Seasonal movements of non‐native lake trout in a connected lake and river system

Abstract

Non‐native lake trout, Salvelinus namaycush (Walbaum), threaten native salmonid populations in the western United States. Effective management of lake trout requires understanding movements within connected lake and river systems. This study determined the seasonal movements of subadult lake trout in the Flathead River upstream of Flathead Lake, Montana, USA using radio telemetry. The spatiotemporal distribution of lake trout in the river was related to water temperature. Lake trout were detected in the river primarily during autumn, winter and spring, when water temperatures were cool. By contrast, fewer were detected when temperatures were warmest during summer and during high spring flows. Downriver movements to Flathead Lake occurred throughout autumn and winter when water temperature decreased below 5 °C, and in late spring as water temperature rose towards 15 °C and river discharge declined following spring runoff. Upriver movements occurred primarily in October, which coincided with migrations of prey fishes. These results suggest that lake trout are capable of moving throughout connected river and lake systems (up to 230 km) and that warm water temperatures function as an impediment to occupancy of the river during summer. Controlling source populations and maintaining natural water temperatures may be effective management strategies for reducing the spread of non‐native lake trout.

Suppression of invasive lake trout in an isolated backcountry lake in Glacier National Park

“…As lake trout abundance increased, lake trout emigrated upstream from Flathead Lake and established self‐sustaining populations in several connected lakes in GNP in <30 years (Fredenberg ; Muhlfeld et al . ).…”

“…The introduction of lake trout into Flathead Lake in 1905 and the establishment of the opossum shrimp, Mysis diluviana (Audzi-jonyt€ e & V€ ain€ ol€ a), in 1981 (Spencer et al 1991) led to the proliferation and subsequent replacement of the bull trout as the dominant top-level piscivore (Fredenberg 2002;Ellis et al 2011). As lake trout abundance increased, lake trout emigrated upstream from Flathead Lake and established self-sustaining populations in several connected lakes in GNP in <30 years (Fredenberg 2002;Muhlfeld et al 2011).…”

Intra‐Annual Variability of Silver Carp Populations in the Des Moines River, USA

“…;McClelland and Sass 2008;Wanner and Klumb 2009;Collins et al 2015), the extent to which seasonality and environmental characteristics affect capture rates has yet to be evaluated. Identification of seasonal sampling variation is important because the capture rates and size structure of fishes captured in sampling gears can vary temporally due to movement patterns (Miller and (Herbst et al 2015), local environmental conditions (Cowley et al 2007;Jones and Stuart 2009;Muhlfeld et al 2012;Gardner et al 2013), prey availability (Bowlby and Hoyle 2011), and the annual flux of young-of-the-year fish recruiting to sampling gears (Bacula et al 2011;Neal and Prchalová 2012). In lakes, seasonal sampling variation has been attributed to surface water temperatures (e.g., Bacula et al 2011) and spawning activity (e.g., Lott 2000;McKibbin 2002;Herbst et al 2015).…”

Multiscale hydrogeomorphic influences on bull trout (Salvelinus confluentus) spawning habitat

“…Bull trout populations declined in the early 1990s, however, as a result of community changes related to the invasion of opossum shrimp (Mysis diluviana) in the 1980s into Flathead Lake and the subsequent boom in the nonnative lake trout population (Ellis et al 2011;Muhlfeld et al 2012). Adfluvial bull trout from Flathead Lake spawn in Ole, Trail, and Whale creeks.…”