| Abstract: | "A new, dynamic reality is unfolding as climate change interacts with historical land management, causing changes in riverscape conditions that affect stream habitat and populations of native fishes. In Alaska, and elsewhere, land managers are facing new challenges as they seek to balance forest use with ecological resilience in rivers that support culturally and commercially important salmonids. In this context, data-driven forest management intended to maintain and restore landscapes relies on information that defines conditions over time. In this study, we analyzed 8 years of stream habitat and fish population data from a robust dataset developed to monitor aquatic conditions on the Tongass National Forest, Alaska. We found that patterns of fish population distribution, abundance (particularly anadromous salmonids), and instream habitat overlap with past forest-harvest site selection intended to maximize timber extraction. Historical riparian harvest disproportionately targeted easily accessible marine-connected subwatersheds that currently support anadromous salmonids such as coho salmon. Hydrologic type and forest stand age also influenced fish habitat. Further, we found that in rain-dominated watersheds with >42 percent old-growth cover, streams had wider channels and deeper pools that may provide some refuge for native fish from summer drought and low-flow conditions. However, as more watersheds transition from snow to rain, and winter storm intensities increase, even streams with wider channels and deeper pools that provide summer habitat may not provide winter refugia for native fish." |
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