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Sturgeon Spawning Update from Ron Bruch on April 27, 2011

April 27, 2011

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

“A little warmer weather today and a few glimpses of the sun this afternoon made a lot of difference with pushing the lake sturgeon along their path towards ramping up their spawning activity today. We tagged fish most of the day again along the Sturgeon Trail on County Highway X west of New London, and then at Pfeifer Park in New London on the Embarrass River. The fish were coming in most of the day at these two sites, as well as at about 4 or 5 other sites on the system in the New London and Shiocton areas. Water temperatures went down from highs reached on Monday due to the cold rain yesterday, but the higher temps we saw on Monday were enough to get fish going at a number of sites. Despite seeing more fish, we did not collect any eggs today for our restoration projects since we only captured a few females and most of these fish were not yet ovulating or ready release any eggs – we’ll take eggs at Shawano this weekend hopefully. A female will come into a spawning site a few hours before she is finally ready to ovulate and begin releasing her eggs. The males aren’t overly interested in her at this time, although they know she is there and will hang around her hoping to be one of the first males to be in the best position to begin spawning with her once she does begin to ovulate. They will hang with her for quite some time, unless there are other females also in the area that are more attractive because they have already begun ovulating and releasing eggs. Once a female begins to ovulate she will blast out about 1000 eggs every 90 seconds or so until she is empty – 8 to 10 hours after she started releasing eggs. At this point she is pretty much exhausted and may hang around the spawning site for perhaps an hour or two or so before she leaves the sites and begins drifting back down towards the Upriver lakes and/or Lake Winnebago. The males will continue to hang on the spawning site for days or weeks to continue spawning with other females. So – lake sturgeon are polyandrous (one female spawning with numerous males) and polygynous (one male spawning with numerous females) – Mother Nature’s way of ensuring genetic diversity in the stock.

One of the real surprises of the day was capturing a very old and very large male lake sturgeon. This fish was 70 inches long, and while we have captured males longer than this, we never captured a male as heavy as this one. We did not weigh the fish (we generally don’t weigh fish we capture in the spring since we get enough weights during spearing season), but we estimated this fish weighed about 150 pounds! This was a massive fish. I’ve attached a photo of this large fish that is probably 100 or more years old. The largest male we have ever seen in the winter spear harvest was 116 pounds.
Typically adult males are 45 to 65” in total length, and 15 to 70 pounds, but occasionally we see a 70 to 100 lb male, but we have never seen one as large as the one we caught today on the Embarrass River.

Photo provided by the DNR

Tomorrow (Thursday) is supposed to be cold and rainy again, so I don’t expect water temperatures to rise at all, although the fish should continue to be active at Cty X if people want to brave the elements and watch us tag some fish. The weather is finally supposed to warm up and be sunny on Friday which I believe should push the fish into the final big run of this spawning season which means fish should start spawning at Shawano Dam. There are more and more fish massing there each day, and the rising water temps we expect to see Friday should push the fish to begin spawning below the dam by late Friday. If this occurs, I expect Saturday and Sunday (or Sunday and Monday) to be huge tagging days for us at this site. Usually during the 2 to 3 day peak of spawning at Shawano dam we will capture and tag over 700 fish, including some over 200 pounds. We saw a couple of females this evening below the dam moving in that were probably in the 230-250 pound class!

The Shawano dam site is a natural spawning area that was part of a large natural rapids in the Wolf River. The dam was built at this site due to the high gradient which attracted sturgeon to this spot to spawn every year for likely the last 10,000 years. This was also a very important site for the Menominee Indians for harvesting lake sturgeon during the spring spawning run after the Tribe made the current reservation its home in 1854 and before the dam was built in the late 1890s. Historical records we found while conducting research for our book People of the Sturgeon: Wisconsin’s Love Affair with and Ancient Fish documented this to be one of the most important sturgeon harvest sites for the Menominee people who would leave the Reservation and come down to Shawano to camp and harvest sturgeon in the spring.

So as the sturgeon return to Shawano each spring, we (DNR Fisheries staff) have also returned for almost 60 years – to capture and tag as many as possible for our population studies and management program. The tagging we do each spring, especially the tagging at Shawano, is critical to our Winnebago sturgeon management program. We use these tagging data to estimate the size of the adult stocks of males and females, to set harvest caps for the winter spear fishery, and to estimate exploitation during the winter spear fishery. We could not manage the fishery without doing this tagging each spring, and being able to tag fish at the Shawano dam site is critical to our management program.

Enough for tonight…………looking forward to the next few days.

When we actually begin tagging at Shawano – I will let you know so you can watch us on the web cam http://wolfrivercam.com/Shawano%20Above.html.

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

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