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Will Winter Wither

by Bruce Auchly

Thursday, February 25, 2016

Is winter done? Kaput, finished, terminated?

It would seem so, though you may not want to bet the farm subsidies on it.

Those who want a winter with snow and cold – ski areas, snowmobile dealers and farmers – sure hope the best is yet to come. For lawnmower dealers or gardeners dreaming of tomatoes an early spring is nice.

For most of us, however, it really doesn’t matter. Our lives will go on with a modicum of discomfort.

For fish and wildlife, it really does matter. And their lives may not go on.

Yes, mild winters help some species like mice and deer to build populations; perhaps to levels the habitat can’t withstand. Along comes a hard winter and those prey species start tipping over. Then it’s a buffet for eagles, coyotes and weasels. Well, until those predators find themselves out of food and their populations fall. But for now, hey, let’s eat.

Fish are the most obvious sufferers of a dry, warm winter. Below average snow in the mountains can translate into below average spring runoff and above average water temperatures in summer.

That’s a long way of saying fish die without water.

We knew that. But did you know that with little to no spring runoff and flooding some species may spawn a lot less.

Consider the native paddlefish.

As spring runoff in the Missouri River at Virgelle, downstream of Fort Benton, hits 14,000 cubic feet per second (cfs), it triggers a large-scale spawning response from paddlefish.

Although paddlefish will still move upstream from Fort Peck Reservoir to spawn at flows less than 14,000 cfs, at increased flows, the fish are able to move further to spawn, giving the appearance of a pulse of fish moving upstream.

Several other species respond in a similar fashion if and when river water levels rise in the spring: pallid and shovelnose sturgeon and blue suckers.

For eons, that’s the way large prairie rivers worked. The onrush of melting mountain snowpack careened down to the floodplain and created nature’s chaos.

Nature’s seasonal disorder may look messy from our perspective, but it worked pretty well in flat-bottomed river valleys for those organisms that evolved there, like insects, amphibians, and northern pike (though not so much in Montana).

Then came dams and everything changed; warm meandering streams and rivers turned cold. But even nonnative fish species that thrive in cold water are affected by a dry, warm spring.

Rainbow trout, at least this year, have started spawning a couple of weeks early.

Rainbows in the wild reproduce over several months, from early March into June, peaking from mid- to late April in rivers and streams with gravel bottoms. This year, rainbow spawning beds, or redds, have been spotted in the Missouri near Great Falls in mid-February.

Rainbow trout spawn in response to increasing daylight length and rising water temperature. Our dry, warmer than average weather of late probably translates into slightly warmer water and fewer winter storms (read: less cloud cover).

In the big, global picture do rainbows spawning a couple of weeks early this year mean much? Meh, maybe not.

But it does give us a snapshot of the intricate web nature weaves. A moment in time we may miss by not paying attention.