Blackmouth Catshark: Galeus melastomus

Family: Pentanchidae

Common names

Blackmouth Catshark.

Binomial

Galeus melastomus.

Synonyms

Galeus melanostomus, Pristiurus melanostomus, Pristiurus melastomus, Pristiurus souverbiei, Scyllium artedi, Scyllium artedii, Scyllium melanostomum, Squalus annulatus, Squalus delarochianus, Squalus prionurus.

Identification

Slender body. Snout pointed. First dorsal origin approximately level with pelvic fin insertion. First and second dorsal fins of equal size, with a pointed apexes. Pectoral fins large. Anal fin very long; extending from level of first dorsal insertion to origin of caudal fin. Caudal fin has a distinct row of enlarged dermal denticles along upper margin. Dorsal coloration predominantly brown with a vivid pattern of large and small brown circles, edged in white. Circles form rows extending from head to tip of tail. Larger animals have more intricate patterns with a greater amount of circles within each row. Fins dark blueish-grey with vague pale circles and pale margins.

Size

Galeus melastomus is one of the largest sawtail catsharks. Maximum length 90cm (Compagno et al. 2005). This record is questionable since other researchers list vastly smaller maximum sizes of 62-67cm (Rey et al. 2002, Costa et al. 2005). Size at birth unknown.

Blackmouth Catshark, Galeus melastomus. A relatively deepwater catshark from Iceland to Senegal including the Mediterranean Sea. Trondheim Fiord, Norway.

Conservation Status

LEAST CONCERN

Although the Blackmouth Catshark is taken as bycatch by demersal trawls and longlines throughout large areas of its geographic range, it is generally discarded. In European waters, it remains one of the most abundant shark species. West African populations are of more concern due to largely unregulated fishing, but over all the population seems to be stable.

Habitat

Rocky, sandy or muddy substrates on outer continental shelf. Usually remains on bottom or close to it. Mostly found between 200-500m. Listed as occurring between 55-1000m, but regularly encountered in certain Norwegian fiords between 25-40m even when no chum is used.

Distribution

The blackmouth Catsharks is present in the Northeast Atlantic Ocean and Mediterranean Sea. From the Faroe Islands and Southern Norway southward to the Azores and Senegal.

Reproduction

An oviparous species, laying up to 13 egg cases. Egg production occurs year round. Hatching occurs mainly in spring and summer.

Diet

Hunts for bottom dwelling invertebrates (shrimps, cephalopods, etc) and small bony fishes including lanternfishes.

Behavior

Little is known about blackmouth catshark behavior. Forages over substrate in search of food, sometimes seen resting in areas where an abundance of food is available i.e. near fish and scallop farms.

Reaction to divers

Fairly easy to approach when resting on the sea floor. Will bolt if approached to quickly or aggressively.

Diving logistics

Rarely encountered south of Norway. Although normally found in water too deep for recreational diving, in certain Norwegian fiords e.g. Namsen Fiord and Trondheim Fiord, run-off at the surface creates a layer of silty water that significantly lowers the light level in the water below it.
In these areas, blackmouth catsharks and other deepwater species (such as velvetbelly lantern sharks), are found much closer to the surface than elsewhere.
Blackmouth Catsharks can often be seen when exploring certain reefs within these fiords but they are even easier to see and approach when bait is introduced.