Estimating Coho Salmon Egg to Fry Survival

We describe a new, holistic field method of assessing sediment effects on salmonid egg survival to hatching and emergence using artificial redds that contain gravel-filled egg baskets, infiltration bags, standpipes, and redd caps that trap emerging fry.  This approach can concurrently measure sediment content, survival, scour and fill, permeability, and dissolved oxygen in the same redd that contains the eggs.  Using a model that incorporates these variables to predict survival to hatching and emergence, the method was very effective at predicting mean egg survival to emergence estimated from natural redds for seven years (within 4%) and explaining 67% of the variance in survival. An advantage of the method is that it more fully captures sediment than other methods and identifies the stage (hatching or emergence) of highest vulnerability to sediment infiltration and the mechanisms of mortality.  A disadvantage is that the method can not be used during deep-scouring flows or in streams where low dissolved oxygen in upwelling groundwater is a strong factor influencing egg survival.