21: Global Status of Trout and Char: Conservation Challenges in the Twenty-First Century
Clint C. Muhlfeld, Daniel C. Dauwalter, Vincent S. D’Angelo, Andrew Ferguson, J. Joseph Giersch, Dean Impson, Itsuro Koizumi, Ryan Kovach, Phil McGinnity, Johannes Schöffmann, Leif Asbjørn Vøllestad, and John Epifanio
Freshwater ecosystems are among the most threatened ecosystems in the world (Richter et al. 1997; Strayer and Dudgeon 2010), and freshwater fishes may now be the most threatened group of vertebrates (Ricciardi and Rasmussen 1999; Vörösmarty et al. 2010; Darwall and Freyhof 2016). Of the 7,300 freshwater fish species globally assessed by the International Union for Conservation of Nature (IUCN; www.iucnredlist.org) in 2013, nearly one of every three species was threatened with extinction (Darwall and Freyhof 2016). Growing pressures from a multitude of direct and indirect human stressors (e.g., habitat loss and degradation, pollution, invasive species, overexploitation, diversion or alteration of biological flows, climate change, and others) threaten the persistence of many freshwater fish species and entire aquatic communities around the globe (Limburg et al. 2011). This pattern is particularly true for salmonid fishes (family Salmonidae, subfamily Salmoninae, belonging to the genera Oncorhynchus, Salvelinus, Salmo, Hucho, Parahucho, Brachymystax, and Salvethymus). Salmonids are globally distributed coldwater species with life cycles restricted entirely to freshwater ecosystems (typically referred to as trout and char), but also include species that migrate from the ocean to freshwater to spawn (e.g., Atlantic Salmon Salmo salar and Pacific salmon Oncorhynchus spp.).