How Bad Is It?

In 2010, scientists named the lionfish a major threat to biodiversity. In some places, lionfish have reduced fish populations by 80 percent. How?

Unlike many other fish, lionfish never say no to food. They can eat one to two fish per minute. This adds up to hundreds of thousands of fish a year. They feed mostly on small fish. Yet, lionfish can wipe out entire groups of crustaceans, like shrimps, too. They also eat the young of larger fish. This makes it hard for some species to grow in number.

A lionfish swims near a mangrove forest.

New Rules

Mangrove forests have always been a safe haven for young reef fish. The underwater roots of mangrove trees provide both food and cover. Few predators hunt in its brackish waters. But lionfish don't follow these rules. They hunt there with ease. This makes them especially dangerous.

This young snapper is being cleaned by humpback cleaner shrimp.

Lionfish disrupt coral reefs, too. Cleaning stations there are “safety zones.” Larger fish line up to get parasites picked off of them by smaller fish. The small fish get a meal. The large fish get clean. And no fish gets eaten while the work is being done. Unless a lionfish comes by!

Lionfish also eat many fish that eat plants and algae. Algae are a type of plant that grow on corals. When the fish that eat them are gone, algae grow out of control.

Algae cover corals, choking out the light they need. This leads to the loss of habitat for all reef creatures.

These lionfish crowd together on a coral reef.