Common names
Bowmouth Guitarfish, Shark Ray.
Binomial
Rhina ancylostomus.
Synonyms
Rhina anclyostoma, Rhina ancylostoma, Rhina cyclostomus, Rhynchobatis ancylostomus, Squatina ancyclostoma.
Identification
A large, heavy-bodied ray with a shark-like body and a broadly rounded head and snout that is well separated from the pectoral fins. Eyes large. Spiracle skin-folds absent. Pronounced ridges topped by very large, broad-based thorns above eyes and spiracles, along median from nape to level of pectoral insertion, and two short rows on each shoulder. Skin evenly covered in very small denticles. Dorsal fins very tall and weakly falcate. First dorsal fin origin slightly anterior to pelvic fin origins. Pectoral fins wide, anterior margins weakly convex, posterior margins straight, apices angular or narrowly rounded. Caudal fin large and lunate, with a defined lower lobe. Well developed lateral keel at caudal base.
Colour
Dorsum bluish-grey to brown. Dorsum and fins posterior of mid pectoral level, densely covered with dark-edged, pale spots. Spotting more distinct towards posterior margins of fins. Juveniles have white-edged, black, V-shaped marking above pectoral fins. Thin, dusky, transverse bands sometimes present between eyes. Markings less distinct with age. Ventrum pale.
Size
Maximum length 270cm. Size at birth 46-48cm.
Conservation Status
CRITICALLY ENDANGERED
Shark-like rays (including sawfishes, wedgefishes, and giant guitarfishes) are considered the best quality fins for human consumption. In the international shark fin trade, their fins have the highest value, which has led to dramatic declines in many species, especially within the Rhinidae family. Their meat is also of high quality and is generally consumed locally.
It is estimated that the Bowmouth Guitarfish population has been reduced by >80% in the last 45 years. Northern Australia is the only area where the bowmouth has some refuge from fishing but this represents a small fraction of the species range.
Habitat
Tropical/ subtropical seas. Demersal on inshore and offshore sand and mud flats, and on coral reefs. To at least 70m.
Distribution
Ind0-West Pacific. Widespread but depleted along most coastlines from South Africa north to the Red Sea and Arabian Gulf, east India and Southeast Asia, to southern Japan and northern Australia.
Reproduction
Aplacental viviparous. Litter size 2-11.
Diet
Feeds on demersal fishes, crabs and shrimp, bivalves, and cephalopods.
Behavior
Poorly known.
Reaction to divers
Generally moves away if approached.
Diving logistics
Although bowmouth guitarfishes are quite rare in most parts of their range, random encounters in southern Queensland, Australia are not that uncommon. Spots where they have been seen include the Yongala Wreck, Wolf Rock, and even Julian Rocks in N.S.W.
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Similar species
False Shark Ray Distinguishable by much narrower head and geographic range; confined to West Africa.