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May 2012    Download the Entire Issue (PDF) Available to the Public Vol. 27, No. 5   RSS Feed for Undercurrent Issues
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More Marine Species on the Brink

these are next on the endangered list

from the May, 2012 issue of Undercurrent   Subscribe Now

We've written often about sharks and the threat posed to them due to the voracious demand of shark-fin soup in upwardlymobile Asian countries. But sharks aren't the only ones under the gun. Mantas, mobulas, whale sharks, even sting rays are under siege. Following are three articles that show the rise in demand -- and decline in numbers -- of species you always thought would be admired more for their beauty than for their meat, fins, so-called medicinal qualities, and even their use as billboards.

Who Would Have Thought Gill Rakers Are in Demand?

A few years ago, something surprising began turning up in Asia's fish markets: the gill rakers of manta and mobula rays. Shawn Heinrichs and Paul Hilton, photographers who have been monitoring the international soaring trade in shark fins, decided to find out what was going on. The appearance of those creatures in the markets "came as a real shock to us," Mr. Heinrichs said by phone from Indonesia. "They don't even taste good, so what was the reason?"

In January, the conservation organizations Shark Savers ( www.sharksavers.org ) and WildAid ( www.wildaid.org ) released a comprehensive global study showing that these species have been driven to the brink of extinction within a chillingly short space of time. The main reason is demand from China, where their gill rakers (filaments that filter the animals' food from the water) are marketed as a supposed cure for a variety of ailments. The southern Chinese city of Guangzhou is the hub of the trade in the dried parts, which retail for as much as $225 a pound. The gills are boiled along with other fish products in a soup that is promoted as a cure for anything from chickenpox to cancer. "I call it endangered species soup," said Mr. Heinrichs, who led the research.

The researchers note that the gills had not previously been prescribed in traditional Chinese medicine, and many of its practitioners conceded in interviews for the study that gill rakers were not effective in treating illness and that many alternatives were available. The rising popularity of the ingredient seems to be the result of traders' efforts to create a market, the report's authors concluded.

The growth in demand has been devastating for populations of both rays -- even more so because these creatures reproduce very slowly. A female manta may produce between 10 and 16 pups during her lifetime, far fewer than great white sharks, for example, which can produce that many in a single litter. And while great whites are protected under international conventions, manta and mobula rays are not, largely because the fishing pressures described in the new report are little understood by conservationists and the public.

"The economics and the moral imperative are clear," Peter Knights, executive director of WildAid, said in a statement. "We need an immediate moratorium on gill raker trade, and measures for complete protection to some populations and to reduce fishing pressure for others."

A silver lining is that these creatures are also viewed as generators of millions of dollars in tourism revenue because divers and snorkelers travel from far and wide to observe them. For the time being, however, this is not helping to curb the trade. In addition, because of the extreme vulnerability of the manta and mobula rays, the race to save them is "an entire factor worse" than the race to save sharks, Mr. Heinrichs said. With manta and mobula rays, "we simply don't have the time to go through years of raising public awareness before action is taken. The race to preserve these species is almost over before it even started."

- - Bettina Wassner, the New York Times' "Green" blog

Turned into Tuna Bait and Billboards

The world's largest shark eats only plankton, and couldn't bite a human if it wanted to. Globally, scuba divers pay an estimated $50 million each year for the chance to swim with the incredible fish known as whale sharks. Their long migrations through international waters makes international cooperation necessary to protect them, which is particularly important because the 30 years it can take for these animals to reach reproductive maturity means that populations will take a long time to recover if they are overexploited. They're listed by the International Union for Conservation of Nature and Natural Resources as "vulnerable" globally. Between their charismatic nature, their inability to harm humans, and their value to ecotourism, it should be easy to convince governments to protect whale sharks, making two recent reports all the more shocking.

It's estimated that more than 1,000 whale
sharks are landed annually. Some of
their huge fins are placed in windows of
shark fin stores as billboards.

At the recent Western and Central Pacific Fisheries Commission (WCPFC) meeting, Australia introduced a proposal to ban intentionally setting tuna nets around whale sharks. You read that correctly: It is currently legally permissible (and not uncommon) for fishing vessels to intentionally deploy tuna purse seine nets around whale sharks. Schools of tuna will often aggregate around anything, including buoys, logs or 50-foot-long sharks that are extremely valuable for ecotourism and extremely vulnerable to overexploitation. Being caught in a tuna net and dragged onto the deck of a fishing vessel is often lethal, and an estimated 75 whale sharks have died since 2009. Unfortunately, Australia's common-sense proposal was stalled by the Japanese delegation, and was not enacted this year. It will be discussed again when the WCPFC meets again in December.

Although whale sharks are protected from harvest in many countries, new research shows that whale shark fishing is on the rise in China. Between 1980 and 2003, only 17 whale shark landings were officially recorded in China. Since 2003, there have been 167 recorded landings, but interviews with shark-processing plant employees indicate that over 1,000 whale sharks are landed annually. While there is a limited market for whale shark meat, it is the fins that are the biggest draw. Whale shark fins, not surprisingly, are enormous, and therefore fetch the highest price at market. Some of the huge whale shark fins are used to make shark fin soup, while others are placed in the windows of shark fin stores to serve as billboards.

Logs and buoys will attract tuna just as effectively as whale sharks, and a sign will advertise the presence of a shark fin store just as effectively as a whale shark fin. Our current inability to protect these charismatic, harmless and vulnerable sharks from being killed as tuna bait and billboards is one of many reminders that nothing about marine conservation is easy.

- - David Shiffman, the "Southern Fried Science" blog

These Popular Cayman Residents are Disappearing

Recently, I assisted team members of the Guy Harvey Research Institute (GHRI) conducting the first census on the stingray population at the Sandbar [near Rum Point Channel in Grand Cayman] since July 2008.

For two years starting in 2002, the GHRI, assisted by the Department of Environment, did a comprehensive population analysis of the rays, the first ever conducted on rays in a marine wildlife interactive program. Basic information such as width, weight, sex, DNA samples, migrations and diurnal behavior were collected. PIT tags, similar to microchips used in pets, were placed in each ray to allow identification of individuals, and therefore tracking of their growth, over a long period. Over successive counts, tag retention was found to be 100 percent. All rays over a certain size had tags; only new young recruits to the sandbar did not have tags.

A sample of 100 rays was taken every month for six months in each year to determine population composition, growth and pregnancy rates. It was likely that every ray visiting the sandbar during that time was sampled and tagged. Site fidelity was strong, with only one animal visiting the nearby Stingray City from Sandbar and then returning. These animals are long-lived, slow- growing relatives of sharks, so it was expected that many rays would visit the sandbar for 20 years or more.

Canadian researcher Christine Semeniuk did more work on stingrays in 2005, mostly to investigate their well-being using blood analysis. The next census was done by GHRI in July 2008. On July 1, the first day of the census, we sampled 51 rays. The next day, it was 40. On the last day, only eight, as most rays had already been caught measured and put back in the water.

In the last year, I have noticed, as have several tour operators, a decline in the number of rays experienced at Sandbar. In January 2012, the same team working with the same methods as before caught and measured 61 animals. That sounds like there are plenty of rays to go around, but that is a 38 percent reduction in Sandbar's stingray population compared to 2008. Forty-three rays were recaptured, and 18 new recruits were tagged. Of particular note, only 43 of the 99 animals counted and tagged in the 2008 census were sampled in 2012.

What has happened to the stingrays? And what are we doing about it? Each stingray is clearly worth in the order of $100,000 per year to the Cayman economy. Over a ray's long lifetime, it is worth several million dollars to the Cayman economy. So how is it that the rays enjoy protection only in the wildlife interaction zone areas? Why are these extremely important animals not totally protected from harvest all around the Cayman Islands?

Our data suggests that the rays have not migrated to other sites, as site fidelity is very strong. We saw no evidence of shark attacks, and all animals appeared healthy -- so fishing mortality remains the main suspect for the sudden decline. The Marine Conservation Law needs to be changed to protect stingrays throughout the Cayman Islands.

-- Guy Harvey, Caymanian Compass

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