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Invasive Species Can be Stranger than Fiction

Just last year the public was fascinated by reports of a 3-foot long, meat-eating northern snakehead fish from China found walking around behind a Maryland shopping center. Snakehead? Walking fish? Real life can sometimes be scarier than the best sci-fi flick.

Typical of an exotic invasive species, these voracious fish were out-competing native fish (because they were eating them!) and wiping out the entire pond ecosystem. Maryland police traced the problem back to a resident who had naively released a male and a female fish into the pond when they outgrew his aquarium two years earlier.

In just two years, the introduced snakeheads proliferated into a population over 100 members strong. The fish needed to be exterminated — and fast — before they escaped and walked to a river nearby.

This scenario perfectly illustrates how non-native and invasive marine hitchhikers can become a threat. "Not only do they disrupt natural ecosystems and prevent the diversity of life that we value, they cost people time and money trying to eradicate them," says Judy Pederson, MIT Sea Grant's specialist on invasive aquatic species.

Non-native plants and animals are those found outside their natural range, transported there by humans. In Massachusetts, water chestnut, purple loosestrife, and the common reed are all established, introduced aquatic plants. The green crab and common periwinkle are examples of their pesky animal counterparts.

Some invasive species spread aggressively, crowding out and often eliminating native species by consuming all of the resources. The dense vegetative cover produced by exotic weeds frequently makes swimming, boating, and fishing difficult or even dangerous.

Nary a water body in Massachusetts has been spared in the human aided migration of these pests, says Pederson. "Roughly 50 percent of freshwater fish are introduced, mainly because they are good game fish like the large mouth bass."

Invasive aquatic species hitchhike on boats, motors, bait buckets, fishing tackle and trailers. To stop their spread, people using boats and equipment in the water need to rinse everything off thoroughly. Algae dangling from motor blades and drain water need to be removed and disposed of on dry land before leaving the dock or boat ramp.

Residents can find out if aquatic weeds in their town's ponds and lakes are native or introduced by using field guides. By identifying these organisms, residents can help their town track and eliminate these nuisance plants and animals. Doing your part can prevent the next sci-fi movie from filming in a neighborhood near you.