Introduced Pacific salmon (Oncorhynchus spp.) deliver novel, pulsed resource subsidies to Great Lakes streams. We explored interactions between native brook trout (Salvelinus fontinalis) and non-native brown trout (Salmo trutta) in the context of this resource pulse. Diets surveyed before and during salmon spawning showed that, regardless of species, trout consumed 4.5-fold more biomass during than before salmon runs. Brook trout grew more quickly than brown trout under controlled feeding regimes due, in part, to their higher food conversion efficiency of 36% compared to 21%. Bioenergetics model simulations explored the influence of temperature on the exploitation of resource pulses and found 35% lower growth rates and increased gorging at colder temperatures. Overall, we found evidence that brook trout and brown trout foraging and growth are modulated by the salmon resource pulse, especially through gorging on eggs. However, these species exhibit distinct physiological adaptations and environmental preferences that may influence their ultimate capacity to exploit resource pulses. The effects of environmental conditions and salmon subsidies on stream-resident trout have broader consequences for fisheries management and conservation efforts.
Environments change across space and time, often requiring organisms to exhibit behavioral responses. In the Arctic, migratory consumers are motivated by spring resources to follow receding ice; however, resident species’ responses to this ephemeral productivity are less well understood. We characterized the movement behaviors of relatively sedentary Arctic species of sculpin (Myoxocephalus spp.) in Tremblay Sound, Nunavut, Canada. Movements of individuals (n = 60) captured during the ice-free periods of 2017-2019 were monitored year-round via an array of acoustic telemetry receivers (n = 37). Telemetry data confirmed year-round residency within the Sound, yet sculpins were consistently more active and wider ranging during the ice-free period versus the ice-covered winters. Sequence analysis revealed distinct patterns of activity differentiated primarily by regional associations. Together, these results indicate sculpin are highly sedentary, but move more during the ice-free season, suggesting the importance of the seasonal productivity pulse to these fish. As resident species adapted to exploit the conditions within their local environment, sculpin provide a valuable indicator species to monitor coastal and benthic Arctic ecosystems that are experiencing rapid change.
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