Shark Spotlight Jordan’s Chimaera

Written by Michelle Scott Jordan’s Chimaera

Taxonomy

The Order Chimaeriformes (subclass Holocephali) includes 53 species from six genera and three families. The long-nosed chimaeras (family Rhinochimaeridae) contain eight species from three genera. The short-nosed chimaera (family Chimaeridae) includes 42 species from two genera, and the plow-nosed (family Callorhinchidae) has three species from one genus. Chimaeras are also often referred to as ‘ghost shark’, ‘rabbitfish’, ‘ratfish’, and ‘spookfish’. The taxonomy of the Chimaeriformes is not well understood, mainly due to the high levels of endemism, offshore distributions of many species, and the fact that many inhabit deep waters, meaning they are rarely encountered and hence challenging to sample.

Morphology

In Greek mythology, the Chimaera was a terrifying creature. Depicted with the body and head of a lion, the head of a goat protruding out of its back and the tail of a serpent or dragon, the Chimaera was a fanciful creature of the imagination. It is therefore clear to see how the Chimaeriformes were named. Their morphology is as fanciful as the mythical Chimaera. The Chimaeriformes are characterised by long tapering bodies leading to ‘rat-like’ tails. The group is recognisable for the incisor-like anterior tooth plates and large nostrils, which give the appearance of a rabbitlike mouth. The common name “rabbitfish” is often applied to members of this family. They range in total length from 0.6 – 1.5 m. Adult chimaeras are scaleless.

Jordan’s Chimaera (Chimaera jordani, Tanaka, 1905) belongs to the family Chimaeridae. The species is even brown to dark black in colour. It has a blunt, fleshy snout that is slightly pointed at the tip. Its body tapers down to a whiplike tail. An anal fin is present in this species, separated from the ventral caudal fin by a notch. It reaches a maximum size of at least 93 cm total length. Like other chimaeras, it is oviparous and lays eggs. The lateral line of Jordan’s Chimaera is straight with very little sinuation along its length.

Range and Distribution

Chimaeras tend to be deepwater fishes generally inhabiting the shelves and slopes off continental landmasses. They typically occur at depths of 500 m or deeper. Jordan’s Chimaera has been recorded at depths of 716–780 m, but its full depth range remains uncertain. Its known deep distribution beyond the reach of most regional fishing activities has resulted in it being rarely encountered. The species is known from only a limited number of specimens collected from eastern Honshu, Japan, in the Northwest Pacific Ocean. Surveys of deepwater chondrichthyans from 2000–2002 and 2005–2008 from the region and surrounding areas failed to find additional specimens.

Conservation measures and IUCN Red List status

Jordan’s Chimaera has been assessed as Data Deficient on the IUCN Red List of Threatened Species. The distribution and depth range of the species mean it is only known from a few specimens. The limited data available makes it difficult to assess the species beyond Data Deficient. With a large proportion of chimaeras being assessed as Least Concern (69%), it would be easy to assume that there is no urgent need for action regarding Data Deficient species. However, the high levels of endemism displayed by species like Jordan’s Chimaera and the lack of data from dedicated deepwater chondrichthyan surveys indicate a need to assess the current status of the population in order to monitor and manage the species. There are no known commercial uses for Jordan’s Chimaera, though it may be consumed locally. For most chimaera species, there is a lack of catch reporting as most species are caught as bycatch and discarded, not reported at the species level, or not reported at all. More data are required regarding species abundance and population as well as the effects of fishing and incidence of bycatch to determine if fishing is causing population reductions.

References Finucci, B., Cheok, J., Ebert, DA., Herman, K., Kyne, P.M. & Dulvy. (2020) Ghosts of the deep – Biodiversity, fisheries, and extinction risk of ghost sharks. Fish and Fisheries. 22: 391–412. DOI: 10.1111/faf.12526 Finucci, B., Tanaka, S. & Kyne, P.M. (2020) Chimaera jordani. The IUCN Red List of Threatened Species 2020: e.T60184A124449238. DOI 10.2305/IUCN.UK.2020-2.RLTS.T60184A124449238. en. Downloaded on 18 August 2021.

Jordan’s Chimaera (Chimaera jordani) lateral male