Relative comparison and perspective on invasive species in the Laurentian and Swedish Great Lakes

The Laurentian Great Lakes and the Swedish Great Lakes both have a long history of being invaded by non-native species, although the total number reported in the former system far exceeds that in the latter. Until about the 1980s, non-native species that had the greatest ecosystem and/or socioeconomic impacts in both systems were controlled, or their negative impacts ameliorated by management actions; most prominent of these species were the Sea Lamprey and Alewife in the Laurentian Great Lakes, and Crayfish plague in the Swedish Great Lakes. In the 1980s, a number of species native to the Ponto-Caspian region were introduced into the Laurentian Great Lakes via the ballast water of transoceanic ships, and these species had significant ecosystem impacts, could not be controlled by management actions, and changed the way these lake resources were managed. Similar introductions have not occurred in the Swedish Great Lakes, but many of the same species that have impacted the Laurentian Great Lakes are spreading in European systems and in the Baltic Sea, and thus could pose an invasion risk to lakes in Sweden. Based on experiences in the Laurentian Great Lakes, it seems prudent to conduct a thorough assessment of these invaders relative to potential vectors of introduction for the Swedish Great Lakes. Also, an assessment of long-term monitoring programs is in order. Long-term data provides baseline information of the ecosystem and tracks ecosystem responses if indeed an invader becomes established.