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Update from Ron Bruch on Feb. 19, 2011

February 19, 2011

Following is the update from Ron Bruch including daily totals and info on sturgeon spawning and more.  I will post later tonight, so check back tomorrow for photos and more from today.  Everyone please stay off the ice or be extremely careful if you need to be out there!  There were multiple incidents on the ice today, for more info read this article in the Post Crescent: “Man dead after three vehicles plunge into Lake Winnebago“.  Please keep the victim’s family in your prayers.

(This update has been posted with permission from the Wisconsin DNR and Ron Bruch.)

“Report – Saturday February 19

See Sturgeon Vignette below: “Where do all the sturgeon in the Winnebago lakes come from?” “Where are all the big fish during the spearing season?”

A fair amount of spearing effort today resulted in a total harvest from Lake Winnebago of 70 fish, and 16 fish from the Upriver Lakes – No, we did not hit the 90% harvest cap trigger on the Upriver Lakes – we only registered 1 adult female on the URL today so we need one more adult female or 7 males to trip a 90% closure trigger on the Upriver Lakes. On Lake Winnebago we need 212 adult females to hit the 90% closure trigger there.

Today there were several vehicles that went through the ice on Lake Winnebago after hitting pockets of bad ice brought on by the recent warm weather and snow melt. At this time I have no information on injuries that may have resulted, but local sheriff’s departments were on the scene for some of these incidents. The problem areas according to spearers coming off the lake, were wash out areas on previously established roads and some sturgeon holes that occurred from the rapid snow melt, wind, and ice movement. As always, spearers need to take every precaution when traveling on the ice and need to make sure they know the path they are taking whether in a vehicle or on foot is absolutely safe and has sufficient ice to carry them and their vehicle. Sturgeon spearers are experts at reading ice conditions, but the quick snow melt, wind, and resultant water movement on the ice this past week can challenge even the most veteran sturgeon spearer.

The overall harvest total for the day was 86 including 5 fish 100 lbs or larger (5.8% of today’s harvest; 5 from Lake Winnebago and 0 from the Upriver Lakes). The largest – a 171.3 pound, 75.6 inch F4 female from Lake Winnebago registered at our Jerry’s Bar Station in Oshkosh by Michael Bartell of Oshkosh.

List of totals by station and the largest fish registered at each station today is in the attached daily report.

Totals by lake area and harvest category:

Lake Winnebago: 13 Juvenile Females
25 Adult Females
32 Males
70 Lake Winnebago Total for the Day – 964 total for season

Upriver Lakes: 3 Juvenile Females
1 Adult Females
12 Males
16 Upriver Lakes Total for the Day – 330 total for season

System-Wide: 16 Juvenile Females
26 Adult Females
44 Males
86 System-wide Total for the Day

1294 System-wide Total for the Season

“Where do all the sturgeon in the Winnebago lakes come from?” “Where are all the big fish during the spearing season?”

Most sturgeon species are quite migratory; as a matter of fact most species actually live in salt water and run up freshwater rivers to spawn, where the resultant young sturgeon spend varying amounts of time before they move downstream into the ocean the adults originally migrated from. Our lake sturgeon is one of the few species that spends all of its life in freshwater.

On the Winnebago System, the story begins at one of the more than 60 spawning sites we have on the Wolf, Embarrass, Little Wolf, upper Fox, and a few other smaller tributaries that our sturgeon lay their eggs at. Our lake sturgeon are not like salmon that go back to the same stream and often spawning site of their beginning; instead they will spawn through their life at different sites, and often in different rivers from one spawning event to the next. We even have males that will spawn at multiple sites and rivers during the same spawning season.

The average adult female lake sturgeon carries around 500,000 eggs during each of her spawning runs, and a 100 year old female sturgeon (the 200 pounders) will have made only 18 to 26 spawning runs in her lifetime since she does not spawn every year. In her lifetime we estimate she will contribute an average of 12 yearling sturgeon to the population after each spawn. Most of the eggs she lays die or get eaten by other fish, including many that are eaten on the spawning ground by male sturgeon at the site. While this may seem to be self-destructive behavior – it is probably one of the factors that better guarantees some production from the eggs laid at a site. Egg eating predators keep the surface of the spawning rocks clean so the eggs lying in the interstitial spaces between the rocks have adequate water flow and oxygen to incubate and hatch out.

About 10 days after the eggs are laid, and the surviving sturgeon eggs hatch, the young fry stay in the safe confines of the rocks for about another 10 days until their yolk sac is used up, and then move out into the river current at night and drift downstream to settle into their new life on sand and pea gravel bars in the river where they live for the first summer eating primarily aquatic insects that live on the bottom of the river.

Between age 1 and 10 our lake sturgeon eventually work their way down to the Upriver lakes where most of them live as juveniles, although some do go all the way down to Lake Winnebago. By the time they are around 36-40 inches about 85% finally make Lake Winnebago their home to take advantage of the rich food resources there in lakefly larvae (“redworms”) and later gizzard shad.

Once these fish mature (males age 14-31, females age 20-34) they start the cycle all over again by running up the rivers to spawn as adults. This is when it gets really interesting though from a spear harvest management perspective. We know from our long-term tagging and telemetry work that about 90% or more of the male and female sturgeon spawning in a given spring begin moving out of Lake Winnebago in September and continue to move out the entire fall and winter. Some of these fish go straight through the Upriver Lakes to spend the winter in the deep holes of the rivers to wait for spring. Some of these fish also short-stop their migration in the upriver lakes to take advantage of the buffet of gizzard shad and other food there for the winter before finishing their pre-spawn movement in late March. These are the fish that make up part of the upriver Lakes spear harvest each winter along with the juvenile fish that just live there.

Finally, we also know that about 85% of the adult sturgeon in the Winnebago System call lake Winnebago their home, while 13% reside between spawning runs in the Upriver Lakes, an 2% never leave the rivers.

As far as the big question that spearers often ask, “Where are the fish likely to be in Lake Winnebago during the spearing season?” We are not able to track fish in the lake very well, but what we know is that wherever you find good food supplies – you will find fish. Basically there are two things that motivate a sturgeon to move: food and spawning. The fish in Lake Winnebago in the winter are mostly fish living there between spawning runs, and their minds are not on sex, so they are looking for the lake fly beds and concentrations of dead and dying gizzard shad on the bottom. This year we have good worm beds over most of the soft bottom areas of the lake, and gizzard shad everywhere in the lake – so the fish are more spread out, with probably the best concentrations being over the best worm beds. Generally – find the best worm beds and you will find fish.

Till tomorrow,

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

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