I Spy our First Sturgeon

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.

Stationary receivers mounted in concrete anchors ready to be deployed.
Stationary receivers mounted in concrete anchors ready to be deployed.

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.

The white dots are our first detection of pings by from a tagged Lake Sturgeon by one of our stationary receivers!
The white dots are our first detection of pings by from a tagged Lake Sturgeon by one of our stationary receivers!

Bridges: We Drive Over them, Sturgeon Swim Under Them

I’ve finally emerged from a long blogging hiatus. This emergence coincides with an emergence from my troglodytic existence in the basement of ABNR Building on Mizzou’s campus. Troglodytic or cave dwelling, is not an exaggeration of how I have spent the winter. Unaccustomed to the brightness of the outside world, my first day in the field left me with a cherry-red face and moderate eye strain.

Soon the first warm days of the season will also rouse the Lake Sturgeon in Missouri’s rivers out of their winter sluggishness. As they begin to move they will likely be rather hungry as well. Hungry enough, we hope, to readily gobble a gob of nightcrawlers on our trotlines. After which we can surgically implant acoustic telemetry tags to track their movements over the next 4 years. But all of this work is for later posts. There are many preparatory activities that need to be made for the field season. 

 

Trotline hooks ready for use to catch some Lake Sturgeon!
Trotline hooks ready for use to catch some Lake Sturgeon!

 

The goals of the first forays into the field were to assess the potential study area which includes the larger tributaries to the Missouri River that we expect Lake Sturgeon to swim up during the spring in search of spawning habitat. My main focus is on the Osage and the Gasconade, but Lake Sturgeon are unpredictable, the Chariton, Grand, Lamine, and Moreau rivers might entice a wayward Sturgeon as well.  This leaves me and my trusty side-kick Brandon with 100’s of miles to patrol for the fish we tag, which unless we can find a house boat that can navigate these rivers, is an unrealistic goal.

However, there is another way around this. We can deploy “eyes” or rather “ears” to patrol these rivers for tagged Sturgeon 24-7. These ears are Vemco stationary receivers. These receivers have microphones built in that can detect the sound “pings” emitted by the tags implanted in our Lake Sturgeon. For example, we may tag a sturgeon in the Osage River. If this fish decides to swim up the Grand River within say 500 m of a stationary receiver, the receiver will log the fish’s tag number for us to download later.

Vemco VRTx Stationary Receiver. The very top point is where the microphone is located.
Vemco VRTx Stationary Receiver. The very top point is where the microphone is located.

The biggest issue with the stationary receivers is choosing the best place to set them to 1. prevent damage or loss during floods and 2. to prevent loss via theft (not sure why anyone would want one of these). One secure place researchers have used in the past are bridge piers, with permission from the Department of Transportation of Course. The river channel is the highway for migrating sturgeon and swimming upstream means they must pass under these bridges where we can observe their presence with stationary receivers during times we aren’t able to manually track them.

A good bridge pier for a stationary receiver is one that is in deep water, and has low flow velocity. Swift flow can create extra noise that interferes with the receiver’s microphone.

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Good bridge
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Bad Bridge

In addition to looking at bridges which isn’t terribly exciting, I also got a first look at some of my study sites. Some were more scenic than others. And some cool wildlife along the way.

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Scenic Gasconade River
Less scenic Chariton River. The Chariton is highly channelized and about 2 feet deep across the entire width of the river. The paddle I am holding is touching bottom.
Less scenic Chariton River. The Chariton is highly channelized because it is in an agricultural region of Missouri and about 2 feet deep across the entire width of the river. The paddle I am holding is touching bottom.
That is the muck that is on the bottom of the Chariton. Woe to the Sturgeon who swims up this river.
This is the muck that is on the bottom of the Chariton. Woe to the Sturgeon who swims up this river looking for spawning gravel.
Eagle nest in a sycamore along the Gasconade River.
Eagle nest with adult in a sycamore along the Gasconade River.