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Sturgeon Spearing Update from Ron Bruch on February 14th, 2012

February 14, 2012

The following update has been posted with permission from Ron Bruch and the Wisconsin DNR. This website is not affiliated with the DNR, Sturgeon for Tomorrow, or any other organization.

“Another slow day with very low effort – basically it boils down to “when the effort is low, low numbers of fish come in”. Add in the poor water clarity in some areas, a dash of bad ice here and there, and you have the perfect recipe for low harvest rates. Despite the low numbers though, some very nice fish brought in. At this point of the season we have seen 22 fish 100 pounds or larger in the total harvest of 347 system-wide; 7 out of 105 on Lake Winnebago (6.7%) and 15 out of 242 (6.2%) during the 2 day season on the Upriver Lakes.

Sturgeon Harvest on February 14, 2012Largest fish registered today was a 130.2 pound, 80.2 inch female sturgeon (F2 stage) speared by Eugene Woelfel of Hilbert, WI (registered at Quinney). See description below of what the stages of maturity mean. Photo attached:

130.2 pound, 80.2 inch female sturgeon (F2 stage) speared by Eugene Woelfel of Hilbert, WI

130.2 pound, 80.2 inch female sturgeon (F2 stage) speared by Eugene Woelfel of Hilbert, WI--DNR Photo

Note – back by popular demand – I am re-running a “Sturgeon Vignette” I sent out last season that describes how and why we sex and stage the maturity of sturgeon in the harvest. So – for all the new folks on my e-mail list here you go – your own personal color “Pocket Sturgeon Gonad Guide” is attached below. For those folks that got this last year – here’s another copy. Enjoy…

“This sexing and staging stuff – what do these numbers, like F1, F6, and M2, mean?”

Lake Sturgeon Sexing & Staging Pocket-Guide 2011

Although we have had mandatory registration of sturgeon harvested during the Winnebago spearing season since 1955, we did not start regularly checking the sex and maturity of the harvested fish until 1991. We expanded the harvest assessment in 1991 to include sex and maturity data because at the time we saw the percentage of large fish over 100 lbs in the harvest drop to historic lows (less than a half of 1%), and knowing the females are typically larger than the males, we suspected that adult females might have been making up a disproportionate amount of the harvest.

The problem at the time though, was that there was no handy manual readily available on how to sex and stage lake sturgeon – so – we ventured into this task knowing we would have to develop our own. Starting in 1991 we examined as many gonads of harvested lake sturgeon during the spearing season as possible; literally dissecting, weighing, examining, sampling, and photographing 100’s and 100’s of sturgeon gonads from both males and females. (I probably have the largest collection of sturgeon gonad photos on the planet – I’m going to have to think hard to whom I will eventually will this collection to.) After collecting, photographing, and studying these lake sturgeon gonads for several years, and after working with a couple of researchers at the University of Manitoba to do histological analyses of the various gonad stages we identified, we were able to put the whole story together in a way that made the most sense to our sturgeon management program.

What we found is that sturgeon, both males and females go through various identifiable stages of gonadal development as part of a continuum of development that is part of their normal reproductive cycle. Keep in mind that our lake sturgeon don’t spawn for the first time until they are relatively old (males age 14-31, females age 20-34), and that prior to their first spawn, both sexes appear to go through an extended period of development (puberty). The stages we settled on that were distinct and readily identifiable were: Fv – juvenile female, F1 – female in first or subsequent maturation cycles but with undeveloped eggs (tiny-white egg fish), F2 – female in early stages of yolk development (early yellow egg fish), F3 – female in later stages of yolk development but prior to egg pigmentation (late yellow egg fish – summer stage), F4 – gravid female with fully developed and pigmented eggs (black egg fish), F5 – ovulating female (spawning fish), F6 – spent female, Mv – juvenile male, M1 – male in first or subsequent maturation cycles but with undeveloped testis, M2 – male with fully developed testes (pre-spawning and spawning), M3 – spent male (late spring – summer stage). Through the financial support of Sturgeon for Tomorrow, we published these findings as the Lake Sturgeon Sexing and Staging Guide in 2001. I also developed a handy two-page “pocket” guide for sturgeon sexing and staging that can be used by spearers to better understand what it means when we shout out “M2, M1, F2, F6, etc” at the spearing registration stations each winter. I’ve attached a copy of the pocket-guide to this report.

The numbers, “1, 2, 4, 6, etc” do not necessarily mean that the fish is in its first, second or fourth year of development between spawns – they simply refer to the stage the fish is in at the time of harvest. For example, an adult female will be an F5 when she is spawning, an F6 immediately after she finishes spawning and for about the next year before she becomes an F1. She will stay in this F1 stage re-building her gonadal fat reserve for about another year before she quickly goes through stages F2, F3, and F4 in the last 16 months or so before she spawns again as an F5 – 4 years after she last spawned as an F5.

So – the next time you hear us shout out your or your spearing buddy’s fish’s sex and stage, you can turn to the crowd around you and confidently say “Yea – that F2’s a yellow egg fish – 14 months from when she would have spawned next – hang around these registration stations enough and you begin to pick up the lingo”.

Till Tomorrow,

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

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