The Assessment of Restoration Efforts on the Nisqually River Delta, WA through Juvenile Chinook Salmon Otoliths

The Nisqually Fall Chinook salmon population is one of 27 stocks in the Puget Sound evolutionary significant unit listed as threatened under the Endangered Species Act.  The population decline was initially mitigated by building hatcheries, but the Nisqually Indian Tribe (NIT) has made it a priority to develop a self-sustaining, naturally spawning population. Toward this end, NIT has worked to preserve and extensively restore the Nisqually delta ecosystem to assist in recovery of the stock, as juvenile Fall Chinook salmon are estuary-dependent. Baseline information including characterization of life history types and habitat use is essential to evaluating the potential response of Chinook salmon to restoration efforts and overall restoration success. Otoliths were used to examine variation in Chinook salmon life history types, growth, and residence in the Nisqually Estuary pre- and post-restoration. This research developed into a collaborative effort with NIT and various U.S. Geological Survey researchers monitoring the response of the Nisqually delta ecosystem following restoration. We will provide a brief overview of this collaboration and report on expression of life history diversity and differential usage of the Nisqually estuary by natural and hatchery reared juvenile Chinook salmon before and after restoration efforts.