BLACKTIP SAWTAIL CATSHARK

You can spot it by its dark fin tips and uniform coloration

The Blacktip Sawtail catshark (Galeus sauteri) is a species of catshark belonging to the family Scyliorhinidae. It is found off the coasts of Taiwan and the Philippines, found deeper than 197 feet. They are slim bodied, somewhat small and are characterized by its plain brownish dorsal coloration with dark tips on the dorsal and caudal fins, and a prominent crest of enlarged dermal denticles on the upper edge of the caudal fin.

 

Family: Scyliorhinidae – Catsharks

Genus: Galeus 

Species: sauteri

Taxonomy:

Phylum– Chordata

Class– Chondrichthyles

OrderCarcharhiniformes

Common NameGround Sharks

Family– Scyliorhinidae

Common NameCatsharks

GenusGaleus

Speciessauteri

Status: IUCN Red List DATA DEFICIENT

Average Size and Length: Adult males have been measured between 36-38 cm/1.1-1.2 feet. Adult females have been measured between 42-45 cm/1.4-1.5 feet. The maximum recorded has been 45 cm/1.5 feet.

Current Rare Mythical Sightings: In 1906, the Carnegie Museum purchased an extensive collection of fishes assembled from the markets of Takao (Kaohsiung), Taiwan by Hans Sauter. American ichthyologists David Starr Jordan and Robert Earl Richardson described several new species from the collection in a 1909 issue of Memoirs of the Carnegie Museum, including a catshark of the genus Pristiurus that they named in Sauter’s honor. Jordan and Richardson referenced six syntypes 30–36 cm/12–14 inches long in their description, of which four survive to the present day. Later authors have recognized Pristiurus as a junior synonym of the genus Galeus.

Teeth and Jaw: The mouth lining is light. The mouth is large and forms a long, wide arch. The corners of the mouth have well-developed furrows. There are about 70–78 upper and 82 lower tooth rows. Each tooth is small and usually has five cusps, with the central one the longest.

Head: The head comprises roughly one-fifth of the total length. The snout is long and pointed, with large nostrils divided by triangular flaps of skin on their anterior margins. The large, horizontally oval eyes have nictitating membranes without prominent ridges underneath. Behind each eye is a small spiracle.

Denticles: There is a distinct crest of enlarged dermal denticles along the upper margin of the tail. They are not found on the lower margin. The body is covered by small, slightly overlapping dermal denticles, which are leaf-shaped with a median ridge and three marginal teeth.

Tail: The tail is elongated. The caudal peduncle is compressed from side to side. It leads to a low caudal fin with a small lower fin and a ventral notch near the tip of the upper lobe.

Demographic, Distribution, Habitat, Environment and Range: The Blacktip Sawtail catshark can be found in the northwest Pacific around Taiwan Island, the Philippines, and possibly Japan including Okinawa (25°N – 21°N). They are found in deep water, over continental shelves offshore at least 197-295 feet in the Taiwan Strait, but possibly deeper elsewhere. Most recently, it has been recorded off Guishan Island from 328-656 feet. They are considered demersal.

Aesthetic Identification: The Blacktip Sawtail catshark is firm, small and slim-bodied, and does not have a pattern of dark saddle blotches. The dorsal fins, and sometimes the upper and lower caudal lobes have prominent black tips. The five pairs of gill slits are short, with the fourth and fifth pairs located over the bases of the pectoral fins. Both dorsal fins are rounded. The first dorsal fin is slightly larger and positioned over the latter half of the pelvic fin bases, while the second is positioned over the latter half of the anal fin base. The pectoral fins are medium-sized and blunt-cornered. The small pelvic fins are low and angular. The claspers of adult males reach the origin of the anal fin. The space between the pelvic and anal fin origins is greater in males than in females. The anal fin is elongated and angular; its base measures 12–15% of the total length, comparable to the distance between the dorsal fins.

Biology and Reproduction: They are oviparous, producing two eggs at a time, year-round. Adult females have a single functional ovary, on the right, and two functional oviducts; a single egg matures within each oviduct at a time. The eggs are enclosed in purse-shaped, translucent golden-brown egg cases measuring about 36–39 cm/14–15 inches long and 15 cm/5.9 inches across. The surface of the capsule is smooth and unlined; there are coiled tendrils on the anterior corners and bundles of long fibers on the posterior corners.

A known parasite of this species is the tapeworm Nakayacestus tanyderus.

A 2005 (Iglésias, Lecointre, & Sellos) phylogenetic study, based on mitochondrial and nuclear DNA, found that this species, G. eastmani, and G. gracilis form a clade apart from G. melastomus and G. murinus.

Behavioral Traits, Sensing and Intelligence: Unknown.

Blacktip Sawtail Catshark Future and Conservation: There is currently not enough data to evaluate. They are sometimes caught by bottom trawlers, and occasionally used as fishmeal in Taiwan. They have been spotted at fish markets.

Blacktip Sawtail Catshark Recorded Attacks on Humans: Not at threat to humans.