Cosmos

HOOK, LINE & THINKER

On a remote Pacific atoll, science has blended with tradition to save a species of fish and the islanders that thrive on it. NATALIE PARLETTA reports.

- NATALIE PARLETTA is a freelance science writer based in South Australia.

NATALIE PARLETTA visits a remote Pacific atoll where a single-minded scientist and motivated locals have worked together to create a sustainabl­e industry – and future.

WITHIN THE DAZZLING turquoise waters of an atoll called Anaa in the South Pacific swims the roundjaw bonefish (Albula glossodont­a), a species that thrives in the coral-fringed lagoon’s shallow waters. But like many fish population­s globally, its numbers are dwindling, threatenin­g the island’s economy and food security. Unlike many regions around the world, a unique blend of science, children’s voices, community cohesion and a return to tradition has set the bonefish on a sustainabl­e trajectory.

It all started with a dynamic Tahitian, Hinano Bagnis. Passionate about helping residents of the surroundin­g islands, Bagnis studied law, but her interests led to a role as the executive director of an NGO helping island communitie­s. She then became frustrated with ventures that failed to address the complex environmen­tal and economic challenges faced by these communitie­s, and wanted to help them become more self-sufficient and manage their resources more sustainabl­y.

She had befriended Sir Douglas Myers, a multimilli­onaire who had fly-fished the atoll Teti’aroa with a company run by Mathew Mchugh. Myers agreed that something could and should be done, saying, “Okay, pick an island and redefine your project”.

So, with funding from Myers, the Anaa Atoll Project was born in 2016. Nestled in the Tuamotu archipelag­o, 350 kilometres west of Tahiti, 38 square kilometre Anaa was chosen by Bagnis and Mchugh as a pilot site because of its declining population of about 500 people with limited education and employment prospects, which also held promise for fly-fishing tourism. In 2018 they created the Island Initiative charity to generate more funds, and identified the island’s popular bonefish as a potential economic driver for other income sources for residents, such as accommodat­ion and locally made souvenirs.

Known to locals as Kiokio, Anaa’s bonefish appears to fly across the island’s lagoons, its shimmering silvery skin tinged with blues and greens. A member of the ray-finned Albulidae family, its speed, eagerness to feed and visibility make it a popular game fish in the warm shallow waters of many tropical regions, including Florida, the Caribbean, Seychelles and French Polynesia.

In Anaa, the locals rely on A. glossodont­a for trade – and it’s also one of their favourite food staples. This is unusual, because, well, it’s full of bones. But the fish tastes better at Anaa.

“It’s one of the few islands where bonefish is a big resource as far as eating it,” says marine biologist Alex Filous from the University of Massachuse­tts Amherst in the US, “but here it’s considered like the best eating fish on the island – and it is really good.”

According to Filous, that’s because of the worms, crabs and clams the bonefish feed on, all of which thrive in the lagoon’s uniquely shallow waters. With an average depth of just 1.5 to 3.5 metres – compared with 20 to 30 metres in other atolls – sunlight is able to freely reach the bottom.

“They’re well fed and well nourished, so they have a distinct flavour that’s different than other bonefish, and their flesh is softer,” he explains.

When Bagnis and Mchugh formed the Anaa Atoll Project, they invited Filous to investigat­e the viability of a fly-fishing venture. After identifyin­g the bonefish as the atoll’s most abundant species, and therefore critical for the islanders’ food security, Filous decided to study it for his PHD research.

From 2016 to 2018 he tracked and tagged bonefish to estimate their age, size and growth, reproducti­on, fertility and natural mortality. He used underwater computers that detect acoustic transmissi­ons from electronic tags within 500 metres. Filous surgically inserted the tags, about the size of a small phone battery, each with a unique beeping sound, inside the body cavities of 40 fish. This enabled him to track and correlate their movements with spawning and lunar cycles. He did encounter a slight hitch: at some point virtually every islander caught one of his tagged fish, which meant retrieving and cleaning the tag, before capturing another fish to track.

With the help of local fishermen, he also attached ID tags to around 2500 other fish to gather informatio­n on growth between captures, the timing of their capture and the timing of spawning with seasons and moon cycles.

To estimate the species’ natural longevity, in 2014 they had collected comparison samples from nearby Teti’aroa, which had no permanent inhabitant­s – and hence an unexploite­d fish population – and a similar predator profile to Anaa.

From the data collected, Filous calculated a spawning potential ratio (SPR) to evaluate the stock’s health. The SPR calculates the theoretica­l number of eggs a female could produce in a given population, divided by the number of eggs it could produce over its lifetime in an unfished population.

The figure is based on fish size, which in a general sense correlates with egg production. A five-year-old, 50-centimetre-long female, for instance, can produce around 300,000 eggs. If she’s allowed to grow to 60 centimetre­s (perhaps seven years and older), she can produce more than a million eggs, so longer-lived females are essential to maintainin­g a sustainabl­e fishing stock.

An SPR ratio of 100%, Filous explains, “means that this population is producing eggs at a rate that would be like it’s virgin stock that has never been touched by fishermen. And 0% means there’s no egg production.”

The data showed that the average age of the roundjaw bonefish in the waters around Anaa was well below the species’ 20-year longevity, with males surviving to eight years and females to 10. The SPR metric hovered between 7% and 20%, a finding Filous published in the Journal of Fish Biology in 2019. So, as many Anaans had already noticed, the numbers weren’t just dwindling, they were unsustaina­bly low.

To address the problem, the Island Initiative isn’t talking about not fishing, says Bagnis, but about leaving enough fish to repopulate. “It’s really man and nature working together.”

The goal is to maintain a threshold above 20%, ideally 30-40%. “The other way to think about 20%,” says Filous, “is that means you can kill 80% of the population’s egg production and still fish.” But it’s a red alert if you dip below that. “My data supported that it was pretty overexploi­ted, and something should be done.”

Filous delivered his findings to Bagnis, who asked, “If we had the full support of the population, what do you think should be done?”

As a rule, reef fish search for safe areas to spawn, Filous explains. The upper section of the atoll is ideal, because it has a deeper water passageway for them

Although the roundjaw bonefish (top left) is – as its name suggests – bony, it’s a dietary staple on Anaa. Use of traditiona­l fishing traps (top right) resulted in the islanders over-exploiting the species. The Anaa Atoll Project recovery program includes creating a new economic driver – a sustainabl­e tourism industry based around catch-and-release fly-fishing (above left). Islanders (above) still use stone traps to fish, but on a schedule informed by science and culture. Left, Anaa schoolchil­dren – with, from left, mayor Calixte Yip, marine biologist Alex Filous and school principal Jean Pierre Beaury – wrote and distribute­d a petition that was instrument­al in gaining island-wide commitment to the fishing changes.

to exit to the ocean but the swell comes from the southwest – so it’s like a rock in a stream that leaves gyres behind it. Fish have easy access because it’s deep, and the gyre helps the spawn to intermingl­e.

Albula are broadcast spawners, releasing eggs and sperm into the water in a big cloud. “Because they’re just basically squirting their eggs and sperm into the water, there needs to be a lot of fish to make sure the gametes meet,” says Filous. “So, what they do is, every fish from every corner of this entire atoll, after the full moon, swims right out here, forms a big, big, big-ass school, thousands of fish. And then it’s like, too-to-too-to-toooo, charge! They just rush through this corridor” and out to sea.

Those gametes that get lucky develop into plankton-like eels – leptocepha­lus –while the current disperses them. Finally, at about two months old, the leptocepha­lus metamorpho­se into juvenile fish.

From the sex ratios of catches throughout the season, Filous worked out that the bulk of the female population moved through the migratory corridors to spawn between March and May, at which time they were being heavily exploited by an ingenious trapping method.

The traps, locally known as kaua, are weirs made from dead coral and rocks that the fishermen drag across the ocean bottom and pile into heart shapes. “It’s like a perfect work of art,” Filous says admiringly of the technique. “I don’t know how they did it.”

Filous knew the best way to allow the bonefish population to recover to above 20% would be to close the fish traps from March to May and shift the fishing towards the end of the season when the proportion of males was greater, and females had completed their breeding. But he also was certain that there was no way the fishermen – who were among the many people he had befriended on the island – would take the traps down.

Bagnis said to Filous at the time: “Well, you have done what we asked you to do. Now it’s my turn to negotiate with those people and hopefully find a solution.” To which Filous replied, “They’re going to kill me if you say that.”

“He was really freaking out,” recalls Bagnis. “Because it was like asking those people to lose a bigger part of their income.”

Bagnis asked Filous to create a poster to help people understand the life cycle of the fish and to explain the problems with current fishing practices.

Enter eccentric, singing school principal Jean Pierre Beaury, an enthusiast­ic student of the island’s historical songs and traditions, and passionate advocate for the children’s future. When Filous sought his help to translate the poster into the local languages (French and Tuamotu), Beaury recognised how important it was to address the issue. He had applied to the French government to create an educationa­l marine area where the students could learn about environmen­tal management and conservati­on – and he saw the migration corridor as the perfect location.

The students also understood the importance of conserving the fish, saying “this is our island too, this is our future”, says Bagnis. The students decided to explain to their community what was at stake, and went door-knocking to gather signatures for a petition to reinstate an ancient Eastern Polynesian tradition – rahũi – which would pull down the traps for three months each year.

“It’s like a gentlemen’s agreement,” says Hagnis. “We are respecting this area and we are all agreeing that during three months there will be no traps.” Although it can’t be legally enforced, she adds, “In the ancient time, if you were not respecting it, they were cutting off your head. So they were very serious about that, because the rahũi is meant to preserve the resource for the whole population.”

Filous was so worried when the children went out to gather signatures that he wedged a bed against his door. But of the 300 people the students spoke to, 297 signed the petition to pull down the public traps, with fishermen who sold their catch accepting compensati­on from the Island Initiative for lost income, using profits from the newly establishe­d fly-fishing enterprise.

In 2019, the traps came down for the first time, in tandem with the reinstatem­ent of a marae – a temple made from rocks – by the children in the area, accompanie­d by a traditiona­l ceremony and music.

The rahũi’s success will be monitored over the next five years by the islanders, with Filous visiting each year.

“We don’t expect to have rahũi and then for all the fish to fall from the sky,” he says. But they expect the fish born now will grow, and 50 centimetre fish will be bigger, so the SPR ratio should increase.

“So, the past and the future met, the science and the traditiona­l too, so it was quite amazing to get it that way,” says Bagnis. “I was very proud because it really embodied the meaning of what we were trying to create with our organisati­on, you know. It started out with a Tahitian girl knowing some issues and willing to do something and now it’s not about a Tahitian girl anymore.

“It’s really about the island taking over and proposing a way to manage their resources.”

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Alex Filous has been collecting data on Anaa atoll (below) for his PHD. His topic is “fisheries science to support conservati­on of bonefish
(Albula glossodont­a) through traditiona­l community base management”.
Opposite. Marine biologist Alex Filous has been collecting data on Anaa atoll (below) for his PHD. His topic is “fisheries science to support conservati­on of bonefish (Albula glossodont­a) through traditiona­l community base management”.
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