Too close to human

Establishing marine reserves far from human activity? A measure which may seem paradoxical, but which could well become a central lever in the preservation of the oceans. In any case, this is what emerges from the latest major global study to survey the fish and shark populations sheltered by coral reefs.

© Nick Graham

It's a study that will surprise even the greatest specialists. "When I received the data, I thought it was a joke. A bad joke," says David Mouillot, an ecologist at the Marbec laboratory (Marine Biodiversity, Exploitation and Conservation) and a member of the international consortium that conducted this major census. The researchers observed 1,800 coral reefs, including 106 in marine reserves, and found that only a third are inhabited by top predators such as sharks.

Away from men

Sharks that prefer to settle far from any human presence: researchers found these large predators on only 1% of reefs located close to man, compared with 59% on reefs located far from man. Not enough to film a new episode of Jaws. " Sharks are particularly sensitive to noise generated by human activities, not to mention the presence of nets in which they can get caught". So many reasons to exile themselves far from man. Away from us.

Can common fish stand our company better? Nothing is less certain. According to David Mouillot, the main reason why the reserves near our coasts remain positive is that "the comparison between the population present inside a reserve and that found outside can only be positive, since outside there's nothing left! It's as if you had a 2/20 and compared your mark with someone who had 0. You've done twice as well, but you've still got 2".

Strong human pressure

To assess the extent of human pressure on these reserves and determine their real effectiveness, the researchers compared their biomass with that of the world's most isolated sites, such as Hawaii, the Chesterfield Islands or the Chagos Archipelago. The results are indisputable: "The biomass in these reserves close to man is no match for these world-renowned sites. There is a gain, but the benefit is not huge compared with the performance of very isolated sites or the most protected reserves".

The cause, of course, is fishing. While these reserves have the merit of existing, they represent only a tiny percentage of total marine areas. " As soon as fish set foot outside the reserve, they are fished out, which prevents the population within the reserve from developing normally," deplores David Mouillot. In 2010, the Aïchi objectives committed UN member states to placing 10% of their marine areas under protection by 2020. Still insufficient to combat overfishing, according to the researcher.

Economic barrier

But how far can we go, or rather, how far can we not go, to find this ocean free of all human pressure? "Twelve hours of sailing! That's the threshold at which the cost of diesel [around 1,000 euros] becomes a deterrent for fishermen and tourists. It's an economic barrier. David Mouillot, like other ecologists, is actively campaigning for higher fuel prices and an end to fishing subsidies. "It's a vicious circle: the more you subsidize, the fewer fish there are, and the fewer fish there are, the more you subsidize.

The researcher also points out the damage caused by recreational fishing, and urges individuals to abandon this cultural practice: "It's easy to take out a fishing rod, but you wouldn't dream of killing a bird in your garden".

Extending reserves

Does this study mean that the divorce between fish and man has been finalized? Are fish stocks near our coasts doomed? No," replies the researcher, "they are still very useful, provided they are drastically extended. As for isolated reserves, far from being useless or easy, "our study shows that they are the only effective protection for top predators .They should not be neglected.