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Sturgeon Spawning Update from Ron Bruch on April 8, 2010

April 8, 2010

“This morning’s nice blanket of fresh snow across Winnebago-land was a wonderful site for me and my crew as we are attempting to complete a number of other spring surveys and work items before we are drawn back to the Wolf River for our annual sturgeon tagging ritual. The early spring had us scrambling trying to fit everything in to our schedules over the last week after we finished tagging walleye on the Wolf River on April 1. We tagged some additional walleye over the last few days on Lake Winnebago to use up some of our tag series for this year, ending up with 10749 new walleye tagged and 875 recaptures for our spring 2010 season. As I mentioned in an earlier update, we use tagging data to estimate annual walleye exploitation rates and population densities.

Sturgeon Spawning Update…………

Upper Fox River – Sturgeon actually began spawning on the upper Fox River at Princeton and Eureka last weekend on Easter Sunday, April 4. The upper Fox is more of a southern watershed that warms more rapidly and sturgeon almost always begin spawning there a week or more before they begin on the Wolf. This first pulse of spawning on the upper Fox is over but will likely be followed by a second pulse in late April. The sturgeon that spawn in the upper Fox are a separate sub-population of fish that generally always spawn in the upper Fox, although we do have some males that spawn in both rivers in the same year. The number of sturgeon that spawn in the upper Fox is relatively small – probably several hundred fish. Historically the numbers were likely much greater, although the series of locks and dams constructed on the river in the late 1800s disrupted spawning runs and closed off many of the natural spawning areas. We have either removed or built fishways around most of the dams, and we still have a remnant stock that uses the river for spawning. We have also been working with Sturgeon for Tomorrow and the University of Wisconsin-Milwaukee WATER Institute since 2002 to collect eggs each spring and rear extended growth sturgeon fingerlings for stocking in the upper Fox River in a long-term effort to rebuild the upper Fox lake sturgeon spawning stock. SFT pays for rearing the fish at the WATER institute in Fred Binkowski’s lab, and we use sturgeon spearing license funds to PIT tag all of the 500-1000 fish released annually, and to implant radio and sonic tags in a dozen or more fish each year to study the behavior and habitat-use of stocked fish. After radio or sonic tagging and tracking a over two hundred young sturgeon since 2002 we have learned a lot about the movement and habitat use of fingerling and larger juvenile surgeon in our system including the best time of year to stock young sturgeon, the seasonal downstream movement of fingerling sturgeon from the rivers into the lakes, and the vital importance of the Upriver Lakes as a nursery ground for young stock.

Wolf River – Sturgeon have been porpoising at several sites on the Wolf and Embarrass Rivers since Easter weekend, but no spawning has been observed to date. People can see porpoising fish at Bamboo Bend just west of Shiocton on Highway 54. Prior to and during the spawning period, lake sturgeon exhibit a porpoising behavior where they come to the surface adjacent to spawning sites and jump out of the water or sometimes just stick their faces out of the water. Depending on the water temperatures, this activity may go on for up to two weeks before spawning actually begins at a particular site. Given the nice snow we received last night and this morning, the water temperatures have begun to drop in the Wolf River which will delay the start of sturgeon spawning activity from earlier expectations. At this point I don’t expect fish to begin spawning at the earliest until sometime next week – dependant upon on how fast things warm up after we get through this current spell of cold weather. With any luck we may see spawning commence close to the same time we open Sturgeon Camp and get our first Sturgeon Guards out on April 15 – although it could start earlier than April 15 – we’ll be watching closely and will let you know when spawning on the Wolf actually starts.”

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

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