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Masters of the Ghaut

Get an inside look at science as it happens in the Caribbean. This week we find out who rules the streams and rivers of St. Kitts.

The Southpaw Crayfish has a huge and hairy left claw.

In nature, every habitat needs an animal at the top of the food chain. Often these animals are called an apex predators. They play crucial role in the health of an ecosystem. By preying on the animals below them in the food chain, they maintain balance in an ecosystem.

In the biggest rivers and streams of St. Kitts the apex predators are often crayfish. Unlike many apex predators, crayfish are not just hunters. They have a diverse diet that includes plants and scavenged food. But their size and powerful claws give them the power to hunt most of the things living in the water with them.

There are at least two of these crayfish in Wingfield River. The smaller species is the Southpaw Crayfish because it develops a huge left claw. They are beautiful shades of red and blue. Adults are easy to identify by their big left claw, which is also covered in fine hairs. A big adult can be about the length of your hand, claws included.

The Bigclaw River Shrimp is much larger, reaching up to a foot long. It is typically cream and brown with bands running down its long tail. Its claws are thin, and almost as long as its whole body. Weighing up to a pound and a half, there’s no question who rules the river when you see a Bigclaw.

The Bigclaw River Shrimp is an freshwater giant.

These amazing crustaceans are not necessarily very common. Due to their size typically need running water—which is richer in oxygen—to live. They tend to live in the larger pools and deeper sections of the river. Bigclaws in particular tend to be territorial, with only one per pool.

So how do these crayfish kings manage their freshwater kingdom? While no one has studied their diet on St. Kitts, they are definitely able to catch and eat aquatic insects, guppies and tadpoles. A careful observer will note that there are no guppies or tadpoles where our predatory crayfish are found. Guppies and tadpoles are often common in still water or streams that are too small for large crayfish.

Long live the masters of the ghaut! Though few in number, they are critical to the of clean water we depend on and the health of the river ecosystem.

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