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Photo by Luke Kelly

Study: Run Timing of steelhead in the Skeena River

Category: Newsletter Articles | Posted by: Jonathan | 7/7/12 | Comments: 0

Summary: Published in the most recent issue of the North American Journal of Fisheries Management, “Population Structure and Run Timing of Steelhead in the Skeena River, British Columbia” increases the previous number of assumed distinct populations of summer steelhead in the river from 5 to 17.  The authors (Beacham, Wallace, et al.) utilized genetic analysis from samples of mainly adult fish collected at the mouth of the river to isolate these populations.
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By Ryan Petzold

Photo by Luke KellyIt is well-known that the early component of the Skeena’s treasured wild summer-run steelhead has been negatively impacted by the prolific commercial fishery at the river’s mouth for its very valuable sockeye salmon.  Published in the most recent issue of the North American Journal of Fisheries Management, “Population Structure and Run Timing of Steelhead in the Skeena River, British Columbia” increases the previous number of assumed distinct populations of summer steelhead in the river from 5 to 17.  The authors (Beacham, Wallace, et al.) utilized genetic analysis from samples of mainly adult fish collected at the mouth of the river to isolate these populations.

Utilizing this analysis, the authors not only identified 17 summer steelhead populations of the Skeena River, but they also identified distinct populations within each sub-region (Upper Skeena, Middle Skeena and Lower Skeena).  The authors expand on earlier genetic studies that found significant differentiation among the Babine River, Morice River and Sustut River populations.  Earlier studies also indicated significant differentiation among populations within drainages which the authors’ findings found to be commonplace in the watershed.

The populations within these sub-regions were found to enter the river at a distinct time.  The Sustut bound run entered the earliest with half the population in the system by the end of July while lower river populations entered the river in force during the second week of August.  As the height of the commercial sockeye fishery occurs in the middle to latter half of July, it is apparent that the authors’ findings back up anglers’ anecdotal evidence that the early component of the Skeena’s populations and thus gene pools have been severely impacted by the commercial fishery.  Those that fished the Skeena many years ago describe very early returning steelhead to the upper reaches of the Morice River; a now depleted race of fish.  The authors found that the peak abundance for Morice River steelhead occurred near July 31st.  One must wonder, if this same study occurred thirty years ago, if they would not have found the peak abundance of this strain to occur earlier in July?

The results presented are based upon data collected from as early as 1992 but the majority of samples were collected from fish sampled from the late ‘90’s through the 2000’s.  Thus, the data allowed the authors to formulate 17 separate Skeena River wild steelhead populations.  However, these are 17 present distinct populations and may not accurately reflect populations and their distinct genetic traits that may have already been eliminated from the system due to the commercial sockeye fishery.  The aforementioned very early returning Morice River strain is a good example.  And, as of 2008, the Upper Sustut river strain, with their peak migration of the third week of July, was considered depressed.

The findings provide steelhead conservationists with the data necessary to put pressure on other Skeena River stakeholders to manage the commercial fishery with as little impact on the wild steelhead of the river as possible.  Secondly, these findings reiterate the motivation behind the Wild Steelhead Coalition’s successful effort to eliminate the sport harvest of early returning wild steelhead on the Olympic Peninsula.  Run component timing is the pipeline of genetic diversity for wild steelhead within a watershed.  As we selectively harvest certain portions of a population, we are not only reducing that population’s genetic diversity and overall fitness, we are removing components of that run that utilize certain portions of a watershed.  This in turn, reduces the productivity of the watershed which ultimately reduces the amount of wild steelhead that are returning to their rivers.

Read the full “Population Structure and Run Timing of Steelhead in the Skeena River, British Columbia” study.

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