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Abstract

Most nonindigenous species invasions can have negative consequences on an environment. Trophic systems may become altered as prey sources are depleted, which can have further implications on community and habitat structure. However, some species invasions can be positive as it can provide another food source for key stone species. The effects of invasive species are reviewed in the following paper for the North American river otter (Lontra canadensis) and the Eurasian otter (Lutra lutra). In the case of the North American river, the introduction of the lake trout (Salvelinus namaycush) has negatively impacted otter populations, foraging behavior and bank ecology in Yellowstone National Park (Crait & Ben-David, 2007; Wengeler et al., 2010). However, for the Eurasian otter, their diet has shifted to include non-native species, which has shown to be beneficial during seasons of drought (Balastieri et al. 2013; Barrientos et al. 2014). The studies utilized scat samples to determine diet content, while the study by Crait & Ben-David (2007) evaluated vegetation at latrine sites for diversity and growth rates of plant matter, and the Balastieri et al. (2013) study used a Random Forest Regression (RFR) to analyze data. In conclusion, even in situations with a positive impact, non-native species introduction influence the foraging habits of otters as native fish species decline. Consequently, the ecological niche occupied by the river otters can narrow, making the otter a bioindicator of wetland and riparian ecosystem health. These implications require major conservation efforts to improve native fish populations.