Lake Sturgeon and Stories of Science
"This is a wonderful story with villainous acts, a profound change, and smelly fish biologists," said John Lindgren, Lake Sturgeon Coordinator and fisheries specialist with the Minnesota Department of Natural Resources. The story, one of Lindgren's favorites, concerns lake sturgeon and their restoration in the St. Louis River, Lake Superior's largest U.S. tributary.
The villainous acts, which at the time were likely not considered so, included logging, overfishing, polluting and damming. Lindgren cites the Clean Water Act of 1972 as beginning the "Era of Profound Change." The smelly fish biologists? Well, that would be Fond du Lac Band of Lake Superior Chippewa and Department of Natural Resources staff, including Lindgren himself.
Until the mid-1800s, lake sturgeon were plentiful in the Great Lakes and rivers such as the Mississippi, St. Croix, and St. Louis. But as European populations grew around the Great Lakes coastlines they drove the number of sturgeon dangerously low through unsustainable harvesting coupled with habitat degradation, destruction and pollution.
The sturgeon of the St. Louis River were hit especially hard. In the early 1900s, people dined on sturgeon meat, used their skin for leather, and made their swim bladders into isinglass (an aspic for pottery cement, waterproofing and clarifying wine and beer). Buildings and industries congregated around the St. Louis River Estuary, releasing pollutants to the water through runoff and, before it became illegal, through direct dumping of waste. After the Fond du Lac Dam was constructed in 1924, the sturgeon's spawning grounds were both altered and restricted. In the wake of these multiple stressors, lake sturgeon vanished from the St. Louis River.
About five decades later when the Clean Water Act was passed, the St. Louis River began to flow with cleaner waters. The Minnesota Department of Natural Resources began working with Minnesota Power to control flows over the Fond du Lac Dam so that walleye and sturgeon could spawn. Wisconsin and Minnesota Departments of Natural Resources along with the Fond du Lac Band began to reintroduce lake sturgeon in the western arm of Lake Superior. They stocked sturgeon for 14 years, until 2001, and placed rocks and boulders downstream of the dam in hopes that the reintroduced fish would spawn there.
A team of Fond du Lac Band biologists had a "Eureka!" moment in 2011. They found four tiny sturgeons in the river, evidence that sturgeon had naturally reproduced. In August 2013, they found another sturgeon fry.
Although the discovery of naturally reproducing sturgeon in the St. Louis River is a step in the right direction, lake sturgeon and the river as a whole have a distance to go before the "smelly biologists," sturgeon fans and the communities around the St. Louis Estuary can point to the river and say, "Success."
Lindgren describes the state of the estuary as "slowly healing." Pollutants remain in the sediment affecting the bottom dwelling organisms that are the basis of the food web in the river. The health of larger species, like sturgeon, depends on the health of these smaller animals. The health of humans eating fish from the St. Louis River depends on the health of these smaller animals.
The lower St. Louis River and its Lake Superior estuary is a binational Area of Concern (www.epa.gov/greatlakes/aoc/stlouis). As such, much effort is being put toward restoring habitat, fish and uncontaminated water ... not only for our benefit, but also for the ecosystem as a whole. To learn more about the state of the St. Louis River Estuary and the efforts being made there, visit the St. Louis Estuary: The Stories and the Science website (www.stlouisriverestuary.org). Find information about this Minnesota and Wisconsin Sea Grant joint project and more information about lake sturgeon at www.seagrant.umn.edu.
Which species of fish has been on Earth for over 100 million years and swims in Lake Superior today? That would be Acipenser fulvescens, the lake sturgeon. Lake Sturgeon are also one of the longest living fish on the planet; a female tagged in Wisconsin was an estimated 125 years old!
Although sturgeon have been around for quite some time, they have remained essentially unchanged and unique among modern fish. Here's why:
- They lack scales! Instead, they have a tough skin that covers their bodies.
- They are protected by rows of boney plates, called scutes; these plates make 5 lines down the length of their body.
- Their skeleton and fins look similar to a shark's. Cartilaginous skeletons, and heterocereal tails, help both species slice through the water.
- They have a torpedo-shaped body and a shovel-shaped snout.
- Whisker-like barbels dangle on the underside of their snout. They're used for sensing food along the river or lake bottom.
- They have a harmless disposition and a toothless grin. Belying their size, they suck their diet of relatively small organisms — mayfly nymphs, other aquatic insects, crayfish, etc. — from the bottom of lakes and rivers.
- Sturgeon have a habit of jumping straight out of the water and crashing back down. Several theories for this behavior have been put forward but it still remains a mystery.
Within a family of some 25 species of Acipenseridae, a sturgeon's size can be impressive. Beluga sturgeon can grow 18 feet long and weigh over 2,000 pounds. The more modest lake sturgeon, which is found in the Midwest of North America, can grow to 8 feet long and weigh over 300 pounds. You could say that sturgeon are the Leviathan and the Methuselahs of freshwater fish.
By Emily Kolodge