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Freshwater biodiversity losses threaten health of people in Peruvian Amazon

A boy holds a freshly caught boquichico, a commonly eaten freshwater fish species, along the banks of Peru's Ucayali River. Photo by Sebastian Heilpern
A boy holds a freshly caught boquichico, a commonly eaten freshwater fish species, along the banks of Peru's Ucayali River. Photo by Sebastian Heilpern

May 28 (UPI) -- Populations in the Peruvian Amazon rely on freshwater fish for a significant portion of their diet. Unfortunately, many of these fish species have suffered significant declines over the last few decades as a result of climate change, land degradation, overfishing and pollution.

According to new research, ongoing freshwater biodiversity losses in the region are likely to result in significant nutritional shortages for many indigenous communities.

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For the study, published Friday in the journal Science Advances, scientists measured the nutritional qualities of the fish stocks popular among the communities of Loreto, Peru's largest department.

The vast region of rainforest is inhabited by roughly 800,000 people, almost all of whom eat fish at least once day.

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On average, the people of Loreto eat 115 pounds of fish per year. By comparison, the average American eats a little more than 16 pounds of seafood per year.

For the people of the Peruvian Amazon, fish is their primary source of not only protein and fatty acids, but also essential trace minerals like iron, zinc and calcium.

Despite their significant fish consumption, a quarter of children in the region are malnourished, while some 20 percent of women of child-bearing age are iron deficient.

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The region's freshwater species face a multitude of environmental threats. As a result, scientists worry the region's nutritional problems are only going to get worse.

"If fish decline, the quality of the diet will decline," study co-author Shahid Naeem said in a press release.

"Things are definitely declining now, and they could be on the path to crashing eventually," said Naeem, director of Columbia University's Earth Institute Center for Environmental Sustainability.

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Many of the region's most important freshwater species are migratory fish, but increasingly, the journeys of these fish are being interrupted by dams constructed for hydroelectric power.

Fish in the region are also threatened by deforestation, increasing water temperature and accelerating sedimentation, which can disrupt both the feeding and reproductive patterns of important fish species.

Fishers in the region are bringing in smaller hauls than they were a decade ago, but the threats facing the region's freshwater species aren't exactly unique. Surveys suggest more than a third of freshwater species around the world are threatened with extinction.

What makes Loreto unique is the importance of freshwater fish to local diets.

To better understand how biodiversity losses are likely to impact local communities, researchers regularly visited the region's fishing docks and food markets, purchasing a variety of the most popular eating fish, including medium-sized scale fish, such as ractacara and yulilla, as well as giant catfish and palometa, a relative of the piranha.

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Researchers shipped specimens of 56 of the 60 most popular fish stocks back to a government lab in Lima for analysis -- measuring the amounts of protein, fatty acids and trace minerals in each variety.

As the availability of larger migratory fish have become less common, local communities have been forced to substitute smaller local species.

The latest analysis suggests this ongoing trend is unlikely to impact protein and fatty acid intake. Some may even benefit from an increase in fatty acids.

However, the lab tests showed most smaller fish species have significantly lower levels of trace minerals.

"Like any other complex system, you see a tradeoff," said lead author Sebastian Heilpern, who recently earned his doctorate degree from Columbia. "Some things are going up while other things are going down. But that only lasts up to a point."

For now, smaller, local fish species can plug nutritional gaps, but researchers predict that once 40 of the 60 most popular fish stocks in the region near extinction, local communities will be forced to start turning to other food sources.

"You have a tipping point, where the species that remain can be really lousy," said Heilpern.

In other places where wild food sources are rapidly declining, local populations have turned to raising livestock, such as chicken, as well as aquaculture -- and in Loreto, chicken and aquaculture production is on the rise.

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But the latest analysis suggests these food sources are nutritionally inferior to the mix of wild fish species that the people of the Peruvian Amazon have relied on for generations.

Chicken production and aquaculture also put additional environmental pressures on the freshwater habitat and ecosystems that host some of the region's most important fish stocks.

While Loreto is unique, researchers suggest the problems triggered by biodiversity losses are common across many parts of the world.

The researchers said they focused on Loreto's fisheries as an example of biodiversity being important for local resident's source of dietary nutrients but expect the findings apply to other food systems reliant on wild sources.

The authors of the latest paper hope their findings will move policy makers to emphasize the connections between biodiversity, wild foods and food security.

They note that inland fisheries support more than 150 million people around the world, and marine fisheries support more than 1 billion people.

"Ultimately, mainstreaming biodiversity into the management of wild-caught species, as we have shown here with inland fisheries, requires investing in policy and practices that sustain biodiversity such as protecting key habitats, maintaining habitat connectivity, and enacting temporary moratoriums on capture," researchers wrote.

"Only when biodiversity is valued alongside harvested biomass and revenue will people be able secure and sustain the full set of nutritional benefits provided by wild foods," they wrote.

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