Along with demand for gill rakers, manta rays are also fished for their skin, which is either consumed or made into leather, and their cartilage, which is used as a filler or a cheap substitute for shark cartilage in shark fin soup (White et al. The value of the international gill raker trade is estimated to be about $11 million per year (Heinrichs et al. The gill rakers are highly valuable in Asian markets, where they are used in traditional Chinese medicine. Aside from incidental catch, mantas are also targeted in many areas of the world for their gill rakers, the stiff projections in their gills that filter food particles. Manta rays are often caught as by-catch in gillnet, purse seine, longline, and trawl fisheries (Marshall et al. The leading threat to manta rays is fishing, both targeted and incidental. birostris is listed as “vulnerable” on the International Union for Conservation of Nature’s Red List. This population decline has been attributed mainly to both targeted fishing and incidental (by-catch) mortality (Marshall et al. Globally, it is suspected that manta rays are declining at an estimated 30%. The rate of population decline in the past 75 years in parts of their range may be as high as 80%. Manta rays are long lived, late to mature, and produce 1 to 2 live pups every few years, making them vulnerable to fishing pressure and slow to recover from population threats or disturbances (Marshall et al. It is thought they gather in these areas to breed and visit cleaning stations (Graham et al. Manta rays aggregate in large groups in areas off the coasts of Mexico, Mozambique, Hawaii, and the Maldives. Manta rays have a broad distribution throughout the world’s tropical and temperate oceans, and little is known about the size of the global population (Marshall et al. Despite their large size, mantas are harmless to humans. The giant manta ray ( Manta birostris) is the world’s largest ray species with a disc width of up to 7m from wing tip to wing tip (Graham et al. Immune Assessment in Wild Shark Populations
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