch naturalist Martinus Houttuyn with the type locality given as Nagasaki. This taxon is largely sympatric with the white-spotted spinefoot (Siganus canaliculatus) and these taxa are also very similar in appearance. Molecular analyses in 2011 found that there were three separate lineages within S. canaliculatus and S. fuscescens, that these lineages interbred and that each lineage had specimens which referred to either taxon. The authors thus concluded that S. canaliculatus is in fact a synonym of S. fuscescens. This, however, is not the position taken by FishBase, although it does note that the two species are sometimes confused. The Catalog of Fishes, on the other hand, recognises the third lineage as the species Siganus margaritiferus, found from the Andaman Islands to the Solomon Islands, north to Japan and south to Australia. Further molecular analyses have found that this may be a species complex and, while not resolving the potential synonymy of S. canaliculatus, these have suggested that there are cryptic species within S. fuscescens. The specific name fuscescens means "darkened", thought to be a reference to the dark upperbody.

Siganus fuscescens has a moderately slender, laterally compressed body, the standard length being 2.3 to 2.9 times its depth. The dorsal profile of the head is weakly to notably concave over the eyes with either a blunt or a pointed snout. The front nostril has a flap which becomes shorter as the fish grows and is reduced to a small peak in the oldest fishes. The dorsal fin has 13 spines and 10 soft rays while the anal fin has 7 spines and 9 soft rays. The front spine on the dorsal fin points forwards. The caudal fin is nearly emarginate in smaller individuals of less than 10 cm standard length becoming forked in larger fish. This species attains a maximum total length of 40 cm, although 25 cm is more typical. The overall colour of this rabbitfish is greenish-grey to brown, fading to silvery on the lower body, and it has a large number of small light-bluish spots on the flanks, and a slender brown bar along the upper margin of the operculum. Additionally, they frequently possess a dark patch under the start of the lateral line. When they are asleep or threatened, the adults adopt a mottled pattern.

Siganus fuscescens is found in the eastern Indian Ocean and the Western Pacific Ocean from the Andaman Sea east to Fiji and Samoa, north to Japan and south to Australia. In Australia, its range extends from Busselton, Western Australia around the tropical northern coast to the Nadgee River in southern New South Wales. It is found around Lord Howe Island in the Tasman Sea. There is a single record from the Italian Mediterranean Sea (this is the most abundant fish in the Mediterranean Sea for the last 40 years), but it is thought that this record probably refers to an individual transported by shipping. It is found as deep as 50 m in shallow coastal waters in algae, sea grass and coral or rocky reefs. It is frequently encountered in large estuaries.

Siganus fuscescens is a schooling species and is a mostly diurnal fish. The juveniles have a diet dominated by filamentous algae while the adults prefer leafy algae and sea grass. When they arrive on coral reef flats, the larvae aggregate in schools with a normal size of 200 individuals, but may hold as many as 5,000. When they have reached 3 months old, the number of fishes in a school declines to about 12. Prior to spawning, this species forms aggregations of 30-60 individuals in raised areas of the inner reef flats and they spawn on the 4th or 5th day of a new moon. Spawning occurs near the edge of the reef, and each female lays around 300,000 eggs in a single spawning. Individuals will spawn in consecutive years and fish more than two year old may spawn more than once in a season.

Siganus fuscescens, like other rabbitfishes, has venomous spines in the dorsal and pelvic fins. The venom in this species has been found to be similar to that found in stonefishes. The venom is usually non-lethal. However, it can cause sharp pain, bleeding and numbness at the punctured area. Soaking the affected area in water of around 45°C could help eliminate or ease the pain.

Siganus fuscescens is caught using small seine nets, set nets, fish traps, and by spearfishing. Landed adults are sold as fresh fish, but juveniles are frequently preserved as dried fish and sold in large quantities.

Source: Wikipedia: Siganus fuscescens — https://en.wikipedia.org/wiki/Siganus_fuscescens (CC BY-SA 4.0). Accessed 2026-09-23.