Rabbitfish  (Chimaera monstrosa)

The rabbitfish is classified as Near Threatened (NT) on the IUCN Red List (1).

An unusual relative of sharks, the rabbitfish (Chimaera monstrosa) is a deep-dwelling fish with a strange, yet distinctive appearance (2) (3). Also known as the rat fish, the body tapers from a short, conical mouth and a large, blunt head to a greatly elongated whip- or rat-like tail (3) (4). The first, tall dorsal fin is triangular-shaped and sits behind an even higher spine that is connected to a poison gland, and the second dorsal fin stretches continuously to the tail fin (2) (4). The body is blue or greenish-silver in colour on the back and sides, often mottled with brown spots and stripes or a net pattern, the undersides are cream, and the fins are greyish (4). The rabbitfish is a weak swimmer, and rather than using side-to-side body movements to power itself forward like most fish, it swims by flapping the large, broad pectoral fins, making the body bob up and down in a clumsy fashion (3).

The rabbitfish is widely distributed across the northeast and eastern-central Atlantic Ocean and western Mediterranean Sea, ranging from the southern Arctic to Morocco, including the Azores and Madeira Islands (1) (2) (4).

The rabbitfish is typically found near the sea floor of continental slopes between depths of 300 and 500 metres, although it has been recorded at a depth of 1,663 metres. In the southern-most parts of its range it is largely found in deeper waters, but in northern areas it migrates during the summer to inshore waters of 40 to 100 metres depth (1) (2) (4).

Living near the sea bed at great depths, the rabbitfish has a number of adaptations to this environment, including large eyes that allow it to see in low light levels and fused teeth, which form crushing plates and enable it to feed on hard, shelled prey such as crustaceans and molluscs (3). It is a rather sluggish, slow-moving species and typically resides in small groups (2). 

Very little is known about the reproductive biology of the rabbitfish, but it is thought to breed slowly, with a slow growth rate, long life expectancy and a high age at which it reaches maturity (1). The male fish has a special clasping appendage on the forehead that is used to hold the female during mating, which is thought to occur in spring and summer (1) (3). The young fish hatch from eggs and start to resemble the adult fish in appearance when they reach ten centimetres in length. Female rabbitfish are thought to reach maturity at 11 years of age, while males reach maturity at 13 years (1) (2).

Large tracts of the Northeast Atlantic are currently subject to intensive deepwater fishing activities with the demand for such fisheries increasing. Regulation, however, is often lacking, leading to concerns that many fish species are being captured at unsustainable rates. The rabbitfish is potentially at great risk from these activities and is regularly captured incidentally in fisheries targeting other deepwater species. Smaller fish are typically discarded back into the water, but as the rabbitfish is a deepwater-dwelling species, it is unlikely that many fish survive the experience. Off the west coast of Ireland, the rabbitfish comprises 13 to 15 percent of all discards from deepwater trawlers, while it was the most heavily captured cartilaginous fish (Chondrichthyes) in a studied French bottom-trawl fleet. The increasing interest in the use of rabbitfish oils in dietary supplements for human consumption also means that demand for the fish is likely to increase (1).  

A ban on deepwater trawling below 1,000 metres that was enforced in the Mediterranean Area in 2005 may have afforded the rabbitfish some degree of protection from fishing, but as the bulk of the species’ population is at depths less than this, the extent of the protection received is unknown (1) (5). It is, therefore, still highly vulnerable to fisheries, and both present and future fishing pressures are likely unsustainable. To develop informed conservation measures, a priority for the rabbitfish is further studies investigating catch rates and population trends, as well as studies into its biology and habitat preferences. National and regional action plans should also be developed so as to promote the conservation and sustainable management of this peculiar species (1).

ARKive is supported by OTEP, a joint programme of funding from the UK FCO and DFID which provides support to address priority environmental issues in the Overseas Territories, and Defra

To find out more about the conservation of fish, see:

• Fish Online:
  http://www.fishonline.org/