Swimmers, take your mark… Lake Sturgeon in the Osage and Gasconade Rivers are on the starting blocks waiting to embark on their spring upstream migrations. A few fish in the Gasconade, may have already jumped the gun. On February 27th, a warm rain had the Gasconade out of its banks, and that was just enough to convince a few over eager sturgeon it was time to move. Three fish moved began moving upstream as the water rose and traveled at least 9 miles from near the confluence with the Missouri River past Fredericksburg. Even in the Osage River Lake Sturgeon were stacking up in the heads of pools just upstream of their winter haunts seemingly antsy to get underway. Except the problem was that a few days later air temperatures and flows began to plummet with water temperatures dipping back under 50 degrees Fahrenheit. The fish responded by, pausing in the lower river. In many populations the first to arrive on the spawning grounds are the males. The females tend to hang back and arrive a few days later. The optimal spawning temperatures are from 52-60 F.
During the cold spell, we switched to setting gill nets to capture and tag a few more staging Lake Sturgeon in the Gasconade. By the end of the week we had tagged 8 Lake Sturgeon bringing our total to 27 in the Gasconade and 93 overall. On the last day, we captured one of the plumpest Lakers we had ever seen. During surgery, developing eggs began bursting through the incision; eggs that that hopefully will be deposited on a rocky shoal sometime later this spring. Females only spawn ever 4-7 years. The year before the spawn the eggs will be yellow turning from gray to black by the next spring. The eggs told the story. She was almost ready. The eggs had a dark bullseye, the germinal vesicle which during development moves to the pole of the egg. Farmers who raise sturgeon for caviar production have often looked at the germinal vesicle to judge egg stage. It would still take a little time before they were ripe. Following fish like this throughout the spring migration will give us an idea where, if at all, the Lake Sturgeon are attempting to spawn. We are expecting some rain next week, and a slow warming could this be the time?
Like the sturgeon, myself and most of my friends and coworkers are ready for spring as well. Going fishing when most of the ponds are too chilly to get a bite, starting to think about checking our favorite spot for morels. Our female sturgeon was a reminder to be patient. Spring will be here soon, and before we know it giving way to the oppressive heat of Missouri summer.
Bruch, R. M., and F. P. Binkowski. 2002. Spawning behavior of Lake Sturgeon (Acipenser fulvescens). Journal of Applied Ichthyology 18:570-579.