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'Saving Nemo': How Australian schools are protecting the clownfish

The humble clownfish is smaller than a human fist.

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Ivan Watson, Rebecca Wright
Tom Booth, CNN
(CNN) — The humble clownfish is smaller than a human fist.

But when a diver approaches its underwater home, among the tentacles of a sea anemone on the world's coral reefs, the little orange creature rears up and adopts a fierce protective posture.

"They're quite aggressive fish," says Karen Burke da Silva, a marine biologist at Australia's Flinders University.

"If you come close to a clown fish, it will come out of its anemone and try to bite doesn't make sense."

Despite its territorial nature, the clownfish is one of the most easily recognized coral-reef inhabitants.

Read: Successful trial of 'coral IVF' gives hope for Australia's Great Barrier Reef

The orange-and-white striped species was made famous by the popular 2003 animated film "Finding Nemo." The film told the story of an adult clownfish searching for his son Nemo, after a diver captures him from the wild. But its box office success had some unintended consequences.

Overfishing threat

Da Silva says the movie triggered a surge of demand for pet clownfish.

"The film portrays quite a different message, which is 'don't take Nemo out of the sea.' And yet people responded quite differently," she says.

"The places where they were getting those fish were actually from the wild," she explains, adding that overfishing led to local extinction in some places.

Da Silva is co-founder of an initiative called "Saving Nemo." It partners with schools to promote clownfish conservation and educate students about marine habitats.

At Belgian Gardens Primary School in the Australian city of Townsville, students volunteer to help breed baby clownfish.

"We breed them so we can give fish that we breed to people who want clownfish. So they don't have to take them out of the wild," explains 11-year old Imogen Everson

She and her classmates clean tanks, cultivate the artemia -- or sea monkeys -- used to feed clownfish, and they monitor the growth of hatchling clownfish.

In one of the tanks, she identifies a small cluster of what appear to be bubbles that line the inside of a clay pot. They are clownfish eggs.

"The dad, the smaller clownfish, will always check on them ... and gives them oxygen," Everson says.

Ryan Pedley, the principal of the school, says captive-bred clownfish are later traded to pet stores for the aquarium supplies needed to help keep the program going.

"It's another way to immerse our students in reef ecology," Pedley says.

"The kids don't actually have to visit the reef. They can do their part by breeding clownfish in captivity and donate them to the fish shops."

Coral reef die-off

Marine biologists say in recent years, the clownfish has been confronted by a newer, potentially more destructive challenge: climate change.

Rising temperatures around the globe are bleaching and killing the coral reefs and the sea anemones with which clownfish share a symbiotic relationship.

In fact, in 2016 and 2017, successive marine heat waves killed off around half of the coral on Australia's Great Barrier Reef, the world's largest reef habitat.

"If the [clownfish] can't find a sea anemone to call home and get protection from, we might see that population die," says Jodie Rummer, a marine biologist at James Cook University.

Read: The Great Barrier Reef is literally in hot water

Rummer's research has concluded that if sea temperatures rise between 1.5 and 3 degrees Celsius, coral reef fish lose between 40 to 70% of their performance -- including swimming, feeding and reproduction.

The scientific consensus concludes global temperatures are roughly 1 degree warmer today than during the pre-industrial era in the late 19th century. Scientific organizations like NASA forecast the planet will continue to warm in coming decades as a result of increasing carbon dioxide emissions.

Rummer argues clownfish and other marine species will likely need more drastic help than school captive breeding programs.

"The way to protect them is a really, really big solution: that's kind of ending our reliance on fossil fuels, which is directly related to the warming of the oceans," she says.

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