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Summer Chum Salmon Conservation Initiative: Supplemental Report No. 1, Revised Estimates of Escapement for Hood Canal and Strait of Juan de Fuca Natural Spawning Summer Chum Salmon Populations

Category: Fish/Shellfish Research and Management - Management and Conservation

Date Published: April 2000

Number of Pages: 296

Author(s): Jeff Haymes


The status of summer chum in the Hood Canal and Strait of Juan de Fuca regions of Washington state became a significant source of concern to both fishery management agencies and the general public in the 1980’s, as runsizes experienced precipitous declines. Some streams even experienced complete extirpation of their summer chum spawning populations in this time periods. In the 1997 the Nation Marine Fisheries Service (NMFS) Endangered Species Act (ESA) review of chum population in Washington, Oregon, and California identified the summer chum populations in the Hood Canal and Strait region to be a unique “Evolutionarily Significant Unit” (ESU) (Johnson et al. 1997). This ESU (the Hood Canal summer chum ESU) was given a “Threatened” status listing in 1998 by NMFS due to populations trends within the ESU, and other concerns (US Dept. of Commerce 1999).

In response to the summer chum populations trends and pending ESA processes the Washington Department of Fish and Wildlife (WDFW), and the member Tribes of the Point No Point Treaty Council (PNPTC) initiated a program in 1997 to develop a recovery plan for the summer chum populations in the region. A co-manager’s summer chum restoration committee was assembled for development of the recovery plan, and proceeded to identify several data analysis needs. One of the identified needs was to re-examine the historical escapement estimations for these populations, and develop a new historical escapement database that applied consistent and well documented analytical techniques to the revised estimates.

WDFW and Washington Treaty Indian Tribes cooperatively conduct annual escapement estimation programs for many Washington salmon populations. The field data collection and analysis methods used to derive the escapement estimates derive the escapement estimates are both species, and region and/or stock-specific. It is assumed escapement estimates derived for most salmon stocks in more recent years have generally higher precision than those for earlier years because field data collection, survey effort, and data analysis methods have become more standardized, and increased knowledge and experience of the biologists conduction the estimates has resulted in more appropriate and consistent analysis of the annual field census data.

In 1997-98 revised estimates of escapement were derived for the 1968 to 1997 return years, utilizing a uniform group of analytical techniques and assumptions. An ordinal rating of the uncertainty in each estimate was also assigned, based on assessment uncertainties associated with each estimate. The same estimation approaches were subsequently applied to the 1998 summer chum escapements for watersheds in the Hood canal ESU (and will continue to be used for future years).

Following is a brief review of anadromous salmonid escapement estimation methodologies traditionally used by WDFW, a description of the rating system developed for the revised estimates, a review of the historical survey effort expended for summer chum salmon in the Hood Canal summer chum ESU, and a presentation and discussion of the revised and new estimates for the 1968 to 1998 return years.