Freshwater Fisheries in Canada: Historical and Contemporary Perspectives on the Resources and Their Management

Chapter 13: Freshwater Fish Introductions in Canada

Nicholas E. Mandrak


Freshwater fishes have been widely introduced beyond their native ranges globally (Dawson et al. 2017), and Canada is no exception (Anas and Mandrak 2022). Various vectors have been responsible for the introduction of freshwater fishes, including legal and illegal stocking, release from ballast water and live trade (bait, food, pets), and dispersal through artificial aquatic connections such as canals (Mandrak and Cudmore 2013). Many introduced freshwater fish species have negative impacts on native species (Taylor et al. 1984; Vitule et al. 2009), and ecosystems and freshwater ecosystems are particularly vulnerable to such impacts (Moorhouse and MacDonald 2015). Impacts can include declines in native species due to competition and predation (Dextrase and Mandrak 2006; Jelks 2008; Mandrak and Cudmore 2013), changes in food webs (Vander Zanden et al. 1999; Ricciardi and MacIsaac 2011), and loss of genetic diversity via hybridization (Vitule et al. 2009). The resulting loss of native species and gain of nonnative species can result in biotic homogenization as has been documented for fish assemblages globally (Rahel 2000; Toussaint et al. 2016) and in Canada (Taylor 2004, 2010; Campbell and Mandrak 2019).

This chapter reviews the history of freshwater fish introductions in Canada, their vectors of introduction and impacts, and potential future introductions. Introductions of species beyond their native range within Canada are termed domestic nonnative species here and are limited to those introduced and established beyond the provinces and territories in which they are native. Introductions of species not native to Canada are termed exotic species here and both known established and nonestablished species are included.