PhD Student Lindsey McCulloch holds a juvenile coho salmon she just weighed, measured and tagged as part of her research in the Cowee-Davies Watershed. Image: Brennen McCulloch

Stream food webs and salmon productivity in Southeast Alaska

ACRC scientists are exploring how the diversity of water sources in Southeast Alaska influences stream food webs that sustain salmon productivity. This research helps inform freshwater fisheries management in the face of climate change.

Rivers and streams in Southeast Alaska provide essential rearing habitat for some of the most productive salmon fisheries on the planet. Within these rivers, salmon rely on a complex and interconnected tapestry of feeding relationships known as food webs for growth and survival. Southeast Alaska’s coastal mountains create heterogenous riverscapes that support diverse food webs. A single watershed can contain a mosaic of silt-heavy glacial rivers, snowmelt creeks, and wetland-dominated rainfall streams that have distinct light penetration, temperatures, discharge, biogeochemistry, and flow event timing. 

Understanding the relationships between these distinct stream characteristics and the food webs within can help forecast ecosystem stability and their capacity to support fisheries as contributions of glacial runoff and snowmelt in these ecosystems change with the climate. Distinct stream characteristics can support food webs with asynchronous resource peaks resulting in more consistent food availability throughout the year. Watershed deglaciation and snow-to-rain shifts could homogenize Southeast Alaska hydrology and food webs, impacting food availability and the capacity to support fish populations.

ACRC PhD student Lindsey McCulloch is currently investigating differences in growth trajectories between juvenile coho living in beaver ponds, glacier-, snow-, and rain-dominated streams in Southeast Alaska, and whether juvenile coho salmon move between these habitat types in order to capitalize on seasonal differences in growth potential. Her research is taking place in the Cowee-Davies watershed within the USDA Forest Service Héen Latinee Experimental Forest where Lindsey is collecting fish and habitat data at three paired sites featuring a beaverpond, rain-, and snow-dominated tributary draining into the glacial mainstem.