Exploring metapopulation-scale suppression alternatives for a global invader in a river network experiencing climate...

Area of Science:

• Ecology
• Conservation Biology
• Invasive Species Management

Background:

• Invasive species significantly alter ecosystems, with eradication being difficult and suppression costly after establishment.
• Uncertainty in invasion potential and impacts can delay suppression efforts, allowing invasive species to establish.
• Metapopulation viability models are essential tools for planning effective invasive species management strategies, especially under climate change.

Purpose of the Study:

• To explore suppression strategies for invasive brown trout (Salmo trutta) in the Colorado River and a tributary.
• To estimate the effectiveness of targeting different life stages and subpopulations.
• To quantify the benefits of a rapid response versus delayed action and assess climate change impacts.

Main Methods:

• Utilized a spatially explicit metapopulation viability model.
• Simulated various suppression strategies including electrofishing, redd destruction, angler harvest, piscicides, and weirs.
• Incorporated scenarios for future hydrology, temperature, and reservoir management.

Main Results:

• Quasi-extinction (QE) was achievable only through metapopulation-wide suppression targeting multiple life stages.
• Brown trout population growth was most sensitive to mortality in age 0 and large adult stages.
• A rapid response to a new invasion required 4 years of suppression for QE, compared to 12 years for an established subpopulation.
• Connected tributary subpopulations acted as climate refuges, enhancing metapopulation persistence.
• Climate change impacts (warming, altered hydrology) would reduce brown trout but still necessitate increased suppression for QE.

Conclusions:

• Invasive brown trout metapopulation dynamics are complex and require integrated management.
• Metapopulation-wide suppression targeting multiple life stages is necessary for effective control.
• Rapid response to new invasions is significantly more effective than delayed action.
• Tributary subpopulations can serve as crucial climate refuges for native species.
• Adaptive management strategies are essential to maintain endemic fish populations against invasive species and climate change.