Is Roughskin Dogfish a freshwater species? What we know of as first-ever live footage captured

The roughskin dogfish, scientifically known as Centroscymnus owstonii, is not a freshwater species. This shark is primarily found in marine environments, specifically inhabiting deep waters over the upper continental and insular slopes. The average depth of its habitat is between 700 and 1,970 feet (or 214 to 600 meters) into the ocean.

The species is found in various geographical zones: the western Atlantic Ocean from North Carolina to the Florida Keys, the northern Gulf of Mexico, the southeast Pacific, and some parts of the Indian Ocean.

Recently, scientists recorded the first-ever live footage of the roughskin dogfish. This historical event was performed in the region of the Cayman Islands, and these researchers made a systematic study of the deep-seabed communities.

An underwater camera was deployed to a water depth of about 3,500 feet (approximately 1,067 meters), and it was filled with sardines to attract animals.

Several members of this now rarely sighted species swam across and in front of the camera giving the researchers some ideas as to where they might be found and what they might be doing. The recording was described as a breakthrough in understanding this normally cryptic predator, often only seen as bycatch in fishing operations.

The findings were published in the Journal of Fish Biology, thus being a valuable contribution to the information about the distribution of the roughskin dogfish in the central Caribbean.

More about roughskin dogfish

The roughskin dogfish is one of the less-known species of sharks from the family Somniosidae. The species lives mostly in deep marine habitats and has gained much attention due to its special characteristics and ecological function.

The roughskin dogfish is a deep-sea fish, distributed around the world, mainly on continental shelves in tropical, subtropical, and temperate seas. Its depth range is from 100 to 1,500 meters (approximately 328 to 4,921 feet) below sea level. This species is found in the following oceanic regions:

• The western and eastern Indian Ocean
• The south-central Atlantic Ocean
• The South Pacific Ocean, especially around Tasmania

The roughskin dogfish is usually reported to have a maximum length of about 121 centimeters, that is, around 4 feet. It possesses a fairly long snout and an elongated trunk that doesn't taper abruptly after the pectoral area.

This shark has black or dark brown skin coloration. Its large, lateral trunk denticles have smooth, round crowns in adults as well as subadults.

Its teeth are unique; the upper teeth are lanceolate while the lower teeth are bladelike with short, oblique cusps.

The roughskin dogfish is an apex predator in its environment. It preys on various fish species, but it also consumes lesser amounts of crustaceans and cephalopods. Some prey items include hoki (Macruronus novaezelandiae) and mesopelagic fish like sea bream (Beryx spp.) and slender tuna (Allothunnus fallai).

It appears that Centroscymnus owstonii is ovoviviparous since eggs develop inside the womb of the female, thus offspring are born alive. They are born in a range of 16 to 28 young, which come approximately 27 to 30 centimeters (about 10.6 to 11.8 inches in length). Males attain sexual maturity at approximately 70 to 79 cm, while females start reproducing at around the time of maturity at about lengths of 82 to 105 cm.

The New Zealand Department of Conservation classifies the conservation status of the roughskin dogfish as Not Threatened under its Threat Classification System. However, this species is listed as Data Deficient by the International Union for Conservation of Nature (IUCN), meaning there is not enough data available to assess it properly against extinction risk.

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The importance of Centroscymnus owstonii as an in situ predator within the communities of deep-sea settings cannot be underestimated in this ecosystem. It largely impacts the biomass and assemblage similarity at depths that fall between 750 to 2,050 meters, sometimes occupying more than 60% of the total biomass within specific areas.

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