Chimaeriformes

## Defining Features

Sometimes referred to as “ghostfish” or “ratfish”, Chimaeriformes are identified by a fleshy operculum that covers a single gill opening. They have a grinding tooth plate and  an immobile upper jaw that is fused to the skull. They have seperate anal and urogential openings and lack a stomach. Males possess a retractable clasper  on the head and paired claspers on the pelvic fins. They are oviparous. Most species have a large head and a whip-like tail.

## Habitat and Range

Chimaeras are deep sea fishes. They are demersal species typically located near ocean floors nearing 200-2,600 m in depth; although, a few species are found in waters shallower than 200 m. Two families are found in temperate and tropical oceans worldwide, although members of the Callorhinchidae family are ounly found in the Southern Hemisphere.

## Fisheries Conservation and Concern

The status of many species is unknown because they live in deep waters. Most are not target species, but some are occasionally caught as bycatch in deep sea fisheries. The lack of data regarding longevity, age at maturity, growth, reproductive rates, and population structures means that some species may be subject to overharvesting.

## Closest Relatives

Elasmobranchii OR Batoidea + [Squaloidea+Galoidea]

## Example Species in Chimaeriformes

### Spotted Ratfish

#### *Hydrolagus colliei*

Defining Features: The spotted ratfish can reach up to 97 cm in total length, including its long tail. It has iridescent brown or gray skin with white spots. There is a venomous spine anterior to the first dorsal fin.

Range & Habitat: The spotted ratfish is located in the Northeast Pacific Ocean from Baja California to Alaska. It is marine oceanic and neritic occurring at depths of 0 - 913 m.

IUCN Concern: This is a species of least concern, but it is a source of bycatch in some deep sea fishing operations.

### Elephantfish

#### *Callorhinchus milii*

Defining Features: The elephantfish possesses a long, flexible, fleshy snout that is used to probe the seafloor for prey. The remaining body is somewhat flattened. It is black or brown in color.

Range & Habitat: The elephantfish is located in the Pacific Ocean surrounding Australia and New Zealand. It is a marine neritic species occurring inshore at depths < 200m.

IUCN Concern: This is a species of least concern. In Australia it is often caught as bycatch, but in New Zealand there is an apparently stable, target fishery.

## Example Species in the Gulf of Maine

### Atlantic Longnose Chimaera

#### *Rhinochimaera atlantica*

Defining Features: The Atlantic longnose chimaera can reach up to 140 cm in total length. It possesses a long, flattened, narrow snout. It is whitish to light brown in color.

Range & Habitat: The Atlantic longnose chimaera is marine oceanic and is widely distributed on the Atlantic’s continental slopes at depths of 500 to 1500 m.

IUCN Concern: The Atlantic longnose chimaera is listed as a species of least concern. It is occasionally caught as bycatch in deepwater trawls, but there is no data to indicate population impacts. Specimens are primarily recovered in research trawls.

## References

Chondrichthyan Tree of Life: sharksrays.org

Florida Museum of Natural History: floridamuseum.ufl.edu

IUCN Redlist: iucnredlist.org

Fish Base: fishbase.org

Aquamaps: aquamaps.org