Bluefin Trevally in Mauritius — The Ocean's Neon Predator

The bluefin trevally (Caranx melampygus), locally known as Carangue bleue, is one of the most visually striking and behaviourally captivating fish a diver can encounter around the reefs of Mauritius. A member of the family Carangidae, this powerful jack is widely distributed across the Indo-Pacific, and Mauritius sits firmly within its prime range, offering divers regular, rewarding sightings throughout the year.

Identification and Appearance

Bluefin trevally are immediately recognisable thanks to their vivid electric-blue fins and the constellation of small blue and black spots that scatter across their silver bodies. Adults typically reach 60–70 cm in length, though specimens exceeding 80 cm and weighing over 10 kg are not unheard of in Mauritian waters. The body is laterally compressed and streamlined — built for speed — with a forked tail that drives explosive bursts of acceleration when pursuing prey. Juveniles display a more yellowish colouration that gradually transforms into the spectacular blue-silver livery of adulthood.

Behaviour and Hunting Strategies

What makes the bluefin trevally so captivating to observe underwater is its sophisticated and often dramatic hunting behaviour. These fish are active, opportunistic predators that feed primarily on smaller reef fish, squid, and crustaceans. They are known to hunt both independently and in small coordinated groups, sometimes corralling prey fish against coral structures or the surface — a spectacle that can send entire reef communities into a frenzy.

One particularly fascinating behaviour observed in Mauritius is their tendency to shadow larger animals such as reef sharks or Napoleon wrasse, using them to flush out hidden prey. Divers who remain still and patient at depth are often treated to this natural drama unfolding just metres away. Early morning and late afternoon dives tend to yield the most activity, as trevally ramp up their hunting behaviour during these transitional light periods.

Habitat and Distribution Around Mauritius

Around Mauritius, bluefin trevally are found across a wide range of reef environments. They favour outer reef edges, coral drop-offs, lagoon passes, and rocky pinnacles — essentially anywhere that provides both shelter and a steady throughput of current to concentrate prey. They are commonly spotted patrolling at depths between 5 and 40 metres, making them accessible to both snorkellers in shallow lagoons and experienced divers on deeper reef structures.

Sites along the west and north coasts of Mauritius are particularly productive, as these areas feature well-developed reef systems with excellent biodiversity. The waters around Coin de Mire (Gunner's Quoin) in the north are especially well regarded, where trevally mix with schools of other pelagic species in the strong currents surrounding this iconic volcanic islet.

Conservation and Ecological Role

As an apex predator of the reef ecosystem, the bluefin trevally plays a vital regulatory role in maintaining healthy fish populations. By preying on weaker and more abundant small fish, trevally help sustain ecological balance across reef communities. While the species is currently listed as Least Concern on the IUCN Red List due to its wide distribution and relatively stable populations, it remains vulnerable to overfishing in some regions. In Mauritius, marine protected areas and responsible dive tourism help ensure that populations remain robust for future generations of divers and reef communities alike.

Tips for Divers

• Stay calm and slow — erratic movements will cause trevally to keep their distance.
• Dive at dawn or dusk for peak hunting activity and dramatic behaviour.
• Look along reef edges and current channels where prey concentrates.
• Wide-angle lenses are ideal for underwater photographers hoping to capture these fast-moving, large fish in their environment.

Whether you are a seasoned underwater photographer or a recreational diver seeking wildlife thrills, the bluefin trevally of Mauritius will rarely disappoint. It is the kind of species that makes you pause mid-dive and simply watch in awe.