| Lethrinidae (Emperors or scavengers), subfamily: Lethrininae |
| 87 cm TL (male/unsexed); max.weight: 8,400.0 g; max. reported age: 28 years |
|
reef-associated; brackish; marine; depth range 10 - 75 m, non-migratory |
| 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. |
|
Dorsal spines (total): 10-10; Dorsal soft rays (total): 9-9; Anal spines: 3-3; Anal soft rays: 8-8. This species is distinguished by the following characters: body moderately deep, its depth 2.5-2.9 times in standard length; head length 0.9-1 times in body depth, 2.6-3.1 times in SL, dorsal profile near eye nearly straight, or in large individuals, distinctly concave; snout moderately long, its length about 1.8-2.4 times in HL, measured without the lip the snout is 0.8-1 times in cheek height, its dorsal profile nearly straight or concave, snout angle relative to upper jaw between 50° and 68°; interorbital space usually convex; posterior nostril an oblong longitudinal opening, closer to orbit than anterior nostril or, about halfway between orbit and anterior nostril eye not close to dorsal profile except in small individuals, its length 3.6-5.9 times in HL; cheek moderately high, its height 2.4-3 times in HL; lateral teeth in jaws rounded with points or molars that often have tubercles; outer surface of maxilla smooth or with a longitudinal ridge; D X, 9 with the 4th or 5th dorsal-fin spine usually the longest, its length 2.7-3.6 times in body depth; A III,8 with the first soft ray usually the longest, its length almost equal to or slightly shorter than length of base of soft-rayed portion of anal fin and 1.3-1.6 times in length of entire anal-fin base; pectoral-fin rays 13; pelvic-fin membranes between rays closest to body usually with dense melanophores; cheek without scales; 46-48 lateral-line scales; 5 ½ scale rows between lateral line and base of middle dorsal-fin spines; 16-17 scale rows in transverse series between origin of anal fin and lateral line; usually 15 rows in lower series of scales around caudal peduncle; 5-9 scales in supratemporal patch; inner surface of pectoral-fin base densely covered with scales; posterior angle of operculum fully scaly. Colour of body 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 fins bordering below lateral line; 3 blue streaks or series of blue spots radiating forward and ventrally from eye; fins whitish or yellowish, pelvic fins dusky, edge of dorsal fin reddish. Juveniles variable with blotches or stripe and changes with habitat (Ref. 114226). |
| 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). Taken by handline, traps, trawls, seines, and gill nets. Marketed mostly fresh. Very important commercial and sport fish in some countries (Ref. 68703). |
|
Least Concern (LC); Date assessed: 09 March 2015 Ref. (130435)
|
| reports of ciguatera poisoning |
|
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. |
Source and more info: www.fishbase.org. For personal, classroom, and other internal use only. Not for publication.
