Native trout restoration in a fire-impacted inland watershed

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Phaedra Budy


Efforts to restore aquatic species to formerly occupied stream habitats must consider the interactions between natural disturbances such as fire, flood, drought, and disease and non-stationary anthropogenic impacts like exotic species expansion, climate change, habitat fragmentation, and water extraction. For instance, a wildfire burned ~18,000 hectares of mixed conifer forest in south-central Utah in 2010; two thirds of the fire burned at medium to high severity, a condition likely exacerbated by fire suppression. Subsequent monsoon-associated debris flows severely altered the stream channel structure within and downstream of the burned area and reduced or extirpated local populations of fishes. As part of the Bonneville cutthroat trout recovery plan, managers installed a fish barrier and chemically removed surviving exotic trout, effectually renovating ~60 km of interconnected perennial stream habitat for reintroduction of native trout, which began in 2012. However, it is unknown how restocked fish will perform because of the lingering impacts of the fire, or if adequate complementary habitat types required by trout to complete their life cycle are still present. I will (1) compare primary production, invertebrate abundance and drift, and growth of Bonneville cutthroat trout between burned and adjacent unburned streams, (2) document dispersal of juvenile trout from stocking locations and assess quality of selected habitat, including identifying complete and semi-permeable migration barriers, and (3) use high resolution aerial imagery and bathymetric lidar to quantify critical habitat such as deep pools, large woody debris, and potential spawning areas between burned and unburned streams at the watershed scale (40 km total). These results will augment the scarce data available about behavior and restoration of inland fish metapopulations, most of which is borrowed from studies of anadromous Pacific salmonids. The development of restoration plans for impacted watersheds is especially important in future scenarios where managers have limited pristine habitat options.

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