Imagine a single fish swimming in the Great Lakes today that was alive 400 years ago.That's around the time of the Pilgrims, even earlier than Michigan's first
Imagine a single fish swimming in the Great Lakes today that was alive 400 years ago.
That's around the time of the Pilgrims, even earlier than Michigan's first permanent European settlers.
A new study on lake sturgeon life expectancy suggests it's possible.
Lake sturgeon, sometimes called "living dinosaurs," have been around since before the Great Lakes even formed. Now, researchers say these massive prehistoric fish may live far longer than previously thought.
A new way of estimating age
For years, scientists estimated a lake sturgeon's age by sampling part of its fin. Under a microscope, they counted growth rings, similar to the rings on a tree.
Edward Baker, manager of the Michigan Department of Natural Resources' Marquette Research Station, said there were inerrant limitations of this method when dealing with sturgeon.
"The older a fish gets, the harder it is to accurately determine its age using those growth rings," Baker said. "As fish age, they tend to grow slower and those rings become very indistinct essentially. They're too close together to accurately count."
Baker, who has studied lake sturgeon since the 1990s, said the prevailing belief early in his career was that most lake sturgeon lived only 50 to 60 years.
"The more time I spent working on sturgeon, the more I questioned that assertion." Baker said. "That's what led us to try this alternate approach to estimating how old these fish might be getting."
A scene from Michigan Department of Natural Resources efforts to capture spring spawning lake sturgeon for egg collection and tagging in the Sturgeon River in Baraga County. This image, taken in 2018, shows Ed Baker, left, DNR's lake sturgeon coordinator. (Michigan DNR/WWMT)Lake Sturgeon have been a species of concern in the region for about 40 years, meaning they've been actively monitored through federal and state fish tagging programs.
In this new study, researchers relied on decades of catch-and-release data from five fish populations across the upper Great Lakes.
By catching, tagging and releasing lake sturgeon over many years, scientists were able to measure the same fish multiple times and develop a growth rate equation.
Baker says the formula provides a better estimate of the maximum life expectancy of lake sturgeon, which can historically grow up to 9-feet long.
"Some of the fish we have, were growing two millimeters a year," Baker said. "That's hard to measure if you're catching fish three or four years apart. We really needed that 10, 20 or 30-year difference between initial marking and recapture to have measurable change in length and be able to estimate the growth rates that are that slow."
A much longer lifespan than previously thought
Using the new growth rate formula, researchers concluded lake sturgeon live much longer than previously believed.
"We've concluded that sturgeon live far longer lives than initially thought based on looking at growth rings and fin ray cross sections," Baker said.
Researchers found males lived anywhere from 90 to 279 years, while females lived from 99 to as many as 427 years.
For perspective, the previous oldest recorded lake sturgeon was estimated to be 152 years old.
The new findings are almost on par with the longest-lived vertebrate on Earth, the Greenland shark, whose lifespan has been estimated at 272 to 512 years.
In order for fish to live that long, they have to have a high annual survival probability. Estimates are around 96% to 98% for lake sturgeon, meaning the vast majority of the population live from one year to the next.
"We know lake sturgeon don't reproduce very quickly. They don't recruit new members to the population very well or very fast," Baker said. "All of that means that we just simply cannot kill a bunch of sturgeon in a population and expect that population to persist."
Implications for conservation efforts
According to Baker, less than 1% of the Great Lakes' historic lake sturgeon population remains.
Once considered a nuisance fish, lake sturgeon were heavily harvested during the late 1800s - nearly wiping out the species.
"The sturgeon that we have in the Great Lakes left today are probably those young ones that survived all of that indiscriminate harvest and made it past 1910," Baker said. "They're now reproducing members of populations."
Baker says the study reinforces the need for strict protections across the Great Lakes.
One of the lake sturgeon raised on site Wolf Lake Fish Hatchery in Mattawan. Visitors can also attempt to spot the massive fish gliding along the bottom of the hatchery's show pond. (Haenni/WWMT)"It sort of reinforces the need to be very restrictive in what we allow in terms of harvesting," Baker said. "It's not a fish that we just allow anybody to go out and catch as many as they want."
The famous Black Lake sturgeon harvest, usually in early February, is limited in this way. Lasting sometimes only minutes, last year's harvest limit was six lake sturgeon total, not per angler.
Baker says he finds hope in the growing public awareness about lake sturgeon and their recovering population.
"We're giving the populations that still exist a chance to expand on their own," Baker said. "We're helping some of those remnant populations to expand by catching their larva and raising them in a hatchery and stocking them at the end of the summer end of the first year of life."
One of those streamside rearing operations is along the Kalamazoo River in Allegan County.
The facility has helped restock 1,591 lake sturgeon into the Kalamazoo River since it was established.
A fish that can live for centuries also takes generations to replace. Researchers say that makes every lake sturgeon important to the health of the Great Lakes ecosystem.
The study, published in the in the Journal of Fish Biology, featured authors representing the Michigan DNR, Michigan State University, Michigan Technological University, and the Wisconsin DNR.
