Manta Rays, although considered to be large animals in the underwater kingdom, still have a number of natural predators, including certain species of sharks, orcas and false killer whales, all of which have been reported predating upon manta rays. It is often possible to see manta rays in the wild with large bite marks, often located on the edges of the manta’s pectoral wings in their ‘blind spot’ (the area behind their head), where they cannot see approaching predators. Amazingly resilient animals, the wound will often heal rapidly, with fresh skin growing over the injury with little to no lasting effect on the manta.
However, as with many animals, the greatest threat to manta rays come from human activities, including over-fishing, habitat destruction and water pollution.
Manta Rays are particularly vulnerable to fisheries. Their life history strategy means manta ray populations simply cannot survive, or sustain, any commercial fisheries for long. Any fishery which annually removes even a relatively small percentage of the breeding adults will results in a rapid decline in the overall population, as the remaining mature individuals simply cannot breed fast enough to replace the losses.
Fishery pressure has increased in recent years, as manta gill rakers have become an important commodity within Chinese Medicinal Trade. The gill rakers, or branchial filaments, are thin cartilage filaments that enable the manta and mobula rays to filter plankton out of the water column. These rakers, once dried, are the most valuable parts of the rays and drive the commercial fishery of these rays around the world, with particularly large fisheries present in India, Sri Lanka and Indonesia. Although the rakers comprise just a tiny percentage of a manta body, their economic value is a driver strong enough to still sustain the hunt in many countries.
Further research into manta rays is required in order to safeguard this species in the future. While Manta Birostris are currently protected in the Philippines, their smaller counterpart reef mantas are not. Other members of the mobula family are not afforded any protection and are currently actively fished country wide.