Caribbean Curiosities: Monster from the Shallows

They may not look scary—especially the inch-long juveniles in the aquarium at Amuseum Naturalis—but tilapia have a host of characteristics that make them fearsome invaders on an island like St. Martin.

A tiny monster may be disrupting local wetlands.

Tilapia are a group of fish from the warm parts of Africa and the Middle East. They are diverse, with about 100 species, and most live in fresh water. Some species are popular as food. They are caught wild in the lakes and rivers of Africa and farmed around the world to the tune of over a million tons per year.

The things that made them successful in their native range and popular with fish farmers also make them a very dangerous invasive species. In recent years, they have been introduced around the world where they wreak havoc on freshwater ecosystems, eating and competing with native species.

Why are they so dangerous? For starters, they are omnivorous, so they have the potential to disrupt aquatic plants and animals. They even have two sets of jaws. The pharyngeal bones in their throat have teeth and muscles to help tilapia use them as a second set of jaws. With this adaptation, they are able to eat more things and do so more efficiently.

Tilapia grow quickly and reproduce with gusto. They can’t handle cold temperatures or very salty water—something we see in the Great Salt Pond when increased salinity causes large die-offs of tilapia. Otherwise, in tropical areas like St. Martin, they can be all but unstoppable. They are extremely common in the Great Salt Pond and in many waterways and ponds on the island. We don’t know for sure how they impact native species of fish, shrimp and aquatic life, but it’s probably not good.

To their credit, they do eat mosquito larvae and may eat things that other fish avoid. Perhaps they eat the algae that grows too much when human-introduced nutrients overwhelm ponds. Unfortunately, the cost to the local ecosystem is probably higher than the benefits.

At Amuseum Naturalis in Grand Case, a surprisingly fearsome gang of inch-long tilapia prowl the aquarium eating the roots of the water hyacinth, algae growing on the backs of snails and any guppies small enough to fit in their mouths. They are the first to devour tiny pellets of fish food, and their appetite seems insatiable. It’s easy to see why they are considered one of the most dangerous invasive species on earth.

Tilapia are part of the Gut Life exhibit at Amuseum Naturalis. Visit the museum for free on Tuesdays and Thursdays from 4-8pm or get more info at

Caribbean Curiosities is a brand new column in The Daily Herald’s Weekender section. Each week, the column will take a closer look at something from the strange and wonderful world of St. Martin’s nature. Everything featured in Caribbean Curiosities can also be found at Amuseum Naturalis.

Leave a Reply

Your email address will not be published. Required fields are marked *