Out of the blue it glides toward me: A huge, dark manta ray swimming effortlessly. It reaches the surface and floats motionless like a creature from another world, then banks left and swims lower in a series of loops just below me, exposing its white underbelly and three-metre wingspan. It dives deep, only to return for another fly-by, its graceful moves and massive size leaving me breathless.



Every diver dreams of encounters like this but are they becoming increasingly rare? There may come a day when few, if any manta rays remain. While working on a book about shark-finning, I noticed a trend in fish markets around the world: Manta rays and their close cousins, mobula rays, lined up in rows to be sold for their meat and gill rakers – the branchial filaments that help filter-feeding animals retain food.

Research and encounters with marine scientists have revealed that mantas and mobulas are becoming increasingly valuable for their gill rakers, which are used in Chinese medicine. Whereas before rays caught accidentally by gill net fishermen hunting tuna were thrown back into the ocean, they are now kept. The meat is dried and salted for human consumption, while the cartilage is used as a filler for shark-fin soup.