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Interesting Info

February 27, 2010

During the 2010 season of sturgeon spearing on the Winnebago Lake system, a total of 1,820 sturgeon were speared.  Black Lake in Michigan also hosts a sturgeon spearing season, but it is slightly different–only 5 sturgeon can be speared.  Read the Michigan DNRE’s report:  “Sturgeon spearing season ends quickly on Black Lake“.

The following information and chart were provided by Ron Bruch with his Feb. 17th report.

“Why more bigger fish now than 20 years ago?

We have been tracking fish 100 pounds or larger in the sturgeon spear harvest from Winnebago since the first year of mandatory registration in 1955.  The 56 year average is 0.9% of the Lake Winnebago harvest are fish 100 pounds in weight or larger.  The plot below shows though that the percentage of large fish has changed through time, starting in the 1950s at a relatively decent average rate of 1.3% which held fairly well around 1% through the 1970s.  The rate began to drop through the 1980s and 1990s to an all time low average of 0.2% (5 times lower than in the 1960s and 1970s)  – due in part to the high minimum size limit of 45″ put in place in 1974 which increased the harvest of adult females – followed by a dramatic increase in the 100 pound plus percentage in the 2000s to an average of 1.58% since the year 2000.  The percentage has very significantly increased since 2005.  There are a number of things going on here that I believe are responsible for the increase we have seen over the last 10 years:

  • The harvest control mechanisms we put in place since 1992 (lowering the size limit to 36″, instituting the harvest cap system, and 20 other changes) were designed to increase the survival of adult female lake sturgeon which are the largest fish in the population and which make up 99% of the fish we see in the harvest 100 pounds or larger.  We are quite confident that our new regulations are doing the job we designed them for which has resulted reducing the harvest rate of adult females and increasing the survival of these fish and the opportunity for them to live to an older age and larger size.
  • We are currently enjoying recruitment of larger numbers of big fish in the population due to apparent strong hatches in the early 1900s; and the fact that the hole created in the population due to excessive illegal harvests in the 1930s, 1940s, and 1950s, and legal harvests in the 1950s has finally passed.
  • The food for sturgeon in the Winnebago System (primarily lake fly larvae and gizzard shad) has been very abundant since 2006, after being in short supply in the early 2000s.  The relative condition or weight of an individual lake sturgeon can change drastically from one year to the next dependent on food availability.  The length of an individual sturgeon although increasing very slowly after maturity, is very stable.  Many of the 100 pounders we see now, in times of lower food supplies would probably not be over 100 pounds and fall below the cutoff for the trophy category.
  • Overall though, there is no doubt that we have more big fish in the system – again a testament to our long running management program designed to give us a stable sturgeon population comprised of adults out to 100 years in age or more.
  • As I mentioned yesterday…………….due to our harvest management system, this is the first opportunity for our fish to express their true longevity potential since pre-settlement times in the mid 1800s.  We’ll know for sure how old they can get in another 50 to 100 years.”

Ron Bruch, Wisconsin DNR

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