During our stay in May of 2014 at Misool Eco Resort in Raja Ampat Indonesia we had the great pleasure of meeting Calvin Beale, the guest operations manager. As a scuba diving instructor with a degree in marine biology his great passion is manta rays. One evening after the day’s diving was done he gave a wonderfully educational and passionate talk about the species of manta rays – their classification, biology, life cycle and behaviors. We learned that there are in fact now 2 distinct species of mantas (reef and oceanic) and that Misool’s local dive site Magic Mountain is actually the only place in the world where both species have been seen on the same cleaning station at the same time. How cool is that?!
Magic mountain is a deep water pinnacle cleaning station, which is a designated location where fish and aquatic mammals congregate to be cleaned. This process involves the removal of parasites from their bodies, which is usually done by various cleaner fish (like wrasses) or shrimp. This neat symbiotic relationship benefits everyone involved.
Both Reef (Manta alfredi) and Oceanic (Manta birostris) mantas congregate at Magic Mountain, along with a ton of other pelagics and fish. It was by far the coolest dive site we got to explore! Calvin taught us how to distinguish between the two species based on their markings, and then about how the different combinations of spots on the underside surfaces are used to distinguish between individuals. Their markings are like our finger prints – no two individuals have exactly the same combination.
In August of 2011 Calvin created the Misool Manta Project and began sifting through several years’ worth of photos and videos from Magic Mountain. Using those distinctive ventral markings, he was able to identify individuals and then created a database. According to Misool Eco Resort, “this contributes valuable data to our knowledge of manta migration patterns and behaviour”. By tagging mantas with satellite trackers, and noting their comings and goings at the cleaning station, they can track interactions between different species, follow breeding patterns, and note seasonal variations. They’ve been using this information to advocate for the increased protection of manta rays in Indonesia, and in fact did recently succeed (in collaboration with Manta Trust, WildAid and the Save our Seas Foundation) in establishing the world’s largest manta ray sanctuary.
We also learned that Raja Ampat’s mantas are unique in that they generally stay within the region. Generally mantas are migratory and cross open oceans, yet Raja Ampat’s mantas tend not to stray too far. Calvin theorized that the abundance of food within the coral triangle and lack of predation by commercial fisheries within the protected No Take Zones may be playing a role in this interesting behavior.
So why do mantas need protection? Well, for starters they have long lifespans, low reproductive rates with long gestation periods, and are not evenly distributed across the oceans but rather concentrated in areas that provide the required food resources. The greatest threat to mantas is currently overfishing, and due to the above factors, overfishing can severely reduce local populations, with little chance individuals from elsewhere will replace them. The flesh of mantas is not considered desirable to eat, but as the world’s other more desirable fish stocks have become dramatically depleted fishermen have turned their attention to the rays.
Mantas are primarily fished commercially now for their gill rakers, which are thin cartilage filaments that enable them to filter plankton out of the water column. Sadly, and with devastating results, gill rakers have become the latest commodity in the often environmentally destructive Chinese Medicine trade. The trade claims the gill rakers can cure various health ailments, yet there is currently no evidence or research documenting the validity of those claims.
As Manta Trust explains, “manta ray populations simply cannot survive, or sustain, any commercial fisheries for long. Any target fishery which annually removes even a relatively small percentage of the breeding adults results in a rapid decline in the overall population within just a few years, as the remaining mature individuals simply cannot breed fast enough to replace the loses. And this is why, even with complete protection from anthropogenic threats, an overfished population of manta rays will take decades to recover to its natural state. A situation which, in the realities of today’s global fisheries management and protective enforcement (or lack thereof), this is never likely to happen to these populations which have already been overfished”.
Another significant threat to mantas worldwide is entanglement. Mantas cannot swim backwards and must constantly move water over their gills to breathe. When they become caught in fishing nets they do backwards rolls in an attempt to free themselves, which often entangles them further. The rays then suffocate and die a slow and painful death. The “lucky” ones may break the lines holding them but then those lines will slice through their skin and muscles and eventually into their vital organs, causing irreversible injury and often death.
So what’s the good news here? Many international conservation organizations and even individual countries are working hard to enact legislation to protect manta populations. Mantas are listed as Vulnerable by the IUCN Red List, and are also covered by CITES. Countries such as the Maldives, Indonesia, Mexico, Yap and Hawaii have instituted their own protections for their mantas, and those with the strongest protections derive the greatest economic benefit from doing so. A dead manta in Indonesia, for example, is worth about $40 to $500 while a live manta can bring in about 1 million throughout its lifespan in tourism revenue. Protecting mantas makes good economic sense.
You can learn more about the Misool Manta Project on their facebook page or through MER’s website. Manta Trust, a registered UK charity, is another awesome organization where you can find tons of information on mantas, the threats they face, what is being done about it and how you can help.
For a feel-good video of my manta encounters at Magic Mountain, check out this post!