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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

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© Rob Elliott
© Rob Elliott

December 2006

Lake Sturgeon habitat restoration

Generating the data fisheries biologists need

Colette Charbonneau

Coordination among U.S. Fish and Wildlife Service, Wisconsin Department of Natural Resources and Purdue University staff led to assessing lake sturgeon habitat in Green Bay and northern Lake Michigan tributaries. The project will provide information to set a plan to preserve, restore and enhance lake sturgeon habitat. Fisheries biologists need this information to focus restoration efforts on the most productive lake sturgeon areas. The project is funded by the Fox River/Green Bay Natural Resource Trustee Council, Great Lakes Fishery Trust and Purdue University.

Contents

Co-funded with $50,000 settlement money, the project has measured different habitat characteristics above and below dams in tributaries of Green Bay and the Manistique River in Michigan during the spring and summer.

Green Bay tributaries include the Fox, Oconto, Peshtigo, Menominee, Escanaba, Suamico and Pensaukee Rivers. Water depth, river current speed, temperature, dissolved oxygen and turbidity have been recorded in known sturgeon habitat and in areas where experts believe sturgeon feed, spawn and rear their young.

All of this information will be used to make maps available of lake sturgeon habitats in each tributary. The maps will then be used by sturgeon experts for ranking:

  • the relative size, type and quality of habitat found
  • if the habitat can be enhanced or restored
  • if the fish can reach the habitat without swimming into existing barriers such as dams.

Rob Elliott, U.S. Fish and Wildlife Service fisheries biologist, explains the importance of understanding this complex fish. "By increasing our understanding of available habitat and habitat quality during all lake sturgeon life stages, the project will direct future lake sturgeon habitat enhancement and restoration efforts."

Lake sturgeon are relics from the dinosaur age. They are non-bony fish with bony plates along the body instead of scales. They have a notochord in place of a spine, a long snout and a tubular mouth. In the United States, Wisconsin and Michigan have the largest remaining populations of these fish.

They can live to be 150-years-old, grow to over eight feet in length and weigh over 200 pounds. Female lake sturgeon do not produce eggs until they are 20- to 25-years-old and spawn only once every four to six years. Male lake sturgeon mature around 15 years old.

For these reasons, these fish have a low reproductive rate. It can take many generations to recover from human intervention. Other population threats include overfishing, pollution and dam construction, which blocks movement to spawning areas.

Early settlers quickly realized the economic value of the fish, harvesting sturgeon eggs for caviar and selling the succulent flesh smoked or fresh. A gelatin extracted from the sturgeon's swim bladder was used to congeal jams and jellies and to clarify alcoholic beverages. The tough hides were used like leather. Wisconsin established a minimum size limit in 1903. Commercial harvest in Lake Michigan was closed in 1929. Highly restrictive fishing regulations continue today. While the lake sturgeon population has started to increase in some Wisconsin river systems, they are still rare in Lake Michigan including Green Bay.

Water quality improvements and harvest reductions have allowed populations to recover in Lake Michigan, but limited spawning and nursery habitat in historically important tributaries is a major problem.

"Assessing past and present habitat availability is necessary to rank efforts to replace, enhance or renew sturgeon habitats for successful restoration," Elliott says.

Colette Charbonneau is restoration coordinator for the U.S. Fish and Wildlife Service in Green Bay. For further information on NRDAR projects, contact Colette Charbonneau, (920) 866-1726.