Changes in fish biodiversity lead to lower nutritional quality

In a new study from Cornell University, experts are describing how declining fish biodiversity can affect human nutrition.

The research was focused on the Loreto region of the Peruvian Amazon, where inland fisheries serve as a critically important source of nutrition for 800,000 people. 

The findings are also applicable to fish biodiversity elsewhere. Worldwide, more than two billion people depend on fish as their primary source of animal-derived nutrients.

“Investing in safeguarding biodiversity can deliver both on maintaining ecosystem function and health, and on food security and fisheries sustainability,” said study first author Sebastian Heilpern.

In Loreto, individuals eat about 110 pounds of fish annually. The experts report that this is one the highest fish consumption rates in the world and about half the amount of meat an average American consumes each year. 

According to catch data, Loreto residents eat a wide variety of fish, including about 60 species like large predatory catfish.  These migratory fish are declining due to overfishing and hydropower dams that block their paths. At the same time, however, the amount of fish caught has remained relatively consistent over time. 

“You have this pattern of biodiversity change but a constancy of biomass,” said Heilpern. “We wanted to know: How does that affect nutrients that people get from the system?”

In collaboration with experts at Columbia University, the researchers took all these factors into account and ran extinction scenarios. They wanted to predict which species are more likely to go extinct, and which species are likely to replace those to compensate for a void in the ecosystem.

The model tracked seven essential animal-derived nutrients, including protein, iron, zinc, calcium and three omega-3 fatty acids, and simulated how changing fish stocks might affect nutrient levels across the population. 

The computer simulations revealed risks in the system regarding fish biodiversity. For example, when small sedentary fish species compensated for declines in large migratory species, fatty acids increased as zinc and iron supplies decreased. The region already suffers from high anemia rates.

“As you lose biodiversity, you have these tradeoffs that play out in terms of the aggregate quantity of nutrients,” said Heilpern. “As you lose species, the system also becomes more and more risky to further shocks.”

The study is published in the journal Science Advances.

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By Chrissy Sexton, Earth.com Staff Writer