Set in Their Ways

Popular media coverage of Lake Sturgeon characterizes them as an ancient fish, and few adjectives could be more apropos. Yes, they are ancient on geological time spans. The fossil record confirms there have been sturgeon like fish swimming somewhere on the planet for 250 million years. However, the characterization as “ancient” works on multiple levels. In terms of an individual’s life history, sturgeon can live to be ancient. By counting rings on fin spines or ear bones scientists have determined that Sturgeon can live to over 150 years old (Pflieger 1997). A final connection I will offer to sturgeon being old is a little more metaphoric and —“gasp”— anthropomorphic. We are beginning to learn that our tagged Lake Sturgeon, like your parents or grandparents that go to dinner at Denny’s every Tuesday evening at 4:30pm and order nothing but the 55+ grilled cheese and soup, (cut diagonally!!), are often creatures of habit. When it comes to where they go and when, Sturgeon can be downright curmudgeonly, obdurate, and immutable.

Case in point, there are fish like Aldo and Cosmopolis that wander about the lower Missouri Basin and then reliably show up in the Gasconade in the spring. There is Moe, which last summer was the lonely soul who braved the soupy bathwater of the lower Gasconade River by himself, returning this summer to its steamy waters. There is Edward, who is the only fish that really seems to like a particular shallow, wood-strewn reach in the lower Osage. He showed up right on time in the early summer just as he did last year. Julio, Liam, the list goes on. Fancy statistical analysis of site fidelity and homing in our Lake Sturgeon will come once we have collected a couple more years of movement data, but the anecdotal evidence is racking up that some sturgeon may be predictable. When you are guessing, correctly, which tag is about to ping as you round the river bend it probably is not a leap to imagine something more than random is occurring. A recent paper showed similar behavior in Lake Sturgeon in the St. Clair system that connects Lakes Huron and Erie. The population of Sturgeon broke out into four movement patterns that were more or less consistent across years (Kessel et al. 2018).

MU Grad Student Corey Dunn holding Moe. Photo Credit: Brandon Brooke

Just like long-lived people, perhaps long-lived fish when making decisions — such as where are good places to find food, where are good places to rest — defer to experience. However, when our environment is changes faster than the population is turning over, what is a sturgeon to do? When the price of the 55+ grilled cheese and soup special raises 30 cents to adjust for inflation you had better believe we are going to hear some grumbling. This is a big ecological question and one that takes decades to address, but it is one worth thinking about. For the sake of our long-lived species and the long-term health of aquatic ecosystems, there is no time like the present to begin.

 

References:

Kessel, S., D. Hondorp, C. Holbrook, J. Boase, J. Chiotti, M. Thoomas, T. Wills, E. Rosman, R. Drouin, and C. Krueger. 2018. Divergent migration within Lake Sturgeon (Acipenser fulvescens) populations: Multiple distinct patterns exist across an unrestricted migration corridor. Journal of Animal Ecology 87:259-273.

Pflieger, W. L. 1997. The fishes of Missouri, 2nd edition. Missouri Department of Conservation, Jefferson City, Missouri.

The Sturgeon Listened!

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.

The second time saying goodbye isn’t any easier than the first.

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.

The skin is healing nicely, already having closed around the three interrupted sutures. Over time the sutures should wear down and fall out.

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.

Massive Production

Last Tuesday our research crew (Brandon, Bailey, and I) made a trip down to MDC’s Lost Valley Hatchery. Our goal was to assist with the fall stocking effort of Lake Sturgeon in Missouri. When we walked through the open garage doors into the main production room we found ourselves on the floor of a veritable fish assembly line. Biologists worked at stations each completing a simple task with efficiency that would have made Henry Ford proud. The purpose of this assembly line wasn’t to build cars or electronics to stock in showrooms and on store shelves, but to tag baby Lake Sturgeon to stock in the Osage and Gasconade rivers.

Volunteers gathered around raceways to tag Lake Sturgeon at Lost Valley Hatchery

On the cuteness scale baby Lake Sturgeon rank somewhere between the Puppy Bowl and a tiny sloth taking a nap. Their long spade-shaped snouts turned ever so slightly upward at the tip. Their camo colored exterior specifically evolved to help them blend into the rocky bottoms of the streams they are born in to. Their five rows of sharp scutes discourage most hungry bass and catfish from trying to gobble them up. And there were 12 runways chock full of the things.

Like the migratory adults these fingerlings were already quite the travelers and you couldn’t blame them for being a little homesick. They started out as eggs obtained from adults in the Yellow River way up in Wisconsin. They were shipped down to Missouri where hatchery staff provided them with plenty of tender loving care to ease the transitions feeding them bloodworms, maintaining clean water and preventing disease.

The main job of the volunteer crews was to make sure Lake Sturgeon received two tags. At the first workstation biologists reached down into the water grab a sturgeon. Then using a scalpel they would scrape off the 9th spine or scute on the fish’s right side. The process was quick and relatively painless for the fish. Think of it like getting your nails trimmed. The marked fish was tossed into another tank to await transport to station #2.

Bailey removes a scute of a fingerling Lake Sturgeon to mark its stocking year.

At workstation #2, each Lake Sturgeon received a coded wire tag. When one worker had the needle in position another pushed a button on a machine to inject a 2 mm surgical steel tag into the fish’s back. This little piece of wire can be detected with a metal detecting wand, like the ones security folks use sometimes at airports. The positioning of this wire, more specifically what scute it is located under, will tell biologists what year it was stocked if they should encounter it in the future. This information can be used to estimate growth and survival in the population. The Sturgeon are tagged twice in case one of the marks is marks is obscured over time (sturgeon can lose other scutes or the coded wire tag may fall out).

Me inserting a coded wire tag into a sturgeon

At the end of the day, while a hungry crew gorged on grilled burgers and hotdogs, hatchery staff scooped up the Sturgeon in nets and hoisted them into the tank on a hatchery truck. A couple hours later they would be shot out of a hose and be swimming free.

The hatchery truck that will deliver lake Sturgeon to the river.

The outpouring of volunteers who showed up to see off the 5,000-6,000 fingerling Lake Sturgeon epitomizes how Lake Sturgeon recovery is a team effort. My work on movement and habitat selection by Lake Sturgeon being just one tiny component. Led and organized by our “foreman”, MDC Lake Sturgeon recovery biologist Travis Moore, we can continue to make progress in bringing this species back from the brink of extinction in the state. Even if it is just reporting and releasing Lake Sturgeon you catch, or practicing good land use practices that keep our water clean, like on the assembly line, each of us can have a small, but crucial, role to play.

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.