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A geologic explanation for two sockeye populations in the Russian River

Posted: May 29, 2014 - 2:20pm
Caption 2: Model based on the blockage of upper Resurrection River by a late-glacial advance of Exit Glacier, impoundment of the drainage in a former lake above the glacier dam, northwestward overflow  from the impounded lake into the upper Russian River, and southeastward drainage through a diversion channel around Exit Glacier into lower Resurrection River.
Caption 2: Model based on the blockage of upper Resurrection River by a late-glacial advance of Exit Glacier, impoundment of the drainage in a former lake above the glacier dam, northwestward overflow from the impounded lake into the upper Russian River, and southeastward drainage through a diversion channel around Exit Glacier into lower Resurrection River.

My interest in the Russian River fishery was suddenly piqued one day about four years ago, when a colleague, Paul Ruesch, asked me a very intriguing question: Could there be a geologic reason for the two genetically diverse sockeye salmon populations in the Russian River drainage?

My initial response was: What do you mean by genetically diverse sockeye stocks in Russian River? Paul, a retired Alaska Fish and Game fishery biologist, was ready with the answer—genetic studies demonstrate that the DNA is different in salmon spawning above and below the falls in Russian River.

A couple of days later, he showed me a complicated-looking diagram that illustrates genetic relations between red salmon that spawn in different Cook Inlet drainages, including Russian River. Simply put, closely related sockeye stocks plot close together in that diagram, and stocks that are not closely related plot far apart. At the top of the diagram, Paul pointed out a population of sockeyes that spawns above the Russian River falls during early and late runs, and the adults are small relative to adult reds that spawn below the falls. I later learned that those red salmon overwinter in the Upper and Lower Russian lakes. In the lower third of the diagram, Paul then indicated a population of red salmon that spawns during the late run below the falls and clusters with other sockeyes spawning in the Upper Kenai River. Those reds overwinter in Skilak Lake.

Actually, the relation of fish distribution to geologic factors has intrigued me since my graduate-school days, when I was assigned to read a classic 1948 paper by Carl Hubbs and Robert Miller on the zoological evidence relating fish distributions and drainage changes in the desert southwestern US. So, I was preprogrammed to try and answer Paul’s initial question.

A guiding principle of my geologic studies is to understand the big picture first, so I initially studied the 1:250,000-scale topographic map of the Seward Quadrangle, where the Russian River, a north-flowing tributary of the Upper Kenai River, is confined in an intensely glaciated mountain valley. I located the Russian River falls, Lower Russian Lake, and Upper Russian Lake, and I noted that the uppermost Russian River is separated by a low drainage divide at ~850 feet elevation from nearby Summit Creek, the uppermost tributary of Resurrection River, which drains southeastward into Resurrection Bay near Seward. Could red salmon somehow have crossed the divide from Resurrection River into Russian River?

Further examination of the topographic map revealed that Exit Glacier near Seward is positioned so that a significantly larger glacier would dam Resurrection River, impounding a large lake upstream of the glacier barrier and potentially trapping sockeyes during a spawning run. If lake level reached ~850 feet elevation, lake waters would decant across the drainage divide and enter the Russian River drainage, carrying along the red salmon trapped in the lake. Could I find evidence for the damming of the Resurrection River by Exit Glacier?

I next looked at aerial photographs of the Exit Glacier area and examined the area stereoscopically, so that I got a good 3-dimensional impression of the topography there. Sure enough, on the northeastern side of the Resurrection River valley across from the modern terminus of Exit Glacier, there is an obvious bedrock channel at ~850 feet elevation through which the river could have been diverted if the valley was blocked by an expanded Exit Glacier. Preparing a model (see graphic) showing the relations of the glacier/lake/drainage system was pretty straight forward.

Unfortunately, I lack the information to date the diversion of Resurrection River reds into the Kenai River drainage. An informed guess is that a larger Exit Glacier likely blocked the Resurrection River near the end of the last major glacial recession, perhaps 11,000 to 12,000 years ago.

I have not proven that such mixing of sockeye populations actually occurred in the manner I propose. Ideally, the model could be tested by comparing the DNA of the Russian River reds with sockeye salmon that spawn today in Resurrection River. Unfortunately, I learned that the modern runs of red salmon in Resurrection River are not native to that drainage, but are composed of a mixture of fish from several different drainages that were initially reared in the Trail Lake hatchery near Moose Pass. So the DNA of those fish cannot be used to test my hypothesis.

Geologic investigations often reach an impasse like this, where the available data are inadequate to provide a definitive solution. Optimists, like me, anticipate that future geologists and geneticists will eventually find the information needed to verify or refute this particular drainage model.

Dr. Dick Reger graduated from Kenai Territorial High School in 1957, and eventually earned a PhD in geology from Arizona State University. He co-authored a 2007 guidebook on the late Quaternary history of the Kenai Peninsula (http://www.dggs.alaska.gov/publications). You can find more information about the Kenai National Wildlife Refuge at http://kenai.fws.gov or http://www.facebook.com/kenainationalwildliferefuge.

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kenai123
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kenai123 05/30/14 - 02:35 pm
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Studying kings or sockeyes?

If Dr. Reger really wants to resolve his "geologic investigation frustrations" regarding where our sockeye salmon genetically came from, he should just include in his studies all those different sockeyes drainage's that were dumped into our Trail Lake hatchery sockeyes. Trail Lake commercial fisheries people have zero DNA corruption concerns regarding their hatchery actions. Their only concerns are for commercial fisheries profits. This same lack of concern is currently going on today as Trail Lake and other commercial hatcheries continue to expand only sockeye populations well beyond their natural levels. This artificially sockeye expansion of only one stock then forces the artificial reduction of any stock attempting to compete along side that stock. Artificial sockeye expansion results in artificial forage and competition factors. Since sockeye primarily feed on crab larva less than a quarter inch in length and juvenal kings also primarily feed on this same larva but after it is larger than a quarter inch, an extensive and ever increasing feeding conflict has therefore been deliberately created by artificially pushing these sockeye stocks to their current levels. This comes down to the simple fact that we currently have excessive sockeye and they are consuming feed that would have normally been consumed by juvenal kings.

Extensive adult king salmon by-catch within our commercial Pollock and Salmon fisheries then combines together with this hatchery induced feeding conflict, thus greatly reducing the survivability of any stock attempting to survive around the highly prize and artificially accelerated sockeye salmon. The truth is that it should be completely illegal to enhance any individual salmon stock beyond its natural ratios. Instead of banning this kind of fisheries experimentation we ignore it and our ADF&G and Dr. Reger spend their time studying what sockeyes had for desert while our juvenal kings are starving to death. Instead of the ADF&G studying what our natural salmon ratios use to be historically, we see articles like this one which generate "a freakish concern" over only sockeye salmon. Dr. Reger and other investigators desire to know what is going on with "only sockeyes" both today and 12,000 years ago. Even with our current great king losses they still do not want to know how the artificial expansion of sockeyes can cause the decline of king salmon. Studying sockeye may be acceptable at times but not when our kings are in trouble. The truth is that it is highly illogical Dr. Reger to be burning the midnight oil studying sockeye geologic history when our kings are about to become extinct.

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