Is solar radiation responsible for declines in marine survival rates of anadromous salmonids that rear in small streams?

There have been profound declines in marine survival rates of steelhead tro ut (Oncorhynchus mykiss), coho salmon (O. kisutch), chinook salmon (O. tsch awytscha), and Atlantic salmon (Salmo salar) since the mid-1980s, and these declines have been particularly acute in sunny regions. We suggest that th e problem may originate in freshwater with radiation (e.g., UV-B) damage to metabolic machinery that is expressed during stressful periods of smelting and ocean entry and that progressively worse damage may soon appear as red uction in freshwater survivals as well. This hypothesis can be tested quick ly by management agencies by comparing survival rates of hatchery-reared fi sh with and without radiation protection during rearing.