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    Bugs are a flat lobster-like animal with a hard external shell which turns red when cooked.

    Bugs are also known as Balmain bugs or Moreton Bay bugs and are often cut in half, drizzled with oil/butter, seasoned with salt and pepper and cooked on the barbeque in their shell.

    Scientific name: Ibacus peronii

    Family: Scyllaridae

    Other names: Butterfly fan lobster, eastern Balmain bug, slipper lobster, shovelnose lobster, flapjack, flying saucer

    Description: Balmain bugs have broad, flat bodies and a large carapace. The body is reddish-brown in colour. They have broad, short antennae and five pairs of legs. Balmain bugs have no claws. The eyes are set closely together at the front of the head.

    Size (length and weight): Up to about 25 cm in length (sometimes longer) and about 0.4 kg. Females grow larger than males.

    Life span: Up to 18 years.

    Habitat: Balmain bugs inhabit soft sand and muddy environments on the sea floor. They are found at depths from 15-650 metres, but are most commonly found at depths of about 150 metres. Balmain bugs are relatively sedentary, with recaptures within five kilometres after 10 years. They are mainly active at night.

    Prey: Small crustaceans and algae.

    Predators: Larger fish.

    Reproduction: Balmain bugs reach reproductive maturity at about 2 years of age. The main spawning period appears to occur in winter and early spring, with a secondary spawning period during December. During the spawning period, the male deposits a spermatophore (sperm package) on the female’s abdomen. It is thought that fertilisation occurs externally, when the female attaches the egg mass to the pleopods (‘swimming legs’) underneath the abdomen for brooding. The eggs are brooded for 3‑4 months. Fecundity per brood ranges from 5000‑37 000 eggs depending on the size of the female.

    Scientific name: Thenus australiensisT. parindicus

    Family: Scyllaridae

    Other names: Flathead lobster, bug, slipper lobster, squat lobster, reef bug

    Description: Moreton Bay bugs have flattened bodies with a rough carapace. They are brown overall and ‘a bit furry’, with five pairs of legs. T. parindicus (‘mud bug’) have vertically striped legs and T. australiensis (‘reef bug’) have spotted legs. Moreton Bay bugs are sometimes confused with Balmain bugs, but have a wider body and eyes set broadly apart on either side of the shell.

    Size (length and weight): Up to 25 cm in length and 0.56 kg. Commonly found at about 0.12 kg in weight. Growth slows as age increases.

    Life span: Up to 4 years for the mud bug and 8 years for the reef bug.

    Habitat: Moreton Bay bugs are found on mud and sandy substrates on the sea floor. They are found at depths from 8‑100 metres, but are more commonly found at 10‑50 metres. Reef bugs are generally found in water depths of 26‑60 metres, while mud bugs usually occur in depths of less than 25 metres. Moreton bay bugs are highly mobile. They are mainly active at night and remain buried on the sea floor during the day.

    Prey: Fish, crustaceans and molluscs.

    Predators: Bony fish, shovel-nosed rays and stingrays.

    Reproduction: Moreton Bay bugs reach reproductive maturity at 1‑2 years of age. Mud bugs mature at a slightly smaller size than reef bugs. Females usually spawn twice during the summer, with about three months between spawnings. During the spawning period, the male deposits a spermatophore (sperm package) on the female’s abdomen. It is thought that fertilisation occurs externally, when the female attaches the egg mass to the pleopods (‘swimming legs’) underneath the abdomen for brooding. The eggs are incubated for about 1 month in a brood chamber formed by the tail fan and the abdominal sections. Fecundity ranges from 4000-20 000 eggs for mud bugs and 5000‑45 000 eggs for reef bugs, depending on the size of the female.

    Other notes: Previously known as T. orientalisT. orientalis was split into five separate species in 2007. T. orientalis is restricted to the Asian region. T. australiensis is found north of Fraser Island to the Torres Strait. T. parindicus is found across northern Australia.

    Fishery found in Gear used Catch of species is targeted or incidental
    Western Deepwater Trawl Fishery Bottom trawl Targeted
    Northern Prawn Fishery Bottom trawl Incidental
    Southern and Eastern Scalefish and Shark Fishery Bottom trawl Incidental

    AFMA manages the catch of bugs by limiting the number of vessels allowed to fish. There is a low level of fishing in the Western Deepwater Trawl Fishery and only a small amount of bugs are caught each season.

    Catch triggers have been developed to control the catch of bugs and potentially limit negative impacts on other marine species assessed as high-risk. We monitor the level of catch and if it reaches a certain level a review of the management arrangements is triggered.

    Commercial fishers record their catches in logbooks, during each fishing trip.

    AFMA also has requirements for carrying scientific observers and satellite tracking of fishing vessels.

    Bugs live in deep water and, depending on the species, can be found all around the Australian coast.

    Balmain bugs can be found in colder waters from the Queensland/New South Wales border south to central Western Australia, including the east coast of Tasmania and Bass Strait.

    Moreton bay bugs are distributed along the tropical and subtropical coast of Australia from northern New South Wales along the north coast to Shark Bay in Western Australia.


    Balmain bugs distribution map

    Balmain bugs distribution map



    Moreton Bay bugs distribution map
    Moreton Bay bugs distribution map

    Bugs are only targeted in the Western Deepwater Trawl Fishery using trawl nets. There have been very low levels of fishing effort within the fishery over recent years (average of 27 fishing days annually since 2009).

    Sometimes, bottom trawling can accidently catch unwanted species of fish. This is known as bycatch and it is recorded by on-board fishery observers for review by the fishery managers. This information is used to assess and manage the risks of fishing on the marine environment.

    The Harvest Strategy for the Western Deepwater Trawl Fishery is part of the management framework and sets rules for managing the fishery to maintain sustainability. The strategy sets specific levels of effort and catch, which if exceeded, trigger a management response.

    The Western Deepwater Trawl Fishery Bycatch and Discard Workplan contains management measures to monitor and reduce interactions with high risk, protected species. Impacts on protected species and impacts to the sea floor have not been of concern in this fishery because of the low amount of fishing in recent years.



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    Page last updated: 15/02/2023