Another intruder has been the round goby Neogobius melanostomus from the Black and Caspian Seas. According to the University of Wisconsin Sea Grant Institute "the gobies belong to a family of fish with a worldwide distribution in both salt and fresh water, but they had not been found in the Great Lakes prior to 1990".
The round goby first turned up in Lake Superior's Duluth/Superior harbour area in 1995. Round gobies are aggressive fish and voracious feeders, which will vigorously defend spawning sites in rocky or gravel habitats, thereby restricting access of other less aggressive fish to prime spawning areas. Gobies also have a well-developed sensory system that enhances their ability to detect water movement. This allows them to feed in complete darkness, and gives them another advantage over other fish in the same habitat.
Gobies also are capable of rapid population growth. They spawn repeatedly during the summer months, and each time, a female can produce up to 5,000 eggs. The males die after spawning.
However, the introduction of the goby may prove some comfort to those trying to fight the zebra mussel - studies show the round goby eats the zebra mussel in the Lakes.
The ruffe Gymnocephalus cernuus, a small but aggressive fish native to Eurasia, was introduced to the Lakes via ballast water in the 1980s. Because the ruffe grows very fast, has a high reproductive capacity and adapts to a wide variety of environments, it is considered a serious threat to commercial and sport fishing. It also has the potential to seriously disrupt the delicate predator/prey balance vital to sustaining a healthy fishery. Under state laws, it is illegal to possess a ruffe, dead or alive, in Michigan, Wisconsin, Minnesota and Ontario.
In May 1993, regulations adopted in 1990 came into effect, making it mandatory for vessels intending to enter the Great Lakes or the Hudson river north of the George Washington Bridge to carry out ballast water exchange at sea, in waters beyond the Exclusive Economic Zone and in a depth of more than 2,000 metres. Alternatively, ships can retain the ballast water on board during the entire voyage within the Great lakes, or use an alternative, environmentally sound method of ballast water management, which must first be approved by the U.S. Coast Guard.
In 1996, the National Invasive Species Act of 1996 was passed. The act is the U.S. federal bill to reauthorize and expand the 1990 federal nonindigenous species legislation. A key element of the legislation is that it provides for ballast water management to prevent the introduction and further spread of nonindigenous species in U.S. waters.
Further reading:
Stemming the Tide - Controlling Introductions of Nonindigenous Species by Ships' Ballast Water
Committee on Ships' Ballast Operation, National Research Council, National Academy Press, Washington D.C. 1996 ISBN 0-309-05537-7
Web sites:
National Invasive Species Act of 1996: http://www.nemw.org/nisa.htm
For more information on ballast water regulations, contact the U.S. Coast Guard, Office of Response (G-MOR), 2100 Second Street, S.W., Washington, DC 20593-0001.
Seaweed spreads in the Mediterranean
The tropical green alga Caulerpa taxifolia was probably introduced to the Mediterranean in the 1980s. It replaces native sea grasses (such as the flowering Posidonia oceanica, only found in the Mediterranean) and limits the natural habitat for larval fish and invertebrates.
In 1984, it was first recorded covering an area of just one square metre off Monaco. It then spread inexorably, covering 3 hectares in 1990, 30 hectares in 1991, 427 hectares in 1992, 1,300 hectares in 1993, 1,500 hectares in 1994 and more than 3,000 hectares in 1996. Today it covers thousands of hectares along the coasts of France, Spain, Italy and Croatia.
