European Shrimps Kill American Invader: How to Beat Invasive Species

A war is being waged across Europe's rivers and lakes. A shrimp from America has been invading European waters for decades, yet something has prevented it from taking a serious foothold. Now, scientists have discovered that battles are being fought against the American shrimp every day and that European shrimps may be winning.

The researchers mapped the occurrence of the American shrimp. Surprisingly, they found that it only existed where native shrimps were absent or rare. When native shrimps were common, the American shrimp simply could not establish and it disappeared.

"We came up with the idea that the native shrimps might be eating the exotic species to the point of local extinction and hence its patchy occurrence," said Jaimie Dick, one of the researchers, in a news release. "So we staged fights between two of our native shrimps Gammarus pulex and Gammarus duebeni, and they both proved very effective at killing and eating the invader Cragonyx pseudogracilis."

In all, the researchers compared the numbers of invaders killed over a range of their densities. In the end, they found that the native shrimps can actually kill most invaders to the point their populations crash. This, in turn, halts the invasion.

"Remarkably, one of the native shrimps, G. pulex, which almost never allows the invader to establish, was the better of the two predators in our experiments," said Dick

The scientists discovered that the other shrimp, in contrast, can sometimes co-exist with the invader. This is probably because it's a less effective predator. That said, it still gives the American shrimp a run for its money.

"Understanding how native species resist exotic species could help us prevent further invasions that damage crops, biodiversity and cost billions each year," said Dick in a news release. "if we act to help native species populations, we can reduce the menace of invaders. Finally we can begin to turn the tide on unwelcome and out-of-control colonists."

The findings are published in the journal NeoBiota.