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

 

The Cold Shoulder

With rows of sharp scutes lining their body, Lake Sturgeon are a little rough around the edges, literally, but I can’t help but love them anyway. I also am afraid I am beginning to develop a common pathology of among scientists  where constant thought your study species, leads to concern about their well being. In the final stage of this condition, the scientist adopts a protectionist role. Let’s call it Mother Hen Syndrome. Each time I release a tagged sturgeon, I feel like the over anxious mother sending their child off on the bus on the first day of kindergarten. Will they be okay? Will the other sturgeon ostracize them for their stitches on their abdomen?

Complicating matters is the fact that, my tagged sturgeon have been giving me the cold shoulder. My running total of tagged Lake Sturgeon is 79 individuals in the Osage and Gasconade rivers. Over the more the 5,000 setline hook nights it took to capture these 79 sturgeon how many recaptures have I had? If you guessed zero, you would be correct.  Again I think of the mom who sends their kids off to college, “you never call!!”

Me being a “helicopter biologist.”

To a population ecologist, there are a couple explanations for low recaptures of marked organisms. First, there is a “trap effect” where the capture process causes an organism to avoid sampling gear in the future and therefore is less likely to be recaptured. And secondly, you have only managed to tag a small proportion of the population and thus are more likely to capture unmarked individuals than marked ones.  I don’t have an answer to explain the lack of recaptures I’ve seen and haven’t found conclusive evidence in the literature as well. I did come across a 2004 report from the Michigan Department of Natural Resources that reports below expectation recapture rates for fish captured in trawls, suggesting a behavioral avoidance of trawls. Although they didn’t notice as striking of a pattern for setline recaptures, it is certainly possible that a Lake Sturgeon might avoid the offering of a juicy earthworm after having been poked by a 8/0 hook once.  Using side-scan sonar, the report’s authors estimated that between 5,000 and 29,000 sturgeon use 1 square mile of habitat in the St. Clair River Delta. In our time on the river we have noticed lots of large bottom dwelling fish on sidescan sonar returns in areas where tagged lake sturgeon are hanging out. With the abundance of large fish species present in the Missouri River basin including Blue and Flathead Catfish or Paddlefish, it can be hard to know if large fish on sonar are definitely Sturgeon. I was reminded of the difficulty in estimating population size as I read the famous quote a colleague had pasted in his email signature “Managing fish is like managing trees, except they are invisible and they move.” The exact same applies to counting them.

Population estimates are beyond the scope of my project which is focused on habitat use and movement of Lake Sturgeon. Some day perhaps another graduate student will devise an ingenious study to answer these very questions in order to better assess the status of Lake Sturgeon in the Missouri River basin. And to all of the biologists out there, please share if you know of any studies addressing this or have anecdotal observations from your own sampling for Lake Sturgeon.

To end on a positive note, all signs point to the fact that my Sturgeon are thriving. They are behaving like a sturgeon should moving, hanging out in predictable habitats. A few weeks ago I even received an email from a biologist who had been contacted by an angler who had accidentally caught one of my tagged sturgeon while Sauger fishing. Updates like these are always soothing, nonetheless, their avoidance still gnaws at me a little bit. I miss my babies. Why the cold shoulder?

 

Literature

Thomas, M. V., and R. C. Haas. 2004. Abundance, Age Structure, and Spatial Distribution of Lake Sturgeon Acipenser fulvescens in the St. Clair System. State of Michigan Department of Natural Resources Report No. 2076.

Navigation, Recreation, or Migration?

The natural history of the Osage River is epitomized by one concept: movement. The battle for the soul of the river has been based on whether it should be a thoroughfare of navigation, a vast pool for recreation, or a corridor for migration. Navigation and recreation, those are human uses, and to attain them you need engineers and tons of rock, concrete, and steel placed strategically to tame the river. Migration, on the other hand, is for the fishes. It was the default state of the river before Anglo-Americans displaced the Osage Indians and settled the river valley. Looking back at the early history of the Osage River and its management we can better understand the current state of the ecosystem and how one mode of movement won out.

When it comes to fish passage in rivers, dams can either be walls or hurdles. Walls, keep things out and are completely impassible in the upstream direction. These are the high-wall dams that are built for hydropower or flood control. The ones that impound large reservoirs lined with houses, docks, and businesses. Hurdles, are impediments but are not necessarily impassible to fish. It may take a little more effort or time waiting for the right conditions, but strong swimming fish can get past them. The Osage is, at least from a Sturgeon or Paddlefish’s perspective, is cursed with both.

The hurdle. Low water reveals the dilapidated condition of Lock and Dam #1. Source: http://www.dammingtheosage.com/tag/osage-river/

Building Hurdles for Navigation

Everyone from Merriwether Lewis to the Osage Indians had realized that the Osage was a poor river for commercial navigation. The blithe optimism of engineers and their philosophy of “river improvement,” meant that reshaping the Osage into a conduit for barge travel from Bonnots Mill to the Kansas Border was worth a try.  The first, and save for numerous rock dikes and training structures scattered around the river, the last major attempt at accomplishing this was Lock and Dam #1. Lock and Dam#1 was  is currently located just upstream of the confluence of the Osage and Maries rivers around 12.1 miles upstream of the Missouri River. NO. 1 was built in 1895 to create slack-water navigation channels in the Osage River by raising the water level upstream to allow barges to ascend an estimated 98 rocky riffles in the river. The Army Corps of Engineers quoted a cost of $187,244 but by the time all was said and done, the cost had ballooned to $417,500. Common trade items mentioned in the report were things like nails, salt, lumber and pork. A great share of this was lumber which is often easier to simply float down an unobstructed, swift-flowing river. Plans for a series of locks and dams to make the river more navigable were discontinued by the 1920’sIn 1951 L&D 1, no longer useful for much of anything was sold along with the surrounding land and buildings for a meager $10,000.

 

Building Walls for Recreation

In the 1920’s investors began thinking about the construction of large reservoirs that would put an end to the dream of an Osage navigable by people and fish. By 1904 congress had officially classified the river above Warsaw as unnavigable, paving the way for hydroelectric development. In 1931, Union Electric built Bagnell Dam and Lake of the Ozarks. The privately owned dam which is maintained today by Amren UE generates hydroelectric power. Bagnell Dam inundated  84 square miles of river valley including the whole town of Linn Creek, MO. In 1979, a second dam was constructed by the Army Corps of Engineers for flood control further upstream to create Truman Lake.

After a slow start, Lake of the Ozarks has become a tourist and vacation hotspot in the Midwest. The Osage left behind a legacy of steamboat travel and towering bluffs over churning waters and embracing a future of luxury yachts, waterskiing, and Netflix dramas starring Jason Bateman. Recreation has firmly supplanted, navigation, and migration as king of the Osage.

Paddlefish, which are related to Sturgeon, can grow huge but fail to spawn in the productive waters of Lake of the Ozarks.
Source:http://www.kansascity.com/sports/outdoors/article16667522.html

Implications for Lake Sturgeon

Lock and Dam #1 is a hurdle for many fish species including Lake Sturgeon and Paddlefish on seasonal migrations.  Neither species can bypass Bagnell or Truman Dam. Non-self sustaining populations of Paddlefish are stocked throughout the watershed including in Lake of the Ozarks and Truman Reservoir. Lake Sturgeon were believed to have been extirpated from the Osage upstream of Bagnell until a resident captured a photo of a Lake Sturgeon swimming near their dock in Lake of the Ozarks in 2017. Whether this fish was introduced  by anglers or is a part of a remnant population that survived after impoundment is not known.

Tailwaters of the wall, Bagnell Dam. You probably can’t see it but at the time the photo was taking there were a bunch of Silver Carp jumping at and bouncing off the face of the dam.

A big theme of my research is to determine what effect the hurdles and walls have on Lake Sturgeon and their recovery in Missouri. Through tracking their movements over the next 4 years we will have a better idea of how they behave in response to unnatural flow patterns and barriers. For instance, we have designed our tracking schedules and stationary receiver deployment locations to be able to identify roughly the time at which a Lake Sturgeon passes Lock and Dam #1. We can relate that to water levels which may allow us to make flow recommendations to improve passage success during key times of the year such as during spring migrations.

In the summer as water levels recede, water cascades over the old dam structure.

No one really knows how far Lake Sturgeon historically swam upstream the Osage in their quest to spawn. Their close relative, the Paddlefish which pre-impoundment had one of its largest populations in the world in the Osage River, required gravelly shoals upstream of the Truman Dam. This has left the Paddlefish utterly dependent on artificial stocking to sustain populations. Our fingers are crossed that Lake Sturgeon are less picky and will still be able to spawn on one of the many shallow rocky areas that still exist downstream of Bagnell Dam.

Recently things have been  pretty quiet around the Lock and Dam. We have had few passages since late spring. However, during a fairly low flow level an intrepid young sturgeon named  Sidney made the leap downstream over the dam. I say leap, because that was exactly what it must have been. The fish would have encountered a fairly large drop whether it passed through the lock chamber or over the dam itself. What cued Sidney in this downstream movement? We don’t know? Opportunities to pass back up will be rare during the typically lower flows of fall and winter. If we presume the sturgeon knows this and is ditching the upper river for the time being, perhaps it is significant.

Small but mighty, Sidney has had no problem passing the dam in both directions this year.

You have to wonder if like a phantom limb, today’s sturgeon can still sense the tinglings of the severed upstream habitats. Will Lake Sturgeon congregate below these barriers on their spring migrations, or will they improvise and find new places to spawn. Perhaps today’s adult Lake Sturgeon population, most of which were Wisconsin Lake Winnebago strain fish, have no memory of those historic spawning grounds and make do with what they have in the lower river.  The hurdles and walls in the Osage aren’t going anywhere anytime soon and hopefully t these barriers to movement won’t prove to be  major barriers to conservation success.

References:

Much of the historical information in this article was gathered from Leland & Crystal Payton’s outstanding and beautifully published book on Osage River History titled: Damming the Osage, the conflicted story of Lake of the Ozarks and Truman Reservoir.

Video Credit: William Masters

 

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!