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An autumn squall

A dark, heavy squall rolled off the face of Blacktail Mountain and charged across the pelagic surface of Lake Pend Oreille like a sword-drawn Cossack heading for Samoan Campground. Winds churned the Monarch waters to a chop white, chasing bold sails before them, taunting the less worthy craft. The dark gray hid the sun, obfuscating the light of day. It was a magnificent display of the balance of forces we call weather, a mean metaphor for another kind of rampage beneath the surface, a contest not of man, but of fish.

    For in the dark deep there is a contest that threatens the valued life of a number of species residing there. Predator versus prey. Large fish against the smaller. It is the eternal play of biological forces.

    In a healthy ecology, it is this swing of the pendulum that controls over- abundance in the prey. As the prey grows in numbers, so the predators populate. As the prey count dwindles, so follows the number of predators that feed on them. In the natural world the balance swings back and forth.

    But Lake Pend Oreille is no longer a natural environment. Mankind has joined the foray, swinging down off the mountains in a sometimes rather furious display of cross-purposes. For 34 years, the lake has experienced 11-foot drops in elevation during the winter months, managed thus for hydroelectric purposes. The drawdowns begin in the fall of the year in anticipation of the heavier winter demand for electricity and the reservoir is filled again in the spring with the runoff of melting snows. This was good for the valley, we were told, because it allowed the Corps of Engineers to manage floodwaters safely.

    But this yearly drop in the elevation of the lake was contributing to the decline in the kokanee population in was that were not understood during most of that time. Kokanee are the freshwater, sockeye salmon once very abundant in this lake. They are fodder to three, well-known species of predator fish also found here: rainbow trout, bull trout and lake trout. The concern is that the kokanee population is in serious decline. The danger is that if it collapses, the predator populations may also collapse.

    Fishery biologists want to prove the consistent annual elevation drop of 11 feet is contributing to the decline in kokanee numbers. Certainly there are other factors, such as the introduction of mysis shrimp (by biologists) and the inadvertent entry of lake trout into the system. The construction of Cabinet Gorge Dam has also contributed to this decline, despite efforts to mitigate with a fish ladder and a hatchery near the dam. Fingers point everywhere.

    Part of the squall is biologists want to prove the drawdown is a player in the decline and they need the Corps to minimize its winter lowering so that aerated gravels are not exposed. They want to conduct a study over a five-year period. The Corps finally agreed awhile back but has consistently found ample justification to draw the water down anyway. Now scientists are resorting to legal semantics, playing off the fact that bull trout are a federally regulated endangered species. They may get their way.

    Though kokanee by species are riparian spawners, part of the population has adapted to spawning in the shoreline gravels where wind and wave action prevent the buildup of silt. Unfortunately, the untimely autumn drawdown exposes the kokanee eggs to air (and thus kills them) or drives the spawning adults into using unproductive gravel where silting is too heavy, smothering the fertile eggs.  

    For the lake to sustain a viable sport fishery of 1,000,000 kokanee, it must produce at least 5,000,000 kokanee on its own…every year. Studies have consistently revealed that in this lake, an 80% mortality rate occurs in the kokanee fry when they are most vulnerable to predation between their first and second year, big enough to enter the open water—hence the numbers concluded above.

    Somewhere in our bio-energetic understanding of the lake and its fish populations there is a point of no return where collapse of the primary prey population will adversely affect the predator populations and consequently the pocketbooks of the area’s economy. A lot of people come here to fish for the outsized rainbows, and now for the mackinaw (lake trout). These predators are a tourist draw as well as a real estate bonus. That’s enough shift in the air currents for a good squall without bringing in the fact that the third kokanee predator is federally listed as a threatened species: the bull trout (freshwater variety of Dolly Varden). You can’t keep bull trout. And federal regulations govern the riparian habitats where they spawn. The fact that it can be shown that a collapse in the kokanee population can adversely affect recovery of bull trout in this watershed adds regulatory clout to the argument of the biologists.

    The winds of the squall have thrown a new gust across the surface of controversy. The biologists are saying that the Corps has to honor its five-year agreement to minimize the winter drawdown so that aerated gravels being used by the spawning kokanee can be evaluated for productivity. The Corps, like any managing body, has its own agenda. They cite good reason, downstream and up, to justify the annual drawdown: flood control, drought recovery, and heavier electrical demand in the winter. We can’t blame them. But we do need their understanding and help because the lake draws enough people into this economy to justify this study. 

    At this point, no one knows the number that, if passed, will define the point of no return. They do know predation in the lake is exacting a greater toll than it should, that the survival rate in the general population of kokanee is shrinking more rapidly than before. Soon, if the reasons are not understood and properly managed, there will be too few spawning adult kokanee to replenish the lake. That undefined number is the point of no return. Once it is surpassed, recovery will be impossible.

    The predators won’t die out instantly. They’ll starve out. They’ll seek other fish surely, but will they change preferred habitats? Not likely. Gradually, we’ll lose them. They’ll get smaller in maturity and fewer in number. The bull trout will likely diminish first. The rainbows will follow. The lake trout, however, will probably stay as they are voracious, competitive and cannibalistic if there’s nothing else to eat.

    The squall soon passes. The sky clears and men live in harmony once again. There’s no real war out there anyway among these fellows and ladies of Idaho, just some healthy arguments. Whatever the outcome, it all represents a microcosm of what the world is doing and must do to manage the waters of its oceans. The universal question is: where’s the point of no return? It’s a squalling answer at best.

 

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Dwayne Parsons Dwayne Parsons

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