Blue bastard (Plectorhinchus caeruleonothus)

Classification (WoRMS)

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

Accepted name: Plectorhinchus caeruleonothus · Authority: Johnson & Wilmer, 2015 · Taxonomic status: accepted · AphiaID: 1042731.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=1042731 (CC BY 4.0). Accessed 2026-09-25.

Biology and life history (FishBase)

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

Maximum length: 100 cm · Depth range: 6–30 m · Habitat zone: reef-associated · Body shape: fusiform / normal · Vulnerability index: 60 of 100 · Fishery importance: bycatch · Aquarium trade: never/rarely.

FishBase notes: This species is found on sand, rubble and reef bottom but mostly in the intertidal zone, or shallow reef; one specimen trawled in a depth of 30 m. The most southerly record is a large individual estimated to be 100 cm in total length. Large individuals are most often solitary, foraging diurnally over relatively open expanses of soft substrate. Agonistic behavioural interactions have been recorded between individuals, individuals have often been observed to interact highly aggressively, engaging in one-on-one conflicts (Ref. 103290).

Source: FishBase species summary (SpecCode 68244) — https://www.fishbase.se/summary/Plectorhinchus-caeruleonothus.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-25.

Distribution and occurrence records (GBIF)

80 georeferenced occurrence records for Plectorhinchus caeruleonothus are published through GBIF from 2 countries or marine areas. The map above plots 20 distinct locations from a sample of 80 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: Australia (79); Indonesia (1).

Source: GBIF Occurrence Search (taxonKey 8591117) — https://www.gbif.org/occurrence/search?taxon_key=8591117&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=1042731 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-25.

Conservation status (IUCN Red List)

The IUCN Red List assesses Plectorhinchus caeruleonothus Johnson & Worthington Wilmer, 2015 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 179941082) — https://www.iucnredlist.org/species/179941082/0; GBIF IUCN Red List category endpoint (taxonKey 8591117) — https://api.gbif.org/v1/species/8591117/iucnRedListCategory. Accessed 2026-09-25.

Description and natural history (Wikipedia)

Plectorhinchus caeruleonothus adults are mostly silvery-grey in colour, but the cheek and the operculum are uniformly bluish-grey. The orbit of the eye and upper edge of the upper jaw are sooty yellow, while the posterior edge of the gill membrane is silvery-grey. The juveniles are blackish brown and marked with 10 uneven, horizontal, slender white stripes on the head and body.

The caudal fin is marked with diagonal white bars that converge on the central margin, while the pectoral fins are yellow with a dark brown blotch in the middle of their inner bases. The dorsal fin contains 12 spines and 18-20 soft rays, while the anal fin has 3 spines and 6-7 soft rays. This species attains a maximum total length of 100 cm.

Distribution

Plectorhinchus caeruleonothus is endemic to Australia. It ranges from Rottnest Island in Western Australia around the northern coast to Lizard Island in Queensland.

Habitat and biology

Plectorhinchus caeruleonothus is found over sand, rubble, and reef substrates, although it prefers intertidal areas or reefs in shallow water. It has been taken as deep as 30 m.

Larger individuals are solitary, spending the day foraging over quite open areas of sand or silt. These fish have frequently been recorded interacting in highly aggressive conflicts with other conspecifics. Such confrontations involve the individuals coming face-to-face and locking their jaws, as well as participating in prolonged and violent struggles close to the top of the water column.

Discovery, systematics and naming

Plectorhinchus caeruleonothus was previously considered to be a legendary fish which existed only in fishermen's tales. The fish is very difficult to catch. Plectorhinchus caeruleonothus was identified through several features unique to it, such as a distinctive pattern on juveniles and small nostrils. It is thought that the fish likely evolved its tough ways to survive the many sharks and crocodiles that share its habitat in reef waters off northern Australia.

It was formally described in 2015 by Jeffrey W. Johnson and Jessica Worthington Wilmer with the type locality given as Boyd Bay, southwest of Weipa in Queensland. Previously, this species was thought to be synonymous with the minstrel sweetlips (Plectorhinchus schotaf) of the western Indian Ocean, as were the sombre sweetlips (Plectorhinchus unicolor) of Japan to northern Australia and Plectorhinchus griseus from India and Sri Lanka, but all are now recognised as valid species The specific name is a compound of caeruleus meaning “blue”, which refers to the blue sheen in life, and nothus meaning “bastard”, reflecting the name given to this species by anglers.

Utilisation

Plectorhinchus caeruleonothus Is sometimes taken as bycatch in commercial fisheries. It is sought after by recreational anglers, mainly due to the difficulty of catching it. The flesh is not regarded as highly palatable.

Source: Wikipedia: Plectorhinchus caeruleonothus — https://en.wikipedia.org/wiki/Plectorhinchus_caeruleonothus (CC BY-SA 4.0). Accessed 2026-09-25.