My last post was a desperate plea to my tagged sturgeon. “Come and see me, I miss you!” I lamented, and guess what, the guilt trip worked! Last week we spent three days gill netting Lake Sturgeon on the Gasconade River and captured 8 individuals. Six were new, but two were fish we had tagged last fall. Our first recaptures!
All jokes aside, as with every field trip, we learned something new. For instance, the fact that our first and only recaptures occurred on the Gasconade River provides more evidence that the Gasconade River is home to fewer Lake Sturgeon than the Osage River. The much smaller Gasconade may simply lack the space to support as many Lake Sturgeon as the Osage, or there may be other habitat factors that make the Osage River more desirable for sturgeon. Now that we have tagged almost 20 Lake Sturgeon in the Gasconade, we have a sufficient sample size to start comparing their movement and habitat selection to the 56 Lake Sturgeon that we tagged in the Osage. This comparison can help us learn how Lake Sturgeon respond to flow manipulations in the regulated Osage River by using the free flowing Gasconade River as a control.
This also provided a good opportunity to check and see how our fish were recovering from surgery. The first recaptured fish was the only fish we had captured on a trotline in the Gasconade River this past fall. The second fish was also tagged last fall but was captured both times using a gill net. The incision sites on both fish seemed to be healing well with no external signs of infection present.
If this blog is really a mysterious communication channel to Missouri River Lake Sturgeon, I’ll put it in writing that all of you should spawn this spring. And make sure you are as conspicuous as possible about it too. Lots of splashing on the rocks please.
The wind ripped out of the south ushering in record warm temperatures. Thermometers were creeping into the 70’s in mid February. The maples had been duped by faux arrival of spring, their branches teemed with red buds along the banks. Under the translucent brownish turquoise water, things were much calmer. The Osage although very low was still pumping 2000 cubic feet of water per second downstream. When this mass of water met the mighty Missouri River less than a mile downstream, it backed up like too many sports fans funneled through the turnstiles at a stadium. This turned the river into a placid backwater. Despite this apparent quiet under the surface, things were beginning getting noisy, we just couldn’t tell yet.
Earlier that morning we set out four of our stationary acoustic receivers and a telemetry tag in a straight line each separated by 100 m. The tag sends out sound signals or “pings” every 12 seconds. The receivers are essentially underwater microphones that record the pings.The goal of this mini experiment was to determine over what distance the stationary receivers were able to detect pings from the tag. If the furthest receiver, 400 m away, could detect most of the pings then theoretically it should be able to catch the pings from any tagged sturgeon that swims up the 300 m wide Osage River when we deploy the receivers for for real. Brandon and I were stretched out on the boat, trying our best to kill time, letting the technology do the work for us. We had four hours to kill while we waited for the receivers to listen for pings.
When the clock finally struck 3:30 we hastily retrieved our gear. Brandon guided the blue F-250 up the winding roads along the loess river hills. I began downloading the data to our field tablet. Luckily, all four receivers seemed to be picking up at least 80% of the tag transmissions which means that the likelihood of a receiver missing at tagged Sturgeon swimming by should be relatively low.
And as proof of our theory, we happened to detect our first tagged Lake Sturgeon by accident! Fish number 26025 is a Lake Sturgeon that was tagged by Missouri Department of Conservation Biologist Travis Moore last Spring. This fish was a big boy too, measuring 48 inches long and weight 32 pounds. Could it be starting its migration up the Osage in search of spawning habitat? Only time will tell. The battery in this fish’s tag should last another couple of years allowing us to collect information on where it moves and what habitat it prefers.