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Lethrinus nebulosus  (Forsskål, 1775)

Spangled emperor
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Lethrinus nebulosus
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Australia country information

Common names: Green snapper, Morwong, North-west snapper
Occurrence: native
Salinity: brackish
Abundance: common (usually seen) | Ref: Kailola, P.J., M.J. Williams, P.C. Stewart, R.E. Reichelt, A. McNee and C. Grieve, 1993
Importance: commercial | Ref: Kailola, P.J., M.J. Williams, P.C. Stewart, R.E. Reichelt, A. McNee and C. Grieve, 1993
Aquaculture: never/rarely | Ref: Kailola, P.J., M.J. Williams, P.C. Stewart, R.E. Reichelt, A. McNee and C. Grieve, 1993
Regulations: restricted | Ref: Kailola, P.J., M.J. Williams, P.C. Stewart, R.E. Reichelt, A. McNee and C. Grieve, 1993
Uses: live export: yes;
Comments: Spangled emperors are distributed between Rottnest Island (near Perth) and northern New South Wales (Ref. 6390), including the Torres Strait Islands (Ref. 13465). Spangled emperors appear to be more common in outer coastal waters to the west and east of Australia than they are in the north (Ref. 6390). Recorded from Shark Bay (Ref. 115274). Stock structure: The taxonomic position of blue-spotted (L. choerorynchus), spangled and blue-lined (L. frenatus) emperors has been confused, with reviews (Ref. 2295, 2334) suggesting they are misidentifications for the 1 species. However, surveys and continuing studies consistently reveal morphological and ecological differences between them, and recent electrophoretic study (Ref. 28017) in Western Australia has confirmed that the 3 taxa are reproductively isolated species. Western Australian populations of blue-spotted emperors and spangled emperors have been shown to be single stocks, yet the relationship of these populations and blue-spotted and spangled emperors from other States is unknown. Commercial fishery: Emperors in general are caught by handlines, rod-and-line, traps and demersal otter trawling - mainly stern trawling but also semi-pelagic trawling in the Northern Territory. Emperors are trawled off northwestern and northern Australia. From 1970 (Ref. 28206, 28207) until 1991, Taiwanese and later Thai and Chinese fleets operated pair trawlers and stern trawlers on the North West Shelf and northern Australia. Emperors and butterfly bream (Nemipteridae) dominated catches on the North West Shelf for the 10 years from 1980 (Ref. 27275), peaking at a retained catch of 2200 t of emperor in 1982. Emperors were far less abundant in retained catches in the Timor and Arafura seas for the same period. The trawlers worked in depths between 30 m and 120 m, and concentrated on waters between 115° and 120°E (Ref. 28206). Domestic fishing interest in trawling in northern Australia commenced in 1985 and increased after 1988 (Ref. 28207). It is focused on grounds on the North West Shelf, the Arafura Sea and in the northern region of the Gulf of Carpentaria (Ref. 28207), and has a large seasonal component caused by prawn trawlers converted to fish trawling during the closed seasons of the Northern Prawn Fishery (Ref. 28207, 27275). Spangled emperors are taken by domestic trawlers near Barrow Island and Glomar Shoal, Western Australia. Trap fishing began on the North West Shelf in 1984 (Ref. 28206, 27266). Fishing is carried out on hard-bottom areas to the west or inshore from main areas worked in the past by Taiwanese pair trawlers. It first concentrated on the Monte Bello-Barrow Island area mainly near the coastal towns of Onslow, Port Hedland and Point Samson (Ref. 27266, 28209). The main area for trapping is now north of Broome. Fish traps used in Western Australia are mostly circular ('O' traps) and are baited usually with pilchards (Sardinops neopilchardus). Spangled emperors are targeted by handline fishers on the west coast. A small quantity of emperors are also taken by dropline. Spangled emperors are the most abundant emperor caught in the North West Shelf Trap and Line Fishery, followed next in abundance by red-throat emperors, L. miniatus (Ref. 27266). In the shallow water (10-50 m) fishery in the Northern Territory, spangled emperors comprise up to 50% of the catch. Spangled and red-throat emperors are the only emperors of significance on the Great Barrier Reef although red-spot emperors are caught in fish traps on the outer slopes of mid-shelf reefs (Ref. 27260). Bottom fishing in Great Barrier Reef shallow lagoons at night catches mainly spangled emperors. Most fish from the North West Shelf fishery are sent to Perth as whole, chilled fish. Some are gutted and brined before freezing. Recreational fishery: Anglers also target spangled emperors to a lesser extent than red-throat emperors, both in Western Australia and Queensland. Emperors are caught with either fresh baits or whole or cut fish, crabs, prawns and squid, and tackle ranges from handlines to casting rigs. The largest emperor recorded by the Australian Anglers Association was 9.6 kg. from Queensland. Spangled emperors are the largest component of recreational angling in the Ningaloo Marine Park, Western Australia. The recreational fishery in that State extends from the Houtman Abrolhos to Dampier Archipelago. Resource status: Emperors comprised 47% of demersal fish in retained catches taken by Russian survey vessels on the North West Shelf between 1962 and 1973. Emperors and sea perch (Lutjanidae) comprised 40-60% by weight in 1962 but the amount dropped to about 10% in 1983 (Ref. 28206) (the emperor component of the total catch fell from 27.9% in 1967 to 5.4% in 1983 (Ref. 28006). This reduction in yield can partly be attributed to the removal of large epibenthos from the sea floor by the action of trawlers and to over-fishing these groups in the mixed species trawl fishery (Ref. 28206, 28207). The size composition also changed, with emperors (probably blue-spotted emperors) larger than 0.6 kg disappearing from the catch after 8 months of fishing (Ref. 28006). By 1986, the catch per unit of effort for emperors had declined by 65% from a peak in 1973. Whereas the abundance of emperors has continued to decline in trawled areas, the catch rate has increased since 1986 due to concentration of fishing effort on emperors by Taiwanese fleets (Ref. 28207). As of 1993, there have been no studies on the resource status of emperors on the Great Barrier Reef and inshore areas of northern Australia. Similarly, there is no information on the resource status of emperors in Western Australian fisheries. Also Ref. 2334, 13465.
National Checklist:
Country Information: https://www.cia.gov/library/publications/resources/the-world-factbook/geos/as.html
National Fisheries Authority:
Occurrences: Occurrences Point map
Main Ref: Kailola, P.J., M.J. Williams, P.C. Stewart, R.E. Reichelt, A. McNee and C. Grieve, 1993
National Database:

Common names from other countries

Classification / Names Common names | Synonyms | Catalog of Fishes (gen., sp.) | ITIS | CoL | WoRMS | Cloffa

Actinopterygii (ray-finned fishes) > Perciformes (Perch-likes) > Lethrinidae (Emperors or scavengers) > Lethrininae
Etymology: Lethrinus: Greek, lethrinia, a fish pertaining to genus Pagellus.

Environment: milieu / climate zone / depth range / distribution range Ecology

Marine; brackish; reef-associated; non-migratory; depth range 10 - 75 m (Ref. 2295).   Tropical; 34°N - 34°S, 25°E - 170°W

Distribution Countries | FAO areas | Ecosystems | Occurrences | Point map | Introductions | Faunafri

Indo-West Pacific: Red Sea, Persian Gulf and East Africa to southern Japan and Samoa. According to a genetic study (Ref. 28017), Lethrinus nebulosus and Lethrinus choerorynchus are two distinct species in Western Australia.

Length at first maturity / Size / Weight / Age

Maturity: Lm 39.4, range 41 - ? cm
Max length : 87.0 cm TL male/unsexed; (Ref. 47613); common length : 70.0 cm TL male/unsexed; (Ref. 5450); max. published weight: 8.4 kg (Ref. 40637); max. reported age: 28 years (Ref. 92312)

Short description Morphology | Morphometrics

Dorsal spines (total): 10; Dorsal soft rays (total): 9; Anal spines: 3; Anal soft rays: 8. Cheek without scales; 5-9 scales in supra temporal patch; inner surface of pectoral fin densely covered with scales; posterior angle of opercular fully scaled. Body color is yellowish or bronze, lighter below. Centers of many scales with a white or light blue spot. Sometimes irregular dark indistinct bars on sides and a square black blotch above pectoral fin bordering below the lateral line. Three blue streaks or series of blue spots radiate forward and ventrally from the eye. The fins are whitish or yellowish; the pelvic dusky, the edge of the dorsal fin is reddish. TL/SL relationship (cm): TL = 1.70 +1.24. Juveniles variable with blotches or stripe and changes with habitat (Ref. 48635).

Biology     Glossary (e.g. epibenthic)

Inhabit coral reefs, coralline lagoons, seagrass beds, mangrove swamps, flat sand bottoms, and coastal rock areas. Adults solitary or in small schools; juveniles form large schools in shallow, sheltered sandy areas, also harbors where seagrasses, algae or sponge habitats are found at various depths. Feed on echinoderms, mollusks and crustaceans, and to some extent on polychaetes and fish. The reproductive nature of spangled emperors is uncertain, although they also may be protogynous hermaphrodites (Ref. 27260, 55367). However, recent study classified juvenile hermaphroditism for this species wherein transition from ovary to testis occurs before ovarian maturation, hence, no true sex-reversal in the sense of protogynous hermaphroditism is observed (Ref. 107020). May have a coppery or iodine taste or smell in the Indian Ocean (Ref. 2295, 11888). It has been shown that this species can survive for long periods in salinities as low as 10 parts per thousand and therefore it is a potential estuarine aquaculture species (Ref. 2295). Utilized as a food fish.

Life cycle and mating behavior Maturity | Reproduction | Spawning | Eggs | Fecundity | Larvae

The reproductive nature of spangled emperors is uncertain,. Though they also may be protogynous hermaphrodites (Ref. 27260), a study on the Great Barrier Reef (Ref. 27264) found no clear evidence of sex change in spangled emperors within the size range 17-54 cm (Ref. 6390). Gonochorism is inferred for this species as sizes of males and females overlapped and male gonad morphology is typical of secondarily derived testes (Ref. 103751). Recent study classified juvenile hermaphroditism for this species wherein transition from ovary to testis occurs before ovarian maturation, hence, no true sex-reversal is observed (Ref. 107020). In the aquarium, pursuit of a female with a slightly swollen abdomen by a male signifies the start of mating. The male uses its mouth to bump and push the female's abdomen. Then eggs and sperm are released at the water surface (Ref. 58706).

Main reference Upload your references | References | Coordinator | Collaborators

Carpenter, K.E. and G.R. Allen, 1989. FAO Species Catalogue. Vol. 9. Emperor fishes and large-eye breams of the world (family Lethrinidae). An annotated and illustrated catalogue of lethrinid species known to date. FAO Fish. Synop. 125(9):118 p. Rome: FAO. (Ref. 2295)

IUCN Red List Status (Ref. 115185)

CITES (Ref. 115941)

Not Evaluated

CMS (Ref. 116361)

Not Evaluated

Threat to humans

  Reports of ciguatera poisoning (Ref. 31637)




Human uses

Fisheries: highly commercial; aquaculture: commercial; gamefish: yes
FAO(fisheries: production; publication : search) | FishSource | Sea Around Us

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Estimates of some properties based on models

Preferred temperature (Ref. 115969): 24.2 - 29, mean 28 (based on 1314 cells).
Phylogenetic diversity index (Ref. 82805):  PD50 = 0.5000   [Uniqueness, from 0.5 = low to 2.0 = high].
Bayesian length-weight: a=0.01660 (0.01383 - 0.01992), b=2.99 (2.95 - 3.03), in cm Total Length, based on LWR estimates for this species (Ref. 93245).
Trophic Level (Ref. 69278):  3.8   ±0.2 se; Based on diet studies.
Resilience (Ref. 69278):  Low, minimum population doubling time 4.5 - 14 years (K=0.09-0.16; tm=4-9; tmax=27).
Prior r = 0.42, 2 SD range = 0.2 - 0.92, log(r) = -0.87, SD log(r) = 0.39, Based on: 20 K, 10 tgen, 5 tmax, records
Vulnerability (Ref. 59153):  Moderate to high vulnerability (46 of 100) .
Price category (Ref. 80766):   High.