I have heard this rumor from two different sources recently and I was wondering if there are any facts to substantiate this: Supposedly there has been a major die off of the Zebra Mussel on the Mississippi river. Has this been verified by the DNR or is it another one of those speculative (wishful thinking) events? Has anyone else heard the same thing? Are there credible sources that could share their views on Zebra Mussel? 
As far as the zebras go yes they are a neusence but as far as that is since they have been in the river it seems that the water has become cleaner. Ten years ago the water was always murky and on your outboard motor you couldn’t see your prop in the water now you can, maybe I am dreaming ,also the zebras have done wonders to the great lakes by cleaning the water at least what Ive been told by a guide from Port Clinton Ohio. The zebras acted as a water filtration on pollution and the past years on Erie have been cleaner water and the fish are making a comeback. As far as a die off of these zebras no clue but I do know that they attatch to stuff and attatch to other zebras eventually killing each other off. Im no biologist but this is my input.
Zebra Mussels die off at a total kill on adult and juvenle when the water temp reaches 78 degrees most in back water will die off the ones in main channel and deep water will not die off because of the cooler water.
What I just read on the Zebras is that while they do make the water clearer it is not nescesarily cleaner. what they are filtering is zoo plankton which is also what baitfish are feeding on.
The only major die off I can remember is when the water was low and got so warm a couple of years back. It’s been a quiet issue since then.
I just got off the phone with a retired Iowa fisheries biologist. He has not heard of any large die offs of the zebra mussels. He believes that most reductions are natural events, later the population recovers to previous levels. He has participated in water clarity studies for a number of years and is convinced the river in the Iowa sections are definitely clearer since the arrival of the zebra mussel. The jury is still out on whether the zebra mussel filters out an excessive amount of material from the food chain or if the filtering has had a negative effect on smaller fishes in that food chain system? Not enough data to categorically make a statement either way! Lastly a personal opinion/question, something is sure as all get out, had a positive impact and caused an increase in the smallmouth population. Dunno, could it be better water quality because of the Zebra Mussel pumping all that water? 
A die-off of zebra mussels did occur on the River during the summer of 2001. This die-off didn’t kill everything, but seemed to have a greater effect the further south you get. It was difficult to find a living zebra mussel in Pool 14. I believe less of an effect was seen up on Pool 4/Lake Pepin. However, it appears the mussels recovered relatively quickly in those southern pools as zebra mussels were frequently observed this past summer.
I’ve also heard that recent zebra mussel abundance in pepin may be oscilating up and down, but don’t believe anything indicates any long-term trends.
Yes, water clarities have improved recently, but I’m not sure if its due to zebra mussels, or improved land-use practices in the upper water shed. I would think there are differences in effects of zeebs to water clarity on lakes vs. rivers.
The jury is also out on the effects of zebra mussels to fish communities. On lakes, the short term has seemed to possibly benefit sight-feeding predators like smallmouth bass. However, it would be way premature (and inappropriate) to say zeebs are a good thing. We have yet to really see what their long term effects will be…. stay tuned.
For my two cents worth on the ‘improved land use’ theory. With the thousands (and probably millions) of acres of CRP in S. Minnesota and N. Iowa that came out of that set aside program and went back into production (majority into row crops) in the late 90’s and 00’s, I have to believe that there is far greater siltation/runoff than we had in the glory years of CRP (1984-1996). When we had the high water in 2001 and last spring, the water boiled as brown and nasty as ever – when it did settle down it definitely seemed clearer than in the pre-zeb era. My observations and opion on the zebra mussels presence in the Miss anyway – I have to agree that the long term effect is yet to be seen.
barc
You must be logged in to reply to this topic.
