Dipping for Diversity

Get an inside look at science as it happens in the Caribbean. This week, we dip into freshwater habitats as part of a biodiversity survey of St. Kitts and Nevis.

Dip-netting for aquatics at Pond Hill on Nevis. (Photo by Jenn Yerkes)

Take a medium-sized mesh strainer and use some duct tape to secure it to the end of an old broomstick. Voilà, you just made a dip net! This simple net is one of the most useful and versatile tools for investigating life in freshwater habitats.

As part of the scientific team surveying the plants and animals of St. Kitts and Nevis, my specialty is freshwater aquatic life. This includes anything living in the streams and ponds and any other place where fresh water accumulates. Despite the clouds that often cling to the peaks of both islands, freshwater habitats are somewhat limited.

Like much of the Caribbean, these islands are recovering from the drought of previous years. The many the ghauts—a regional term for narrow valleys—on these islands that channel rainwater down the mountain to the sea in wetter times are mostly dry. At a few points on the forested slopes, water is running, but much of it is taken to provide water for the people living here.

Still, life is persistent. Multiple species of freshwater crayfish and a couple fish species manage to survive in the mountain streams. During times of rain, they take the temporary streams downhill and survive in pools as long as they last.

A River Goby clings to a rock in the Wingfield River.

Caribbean crayfish and freshwater shrimp have a complex life cycle. They typically spend their larval phase in the sea, or in the brackish water a the mouth of a river or stream. It is a bit of a mystery how they manage to survive in these mountain streams during extended periods when they are not connected to the sea, or connected only briefly.

In lower elevations, the primary freshwater habitats are ponds, mostly manmade ones. The native animals living in these ponds are primarily insects: aquatic beetles, dragonfly and damselfly larvae and water bugs. Introduced species, particularly the tadpoles of marine toads and Cuban tree frogs, are also present.

Although widespread in the Caribbean, including Nevis, the Cuban tree frog has only recently been documented on St. Kitts. Surveying freshwater sources might give us an idea of how the Cuban tree frog spreads after arriving on an island. While we race to document the biodiversity of these islands, the islands themselves are changing right before our eyes. It is a challenge and an opportunity that makes our work here even more rewarding.

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