Common name: Brotulas, Cuskfishes, Live-bearing Brotulas


A diverse family of live-bearing fishes, differing mostly from the similar ophidiids, in having internal fertilization and associated copulatory organs. While many species are found in deep-sea habitats, other small, secretive species shelter in crevices occur on shallow reefs. Some species inhabit fresh and brackish waters.
Species are difficult to identify as the structure of the male reproductive organ is the most important diagnostic character, along with scale patterns on the head.

Cite this page as:
Dianne J. Bray, 2012, Live-bearing Brotulas , BYTHITIDAE, in Fishes of Australia, accessed 29 May 2016,

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Family Taxonomy

Family with more than 170 described species in about 48 genera.

Family Distribution

Worldwide, marine, rare in fresh or brackish waters; benthic mostly in shallow reef areas, others on continental shelf and slope, several species at abyssal depths, several to about 2000 metres. Some species inhabit caves and sinkholes.

Family Description

Body elongate, eye small, anterior nostril immediately above upper lip mouth large, opercle usually with strong spine, first gill arch rarely with more than 7 long rakers, head pores present. Dorsal and anal fins long-based, continuous with caudal fin in subfamily Bythitinae, separate from caudal in Brosmophycinae; pelvic fins reduced, slightly before pectoral fin base, with single ray or absent. Scales, swim bladder and pyloric caecae present. Male copulatory organ variable.

Family Size

Reach 2 m in length, but most are smaller than 13 cm; many coral reef species only reach 5-10 cm.

Family Feeding

Known to feed on a range of invertebrates and fishes; some species feed mostly on small benthic crustaceans (amphipods and isopods) and polychaete worms.

Family Reproduction

Bythitids are live bearers (ovoviviparous) and males possess a copulatory organ for internal fertilization. Larvae are rare, with some collected near the bottom, while others are epipelagic. The larvae are generally unspecialised with a short pelagic phase; gut short, coiled, dorsal and anal fins long-based, some species relatively large at birth.

Family Commercial

Of no commercial importance.

Family Remarks

Some species inhabit fresh to highly saline limestone caves and sink-holes and are blind or partially blind.


Dianne J. Bray


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