Round Goby - Invasive Species

Invasive Species

The species was accidentally introduced into the North American Great Lakes by way of ballast water transfer in cargo ships. First discovered in North America in the St. Clair River in 1990, the round goby is considered an invasive species with significant ecological and economic impact; the consequences are quite complex as the fish both competes with native species and provides an abundant source of food for them while consuming other invasive species. In other words, the round goby behaves much like most biological invasive controls. An aggressive fish, the round goby outcompetes native species such as the sculpin and logperch for food (such as snails and mussels), shelter and nesting sites, substantially reducing their numbers. Round gobies are also voracious predators of eggs of native fish, many important to the angling industry. The goby's robust ability to survive in degraded environmental conditions has helped to increase its competitive advantage compared to native species. Many native predatory fish such as smallmouth bass, largemouth bass, walleye, salmon and trout have begun to prey on round gobies. These game fish feed so heavily on the abundant gobies that a bait company, called Culprit, has created a soft plastic bait called the "Great Lakes Goby" to exploit this behavior. The incorporation of the round goby into native foodwebs, coupled with the goby's ability to consume large numbers of invasive mussels (zebra and quagga), may result in greater bioaccumulation of toxins such as PCBs higher in the food chain, since these mussels filter-feed and are known to accumulate persistent contaminants. However, this is partly beneficial because even though they do not reduce the population of zebra mussels, they do control their population. Hence, it prevents a large scale spread of the zebra mussel, which is also an invasive species in the Great Lakes.

An unintended benefit of the round goby's introduction is that the Lake Erie Watersnake, once listed as a threatened species, has found it to be a tasty addition to its diet. A recent study found the introduced fish now accounts for up to 90% of the snake's diet. The new food supply means that the water snake is now staging a comeback.

The round goby is also considered invasive in parts of Europe. The processes of invasion of the round goby in Europe were started by its introduction to the Gulf of Gdańsk (Southern Baltic Sea) in 1990. Recently the cases of the round goby invasion are mentioned in the Aegean Sea, in the different parts of the Baltic Sea, North-Sea basin, and basins of the rivers Danube and Rhine. In the German part of the Baltic Sea this fish was first noted near the Rügen Island. Now it is distributed along all south-western Baltic Sea coast includes the Stettiner Haff (Szczecin Lagoon), the Unterwarnow (the Estuary of the Warnow River), the mouth of the Trave River, and in the Nord-Ostsee (Kiel) Kanal.

At this time, the westernmost site of the round goby occurrence in Europe is the Lower River Scheldt, the tidal zone in the river mouth, and Albert Canal, Belgium.