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Native Species, Invaders, and Parasites: The Good, the Bad, and the Ugly


Photo showing three species of fish that are representative examples of native species (the good: logperch), invaders (the bad: Round Goby), and parasites (the ugly: Acanthocephalan) | © EC, Andrée GendronEnvironment Canada scientists have discovered that populations of Round Goby (Neogobius melanostomus) recently introduced in the St. Lawrence River were considerably less parasitized than two indigenous fish species, whereas the Round Goby is highly infected with parasites in its native range. Such parasite-escape could have translated into a temporary increase in the competitive ability of this invasive species, contributing to its successful establishment. 

Results suggest that this potential advantage over native species may be of relatively short duration. Within 15 years, the parasite abundance and richness in Round Gobies in Lake St. Clair has more than doubled. The number of parasite species per fish has also increased, now matching levels of those typical of fish indigenous to the St. Lawrence-Great Lakes watershed. Results suggest that the goby may be integrating itself more fully into the Great Lakes food web over time.

Source: Gendron AD (514-283-9995,, Marcogliese DJ (514-283-6499,, Thomas M. 2011. Invasive species are less parasitized than native competitors, but for how long? The case of the round goby in the Great Lakes-St. Lawrence Basin. Biol Invasions 10.1007/s10530-011-0083-y

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