Could an Invasive Species Save Caribbean Coral Reefs? - Pacific Standard
Coral ecosystems around the globe are collapsing thanks in large part to human activities. How far should we go to save them?

We know by now that our coral reef ecosystems are screwed—the obituaries are already being penned. To date, there’s been little we could do to stop reefs’ destruction (well, little outside of curbing our emissions). Rising temperatures, acidifying oceans, and over-harvesting of algae-eating fish have left reefs on their last legs. But James Cook University researchers David Roy Bellwood and Christopher Harry Robert Goatley see a potential solution in another ecological disaster: invasive species.

Bellwood and his colleagues have been studying reef fish for decades, but it was a recent trip to the rocky coasts of the Mediterranean that tipped them off to this potential solution. Rabbitfishes are typically found in tropical waters, but, in recent years, they have migrated into the Mediterranean Sea by way of the Red Sea. There, the rabbitfishes munch on microalgae, out-competing other herbivorous fish that are native to the region. The rabbitfish invasion in the Mediterranean is arguably bad news, but, they argue in a new correspondence in Current Biology, a similar invasion into the Caribbean could be just what the coral reefs there need.

Bellwood knew that, in the Caribbean, a lionfish invasion has driven down the population of algae-eating fish, which was already in decline due to overfishing. Subsequent algal outbreak combined with coral disease and other environmental stressors are causing coral ecosystems there to collapse. The authors wondered, could a rabbitfish invasion in the Caribbean be a good thing?

The research suggests they might: Rabbitfisheshave already proven resilient in the face of overfishing; they may be less likely to become lionfish food than Caribbean species; and their feeding behaviors may be different enough from other herbivores that rabbitfishes won’t have to compete with other plant-eating fish.

Theoretically, rabbitfishes seem like a perfect fit, but it’s impossible to say for sure that there wouldn’t be any negative consequences of introducing them into Caribbean waters.

“The Caribbean will never be the same again. We cannot eradicate lionfishes. Along with the widespread overfishing and the extensive loss of the two major coral species, we have produced a new Caribbean ecosystem,” says David Roy Bellwood, a professor of marine biology and lead author on the correspondence. “The question is whether rabbitfishes will help ameliorate some of the problems that we have created or will it make things worse?”

In other words, humans have created a very precarious situation in coral ecosystems, and Bellwood’s findings suggest that there are ways that humans could intervene. But should we?

“The fact that we are having to consider the possible advantages of a rabbitfish invasion points to the fact that our management of these ecosystems to date has effectively failed,” Bellwood says. “We are now faced with the real possibility of having to consider risky interventions. This is a sobering reality.”

Of course, rabbitfishes could eventually make its way to the Caribbean on its own. The fish have thrived all along the Mediterranean coast, and are poised to invade the eastern Atlantic. Then it might be only a matter of time before they migrate to the Caribbean; about one-fifth of all Caribbean fish lineages got there by crossing the Atlantic sometime in the past. But humans may have already jumped the gun: Bellwood says they’ve seen a rabbitfish in the Caribbean, and it probably got there the same way lionfish first arrived — by escaping from man-made aquariums.

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