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Lake Sturgeon - Identification

With its heavy, torpedo-shaped body thick in front and tapering toward the turned-up tail in back, the young sturgeon resembles a shark but lacks the overall sleekness of the revered marine dweller. As befits a representative of fishdom's medieval era, the lake sturgeon wears "armor" in the form of bony, shell-shaped plates, or scutes, arranged in five rows - two on each side and one along the back - that run along the length of the body. Each scute comes to a peak with a sharp-pointed spur. As the fish grows older, the rows of spine-tipped bony scutes smooth out; on old, large individuals the scutes are barely visible and the fish appears relatively smooth. The sturgeon have never evolved to the point of replacing the cumbersome plates with smaller, thinner, flexible scales found on more modern species of fish.

While the lake sturgeon isn't likely to be mistaken for Jaws, it does have a heterocercal (sharklike with the upper lobe being longer than the lower) caudal (tail) fin. And instead of a backbone with separate vertebrae, the sturgeon has a continuous, flexible, cartilage-encased rod called a notochord that runs the length of the body and ends at the tip of the upper lobe in the tail fin.

Lake sturgeon have long, tapering snouts that become shorter and blunter with age. Four barbels, or feelers, dangle in a row on the lower side of the snout just in front of the mouth. The barbels are important sensory organs that alert the fish to the presence of food as the fish coasts slowly over the bottom. The mouth and lips of the lake sturgeon protrude to suck up food and retract when not in use - and this venerable fish need never fear a trip to the dentist, since it has no teeth. Two spiracles (vents) are located on top of the head just forward of the gills.

Lake sturgeon exhibit considerable color variation due to age and differences in locality. Wisconsin's lake sturgeon are generally slate-gray, olive-brown or black over the body with a milky or yellow-white underside. Young lake sturgeon are usually lighter in color than the adults and have dark blotches on their sides and snounts.

Young lake sturgeon caught in Wisconsin waters that drain into the Mississippi River are frequently confused with the smaller shovelnose sturgeon. This distinct species can be distinguished from the lake sturgeon by the long, rounded, shovel-shaped snout; the bony plates that cover the caudal area; a long filament that extends from the upper lobe of the caudal fin; and the lack of spiracles.

Lake Sturgeon

Lake Sturgeon Identification

Contact information
For more information, please contact:
Karl Scheidegger
Fisheries biologist
Last revised: Monday August 26 2013