Corps of Engineers employees volunteer to scrape barnacle buildup along the filling tunnels at Lake Washington Ship Canal and Hiram M. Chittenden Locks, Seattle, Dec. 12, 2023. Barnacles pose a threat to salmon migrating through the Locks out to sea. Before, during and after migrating, salmonids encounter many threats such as predators, environmental conditions, disease, oceanic parasites, spawning streams and the Locks structure itself.