Winnebago Sturgeon Harvest Report Monday, February 15, 2010

Winnebago Sturgeon Harvest Report Monday February 15

Somewhat faster harvest pace than typically seen on a Monday during the spearing season today on both Lake Winnebago and the Upriver Lakes. Total of 241 fish registered today including 12 fish larger than 100 pounds.

Totals for the day Monday February 15, 2010:

Lake Winnebago: 32 juvenile females; 92 adult females; 74 males; TOTAL of 198
Upriver Lakes: 1 juvenile females; 13 adult females; 29; TOTAL of 43

SYSTEM-WIDE: 33 juvenile females; 105 adult females; 103 males; TOTAL of 241

Total for the Season to date:

SYSTEM-WIDE: 194 juvenile females; 571 adult females; 530 males; TOTAL of 1295 (including 63 fish 100 pounds or larger)

Station totals attached

2010 Season Projections

Lake Winnebago is at 76.7% of its adult female harvest cap (88 to go to hit 90% closure trigger; 155 to go to hit 100% closure trigger)
Upriver Lakes are at 81.1% of their adult female cap (7 to go to hit 90% closure trigger; 14 to go to hit 100% closure trigger)
At this rate the 90% trigger and possibly the 100% trigger could pop tomorrow (Tuesday) on the Upriver Lakes; and the 90% trigger could possibly pop on Lake Winnebago tomorrow (Tuesday). If at the end of the spearing day tomorrow 90-95% of any harvest cap is reached, the fishery on the respective water would close Wednesday at 12:30 PM. If 100% of any harvest cap is reached by the close of spearing Tuesday, the 2009 season would be over on that respective water.

How do we determine the age of a lake sturgeon

Most agree that sturgeon can live a long time, but just how long has been a subject of debate over the decades. Also, their growth rates have been somewhat difficult to describe accurately as well. The accepted method of choice for estimating the age and growth rates of sturgeon around the world for nearly 100 years was developed in Russia prior to World War I, and has been counting the rings seen in the cross section of the pectoral fin spine (the leading ray of one of the front fins). Although this fin spine has been used extensively to estimate age of all 25 species of sturgeon throughout China, Russia, Europe, and North America, until recently, nobody had ever shown that the number of rings seen in the spine cross section actually matched the true age of the sturgeon it was taken from. In 2008, Dr. Ron Bruch, Winnebago Sturgeon Biologist, and his WI DNR Fisheries staff, with help from Dr. Steve Campana of the Bedford Institute of Oceanography, Fisheries and Oceans Canada in Dartmouth, Nova Scotia, proved for the first time that the true age of lake sturgeon from the Winnebago System is on the average significantly greater than the number of rings one can count on the pectoral fin spine cross sections. Using a combination of sophisticated dating of the carbon in the cores of the sturgeon ear bones (otoliths) originally from atomic bombs tested in the 1950s and 1960s, and known age fish, Bruch, Campana and crew were able to unlock the secrets of true sturgeon age. The significance of the results of this study has been recognized throughout the sturgeon world. Ages are the most important data collected by fisheries managers, used to estimate mortality and growth rates, both vital statistics in effective fisheries management programs. Bruch and his staff continue to collect fin spines from harvested lake sturgeon though, as he was able to work out a formula for converting the age estimated from the fin spine cross section to an estimate of true age [True Age = Fin Spine Age1.054796]. The study results have been published in the scientific journal Transactions of the American Fisheries Society (Vol 138, pages 361-372; copy of paper attached) .

The new methodology shows that female lake sturgeon in the Winnebago System can live in excess of 100 years and males in excess of 80 years, and that Winnebago sturgeon grow fast in length their first 11 years to reach the 36″ minimum size limit in the spear fishery, but growth rates slow almost to a crawl, especially for the males, at the onset of puberty which occurs for both sexes after about age 14.

See you tomorrow……

Ron

Ronald M. Bruch, PhD
Upper Fox-Wolf Fisheries Work Unit Supervisor
Wisconsin Department of Natural Resources
625 E County Rd Y, Suite 700
Oshkosh, WI 54901
USA

(() phone: (920) 424-3059
(() fax: (920) 424-4404
(+) e-mail: ronald.bruch@wisconsin.gov
Sturgeon Hot-Line: (920) 303-5444