Research Document - 2007/070

Conservation Units for Pacific Salmon under the Wild Salmon Policy

By L. Blair Holtby and Kristine A. Ciruna


The initial steps in protecting biological diversity and the primary roles of scientific research, are to identify the diversity and then take inventory of the units of diversity that require conservation. Consequently, the first of six strategies in the Wild Salmon Policy concerns the identification of the units and determining their conservation status. The primary purpose of this document is to describe the method that was developed to identify the “Conservation Units” for the five species of Pacific salmon in British Columbia. The description of units in most of the Yukon and Northwest Territories will proceed using this method once the ecotypology of those areas is completed.

The approach of Waples et al. was modified to characterize diversity in Pacific salmon along three major axes: ecology, life history, and molecular genetics, and then to compartmentalize that diversity into Conservation Units. The three descriptive axes are used to map local adaptation in a variety of ways. The maps are then examined and combined to locate and describe the Conservation Units. The first stage in the description of the Conservation Units is based solely on ecology. The ecotypologies used include a characterization of the near-shore marine environment in addition to one for fresh water. The second stage of the description involves the use of life history, molecular genetics, and further ecological characterizations to group and partition the first stage units into the final Conservation Units. The result is Conservation Units that are described through the joint application of all three axes.

There is a high degree of concordance between ecotypic, biological (life history) and genetic characterizations of intraspecific diversity, confirming the principal conclusions of Waples et al.4 Molecular genetics was essential in areas of high genetic diversity but once identified, ecotypology appeared capable of mapping the genetic diversity. Similarly, there were instances where life histories differed and where ecological descriptors mapped that diversity. The high levels of concordance between the three axes strongly suggest that the Conservation Units describe real and presumably adaptive diversity.

In addition to the pragmatic advantages of a method that uses all available information to describe intraspecific diversity, an ecotypic approach has benefits stemming from characterizations of salmon habitat in its broadest sense. Importantly, the method supports the intent of the WSP to use CUs for the conservation of both pattern and process.

One general conclusion from this exercise is that Pacific salmon in Canada are very diverse. This diversity is reflected in the estimated numbers of CUs by species shown in the following table:

Estimated Numbers of CUs by Species
Species Number of CUs
pink-odd 19
pink-even 13
chum 39†
coho 43
chinook 68†
sockeye-river 24
sockeye-lake 214

† Additional CUs will be described in the Yukon River. Additional CUs are possible in the Mackenzie River, although currently they would be outside of the geographic purview of the Wild Salmon Policy.

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