The fall of Native Fishes and the rise of Non-native Fishes in the Great Lakes Basin

Over the last 200 years, the fish fauna of the Great Lakes has changed significantly as a result of declines in native species and the deliberate and inadvertent stocking of non-native fishes. These changes have resulted in the global extinction of three taxa and the extirpation of 18 species lowering the number of currently extant native species in the Great Lakes basin from 169 to 148 species. A further 82 species have declined to the point of endangerment in at least one jurisdiction in the basin. The causes of these declines are primarily habitat alterations, aquatic invasive species, and overexploitation. Some significant changes in the fish fauna of the Great Lakes basin have also been the result of the successful introduction and establishment of 35 non-native species. In addition, 34 non-native species have been found in the basin, but have not, or are not thought to have, established reproducing populations. These species have been introduced through a variety of pathways including commercial shipping, dispersal, live trade, recreational boating and angling, and stocking. Many of these species have substantially impacted the Great Lakes ecosystem directly through predation and competition or indirectly through trophic disruption and disease transmission. The relative importance of pathways as a source of new introductions has changed over time, and can be expected to continue to change as a result of evolving regulations and trade patterns. The fish fauna of the Great Lakes basin will continue to change as the result of continuing threats to native species and ongoing introductions of non-native species, and such change will undoubtedly be influenced by climate change and human population growth.