Common name: Pearlfishes


A group of highly specialized eel-like fishes fishes living in depths ranging from shallow coastal to moderately deep continental slope waters As adults, most species are either commensal or parasitic in an invertebrate host. Although some species are free-living, members of the genera Onuxodon, Carapus and Encheliophis usually live inside invertebrate hosts, including sea-cucumbers, sea-stars, bivalve molluscs and ascidians. Some species are commensal and leave the host to feed, whereas others are parasitic, feeding on the internal organs of their host. One species is pelagic in deepwaters. 

Cite this page as:
Dianne J. Bray, Pearlfishes, CARAPIDAE in Fishes of Australia, accessed 04 Mar 2024,

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Family Taxonomy

Seven genera and 34 species in three subfamilies. Seven genera with 17 described species are known from Australian waters.

Family Distribution

Worldwide in all tropical and subtropical oceans; mostly benthic in shallow to moderately deep waters on the continental slope to 2000 m; (rarely pelagic or epi-benthic in deepwater).

Family Description

Adults - body long, slender, tapering, compressed to rounded; head large, eye subequal to snout length, mouth large, terminal, jaws extending well beyond eye, teeth either fang-like or heart-shaped; supramaxilla absent; gill openings wide, extending far forward; opercular bones without spines. Dorsal and anal fins long-based, anus and anal-fin origin far forward, usually below pectoral fin base; caudal fin usually absent, dorsal and anal fins continuous, tapering to a firm tip, allowing tail-first entry to host; anal-fin rays longer that those of dorsal fin; pectoral fin shorter than head, pelvic fins absent in most, or reduced to a single ray. Scales absent.

Family Size

Maximum length 36 cm.

Family Feeding

Carnivores. Although some species are free-living, most are commensal or parasitic on an invertebrate host. Some leave the host to prey on polychaete worms, rustaceans and small fishes. Other species are parasitic, always remaining inside to feed on the internal organs of the host, mostly the gonads and the respiratory tree.

Family Reproduction

The sexes are separate and fertilisation is external. Reproduction and early life history is poorly known for most species.Oviparous - the eggs of most species are undescribed. Eggs small, up to 1 mm in length, oval or ellipsoid, laid in a gelatinous raft, single oil globule present, yolk segmented. Larvae conspicuous, extremely elongate, 2.6-6.0 mm at hatching, with two distinct larval stages - the first, a planktonic vexillifer stage, characterized by larvae possessing a peculiar long, movable, ornamented predorsal filament or vexillumexillum; the second tenuis stage is demersal (possibly absent in the free-living species). In the tenuis stage, the vexillum is absent, the total length is reduced and individuals can enter the host at this stage.

Family Commercial

Although pearlfishes are taken as bycatch in some sea cucumber fisheries, they are of no commercial importance.

Family Conservation

The IUCN Redlist status of several species has been evaluated.

Family Remarks

The unique assocation of pearlfishes and invertebrate hosts may include male-female pairing within the same host, cannibalism and parasitism on various internal organs such as the gonads or respiratory tree. In addition, several species may be commensal on the same holothurian host.


Dianne J. Bray


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Gomon, M.F. 2008. Family Carapidae. pp. 350-351 in Gomon. M.F., Bray, D.J. & Kuiter, R.H (eds). Fishes of Australia's Southern Coast. Sydney : Reed New Holland 928 pp.

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Nielsen. J.G. 1999. Families Carapidae, Ophidiidae, Bythitidae, Aphionidae. pp. 1978-1985 in Carpenter, K.E. & Niem, V.H. (eds). The Living Marine Resources of the Western Central Pacific. FAO Species Identification Guide for Fisheries Purposes. Rome : FAO Vol. 3 1397-2068pp.

Nielsen, J.G. 1999. Family Carapidae: Pearlfishes, pp. 1978 In Nielsen, J.G., Cohen, D.M., Markle, D.F. & Robins, C.R. (Eds.), FAO Species Catalogue, Vol. 18, Ophidiiform Fishes of the World (Order Ophidiiformes), An annotated and illustrated catalogue of pearlfishes, cusk-eels, brotulas and other ophidiiform species known to date. FAO Fisheries Synopsis No. 125 Vol. 18 178 pp.

Olney, J.E. 2006. Ch. 50 Carapidae: Pearlfishes, p. 749 In W.J. Richards (ed). Early Stages Of Atlantic Fishes: An Identification Guide For The Western Central North Atlantic. CRC Press, Taylor and Francis Group, Boca Raton, FL, 2640 pp.

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