The Bowmouth Guitar Shark in Mauritius

The bowmouth guitar shark (Rhina ancylostoma), locally known in Mauritius as the Requin guitare, is one of the most visually striking and biologically fascinating sharks found in the Indo-Pacific region. A living relic of ancient ocean evolution, this species belongs to its own unique family — Rhinidae — and sits at the fascinating crossroads between sharks and rays. While true sightings in Mauritius are exceptionally rare, encounters with this species leave an indelible mark on anyone fortunate enough to witness one.

Identifying the Bowmouth Guitar Shark

The bowmouth guitar shark is unmistakable once you know what to look for. Its body is broad and flattened, much like that of a ray, yet its gills are positioned on the sides of its head rather than beneath it, confirming its shark heritage. Adults can reach up to 2.7 metres in length and weigh over 135 kilograms, making them an imposing presence on the reef. The head is rounded with a distinctive strongly bowed mouth — hence the common name — and the body is adorned with white spots scattered across a grey-brown background. Most striking are the sharp, ridge-like crests of thorny tubercles running along the shoulders and above the eyes, giving the shark an almost armoured, dinosaur-like appearance.

Behaviour and Habitat

In Mauritius, the bowmouth guitar shark is most likely to be encountered in sandy lagoon areas, shallow reef flats, and deeper sandy bottoms adjacent to coral structures. Like many bottom-dwelling sharks, it is largely nocturnal, spending daylight hours resting partially concealed on the substrate. At night, it actively hunts crustaceans, molluscs, and small fish using its powerful, crushing dentition — perfectly adapted for breaking open hard-shelled prey.

This species typically prefers depths ranging from the shallows down to around 90 metres, though in Mauritius most potential sightings are reported in relatively accessible depths of 10 to 40 metres, often near the outer reef slopes and sandy channels that characterise the island's diverse marine topography.

Conservation Status and Threats

The bowmouth guitar shark is classified as Endangered on the IUCN Red List, facing significant pressure from targeted fishing, bycatch, and habitat degradation across its Indo-Pacific range. Its large fins are highly prized in the shark fin trade, and its low reproductive rate makes population recovery extremely slow. In Mauritius, the species benefits from the country's broader marine conservation framework, but dedicated protections for this specific shark remain limited. Responsible diving practices — maintaining distance, avoiding disturbance, and never touching resting individuals — are essential to protecting these rare visitors.

Diving with the Bowmouth Guitar Shark in Mauritius

Given its rarity, there is no guaranteed dive site for the bowmouth guitar shark in Mauritius. Sightings are opportunistic and often reported by divers exploring the outer reef systems and sandy passes around the island, particularly in the waters off the west and south coasts. Night dives on sandy-bottomed reef edges offer arguably the best chance of an encounter, as the species becomes active after dark. Dive operators in Mauritius with extensive local knowledge are your best resource for up-to-date sighting information.

When diving in search of this species, patience is key. Scan sandy patches carefully, look for the telltale outline of a broad, flattened body and the distinctive spiny ridges — a resting bowmouth guitar shark can blend surprisingly well with the seafloor. Approach slowly and calmly; any sudden movement is likely to send it gliding away into the blue.

Why Mauritius Matters for This Species

Mauritius sits within the broader Western Indian Ocean range of Rhina ancylostoma, and its well-maintained reef ecosystems offer important potential refuge habitat. As global populations decline, even rare appearances in Mauritian waters represent ecologically significant events. Supporting marine conservation initiatives and choosing responsible dive operators contributes directly to the long-term survival of this extraordinary shark.