The mushroom cloud’s silver lining: how the Cold War is helping the biggest fish in the sea

United States Department of Defense/Wikimedia

Mark Meekan, Australian Institute of Marine Science

It might surprise you to learn that nuclear bomb tests during the Cold War are now helping conserve whale sharks, the largest living fish.

Growing up to 18 metres – longer than the average bus – whale sharks live in all tropical oceans. In Australia, they are found off tropical coasts in the north, particularly in Western Australia.

Whale sharks face a number of threats. Globally they are listed as endangered, and their numbers continue to decline.

Until recently, key information about the life history of whale sharks was missing, which prevented informed choices about how they were managed. In particular, scientists were not able to accurately assess their age and growth patterns.

Our research, published today in Frontiers in Marine Science, changes that. We examined the skeleton of whale sharks, using carbon from Cold War atomic bomb testing as a “time stamp” to reveal their true age. The findings will help protect these beautiful animals into the future.

Until now, it’s been difficult to assess the age of whale sharks.
Wayne Osborn

Gentle giants

Whale sharks are placid “filter feeders”, which basically means they eat by opening their massive mouths and straining small fish and plankton that pass through the gills.

They are covered in a pattern of stripes and spots that provide camouflage as they bask at the surface. Whale sharks’ gentle nature and striking appearance has made them a drawcard for tourists who pay to snorkel or dive with the animals.

Whale shark ecotourism is big business. At Ningaloo Reef off Western Australia, the industry is worth an estimated A$12.5 million per year.

The industry is also valuable for small island nations such as the Maldives and developing countries including the Philippines and Indonesia. It has lifted thousands of villagers from poverty and provided an impetus for governments to protect whale sharks.

But all is not plain sailing for these animals. In some parts of the world they are hunted for their fins, meat, oil and skin. The flesh resembles tofu when cooked, and is a popular menu item in parts of Asia, particularly China.

When shipping lanes are established near whale shark habitat, the animals are frequently struck by vessels and either die or suffer propeller injuries such as fin amputation. Their habit of basking at the surface of the ocean during the day puts whale sharks at particular risk of ship strike.

This combined with other threats – such as warming sea surface temperatures due to climate change – has created an uncertain future for these charismatic and valuable animals.

A whale shark carcass on the shore of Teluk Betung beach in West Sumatra, Indonesia, last year. The animal is considered endangered.
RAJO BATUAH/EPA

The silver lining on the mushroom cloud

Just how vulnerable whale shark populations are to these threats is not clear. Growth rates of fish species – or how many years they take to reach a certain size – determine their resilience, and how fast populations are likely to recover if severely damaged.

But determining the age of whale sharks has, to date, been very difficult. Their vertebrae feature distinct bands, similar to the rings of a tree trunk, which increase in number as the animal grows older. But the bands could not conclusively be used to determine age because some scientists believed a ring formed every year, but others suggested one formed every six months.

Cross section of a whale shark vertebra from Pakistan, showing 50 growth bands.
Paul Fanning/ Pakistan node of the UN Food and Agricultural Organisation

To settle the debate, we turned to the radioactive legacy of the Cold War’s nuclear arms race – specifically, carbon-14.

Carbon-14 is a naturally occurring radioactive element. But in the 1950s and early 1960s, nuclear weapons tests by the US, Soviet Union, Great Britain, France and China released enormous amounts of carbon-14 into the air.

It travelled into the world’s oceans, and into every living organism on the planet – including the skeletons and shells of animals.

We analysed the vertebrae of two whale sharks collected many years ago in Taiwan and Pakistan. By counting back from the peak carbon-14 level, we concluded the rings were formed once per year. This meant that for the first time, the age and growth rate of a whale shark could accurately be determined; a 10-metre shark was 50 years old.

We know whale sharks can grow to almost twice the length of the animals we analysed, and have been estimated to live as long as 100 years. The results of our study makes that prediction now seem more likely.

Whale sharks can live as long as 100 years.
Wayne Osborn

What does this mean for whale sharks?

Slow-growing species with long lifespans are typically very susceptible to threats such as fishing. This is because it takes many years for animals to reach reproduction age, and the rate at which individuals are replaced is very slow.

Our study explains why fisheries targeting whale sharks almost immediately collapse: the species is not built to cope with the added pressures of human harvests.

Whale sharks populations take a very long time to recover from over-harvesting. Governments and management agencies must work together to ensure this iconic animal persists in tropical oceans – for both the future of the species, and the many communities whose livelihoods depend on whale shark ecotourism.

Mark Meekan, Senior Principal Research Scientist, Australian Institute of Marine Science

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Poor Filipino fishermen are making millions protecting whale sharks

Whale sharks at Oslob are now part of a new ecotourism industry.
Wayne Jones, Author provided

Judi Lowe, Southern Cross University

A group of the world’s poorest fishermen are protecting endangered whale sharks from being finned alive at Oslob in the Philippines.

The fishermen have stopped fishing and turned to tourism, feeding whale sharks tiny amounts of krill to draw them closer to shore so tourists can snorkel or dive with them.

Oslob is the most reliable place in the world to swim with the massive fish. In calm waters, they come within 200m of the shore, and hundreds of thousands of tourists flock to see them. Former fishermen have gone from earning just a US$1.40 a day on average, to US$62 a day.

Our research involved investigating what effect the whale shark tourism has had on livelihoods and destructive fishing in the area. We found that Oslob is one of the world’s most surprising and successful alternative livelihood and conservation projects.

A drone shot of whale shark tourism, about 100 metres from shore. The small boats with one person are feeders. The longer boats are for the tourists swimming with face masks to see the whale sharks.
Luigi Borromeo

Destructive fishing

Illegal and destructive fishing, involving dynamite, cyanide, fish traps and drift gill nets, threatens endangered species and coral reefs throughout the Philippines.

Much of the rapidly growing population depend on fish as a key source of protein, and selling fish is an important part of many people’s income. As well as boats fishing illegally close to shore at night, fishermen use compressors and spears to dive for stingray, parrotfish and octopus. Even the smallest fish and crabs are taken. Catch is sold to tourist restaurants.

Despite legislation to protect whale sharks, they are still poached and finned alive, and caught as bycatch in trawl fisheries. “We have laws to protect whale sharks but they are still killed and slaughtered,” said the mayor of Oslob.

“Finning” is a particularly cruel practice: sharks’ fins are cut off and the shark is thrown back into the ocean, often alive, to die of suffocation. Fins are sold illegally to Taiwan for distribution in Southeast Asia. Big fins are highly prized for display outside shops and restaurants that sell shark fin products.

Whale sharks come close to the coast to feed on krill.
Andre Snoopy Montenegro, Author provided

To protect the whale sharks on which people’s new tourism-based livelihoods depend, Oslob pays for sea patrols by volunteer sea wardens Bantay Dagat. Funding is also provided to manage five marine reserves and enforce fishery laws to stop destructive fishing along the 42km coastline. Villagers patrol the shore. “The enforcement of laws is very strict now,” said fisherman Bobong Lagaiho.

Destructive fishing has declined. Fish stocks and catch have increased and species such as mackerel are being caught for the first time in Tan-awan, the marine reserve where the whale sharks congregate.

The decline in destructive fishing, which in the Philippines can involve dynamite and cyanide, has also meant there are more non-endangered fish species for other fishers to catch.

Strong profits means strong conservation

The project in Oslob was designed by fishermen to provide an alternative to fishing at a time when they couldn’t catch enough to feed their families three meals a day, educate their children, or build houses strong enough to withstand typhoons.

“Now, our daughters go to school and we have concrete houses, so if there’s a typhoon we are no longer afraid. We are happy. We can treat our children to good food, unlike before,” said Carissa Jumaud, a fisherman’s wife.

Creating new forms of income is an essential part of reducing destructive fishing and overfishing in less developed countries. Conservation donors have invested hundreds of millions of dollars in various projects, however research has found they rarely work once funding and technical expertise are withdrawn and can even have negative effects. In one example, micro-loans to fishermen in Indonesia, designed to finance new businesses, were used instead to buy more fishing equipment.

Former fisherman Jesson Jumaud with his daughter Kheny May, who now goes to school. The profits of whale shark tourism mean they now have a brick house, and Jesson was able to buy a motor bike. He can feed their family three times a day with good food.
Judi Lowe, Author provided

In contrast, Oslob earned US$18.4 million from ticket sales between 2012 and 2016, with 751,046 visitors. Fishermen went from earning around US$512 a year to, on average, US$22,699 each.

Now, they only fish in their spare time. These incredible results are the driving force behind protecting whale sharks and coral reefs. “Once you protect our whale sharks, it follows that we an have obligation to protect our coral reefs because whale sharks are dependant on them,” said the mayor.

Feeding whale sharks is controversial, and some western environmentalists have lobbied to shut Oslob down. However, a recent review of various studies on Oslob found there is little robust evidence that feeding small amount of krill harms the whale sharks or significantly changes their behaviour.

Oslob is that rare thing that conservation donors strive to achieve – a sustainable livelihoods project that actually changes the behaviour of fishermen. Their work now protects whale sharks, reduces reliance on fishing for income, reduces destructive fishing, and increases fish stocks – all while lifting fishermen and their families out of poverty. Oslob is a win-win for fishermen, whale sharks and coral reefs.

Judi Lowe, PhD Candidate, Southern Cross University

This article is republished from The Conversation under a Creative Commons license. Read the original article.