Many Threats for Manta Rays

Defenders calls for Endangered Species Act protection for all three species of manta rays

At up to 23 feet wide and 5,300 pounds, calling a manta ray “giant” is an understatement. Manta rays have the biggest brain of any fish, so underwater genius is more like it. Disproportionately large as compared to the rest of its body, a manta ray’s brain more closely resembles that of an equally large mammal. Though enormous, these planktivores are truly gentle giants. Scientists’ best guess puts a manta ray’s lifespan at 40-50 years, but, as scientific tracking of individuals increases, we could find that the massive fish live as long as 100 years.

Three different species – all needing protection

As its name suggests, the giant manta ray is the biggest ray out there. While the Caribbean and reef manta rays are slightly smaller, they are still massive, and can reach more than 16 feet wide and 3,000 pounds. Scientists believe that many of the manta rays that they originally considered giant manta rays are actually a similar, but genetically and physically distinct third species, tentatively described as the Caribbean manta ray.

Earlier this year, Defenders of Wildlife submitted a petition to the National Marine Fisheries Service (NMFS) asking the agency to protect the giant manta ray, reef manta ray, and Caribbean manta ray (all known manta ray species) by listing them as endangered, or at least as threatened, under the Endangered Species Act (ESA). In 2013, the United States supported the successful listing of all manta ray species under the Convention on International Trade of Endangered Species (CITES) Appendix II, which regulates but doesn’t ban trade. The CITES listing was a positive step in the right direction, but mantas need greater protection as habitat loss and overfishing continue to threaten their existence.

As coral reefs disappear, so do mantas

Manta rays live around the world in tropical to temperate waters. The giant manta ray migrates more than its smaller counterparts, and is more widely distributed thanks to its greater tolerance for cold, deep water. Reef manta rays prefer more tropical waters and stay closer to shore, oftentimes having populations focused around a single island. Caribbean manta rays have the most constrained range, with all populations existing in the Gulf of Mexico, southeast United States, and, of course, the Caribbean. No matter their location, all mantas rely on coral reefs, which make up only 0.2% of the marine environment, but house 25% of all marine life. The fish species that live around reefs provide “cleaning stations,” where they help rid the rays of parasites – a process that can take up to eight hours, but benefits both the mantas and the fish. Coral reefs also serve as important feeding and breeding locations for mantas. Yet as coral reefs are quickly disappearing due to climate change, manta rays are losing this vital habitat. Climate change also affects the amount of plankton in the ocean, which is a big problem for a giant fish that feeds exclusively on these tiny sea creatures.

From shark finning to manta gilling

The most alarming threat facing manta rays is targeted overfishing due to the increasing trade of manta ray gill plates. Manta rays have recently become victim to an all-too-familiar exploitation, where a big animal is killed for a small, but very lucrative part of its body. For manta rays, that part is their gill plates, which filter plankton out of the water as the rays use their horn-like fins to funnel water into their large mouths. This filtering process has likely led to the unsupported, recent belief in Chinese medicine that eating dried and crushed manta ray gill plates detoxifies human blood and aids in curing everything from chicken pox to cancer. Manta ray meat is of little value, but these false medical claims have led to one pound of manta ray gill plates being worth more than $300, and a mature giant manta ray can yield up to 15 pounds of dried gill plates. As other valuable fish stocks become depleted, fishermen are now tapping into mantas, targeting them not only for their gill plates, but also as a cheap substitute or filler for shark fin soup.

Manta rays reproduce slowly. Some mantas don’t reach sexual maturity until they’re 15 years old, and even then they only typically have one pup every two to five years. This means that they can’t bounce back from the decimation wrought by overfishing. They are literally being pulled from the oceans faster than they can reproduce. Even with the strictest protections, it will take decades for manta rays to recover from the unsustainable overexploitation they have experienced. As population numbers continue to plummet, an ESA listing would provide increased legal protections for manta rays to help ensure their survival, including a focused recovery plan identifying specific management measures that could be taken to help mantas rebound to healthier population levels. With our petition to NMFS to list the giant manta ray, reef manta ray, and Caribbean manta ray, we strive to protect these gentle giants from the very real threat of extinction. We still have so much to learn about these mysterious and fascinating creatures, and their loss would be a tragedy. Our similar petitions to NMFS over the thorny skate, smooth hammerhead shark, and bigeye thresher shark have been successful, and the agency has begun status reviews as the first steps in granting these species protection. We hope to have a similar positive outcome for our petition to list manta rays, and should hear from NMFS in early 2016.