Hierarchical controls on native larval lamprey habitat in the Umpqua basin, southwestern Oregon, U.S.A.

Abstract:

Interactions between streamflow and geomorphic processes at multiple spatial scales shape the ranges of habitats, species, and life stages that a river can support. Understanding these processes within a hierarchical context for Pacific Northwest rivers may be helpful for proactive monitoring and restoration of native western brook lamprey (Lampetra richardsonii) and Pacific lamprey (Entosphenus tridentatus). To that end, our study assessed the processes creating thick, fine-grained sediment deposits that lamprey larvae rely on as rearing habitat in the Umpqua River basin, southwestern Oregon. We first developed a spatial framework for characterizing basins based on expected fluxes of suspended and bed-material sediment and transport capacity. We then assessed the reach-scale controls on sediment deposition and erosion. Coupling remotely based watershed analyses and field sampling helped us assess the broad-scale spatial controls on sediment supply imposed by geology, and in turn, local factors that control sediment deposition and create larval lamprey habitat. Collectively, the results of this work aid in understanding the critical physical controls influencing the patterns in local habitat availability for larval lamprey within river networks.