Threespine, Gasterosteus aculeatus, and Fourspine, Apeltes quadracus, Sticklebacks in the Lake Superior Basin

The Threespine (Gasterosteus aculeatus) and Fourspine (Apeltes quadracus) s ticklebacks an: unintentionally introduced species to Lake Superior with in itial populations established near Thunder Bay, Ontario. An examination of annual seining and trawling records show that native sticklebacks have decl ined in abundance in their native habitats as a result of these introductio ns. Assuming a single colonization event for Lake Superior, the distributio n of Gasterosteus has been extended to the Black River, Ontario, in the eas t as well as both the Minnesota and Michigan coast:; of Lake Superior. Apel tes quadracus is not known from Great Lakes populations outside of Lake Sup erior. However, specimens have been collected in Lake Superior waters dista nt from Thunder Bay. Gasterosteus has spread rapidly while Apeltes has not spread as quickly. Apeltes, due to its preference for nearshore areas, has the greatest potential to affect the native fish community negative ly. Thi s may occur through competition for habitat and food resources which can ul timately change the food web structure.