Manta rays, surely one of the oceans most impressive and majestic creatures, are in trouble from overfishing. Both of the manta rays (the larger Manta birostris, and the smaller Manta alfredi) are classified among the Elasmobranchii (sharks and rays). Giant manta rays can grow to a massive 7 metres in width, however nowadays the amount of overfishing in the oceans means that there are few mantas that ever get the chance to grow that big.
The threat from overfishing is due to both so-called bycatch and targeted fishing. Due to the fact that they are unable to swim backwards, manta rays are especially prone to getting tangled in fishing lines and gill nets intended for smaller fish. Demand has risen in China for the mantas’ gill-rakers, which are the cartilaginous structures that increase the surface area of the gills to allow more oxygen to be extracted from the water. Targeted fisheries have developed in several countries in order to feed the demand from the Chinese medicine market.
Manta rays are slow growing and only produce one or two young, usually at intervals of two years. They are slow to mature and can live as long as fifty years, if given the opportunity to do so. Both species were classified in 2011 by the IUCN as vulnerable to extinction. Manta rays were afforded some degree of protection in 2011 by their inclusion in the Convention on Migratory Species of Wild Animals and several countries have laws which protect manta rays to varying degrees. In 2013 manta rays were also included in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
Mantas will continue to suffer, though, as long as there is a demand for their gill-rakers, and as long as indiscriminate and wasteful fishing methods such as longlines and gill nets are used.
Well, what can we do about it? To put it bluntly, wildlife has to be worth more alive than dead. A key revenue stream that will encourage coastal communities to conserve manta rays is tourism. There are many parts of the world where manta ray tourism is worth millions of dollars every year, with people happy to pay to dive with mantas, or just to observe them from a boat. This is something which needs to continue to grow.
And we need to vote with our wallets by refusing to buy fish that has been caught in non-sustainable ways. Currently this means most fish. The oceans are seriously over-fished; we need to give them a break. If you must eat fish, try to buy pole and line caught tuna from the Maldives. Remember, when you buy unsustainably caught species you do not know how many other marine animals died in order to get that fish onto your plate.
For more information and to find out other things you can do to help manta rays, visit the Manta Trust.