This multi-year study quantifies the distribution and density of aquatic vertebrates throughout Lookout Creek stream network, including Mack, McRae and Upper Lookout Creeks. We are examining how predictable and consistent the densities and sizes of cutthroat trout and coastal giant salamanders are throughout the network and whether they fluctuate synchronously with vertebrates sizes and densities in Mack Creek that have been measured since 1987 (AS006). We are also examining biomass and condition of individuals across sites. Density and developmental stage of coastal tailed frog tadpoles are noted. We use electroshocking in discrete blocked reaches (depletion and mark-recapture methodologies) to collect individuals that are then weighed, measured and released. Site specific characteristics are measured at each sampling event, including wetted widths and water depths. Broader landscape metrics, including stream gradient and watershed area, were calculated for sites.
Brooke E. Penaluna, Dana Richard Warren, Emilee Mowlds, Ivan Arismendi, Sherri L. Johnson
Stream networks expand and contract seasonally; these changes in stream network connectivity affect transfer of matter and energy across trophic levels and between aquatic and terrestrial ecosystems (Ward 1989, Gregory et al. 1991). Although many organisms that live in the headwaters of the stream network are well adapted to seasonal low flows (Frady et al. 2007, Banks et al. 2007), some organisms (e.g., trout) may experience stress from reduced summer habitat and instream food, increased water temperature, and increased vulnerability to predators (Berger and Gresswell 2009). Climate change has the potential to further contract summer stream networks and lead to reduced viability of trout populations in small streams (Wenger et al. 2011, Penaluna et al. 2015). Because long-term research in Mack Creek at the Andrews Forest on two co-occurring aquatic vertebrate species, Mack Creek cutthroat trout, and coastal giant salamander, has revealed complex population dynamics and variable responses to hydrologic variability (Dodds et al. 2012; Arismendi et al. 2020), we are interested in examining whether other stream reaches show these same or different dynamics.
Trout and salamanders are expected to have very different responses to climate change and stream drying because of their habitat requirements and mobility. Areh salamanders able to inhabit and dominate smaller or more disconnected streams than trout? In this project, we are extending our study of these top predators to examine how stream trophic structures differ from headwaters to larger streams across the Lookout Creek stream network. This research will allow us to examine how varying instream and aquatic-terrestrial connectivity influences the ways in which instream predators, fish and salamanders, shape food webs and ecosystem dynamics.