Getting Antsy

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.

A muddy post-flood Gasconade River

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?

Me about to release the 40 lb female.
Eggs peeking through a surgery incision. The fish was sutured up and released unharmed.

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.

 

Citation

Bruch, R. M., and F. P. Binkowski. 2002. Spawning behavior of Lake Sturgeon (Acipenser fulvescens). Journal of Applied Ichthyology 18:570-579.

http://www.glsturgeon.fw.msu.edu/sturgeon/life-history/egg-stage

 

Should I Stay or Should I Go

Human personality traits are often presented as dichotomies. You can get online, take a short test, and within minutes know if you are an extrovert or an introvert, a thinker or a feeler, a judger or a perceiver, and the list goes on. After about two months of tracking we are learning that Lake Sturgeon can be divided into two major categories: the movers and the stayers.

When you release a Sturgeon you never know how far it will go!

Some sturgeon just can’t seem to sit still for long. Adventurous sturgeon like Richard, Joe, Sigurd. Sigurd, named after one of my favorite nature writers and explorer of Canadian glacial lakes Sigurd Olson, was tagged back in 2015 by the Missouri Department of Conservation. Sigurd moved further upstream than any of our Sturgeon and came within a few miles of bumping his snout into Bagnell Dam in June. Over the past two months, Sigurd has moved at least 81.8 miles. And since it was tagged the total is at least twice that distance. Richard and Joe were Sturgeon we tagged this year. They quickly recovered from the tag implantation procedure and made significant upstream and downstream runs totaling at least 103 and 82 miles respectively. What is driving the restlessness in these fish remains unknown, but it may be related to characteristics of the individuals — our most mobile Sturgeon have been 20-30 lb males— and environmental conditions — sustained high flow releases from Bagnell Dam to combat upstream flooding gave way to lower summertime flows by mid June and as a result our big movers have transitioned back downstream to a few key pools.

Lake Sturgeon swimming away slowly into the depths of the Osage River.

We tagged plenty of homebodies too. Fish like Joe, Richard, and the ironically named Miles have found good homes and are content to stay there. These fish have remained within a 0.5 mile stretch of river since tracking began. We might worry that they were dead if it were not for subtle upstream movements between tracking periods.

The seasons also likely have an impact on Lake Sturgeon movement patterns. Most fish seem to be moving less as water temperatures rise to potentially stressful levels. Other papers have been published suggesting that water temperatures over 28 C are stressful for Lake Sturgeon. Our research may be able to highlight temperature or flow characteristics that Lake Sturgeon select for during these stressful periods. Perhaps by knowing a little bit about an individual Lake Sturgeon and the environmental conditions we will be able to predict its answer the proverbial  question that separates the movers from the stayers: Should I stay or should I go?