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Location: Essexville, MI./Saginaw Bay. | I e-mailed my buddy recently, who is the head DNR biologist for Saginaw Bay and asked about why he thinks the Saginaw Bay has stayed more stained and turbid this year then in many of the past years. I did so wondering about the correlation between this turbididy and the percived come-back of our perch populations number and size this past season, starting with this past winter. This turbid (cream in the coffee) condition was the Bays natural condition in all the years I remember it while growing up in the 50's, 60's and early 70's before the zebra mussles arrival that cleaned the waters crystal clear in some cases up to 12' deep. I also inquired about this Septembers trawl to check on the Bays fish populations and the 2012 spring walleye hatch survival. Below is my original question and his answers to all of the above.
Hey bud.
I wonder if you could answer this question for me. How long (if you know) does NOAA keep or store the Satellite Modis images from Saginaw Bay? I've been wondering about the correlation between the cloudiness of the waters of Saginaw Bay for over a year now and it's possible connection to our perch populations come back. For a few years after the zebra mussels took over the Images of the Bay was as blue as the Lakes themselves for extended periods of time, even soon after the spring run-off of snow melt. But now seem to be stained all the time, even during long periods with no rain. This of course was what Saginaw Bay looked like all the time when I was growing up, mainly because of the Phosphorus amounts in the water back then and the billions of organisms living in the Bay that thrived because of it. But back then the amount of perch and their size was off the charts. I'm thinking the Alewife demise has also played a big part in these things as many other smaller fish species are showing signs of returning in droves. But the waters cloudiness may be key, especially when it comes to Cormorant and other predation on the younger perch after they hatch. Am I on the right track? Not that I'm complaining, just wondering.
My DNR Bio-Buddies feedback from my post.
Good theories and the right kind of reasoning Dan. First, everyone keeps talking abut the perch comeback. I’ve heard lots of stories about good perch fishing and catches on the bay this past year but our creel survey (year-round) still indicates that the yellow perch fishery overall is greatly down, a fraction of what it once was (both sport and commercial). Our survey netting hints at some improvement but even there, there isn’t much evidence of it. I think perch are schooled up and at times, there are good catches and of course everyone talks about those so the sense out there is things are looking up for perch, but all our measurements don’t really support that. Maybe things just need to catch up. We’ll have this years creel survey statistics around in January so that will be another look at it.
As for the water clarity, zebra mussels are way down and quagga mussels are maybe contracting some too. This definitely could affect water clarity and turbidity. Generally the more productive the water body, the more turbid it is. I’m not sure that there is more productivity in the bay, but may be more of the existing productivity is being freed up to grow plankton which is a better result than more mussels (better for fish any ways).
His last E-mail answer:
Dan.
Zebra mussels are rare in Saginaw Bay any more. Almost all the mussels our there are quaggas. They look nearly identical so everyone thinks they are zebras but you’ll notice the flat edge and lesser stripping tells you it’s a quagga. No one is certain why the transition, but quaggas seem to have the upper hand at the moment.
As for the un-official survey results; The catch rate of the young-of-the-year walleye (in the trawl collection) was down compared to the last three years but still strong by the old standards. If we sampled that many in 2002, we’d be marveling at what a huge catch it was. Our yearling catch in the gillnets, (our primary indicator of year class strength) indicates that the 2011 year class (yearlings in 2012) is modestly strong. These are very preliminary impressions. We won’t know for sure until after the aging is done to confirm that what we are looking at is really yearlings and young-of-the-year. Also, we’ve discovered that the young-of-the-year catch rate isn’t a strong predictor any more. We have had some very strong yearling year classes result from relatively weak YOY catches, and the other way around too. So even though the YOY catch was modest, it might still survive well and result in a strong year class. We’ll find that out next year.
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Zebras/Quaggas and Walleye trawl results for Saginaw Bay.