The Great Lakes Maybe Threatened by a New Aquatic Invader

The Great Lakes Maybe Threatened by a New Aquatic Invader

Scientists worried by the rapid spread of a small crustacean throughout Europe's rivers; and canals could be the next exotic invader in the Great Lakes. Dikerogammarus villosus, a small shrimp, is a hardy invader tolerant of a wide range of temperature, oxygen levels and salinity. Dikerogammarus villosus likes to take a bite out of other species, the ones it doesn't eat entirely will often die of infections. Scientists have nicknamed Dikerogammarus villosus, the killer shrimp. The shrimp comes from around the Caspian Sea and Black Sea and has spread through Europe by ballast discharge and canals. They average size for Dikerogammarus is 6 mm to 30 mm long and are voracious eaters and are blamed on the decline of native shrimp where they have invaded. If it does become established in the Great Lakes, it is feared it could alter the forage base. Its habit of attacking and biting other species including small fish, it could be very negative for the fishery. It is suspected it might feed on fry and fish eggs as well. Dikerogammarus may also be an intermediate host of acanthocephalan worms (a parasite of birds and fish) it is possible to infect humans. This worm lives in the digestive tract getting nutrients from its host.

Current recommendations that ships exchange ballast water at sea will do little in preventing the killer shrimp from finding its way into the Great Lakes. This shrimp is tolerant of salt water. Many ships crossing the Atlantic are loaded with cargo and therefore are considered not to have ballast water on board (NoBoB) because their tanks are nearly empty. These ships do not exchange any ballast water at sea. Ballast tanks are never emptied completely and can hold invaders. It is imperative that we adopt some strategy that will prevent invasive species from reaching the Great Lakes. I have made suggestions in the past, there is technology available, none will be effective until there is the political will to pass the laws that will prohibit exotic species introductions

By Tom Marks

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