DUSKY CATSHARK

Taxonomy:

Phylum– Chordata

Class– Chondrichthyles

Order– Carcharhiniformes

Common Name– Ground Sharks

Family– Scyliorhinidae

Common Name– Catsharks

Genus– Bythaelurus

Species– canescens

Status: IUCN Red List DATA DEFICIENT

Average Size and Length: Adults measure at 59 cm/1.9 feet. The maximum recorded is 70 cm/2.3 feet.

Teeth and Jaw: The mouth is long and arched.

Head: The snout is short and rounded. The mouth reaches slightly in front of the eyes. The eyes are large and cat-like in appearance.

Tail: The tail is relatively short.

Demographic, Distribution, Habitat, Environment and Range: The Dusky catshark can be found in the southeast Pacific in Peru, Chile and the Straits of Magellan (2°S – 56°S, 81°W – 70°W). They are a deep-water species of shark, found on mud and rock of the upper continental slope between 820-2,297 feet. They are considered bathydemersal.

Diet: They feed on bottom invertebrates. There is a lot of stomach sample data from past research (however most samples were taken from juveniles). Their most important prey was reported to be the squid Loligo gahi, the siphonophore Sulculeolaria quadrivalvis, and the bony fishes Muggiea atlantica and Coelorhynchus fasciatus. Overall, the bulk mass consumed consisted of siphonophores. Other prey options such as octopus or crustaceans would depend on environmental availability, making the Dusky catshark a general bentho-demersal predator that eats what fits in its mouth. Its diet is similar to those of other Scyliorhinidae sharks in the Chilean deep sea which are opportunistic hunters. It is also possible it undergoes vertical migration while following its food source (Lopez, S.; Zapata-Hernández, G.; Bustamante, C.; Sellanes, J.; Meléndez, R. (2013-01-16). “Trophic ecology of the dusky catsharkBythaelurus canescens(Günther, 1878) (Chondrychthyes: Scyliorhinidae) in the southeast Pacific Ocean“. Journal of Applied Ichthyology. 29 (4): 751–756.) In a separate study, the deep-sea shrimp Heterocarpus reedi is reported to be the main food source for the Dusky catshark.

At an active methane seep off the coast of Chile, the Dusky catshark was reported to be one of the top predators, with a highly variable diet.

Aesthetic Identification: The Dusky catshark is a relatively large shark. It is plain dark brown with no markings on adults. The young do have white fin tips. There are two small dorsal fins. The first dorsal fin base is over the pelvic fin bases. The anal fin is almost as large as the second dorsal fin.

Biology and Reproduction: They are oviparous. They lay pairs of eggs. They drop egg cases on the sea floor or attached to rocks. They are shaped like purses and carried two at a time, one in each uterus.

An egg case is light yellow-brown, and darken to brown after fixation to the sea floor. The capsule is slightly translucent, elongated and flattened, and ridged lengthwise, with a long tendril extending from each corner. Fixation occurs by two of the four tendrils, with two strong, coiled posterior tendrils designed to hold onto substrate. Development occurs after the egg has been laid, with no aid from the parents. Accurate measurements of the egg cases have not been recorded.

Behavioral Traits, Sensing and Intelligence: Unknown, but could be considered an important mesopredator.

Dusky Catshark Future and Conservation: There is not enough data to evaluate, however they are common in deep water. They have been abundant bycatch of deep-water trawls. Statistics show that the Dusky catshark has made 20.3% of total catch.

Dusky Catshark Recorded Attacks on Humans: Not a threat to humans.