Topic: Rabbit fish

The chimaeras diverged from other cartilaginous fishes early in the group’s evolutionary history. They have retained characteristics of cartilaginous fishes: they have a cartilaginous skeleton, and mature males possess two claspers used to internally fertilize females. Females lay egg cases known as Mermaid’s purses. In other ways, they resemble bony fishes: they have gill coverings called opercula and their upper jaw is fused to the head.

The rabbit fish, also known as the rat fish, is one of around 40 known chimaera species. This species occurs in deep areas of the continental shelf and along the continental slopes across the Northeast Atlantic, but also in parts of the Mediterranean and off Northwestern Africa. They are commonly found between 300–500 m deep. Its large eyes and head, long tapering tail, and mottled golden-brown coloration make it easy to identify. It has a lateral line that branches out onto the head, and a large dorsal spine that is mildly venomous.

Unlike many sharks that have sharp and regenerating teeth, chimaeras have teeth that are fused into beak-like plate structures, which they use to feed on primarily bottom-dwelling invertebrates, though larger individuals may also eat fish. Their pectoral fins are also large and wing-like, and they use these to elegantly ‘fly’ through the water. It’s perhaps not surprising that they’ve been named Chimaeras, in reference to the Greek mythological creature composed of different animal parts.

Population status, fishery and management

There is no longer a directed commercial fishery for rabbit fish, and today catches are mostly restricted to bycatch in trawl fisheries. Historically the species was sought after for its large oily liver, as was the case for several other cartilaginous fish species.

Rabbit fish is not directly monitored or managed, so our knowledge of its biology and population structure are limited. Nonetheless, we frequently encounter rabbit fish on our seagoing surveys in the Skagerrak and along the coasts of central and northern Norway. Their abundance on these surveys has been stable over the past decade. Landings have increased since the 2000s and have remained around 200 t per year in Norwegian waters over the past decade. Attempts have been made to estimate their age based on growth rings in their dorsal spine, but these do not seem to necessarily correlate with age.