Grey Reef Shark

Photo: CORDENOS Thierry · CC BY-NC

Grey reef sharks patrol the outer walls and current channels of Nosy Mitsio in numbers that indicate a healthy, lightly fished ecosystem. They communicate threat through a distinctive hunched posture combined with exaggerated lateral swimming — a warning display rarely seen in heavily dived locations where sharks have become habituated. Their role as mesopredators structures the entire reef community below them, and their abundance here is a proxy indicator of overall ecosystem health.