Bull Trout Redd Inundation Studies Survey

Bull Trout Redd Inundation Studies

bull trout redd

Bull trout redd marked with a biodegradable bag and flagging.

A significant portion of bull trout redds in the lower reaches of the Rex and Cedar rivers upstream of Chester Morse Lake are regularly inundated (covered by non-flowing water) by rising reservoir levels during spring refill. This inundation is assumed to have some adverse impacts on egg and alevin survival as a result of sedimentation.

Seattle Public Utilities and R2 Resource Consultants conducted a collaborative study using artificially constructed redds containing fertilized bull trout eggs to determine the effects of inundation on survival.

The experiment included multiple sites within reaches of the river that experience varying depth and duration of inundation during incubation and emergence periods. Natural redds within these reaches were also monitored to document emergence of fry. The results of this study provide a basis to evaluate inundation effects on egg and alevin survival, predict reservoir impacts on redds in any given year, and ultimately serve to guide more informed reservoir management decisions.

View a progress report on the Bull Trout Redd Inundation Study on the bull trout species web page.