DURHAM, NC — The killer shrimp (Dikerogammarus villosus) is one of many species worldwide that has expanded beyond its native habitat and become known as an aquatic nuisance species. Originally found only in central-eastern Europe, it has invaded waterways throughout the continent, where it attacks and eliminates native gammarid species. With large, powerful mandibles, the killer shrimp is capable of consuming a variety of prey and outcompeting other amphipods. It gets its name from its destructive behavior, killing far more prey than it can eat, and has even been known to attack small fish. Within a short time after invading a new area, it can eliminate a wide range of species from the ecosystem, drastically altering the interactions of the food web.
At present, there have been no reports of killer shrimp in North America. However, the transportation of this destructive invader to the U.S. is not out of the question, as everyday thousands of gallons of foreign water are brought into the country through the ballast water of ships. This is one of the most common means by which species are transferred between continents, and has been responsible for countless aquatic invasions in the past.
In hopes of preventing the establishment of a killer shrimp population in the U.S., Bernard Jiang of Duke University has proposed a study to test the effectiveness of ballast water treatment on killer shrimp. Jiang’s study will examine the four main types of ballast water treatment: mid-ocean ballast water exchange, biocides, heat treatment, and filtration, in an attempt to determine which is best suited to eliminating the shrimp from a ship. Jiang intends to use tanks of water to simulate a ship’s ballast container, controlling temperature, salinity, oxygen level, and all other abiotic factors. The researchers will put live shrimp specimens at every stage of life into the tanks, perform one of the treatment methods on each tank, and record the number of live shrimp still in each of the tanks after treatment.
The goal of this study, according to Jiang, is “to determine which ballast water treatment is most effective at controlling the shrimp”. This in turn, he elaborates, “will help prevent the spread of killer shrimp, and will also provide insight into the effectiveness of treatment methods in general”. There have been previous experiments testing the relative effectiveness of different methods of ballast water treatment, but this would be the first study to focus specifically on killer shrimp. As such, it would provide species-specific results that would suggest the best way to prevent the introduction of the shrimp into the U.S., explains Jiang, as well as contributing to the general body of knowledge regarding ballast water treatment as a whole.
According to the researchers, killer shrimp should be one of the main priorities targeted by invasive species policy creators, as it could “cause unprecedented amounts of damage” if introduced, yet there is still the possibility of preventing it from doing so. “Killer shrimp have only appeared on the invasive species radar in the last decade,” says Jiang, “but they have been particularly effective in their invasiveness.” For this reason, he argues, it is essential that research be done immediately to determine how best to keep the shrimp out of North America, while there is still the chance to do so.