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|A lake sturgeon|
The lake sturgeon (Acipenser fulvescens), also called rock sturgeon, is a North American temperate freshwater fish, one of about 25 species of sturgeon. Like other sturgeons, this species is an evolutionarily ancient bottomfeeder with a partly cartilaginous skeleton, an overall streamlined shape and skin bearing rows of bony plates on its sides and back, resembling an armored torpedo. The fish uses its elongated, spadelike snout to stir up the substrate and sediments on the beds of rivers and lakes while feeding. The lake sturgeon has four purely sensory organs that dangle near its mouth. These organs, called barbels, help the sturgeon to locate bottom-dwelling prey. Lake sturgeons can grow to a relatively large size, topping 6 ft (2 m) long and weighing nearly 200 lb (90 kg).
The lake sturgeon has taste buds on and around its barbels near its rubbery, prehensile lips. It extends its lips to vacuum up soft live food, which it swallows whole due to its lack of teeth. Its diet consists of insect larvae, worms (including leeches), and other small organisms (primarily metazoan) it finds in the mud. Fish are rarely found in its diet and are likely incidental items only, with the possible exception of the invasive round goby. Given that it is a large species surviving by feeding on very small species, its feeding ecology has been compared to that of large marine animals, like some whales, which survive by filter-feeding.
This species occurs in the Mississippi River drainage basin south to Alabama and Mississippi. It occurs in the Great Lakes and east down the St. Lawrence River to the limits of fresh water. In the west, it reaches Lake Winnipeg and the North and South Saskatchewan Rivers. In the north, it is found in the Hudson Bay Lowland. This distribution makes sense in that all these areas were linked by the large lakes that formed as the glaciers retreated from North America at the end of the last ice age (e.g., Lake Agassiz, Lake Iroquois).
Growth, age and Reproduction
Lake sturgeon are also extremely long-lived fish, and may live some 55 years. The lake sturgeon does not reach sexual maturity until its first decade of life.
These fish were once killed as a nuisance bycatch because they damaged fishing gear. When their meat and eggs became prized, commercial fishermen targeted them. Between 1879 and 1900, the Great Lakes commercial sturgeon fishery brought in an average of 4 million lb (1800 metric tons) per year. Such unsustainable catch rates were coupled with environmental challenges such as pollution and the construction of dams and other flood control measures. Sturgeon, which return each spring to spawn in the streams and rivers in which they were born, found tributaries blocked and spawning shoals destroyed by silt from agriculture and lumbering. In the 20th century, drastic drops in sturgeon catches, increased regulations, and the closure of viable fisheries occurred. Currently, 19 of the 20 states within the fish's original U.S. range list it as either threatened or endangered.
This sturgeon is a valuable gourmet food fish, as well as source of specialty products including caviar and isinglass. The exploitation of the sturgeon typifies human exploitation of large animals in general. "In 1860, this species, taken on incidental catches of other fishes, was killed and dumped back in the lake, piled up on shore to dry and be burned, fed to pigs, or dug into the earth as fertilizer."  It was even stacked like cordwood and used to fuel steamboats. Once its value was realized, "They were taken by every available means from spearing and jigging to set lines of baited or unbaited hooks laid on the bottom to trapnets, poundnets and gillnets." Over 5 million lb were taken from Lake Erie in a single year. The fishery collapsed, largely by 1900. They have never recovered. Like most sturgeons, the lake sturgeon is rare now, and is protected in many areas.
In addition to overharvesting, it has also been negatively affected by pollution and loss of migratory waterways. It is vulnerable to population declines through overfishing due to its extremely slow reproductive cycle; most individuals caught before 20 years of age have never bred and females spawn only once every four or five years. The specific harvesting of breeding females for their roe is also damaging to population size. Few individuals ever reach the extreme old age or large size that those of previous generations often did.
Today, limited sturgeon fishing seasons are permitted in only a few areas, including some locations in Minnesota, Wisconsin, and Michigan. Fishing for sturgeon is allowed on Black Lake in Michigan, for example, but the fishery is limited to five total fish taken each year, each over 36 in (910 mm) and taken through the ice with spears.
Anglers in Minnesota have the opportunity to harvest one lake sturgeon per calendar year between 45 and 50 in on the Rainy River and Lake of the Woods on the Canadian border. The early season runs from April 24 to May 7 each year with the late season running from July 1 to September 30. Anglers must have a valid Minnesota fishing license and purchase a sturgeon tag to harvest a lake sturgeon.
Also, an annual sturgeon spearing season is open on Lake Winnebago in Wisconsin. It has changed from a 16-day season in the past to a season with a marked quota, but the season can still run for the full 16 days. If 90–99% of the quota is reached on any day, the season is over at 12:30 pm the following day. If 100% (or more) of the quota is reached, the Wisconsin Department of Natural Resources can enable an emergency stoppage rule. In 2012, the largest sturgeon ever caught on Lake Winnebago (a female) was 125 years old, weighed 240 lb, and measured 87.5 in in length. It was tagged and released by scientists from the Wisconsin Department of Natural Resources.
The sturgeon is also present in Quebec in the St. Lawrence River, where it is targeted by commercial fisheries. It is also a game fish with an harvest limit of one per day.
Wolf Lake State Fish Hatchery in Kalamazoo, MI, raises and releases lake sturgeon, and is the only fish hatchery in Michigan to do so. The lake sturgeon are produced mainly for inland waters, although a few are stocked in Great Lakes waters.
- St. Pierre, R. & Runstrom, A. (U.S. Fish & Wildlife Service) (2004). Acipenser fulvescens. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 23 February 2009.
- "Sturgeons". New York State Department of Conservation. Retrieved 2014-06-12.
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- Scott, W.B. and E.J. Crossman. 1972. Freshwater Fisheries of Canada. Fisheries Research Board of Canada, Department of the Environment, Ottawa. p. 83-84.
- Scott, W.B. and E.J. Crossman. 1972. Freshwater Fisheries of Canada. Fisheries Research Board of Canada, Department of the Environment, Ottawa. p. 82-89.
- Scott, W.B. and E.J. Crossman. 1972. Freshwater Fisheries of Canada. Fisheries Research Board of Canada, Department of the Environment, Ottawa. p. 88.
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- Froese, Rainer and Pauly, Daniel, eds. (2005). "Acipenser fulvescens" in FishBase. 10 2005 version.