Up to 26 times more fish found on reefs near mangrove forests

WWF

A study published in the science journal Nature has found the strongest link to date between the productivity of coral reef fisheries and the health of nearby mangrove forests.

The study compared the numbers and amount of fish on reefs near mangrove forests to reefs far from any mangroves. One species, blue striped grunt, was found to be 26 times — or 2667 per cent — more abundant on reefs near healthy mangroves, measured in total biomass.

"There is nothing subtle about these numbers," said Dr Peter Mumby, a researcher from the University of Exeter in England and the study’s lead author. "This research shows a direct link between mangroves and the number of fish on coral reefs including several species of snapper that are heavily fished. Protecting mangroves in association with reefs will provide a much bigger return on investment than only protecting reefs in isolation."

The study measured 164 fish species, including well-known fish like snappers, parrot fish, and grunts. Among their findings, researchers discovered that the biomass of several commercially important species more than doubled when adult habitat was connected with mangroves. One ecologically important fish, the rainbow parrotfish — the largest herbivorous fish in the Atlantic — is so dependent on mangroves that it became locally absent after the forests were removed.

"Reefs alone are not responsible for the productivity of some coral fisheries," said Dr. Kenyon Lindeman, senior scientist with Environmental Defense and a co-author of the report. "There is a strong economic rationale for protecting mangroves since coral reef fisheries have an estimated annual value of US$5.7 billion and many people also depend on them for subsistence."

In the Americas, mangroves are being cleared at a rate faster than tropical rainforests. More than 35 per cent of the world’s mangroves are already gone. Mangroves buffer the effects of violent storms, filter pollution and provide critical habitats for many fish species, particularly in juvenile stages.

Mangroves will be discussed next week at the meeting of the Convention of Biological Diversity in Kuala Lumpur, Malaysia. Delegates there are scheduled to vote on a proposal to create networks of marine protected areas. The meeting takes place in the heartland of marine biodiversity, where mangroves reach their greatest diversity.

"Networks of marine protected areas work for both people and fish," says Dr. Ghislaine Llewellyn, a marine scientist with WWF-US and a co-author of the report. "This study is yet more evidence that systems of marine parks are urgently needed to safeguard biodiversity and secure food resources."

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