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Message Subject: How old is that Dink?

walleye express

Posted 2/3/2011 12:05 PM (#96447)
Subject: How old is that Dink?

Member

Posts: 2680

Location: Essexville, MI./Saginaw Bay.

With the magnitude of sub-legal walleyes being caught on both the river and the bay this year, there seems to be some confusion on just how old these little dinks are. And beyond that, just how old they have to be to achieve that 15 inch keeper length. I always assumed a 3 year old walleye would make that 15 inch minumum and it seems I was right. But I think we all know that the length/size to age ratio has changed in the past few years due to a variety of things happening on the Bay. But to put some of those things into professional perspective, I called on my DNR bio-Buddy for some documented answers. Below is his answer and his findings concerning these little Saginaw Bay rascals.

Dan:

Sorry to take so long to get back to you on this. Attached are some slides in the form of a PDF file that address trends in walleye growth rate on Saginaw Bay. Slide 1 shows trends in overall walleye abundance as determined by our annual survey catch rate in our nets (September survey work) This includes data up through Last year (2010). That’s the yellow line. The red line is the average (mean) length of age-3 walleyes (sexes combined). You can see that mean length has gone down as abundance (survey net CPUE) has gone up. This was expected. As you have more mouths to feed, they are going to have to share a limited amount of prey and habitat (space). Back before 2003 the growth rate was exceptionally high. That might sound good but it really was a reflection of not having as many walleyes as the bay could support. That’s why with our recovery plan, we identified a target of increasing abundance of walleye such that the growth rate of age-3 walleyes would decline to 110% of the state average rate. Yes we know what the average growth rate of walleyes are for Michigan and that’s indicated for age-3 walleyes on the graph.

http://www.walleye-express.com/albums/Miscellaneouos/sb_walleye1.pn...

Slide 2 in the presentation is the same sort of data for age-2 walleyes. These have actually declined below the state average rate (for age-2 fish) but not by an alarming amount. Their growth rate will bounce around and I expect it to be around the state average rate in most years.

http://www.walleye-express.com/albums/Miscellaneouos/sb_walleye2.pn...

Slide 3 is the same sort of data but this time for age-1 walleyes (yearlings). Notice they are at or just above the state average rate.

http://www.walleye-express.com/albums/Miscellaneouos/sb_walleye3.pn...

Lastly is a table of the state average lengths (in inches this time) and where we are at in 2010. You can see that we are just above average for yearlings, a little below for age-2 fish and right on for ages 3-5. Some of the older ages are behind the state average rate but I think that’s partly because those ages stem from some of those record year classes we had (lots of competition) and the state average rates are calculated from a lot of inland waters where temps may be warmer (longer growing season).

http://www.walleye-express.com/albums/Miscellaneouos/sb_walleye4.pn...

On the whole, I am not alarmed at all about walleye growth rates in Saginaw Bay. In fact, their decline is a very positive indicator of the greatly increased reproductive success (increased recruitment). Our recovery plan said that declines in growth was an acceptable trade off for increases in fish density (abundance). A lot of the smaller walleyes anglers are encountering are simply young fish. They are not stunted walleyes. If anglers are feeling that there are not enough trophy sized walleyes or even keeper walleye, then we need to explore that more as a longevity question (mortality rate issue) than a growth issue. Also growth is largely out of our hands any ways since we stopped stocking in 2006. Walleye are on their own path now as it pertains to abundance and the resulting growth rate. They will find their own sweet spot (equilibrium) over time. This is really as it should be when it comes to these situations. At present I think our current length limits are still appropriate at they generally protect fish until first maturity.

Edited by walleye express 2/3/2011 12:08 PM

sworrall

Posted 2/4/2011 8:36 AM (#96475 - in reply to #96447)
Subject: Re: How old is that Dink?

Location: Rhinelander

Very nice information, Dan, thanks!

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