From a great piece in the NYT by Carl Safina.
About 20 years ago, one of the world’s most beautiful and otherworldly fish, the red lionfish, started showing up in south Florida and the Caribbean. Now, they’re a plague. Millions of them live from northeastern South America to New York, from water you can stand in down to depths of a thousand feet.
In a world where the main concern about fish is overfishing, and the main demand on fish is to feed an increasingly hungry human-dominated world, it may see odd to complain about abundance. But theirs is an abundance that produces widespread scarcity. That’s because invaders from afar often crowd out or gobble a wide array of desirable natives. And as an invading saltwater fish — the lion is king.
Lionfish are native to the west Pacific, Indian Ocean, and Red Sea; they’re quilled with venomous spines. The sting is not fatal, but from the descriptions I’ve heard of the pain, victims might wish it were. (Yesterday while working underwater with a scientist I got barely nicked through a glove; it produced an immediate sensation and a bump).
Lionfish are here in the Atlantic, it seems, because of owners of living room aquariums who tired of the upkeep but didn’t want to kill their fish. With compassion in their breasts, they released them, in numbers sufficient to get them established. Then—remember the phrase, “balance of nature?” Well…
No native fish in the Atlantic looks like the lionfish, hunts like it, or stings like it. Result: No native fish in the Atlantic recognizes it as a predator. No native fish in the Atlantic gets alarmed when lionfish are on the “hunt,” because a hunting lionfish looks like a drifting piece of seaweed. And no native predator — sharks, say, or barracuda — wants anything to do with those venomous spines.
And so, as I said, there are millions of them. The problem: they’ll eat anything in sight. Forty-plus kinds of native fishes have been found in their bellies, including young snappers and groupers and others of commercial, ecological and culinary value. They eat juvenile surgeonfishes and parrotfishes that, crucially, graze algae off of reefs and make it possible for baby corals to get established and grow.
Atlantic coral reefs are in a world of hurt as is. The most formerly abundant corals have collapsed throughout the Caribbean, thanks to new diseases, pollution, silt, overfishing, over-warming, and acidifying seawater. (The same combustion-produced carbon dioxide that causes climate warming dissolves in seawater to form carbonic acid, hampering growth of corals and edible shellfish.)
As corals die, seaweed takes over. Where seaweed takes over, baby corals can’t grow. One of the only hopes for the reefs is the recovery of fishes — especially parrotfishes — that graze-off the seaweed that is smothering many reefs. Reefs can’t afford a new predator that has no predators and that eats all the babies of the fish that graze. They can’t afford lionfish.
read it all here