Conservation Minnesota

Zebra Mussels II

Last summer in this column I advised lake associations,

“If your lake has zebra mussels, don’t waste much time, effort or expense on controlling them. Solutions may be coming, but for now they are not here. Hope is not a game plan. Focus on keeping additional AIS out.”

The recent “re-discovery” of zebra mussels in Christmas Lake, unfortunately, bears this out.

We know we can kill zebra mussels in small, confined areas. In the case of Christmas Lake, three treatments, all of them lethal and non-selective, almost certainly killed zebra mussels within the contained area. The hope was that the mussels were discovered early enough after their introduction that they were still confined to a known, small area that could be contained and treated.

Here is the bugaboo – the chances of discovering zebra mussels early enough to contain and eradicate them are extremely slim. It was claimed that the zebra mussel discovery in Christmas Lake was within weeks following their introduction, and even if true, they were not confined to the treatment area. So, it doesn’t matter if we can kill them in small areas if our aim is to eliminate them from an affected lake. It was a long shot then and an even longer shot now.

I am concerned that by continuing these attempts we are falsely raising hopes there is a cure.

This summer, many lake associations are being asked to deploy samplers around the shore as an early detection method. However, finding evidence of zebra mussels on samplers of this type almost certainly indicates a reproducing population in the lake, meaning it is too late.

If other lakes decide to attempt an early response to eradicate zebra mussels, what have we learned about the tools applied in Christmas Lake?

Zequanox, a natural bacterial product that can selectively kill zebra (and quagga) mussels is expensive (tens of thousands of dollars per acre) and as applied in Christmas Lake was not selective as the dissolved oxygen in the treatment area was totally depleted for at least a week, likely killing all oxygen-requiring animals.

Copper sulfate is cheap and readily available. However, we are not sure of its kill rate.

Potash kills zebra mussels (and many other animals), but it requires special permission for this use. Because it followed the other treatments, we have not learned much about its sole use.

The objective for Christmas Lake was to do anything and everything possible to get rid of those pests. By using the everything-but-the-kitchen-sink approach to kill them, we have not learned much more than we already knew. What we did learn was it was too late – zebra mussels were not contained in the first place.

What about research? It would appear that the tools we now have offer little promise for eradicating zebra mussels from lakes. Research can (and should) explore other methods and techniques. This kind of research takes a lot of time and money. Right now, there is very little funding, so with this slow start, a silver bullet will likely be a long way off.

What next?

There are two logical approaches that can be for Christmas Lake or other lakes, both with serious drawbacks. We can attempt to eradicate zebra mussels or we can design demonstrations to learn more about how they can be eradicated – but not both.

If we attempt to eradicate zebra mussels, as was done in Christmas Lake, we compromise learning about the best eradication protocol. Because three products were used in Christmas Lake, we don’t know which one or which combination killed the mussels. Actually, we don’t even know for sure that the mussels were all killed. Extensive searches in the containment are found no mussels, but neither were mussels found in the lake and we now know they were there. And the boat access was re-opened. Were mussels re-introduced? There are also operational difficulties to refine. We have not learned much.

If we attempt to learn about how best to eradicate mussels, we compromise chances at eradicating them. A systematic approach aimed at refining an eradication method would involve controlled studies in multiple sites spanning several years. To learn the most, we would expect and want some failures in this approach.

More and more lakes will become infested. If we are going to invest public money and inappropriately raise hopes, we should do so with our eyes open and our expectations realistic.

About Dick Osgood

Dick Osgood

Dick Osgood has authored numerous scientific journal papers, made hundreds of presentations at professional meetings, and recently co-authored his first book.  Now he’s working on his second book titled A Lake Manager’s Notebook.  Dick is a Certified Lake Manager and offers lake management consulting services through his business Osgood Consulting LLC.

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