150. 150 million years is how long lake sturgeon have inhabited the planet. $150 is the cost for a hydrophone used in the Wolf River back in 2011. The intersection of these two 150s has led to a deeper understanding of a fish that have been around since the time of the dinosaurs.
Sturgeon at the Shedd Aquarium, Chicago. Photo by Shedd Aquarium.
Let me back up a bit and explain. I played a part—a very tiny part, but to me a rewarding part—in learning more about these charismatic fish. Lake sturgeon are gentle giants, the largest fish in North America. They can weigh upwards of 200 pounds and exceed eight feet in length. They can live for a century. The fish are cartilaginous, like sharks, but eat small animals and fish eggs on lake, river, and stream bottoms. They use dangling barbels on either side of their face to sense their prey and filter feed through mouths with no teeth.
Despite their millions of years of staying power, sturgeon are in trouble because their watery homes are threatened. Nearly all the species of sturgeon across the world are endangered, and most wild populations only persist due to human stocking from aquaculture facilities. They face challenges posed by polluted waters, climate change, and dams that block their passage.
In 2009, my colleagues at Wisconsin Sea Grant, Kathy Kline and Fred Binkowski, along with Ron Bruch, a fisheries biologist with the Wisconsin Department of Natural Resources (DNR), published People of the Sturgeon, Wisconsin’s Love Affair With an Ancient Fish. It’s a lovely coffee table book detailing the good-news story of bringing the lake sturgeon back from the brink in the Fox-Wolf watershed and Wisconsin waters of Lake Michigan thanks to the efforts of Sea Grant, the DNR, and a local conservation group called Sturgeon for Tomorrow.
Flash forward a few years. As the communications lead for Sea Grant and the University of Wisconsin Water Resources Institute (WRI), I hired an acoustic ecologist named Chris Bocast. He was a Ph.D. candidate at the University of Wisconsin-Madison’s Nelson Institute and he began producing audio podcasts for us. Having just completed an informative and compelling series on mercury in the environment for WRI, Chris suggested a new project: an audio adaption of People of the Sturgeon.
Chris Bocast with the $150 microphone. Photo by Tim Campbell.
As part of my duties as a green-eyed expenses approver, I told Chris to, sure, go ahead and spend that $150 for a new underwater microphone before heading up to the Wolf River during sturgeon spawning season to gather background audio for the project.
What he came back with is scientifically significant. Chris captured the first-ever recorded and validated proof of infrasonic sturgeon “thunder.” Those living near waters populated by sturgeon have long reported faint drumming sounds and vibrations. Native-Americans in the watershed characterize the arrival of this mysterious “thunder” as the onset of spring sturgeon spawning runs. Our small purchase had blossomed into authentication of indigenous knowledge.
Wolf River. Photo by Wisconsin Sea Grant.
Sound, as it turns out, could be contributing to sturgeon survival skills in a big way. Along with Ron Bruch and another DNR fisheries biologist Ryan Koenigs, Chris wrote an article in the December 2014 Journal of Applied Ichthyology, explaining that size may be one of the reasons how the fish achieve sounds that escape normal human hearing. The sounds apparently aid reproductive success. At one time, Bruch had thought the sound was the result of the force of the large fish hitting each other or the water.
However, thanks to the interdisciplinary scope of the research, sturgeon now officially join the surprising company of whales, elephants, and other large creatures whose sonic capabilities reach into the infrasonic. Of course, sturgeon are fish, not mammals. But fish are beginning to be recognized for their ability to produce wide varieties of sounds using all parts of their bodies.
In fact, in addition to the drumming “thunder,” Chris collected sounds the journal article describes as “crisp crackles”—sharp knocks or raps, similar in tonal character to humans snapping their fingers or rapping a tabletop. Chris also identified what he now calls “squeaky whistles”—sounds sonically resembling a dolphin or human whistle.
In each instance, the sounds seemed to play a role in reproduction as they either precede spawning or were timed with gamete release. Communication through sound may be key to reproductive success—matching gamete release to the presence of females as well as attracting multiple individual males to spawn, thereby increasing genetic diversity. The article noted that previous research observed sturgeon in the field responding to drumming from distances up to nearly 17 feet.
Young sturgeon. Photo by Kathy Kline.
I played such a small part in this whole scientific journey but I am so gratified that I did. We have learned a lot from that $150 microphone. The microphone remains part of the ongoing effort to raise this magnificent fish back to its former numbers and add to a rich and diverse ecosystem. It’s also brought the anecdotal account of sturgeon “thunder” into the realm of science.