Manta & Mobula Rays

From the blue, it glides towards me: a huge, dark manta ray, swimming effortlessly from the depths. It reaches the surface and floats motionless like a creature from another world. Then it banks left and swims lower in a series of loops just below me, exposing its white underbelly and 3 metre wing span. Then it dives deep, only to return for another fly-by. Its graceful moves and massive size leave me breathless.

Every diver dreams of encounters like this but are they becoming increasingly rare? There may come a day when few - if any - manta rays remain.

While working on a book about shark finning, I started to notice a trend in fish markets around the world, manta rays (Manta birostris) and its close cousin the devil ray (of the Mobula genus) lined up in rows to be sold for their meat and gill rakers. Research and encounters with marine scientists revealed that mantas and mobulas are becoming increasingly valuable for their gill rakers ( branchial filamnets that help filter-feeding animals retain food), which are used in Chinese medicine. Rays caught accidentally by gillnet fishermen hunting tuna are now always kept. The meat is dried and salted for human consumption while ray cartilage is used as a filler for shark fin soup. Demand for gill rakers has given rise to unsustainable ray fisheries off the coasts of Mexico, Philippines and Indonesia.

In 2004, manta rays were identified by the Convention on International Trade in Endangered Species (www.cites.org) as a group associated with significant unregulated, unsustainable fishing and severe population depletion. In 2005, the IUCN Red List of Threatened Species (produced by the International Union for Conservation of Nature and Natural Resources) classified the manta ray as "near threatened". For a time the governments of Mexico and the Philippines made it illegal to capture and kill mantas, then Mexico lifted the ban. Both countries list their local stock of manta rays as DD/NT - "data deficient" and "near threatened".

 

It is illegal to kill manta and mobula rays in the Philippines today. However manta and mobula fisheries has been operation for over a century, traditional fishermen used home made harpoons and only took the largest of rays and operated for three months of the year, now according to local source the fishermen operate for most of the year, with catches peaking in November, January and February and sadly the harpoons have been replaced with gillnets allowing them to catch many more.

According to Dr Andrea Marshall, lead scientist and director of the Manta Ray and Whale Shark Research Centre, in Mozambique: "The IUCN assessment states that if current fishing practices continue, certain populations are vulnerable to extinction in the future. I don't think it is likely that they will go globally extinct but it is possible that populations will go, or have gone, regionally extinct. I also think some species of rays are more vulnerable than others and need more comprehensive management efforts."

In Sri Lanka, at the small fishing port of Mirissa, we count 23 dead mobula rays in one morning. According to the fishermen, the rays are landed every day here, in just one port in one town in one country. The next day, at the same spot, we count 20, the following day, 15. I have never seen so many rays in one place. The rays are sold in two parts: the head and the rest of the fish. The head fetches 500 rupees (HK$33), including all 10 gills. Once sold, the  head is hacked up to get to the gills.

The same fishmongers who were finning sharks, now go to work on the heads, separating the gill rakers from the fleshy parts that hold them in place. These concertina-looking filters are much in demand by Asian restaurants and diners. The rest of the ray is either sold cheaply to locals for use in fish curry or is left to waste.

We are told that the gill rakers and shark fins are taken to a warehouse in Matara, 30 minutes from Mirissa.

Upon arrival, we find shark fins all over the floor, divided into piles according to species; long-finned mako sharks, hammerheads, oceanic white-tips. The traders are keen to talk and invite us to take a closer look. Inside, on shelves, are clear plastic sacks crammed with dried manta and mobula gill rakers. The proprietor tells us that each of the four sacks contains gill rakers from about 100 rays. We are taken to the roof, where gill rakers and shark fins are being dried. According to the staff, 1kg of shark fin sells for 1,500 rupees while the same weight of gill rakers sells for 4,000 to 5,000 rupees.

Until recently the gestation period of manta rays was uncertain. Estimates ranged from one to three years. But in June 2007, a manta ray was born in captivity for the first time, at the Okinawa Churaumi Aquarium in Japan, after a gestation period of one year and nine days, giving scientists a better insight into one of the strangest and least-understood marine animals. Unfortunately, the baby manta ray died five days later - in part from injuries inflicted by its father for unknown reasons - but it provided data for what had been a largely blank page.

The birth allowed scientists to determine that mantas deliver in the wild every one to three years, although they have an annual ovulation cycle. However, scientists still don't know at what age they reach maturity. Some believe it is about six to eight years for females, who grow to between 3.8 metres and 4.5 metres across (depending on region and species). They usually have a single pup - but twins are not unknown - born measuring about 1.5 metres to 1.9 metres across. No one knows how long manta rays naturally live for but it is at least 30 years. For all scientists know, they could live for more than 100 years, like some whale sharks but of the 9 species of devil rays we still really know very little.

Scientists fear that a combination of slow maturation, long gestation and infrequent pregnancies means manta and mobula populations cannot replenish themselves as fast as man is catching and killing them.

According to Marshall, mantas and mobulas, which are found worldwide in tropical and temperate waters, are divided into eleven species, nine mobula and two manta, with visually identifiable characteristics, as well as unique behaviour and lifestyles.

They rays could attract millions of dollars in eco-tourism, which could play a part in their conservation. Eco-tourism generates the money and attention needed to influence governments and increase public awareness of the plight of creatures such as the manta ray. Hawaii generates US$2.5 million annually through manta ray eco-tourism. But experts warn that eco-tourism can also be destructive and unsustainable if it is not controlled or regulated and it can have just as negative an effect on a population as fishing.

   On the island of Lombok, Indonesia in a small fishing market I witnessed several large manta rays being cut up and sold for meat and the gills apparently heading for Jakarta. In eastern Indonesian port of Lamakera, catches of manta have rocketed from a few hundred to about 1,500 a year.

Demand for dried gill rakers for traditional medicines has increased dramatically; the skin, meat and gill rakers of a mature Indonesian manta sell for up to HK$125, according to the Manta Pacific Research Foundation.

  In Hong Kong, gill rakers - called peng yu sai - are believed to reduce toxins in the blood by purifying and "cooling" it, especially in those whose core temperature is too warm, according to traditional Chinese medicine practitioners .

Further north in Southern Chinese city of Guangzhou, shop after shop is filled with plastic sacks of gill rakers of all sizes and species. Prices ranged from 100USD to 220USD per kilo. According to my translator the labels on the sacks read Mobula gill,  large,  and extra large mobula gill, also on the label: health benefits where listed, from an anti-inflammatory to a blood purifier and it is consumed mostly by women as a health tonic in soup.

 

Manta and mobula rays may not be endangered yet but soon will be unless they are given some protection, these creatures soon will be. It's time to reflect on the mistakes we have made and move to a more sustainable and frugal way of life - for the future of all living creatures, including ourselves. Our time is now. By Paul Hilton