Comment on "Rate of species introductions in the Great Lakes via ships' ballast water and sediments"

The four species of freshwater copepod crustaceans found in ballast water or sediments in ships and characterized as "nonindigenous" to the Laurentian Great Lakes region by Drake and Lodge (Can. J. Fish. Aquat. Sci. 64: 530-538 (2007)) are all widespread, North American natives. Drake and Lodge's use of these native species to estimate the size of the "source pool" of the richness of potential invasive species resulted in an overestimation of its size. We list the fresh- and brackish-water species of copepods found in or on ships in the Great Lakes and discuss taxonomic and other questions pertaining to some of them. We suggest that Skistodiaptomus pallidus, Cyclops strenuus, Salmincola lotae, Nitokra incerta, and Onychocamptus mohammed be removed from the current list of nonindigenous copepod and branchiuran species established in the Great Lakes system, leaving seven species: Eurytemora affinis, Megacyclops viridis, Neoergasilus japonicus, Heteropsyllus nunni, Nitokra hibernica, Schizopera borutzkyi, and Argulus japonicus.