The lake sturgeon is not only the largest fish in Lake Michigan, but it's also the oldest.

"Sturgeons have been around since about the Jurassic period, the time of the dinosaurs," said Rob Elliott, a U.S. Fish and Wildlife Service fisheries biologist. "The lake sturgeon were also one of the first species in the Great Lakes after they were formed by the glaciers nearly 10,000 years ago."

By looking at the lake sturgeon, one can see they are a little different from other fish species.

"Sturgeon are quite different physically," Elliott said. "They have no scales (and) their bodies are protected by plates. They also have no bones (or) no rib cage. It is all cartilage."

Sturgeon do not have teeth, but will swallow insects, larva, leeches, small fish and other life forms they find whole. Sturgeon are bottom-feeding omnivores that ingest just about anything they find down in the mud, and they prefer shallower, warmer water at depths between 25 and 50 feet.

This species of fish can live in excess of 100 years, but it is rare to find any in Lake Michigan beyond 60 or 70 years of age. They generally weigh between 150 and 200 pound, although some get as heavy as 300 pounds while reaching lengths of 7 feet.

"The ideal habit for them exists up north around the Green Bay area," Elliott said. "There are some areas at the southern end that are suitable as well."

Sturgeon spawn usually around late April or early May, but they take a long time to mature before they begin to spawn.

"Males become mature at around 12-to-15 years, while females are at 20-to-25 years," Elliott said. "This gives some of these fish 25 years to wander around the lake before they return to their river of origin for the first time to spawn."

Although they were here first and are big, lake sturgeon are on the endangered list in Indiana, Illinois and Michigan.

"The sturgeon population was almost wiped out starting in the late 1800s," Elliott said. "Dams built on spawning grounds, pollution and actively being fished brought about a serious decline in their numbers.

"At the height of their population, it is estimated that there were somewhere between two and 11 million sturgeon in Lake Michigan. They were as common as carp are now. There are probably only around 5,000 adult fish throughout the lake now."

Efforts are being made to secure and improve the numbers of sturgeon in Lake Michigan.

"There has been a concern for their survival over the last 20 years," Elliott said. "There has been more active management over the past 10 years with stocking programs beginning over the last five years. Our goal over the next 20 years is to increase their numbers and their habitat."