Most predatory fish, marine mammals, and birds that eat salmon rely primarily on vision to feed. Natural processes and anthropogenic change affect visual conditions underwater which in turn profoundly affect the magnitude of predation risk on juvenile and adult salmon as well as forage fishes and other species in shoreline and pelagic environments. I will discuss the implications of how natural and anthropogenic changes in water transparency and artificial light pollution have significantly increased the predation threat environment for juvenile salmon in the Salish Sea and relate these to some of the major infrastructure projects in the Pacific Northwest. High levels of artificial light pollution are pervasive throughout Puget Sound and the southern portion of the Strait of Georgia. Over the past 30-40 years, increasing light pollution in Lake Washington, a useful surrogate for the greater Salish Sea, has expanded the peak twilight predation periods of juvenile salmon predators from just dusk and dawn to predation increasing throughout the night. Moreover, changing hydrology and water quality due to dams, climate, and land-water use have changed the magnitude, timing, and spatial patterns in water transparency from sediment plumes and plankton blooms. Collectively, these changes in underwater light penetration and transparency have fundamentally changed the predation environment with important implications for marine survival of salmon, functional sustainability of forage fish populations and the services they provide to the broader ecosystem
