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Checking the changes

July 10, 2020 by Ted Rulseh

All lakes change with time, some more rapidly than others, and some also more significantly. One way to track what’s happening in your lake is to do a periodic deep dive, literally.

That means exploring by way of scuba gear or, in my case, fins, mask and snorkel. Last Saturday I took a reconnaissance trip along our shoreline on Birch Lake and was surprised at what I found.

Birch Lake became infested with rusty crayfish a couple of decades ago, and one of their effects was to defoliate the lake. They cleared out huge beds of cabbage weeds about as effectively as an herbicide could do, leaving just a few remnant weed stands in shallow, mucky bays.

The crayfish population came under control through the combined impacts of predation by fish, trapping by the Friends of Birch Lake and, possibly, a lethal parasite that is known to infect populations of rusties in some lakes.

On my snorkel expedition last summer, I saw almost no crayfish at all. I also observed new coontail weeds popping up in scattered places. This summer’s trip (the first and not the last) was a revelation.

For one thing, off the end of our pier where there had been a small patch of coontail, there is now a much more extensive growth, with quite a bit of cabbage weed in the mix. For years the bottom along our frontage, out beyond the near-shore bulrushes, was mostly austere silty sand. For that reason I rarely tried fishing from our pier, and when I did I caught little to nothing.

Now the new weeds attract fry and young-of-the-year fish, and they in turn attract predators, notably walleyes. So, suddenly, the fishing from our pier is good.

Ranging much farther I found a great deal more coontail and cabbage weed, including some patches I would have to call luxuriant, and some spots that before long likely will be so. That is, unless the crayfish make a resurgence.

And through my mask that is what I observed, at least in comparison to last year. The crayfish are now abundant. The numbers are not comparable to those of the peak years, but there are plenty, and in a full range of sizes. That’s a cause for concern.

These changes in the population of an invasive species and in the amount of aquatic vegetation could portend substantial changes in the structure of the fish populations. Since I’m not a lake biologist I’m not prepared to speculate on what those changes will be. 

I do know, for example, that 30 years ago when the weeds were prolific, largemouths were the primary bass species; smallmouths now dominate. Could a resurgence in weeds flip that relationship back to where it was? What other changes await? Or perhaps the crayfish will proliferate again and knock the weeds back down. Time will tell.

More questions than answers, it’s true, but an hour behind a mask brought interesting observations of my lake. I bet it could do something similar for you.

Ted Rulseh resides on Birch Lake in Harshaw and is an advocate for lake protection and improvement. His Lakeland Times and Northwoods River News columns are the basis for a book, “A Lakeside Companion,” published by The University of Wisconsin Press. Ted may be reached at [email protected]


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