What Is the Impact of Fishing on Coral Reefs?

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A study of Caribbean reefs suggests commercial fishing could drastically reduce the supply of key nutrients.

By Nathan Collins

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Fishing boats in the harbor at Nassau in the Bahamas, circa 1939. (Photo: Horace Abrahams/Fox Photos/Getty Images)

Many of the nutrients stored in coral reef ecosystems reside in organisms like fish. So it’s no surprise to learn that commercial fishing could drastically affect those reef ecosystems’ access to the key ingredients of life. In fact, according to a new study, fishing in Caribbean coral reefs could cut nearly in half the nutrients stored in fish.

“Rebuilding coral reef fish communities is of critical importance for food security and the livelihood of billions of people,” writes a team led by Jacob Allgeier in Nature Communications. “We suggest that in addition to well-acknowledged conservation targets such as biodiversity protection, a broader perspective that incorporates predictable impacts of fishing pressure on nutrient dynamics is imperative for effective coral reef conservation and management.”

Although fishing is widely thought to harm biodiversity in marine environments, Allgeier and his colleagues write, less is known about how pressures from fishing affect ecosystem services, such as the flow of nutrients in coral reefs. To find out, the researchers studied 143 fish species living in 110 communities across 43 Caribbean coral reefs, keeping track of biomass, the number of each fish species, and how those fish used different nutrients.

“Rebuilding coral reef fish communities is of critical importance for food security and the livelihood of billions of people.”

The main result: After controlling for the total fish biomass, the most important factor affecting nutrient levels was the distribution of biomass—in particular, whether a community was made up mostly of small fish low on the food chain, or a more even distribution of small and larger fish, the latter of which land higher up on the food chain.

Fishing has a big impact on nutrients, the team argues, in large part because it affects the distribution of fish sizes. Fishing obviously removes a lot of fish biomass (taking a big chunk of nutrients with it), and it tends to do so in the form of the largest fish at the top of the food chain. That interrupts the flow of nutrients through coral reef ecosystems and cuts nutrient levels by upwards of 40 percent.

Ultimately, that’s bad for coral themselves, since their survival depends on nutrients recycled through fish. “Our findings underscore the growing need to incorporate animal-mediated nutrient dynamics in models of ecosystem function,” the researchers write, “particularly in light of the rapid rate of exploitation of animal biomass throughout the world.”

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