Research Document - 2000/125

Stock Status and Genetics of Coho Salmon from the Interior Fraser River

By .R. Irvine, R.E. Withler, M.J. Bradford, R.E. Bailey, S. Lehmann, K. Wilson, J. Candy, and W.S. Shaw

Abstract

The authors evaluated the impacts of continued restrictions in salmon harvest on the status of coho salmon of the interior Fraser River, including the Thompson drainage in 1999. Total exploitation rate on the aggregate in 1999 was estimated to be ~9% (~3% Canadian, ~6% US), which is similar to 1998, and much lower than in previous years. Various indices of escapement suggest the total spawning population in 1999 was about the same as in 1998, but higher than the 1996 parental escapement. Total abundance in 1999 was about 10% of that observed 10-15 yrs ago, and spawning populations in many streams are small or non-existent. We conclude that the status of the aggregate is largely unchanged from 1998, and remains poor. It is premature to draw any conclusion about whether the better survival of the 1996 brood (1999 return) represents a trend towards improved survival in the future. We have no basis to alter the conclusion reached in this year's forecast document (Holtby et al. 2000) that it is unlikely that stock size will increase in 2000.

The potential for traditional ecological knowledge to assist in stock assessment was discussed, as were recent enhancement activities in the interior region. Analysis of genetic information on interior Fraser coho supported the idea that non-Thompson coho can be grouped with Thompson coho as a single management or conservation unit that is distinct from lower Fraser.

The major recommendations from this paper are:

Target and limit reference points for Interior Fraser River coho are needed to provide management advice relative to current abundance levels and forecast trajectories. 

Policies on the role and evaluation of strategic enhancement to restore declining populations such as the Thompson need to be formulated.

More extensive baseline coverage of interior Fraser coho for genetic sampling (e.g. Nahatlatch) are needed to aid in the delineation of populations, and provide more precise estimates of the distribution and numbers of interior Fraser coho in catches.

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