Missouri's Aquatic Dinosaurs
Sturgeon evolved more than 150 million years ago during the Jurassic Era when dinosaurs roamed the earth. These prehistoric fish have an unusual appearance and resemble sharks, which are also ancient, primitive fish.
Range
Three of the eight species of sturgeon that occur in North America are native to Missouri. These are the pallid sturgeon, the lake sturgeon and the shovelnose sturgeon. They are found in the Missouri and Mississippi river basins and spend most of their time in the main channels of these large muddy rivers.
Status
Both the pallid sturgeon and the lake sturgeon are endangered. The shovelnose sturgeon, the most common of the three, has recently become a species of concern. A lot of factors have contributed to the decline of these species including habitat alterations by man to the Missouri and Mississippi rivers, overharvest, pollution and hybridization. However, habitat loss and past, unregulated commercial fishing are the primary reasons for their decline.
Physical adaptations
Sturgeon have long, streamlined bodies; long, bony snouts and are armored with lengthwise rows of sharp, bony plates called scutes. Their sucker-type mouth is located under their snout. They also have four barbells, which are similar in appearance to the "whiskers" on a catfish, that dangle from the snout in front of the mouth. The barbels help them locate food and find their way along the bottom.
Sturgeon are highly adapted for life in our big rivers. Their long, flat snouts, large pectoral fins and long, streamlined bodies help them move about and hold their position in the strong current.
Habitat and feeding
These bottom-dwelling fish prefer strong current and live in areas having firm substrate. At certain times of the year, they can be found along sand and gravel bars or in deeply scoured holes.
Sturgeon feed on the bottom using their flexible mouth, which can stick out from their faces, to suck up their food. Their diet consists primarily of larval aquatic insects, crayfish, snails, small clams and small fish. As lake and pallid sturgeon grow larger, their dependency on small fish for food increases. However, sturgeon can be scavengers at times, feeding on dead animal matter and are often caught by catfish anglers using worms or cut-up bait.
Life span and rate of development
Sturgeon are very long-lived fish and mature slowly. Lake sturgeon can live up to 150 years, reach eight feet in length and a weight of 300 pounds. Pallid sturgeon can live more than 40 years, reach five to six feet in length and weigh up to 65 pounds. Shovelnose sturgeon, the smallest of the three species, can live over 20 years but rarely exceed 30 inches in length and a weight of 5 pounds.
Department biologists conducted an age and growth study on sturgeon in the Missouri River in 2001. Their work revealed that five-year-old shovelnose sturgeon averaged 16.7 inches fork length and averaged 18.6, 18.6, 19.9, 21.1, 21.4, 22.4, and 23.1 inches in succeeding years. In 2002, a biologist recaptured a shovelnose sturgeon that was originally tagged 23 years earlier. This shovelnose turned out to be 37 years old!
Reproductive cycle and migration
Like most other long-lived species, sturgeon take a long time to reach sexual maturity. It takes 15 to 20 years (25 to 40 pounds in size) before a lake sturgeon can spawn for the first time; seven to 12 years (six to 12 pounds) for a pallid sturgeon; and five to seven years (two to three pounds) for shovelnose sturgeon.
Sturgeon also have an unusual reproductive cycle in that they don't spawn every year like most other fish species. A female lake or pallid sturgeon only spawns once every three to five years, and a female shovelnose sturgeon will spawn once every two to three years. Because of this fact, sturgeon are very susceptible to overharvest.
Each spring, rising water levels and water temperature trigger sturgeon spawning migrations. Spawning for Missouri's sturgeons usually occurs when water temperatures are from 55 to 65 degrees Fahrenheit, with the peak of spawning occurring during the first week or two of May.
Sturgeon are extremely migratory fish, and it's not unusual for shovelnose sturgeon to move 200 to 300 miles during their spring spawning migrations. In April of 2003, researchers tagged a shovelnose sturgeon in the Mississippi River at Cape Girardeau. Three weeks later, a commercial fisherman recaptured it near Hannibal, more than 240 miles upstream of where it was originally tagged.
