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.

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?