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Sturgeon Spawning Update from Ron Bruch for May 5, 2011

May 6, 2011

This update has been posted with permission from Ron Bruch and the Wisconsin DNR:

“We think we wrapped up our 2011 sturgeon spawning assessment yesterday Thursday May 5 with two crews capturing over 220 fish at the Shawano spawning site below the Shawano dam. I say “we think” because water temperatures never got close to optimum and the slightly lower than normal fish densities at Shawano indicate that we could see a significant “2nd run” there when water temperatures get up to around 54-56 degrees F (12-13 C) within the next couple of weeks. We’ll be keeping an eye on it. There may be a few fish spawning today and possibly this weekend at Shawano for people to see, but the sex ratio and behavior of the fish yesterday indicated that this run there is almost over. You can still see a few fish on the Shawano Wolf River Cam at http://wolfrivercam.com/Shawano%20Dam.html.

Our data management Technician Doug Rinzel has been entering the data into our computer files each day after we collect them, and should have everything we collected to date entered and proofed soon. At this point it appears we may have broken the single season tagging records for both spawning males and females, with numbers coming in somewhere in the neighborhood of 1400 males and over 200 females. As soon I get the final tallies from Doug and have time to put my final report together I will pass on the information to you. We (WI Fisheries staff) have been tagging sturgeon during the spawning runs on the Wolf River since 1954.

As I mentioned in an earlier e-mail our tagging target is driven by females – we need to get at least 100-150 females tagged each year to ensure we can accurately estimate adult female population densities, set harvest caps, and estimate annual exploitation – the more we tag, the more accurate our estimates. I’ve attached a photo of a 140 lb female we captured and tagged yesterday at Shawano. In the photo with this fish is one of our best sturgeon dip netters Bob “Hermie” Marin. We know from experience – don’t ever try to take Hermie’s dip net away from him. He alone probably dip netted over 1000 sturgeon this year with a total weight of over 50,000 pounds (~ 23000 kg).

Photo provided by the Wisconsin DNR

The long drawn out spring this year due to the persistent cold weather and cold water temperatures was often miserable to work in, but did bring the fish on more slowly from the southern spawning sites to the northern spawning sites giving us more days to work fish and to get our tagging numbers up. In addition to likely breaking the all time tagging records for males and females I believe we also broke the record for duration of the spawning run – 21 days; and it may not be over yet depending on what we expect to happen with the 2nd run at Shawano and other northern spawning sites. We also saw fish spawn at temperatures lower than we have ever seen since 1954 – as low as 39 degrees F (4 C).

As soon as I have my final report for the spring put together I will send this out to you. If the sturgeon start up a second run at Shawano or other sites that the public has access to I will let you know as well.

Till then.

Ronald M. Bruch, PhD
Upper Fox-Wolf Fisheries Work Unit Supervisor, Wisconsin Department of Natural Resources”

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