Dry Equipment Poor Habitat for Invaders

Reducing the spread of some invasive species into lakes could be as simple as asking boaters and fishers to dry out their equipment, said Shelley Arnott, Ph.D., a biology professor at Queen's University in Canada.

When anchor rope, fishing line, and boats are thoroughly dried, the invasive species and their eggs will die, she explained. "It's such a simple thing for the general public to do, and yet it could make a big difference in the way that our lake ecosystems function."

Arnott's research focuses on the spiny water flea, a small invertebrate predator that has invaded more than 100 North American lakes since the early 1980s, after being transported from Eurasia in the ballast water of ships. With graduate student Angela Strecker, she compared the levels of zooplankton – microscopic, free-floating animals that live on algae and are in turn eaten by small fish – in Ontario lakes invaded by water fleas.

They discovered that production of zooplankton in the warm, upper layer of water in invaded lakes was reduced by almost 70 percent, compared to lakes that are not invaded. "This reduction in productivity was likely caused by the direct consumption of zooplankton by the fleas," said Arnott. Another explanation for the reduction is that zooplankton may have migrated to colder, darker waters, where they would be less visible to predators, she added.

As a result, there is less available food for the small fish that forage in surface waters, such as lake herring, which are in turn are eaten by larger fish, such as lake trout. Biology master's student, Leah James, is now studying herring growth in lakes invaded by the spiny water fleas.

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