It’s March and as you read this it will officially be spring. That’s kind of funny because it’s seemed like spring for a month now. This will go down as the mildest winter I’ve spent in the Northern Rockies in the 20 odd years I’ve been kicking around the joint.
Last week it was 71 degrees in Billings. That’s a nice high temperature for May. March, however, is a little early for T-shirt weather.
The trout in the local reservoir have been feeling the warm temperatures too. Maybe a month earlier than they normally do, rainbows and cutthroat are feeling the tug of that instinct which compels them to move out of still water and head upstream. Trout, with the exception of a few pesky species such as the Mackinaw that have become such a management problem in Flathead Lake, only spawn in streams and rivers. To develop, trout eggs, once fertilized, require the steady flow of highly oxygenated water over their resting place in clean river gravel.
So the trout head upstream.
But unlike the journey of Pacific salmon, which undergo dramatic morphological changes once they leave the ocean and head upriver to breed and die, trout spawning runs are not a death march. The fish continue to eat along the way, and once their boy-girl business is attended to, they return to the lake (or in the case of steelhead trout, the ocean) to live out their lives, at least until the following spring.
The living is easier in the lake. Trout don’t have to expend energy just to hold their place as they do in the current of a river. And the grocery store in a lake is better stocked. Instead of feeding on aquatic insects, these lake trout get fat feasting on minnows and other protein dense forage. All this means bigger trout.
It’s the spawning run that makes them available to fly fishers. In the lake these bigger trout tend to hang out in deeper water where you need weights and downriggers to reach them. That’s all fine and good, as trolling is one of the most relaxing ways to fish, but it ain’t fly fishing.
Those fat lake fish in a stream or small river are a hoot. The professor and I have been dragging nymphs through likely looking runs. The good spots are often just below small rapids, where the fish gather themselves preparing to push through the whitewater.
It’s a poor man’s version of nymphing for steelhead. The fish are toads compared to what we’re used to catching. Where we might normally hook a bunch of 12-inch trout, suddenly the average fish is somewhere around the 20-inch mark. And there are lots of them, sometimes.
The way the fishing turns on and off has convinced the Professor and I that the fish come up out of the lake in waves: gangs of rough-around-the-collar trout looking for some action upstream. I don’t have the slightest idea if this is true, but it’s the story we tell ourselves when the fishing slows down.
Soon enough all this fun will be over. The fish will have moved on, to the spawning redds where they’re off limits in my book. Then they’ll head back to the lake where they’ll only be bothered by the deep-water trollers.
The next generation comes later. The trout eggs will develop in the cool water of the headwater streams. Once hatched, the trout fry spend considerable time living in the space within the gravel itself, slowly digesting their yolk sac until they are large enough to venture out into the current, feeding on the tiniest of aquatic organisms. They’ll eventually drift downstream to the lake, and if they’re not consumed by their predatory aunts and uncles, the small trout will repeat the spawning run upriver.
I intend to be there to greet them.