“…Migration is an important determinant of steelhead population structure, and numerous studies have examined the genetic structure of O. mykiss populations in California coastal and Central Valley watersheds (Arciniega et al, 2016;Clemento et al, 2009;Garza et al, 2014;Nielsen, Carpanzano, Fountain, & Gan, 1997;Nielsen, Pavey, Wiacek, & Williams, 2005;Pearse, Donohoe, & Garza, 2007;Pearse & Garza, 2015). Garza et al (2014) highlighted the correlation between genetic variation and geographic distance, a relationship known as isolation by distance, which is influenced by major geographic features but has also changed over time (Pearse, Martinez, & Garza, 2011).…”