Science Advisory Report 2008/052

Framework for characterizing Conservation Units of Pacific salmon (Oncorhynchus spp.) for implementing the Wild Salmon Policy

Summary

• The first step in the implementation of Canada’s Policy for Conservation of Wild Pacific Salmon (the Wild Salmon Policy or WSP) is the identification of units for their conservation.
• The WSP defines these units, called Conservation Units or CUs, as “a group of wild salmon sufficiently isolated from other groups that, if extirpated, is very unlikely to recolonize naturally within an acceptable timeframe”. This definition embodies the concepts of reproductive isolation, adaptive variation and ecological exchangeability that underlie commonly used units for the conservation of species diversity.
• 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 were 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 included 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 was 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. 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 diversity in life histories (age structure, juvenile ecology) was mapped through ecological descriptors. The high levels of concordance between the three axes strongly suggest that the Conservation Units describe real and presumably adaptive diversity.
• The described method is data intensive and we anticipate that the CUs identified will be regularly modified as new information becomes available and our interpretations of it improve.
• One general conclusion from this work is that Pacific salmon in Canada are very diverse. This diversity is reflected in the estimated numbers of CUs by species in Western Canada (exclusive of the Yukon and Mackenzie Rivers and the Arctic Coast): pink salmon – 32, chum salmon – 39, coho salmon – 43, chinook salmon – 68 and sockeye salmon – 238.
• 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.

Complete document (PDF, 938 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.