It takes about 15 years for male lake sturgeon to reach reproductive maturity and years for females. In early spring, adult sturgeon enter fast-flowing rivers to spawn.
Female lake sturgeon spawn once every four years, each depositing million of eggs on gravel bars. It is estimated that only about percent of adult lake sturgeon within a population spawn during a given year. Lake sturgeon were historically abundant in all of the Great Lakes. They served as an important food source for many Native American tribes. When European settlers arrived in the region, sturgeon were so numerous during the spring spawning run that they were reportedly capable of capsizing fishing boats.
Early commercial fishermen scorned sturgeon as nuisance fish that destroyed their gill nets. A single thrashing sturgeon could tangle an entire net, reducing opportunities to catch valuable lake whitefish or lake trout. Sturgeon can live to be more than years old! The white sturgeon can grow 20 feet long and weigh more than 1, pounds! White sturgeon from the Columbia River have been known to go as far south as the Sacramento River in California and as far north as the Frasier River in Canada.
But that changed with hydroelectric dams and habitat destruction from changing land uses, which have severely lowered sturgeon populations. Some sturgeon are now limited to living in the river between the dams, and do not migrate to the ocean.
In their natural habitat, sturgeon feed on clams, mussels, crayfish, worms, lamprey, smelt, anchovies, shad, fish eggs and other dead fish. They have no teeth, but use their mouth to crush prey and have a special spiral valve digestive system to help them absorb food and other nutrients. A variety of predators prey upon sturgeon eggs and young ones, but humans are the main predator for large, adult sturgeon.
Are sturgeon bony? Sturgeon bodies are a combination of bones and cartilage, but most of their body is cartilage like the tip our nose or our ears. What are the bumps on their backs? They are circular pieces of bone with a point in the middle. Females are reported to spawn once every two to 11 years.
They will eat almost any available organism; though they feed mostly on fish, they also eat crustaceans, mollusks, worms, and plant material. They are bluish-black or olive brown dorsally on their back with paler sides and a white belly. Atlantic sturgeon are similar in appearance to shortnose sturgeon , but can be distinguished by their larger size, smaller mouth, different snout shape, and tail scute pattern.
Adult spawning runs of Atlantic sturgeon are still not completely understood. In rivers from Georgia to the Chesapeake Bay, scientists have confirmed that adult sturgeon spawn during the late summer and fall.
In rivers from Delaware to Canada, adults spawn in the spring and early summer. Some researchers have hypothesized that spawning may occur in both the spring and fall, particularly likely in the mid-Atlantic, but that is yet to be confirmed in any river.
Because adult Atlantic sturgeon migrate along the coast when not spawning and tend to preferentially use estuaries, estuarine-oriented adults may appear to be preparing to spawn in the spring or fall, but are actually just feeding. Juvenile fish can leave their natal rivers as early as one year of age, so sometimes juvenile aggregations within a river may be composed of two or more different natal populations of fish.
After spawning in northern rivers, males may remain in the river or lower estuary until the fall; females typically exit the rivers within four to six weeks after spawning. Upon hatching, larvae hide along the bottom and drift downstream until they reach brackish waters where they may reside for one to five years before moving into nearshore coastal waters. Tagging data indicate that these immature Atlantic sturgeon travel widely once they leave their birth rivers.
Atlantic sturgeon are bottom feeders. They typically look for food that includes invertebrates such as crustaceans, worms, and mollusks, and bottom-dwelling fish such as sand lance. Historically, Atlantic sturgeon ranged along the Canadian and U. Atlantic Coast from Labrador to Florida. Due to overfishing, the abundance of natal populations is much less than historic levels, but breeding populations still exist in at least 22 U.
Atlantic sturgeon are anadromous fish—they are born in freshwater, then migrate to the sea and back again to freshwater to spawn. Most juveniles remain in their river of birth natal river for at least several months before migrating out to the ocean.
Tagging data indicate that these immature Atlantic sturgeon travel widely up and down the East Coast, and as far as Iceland, when they are at sea. Atlantic sturgeon lifespan is correlated with how far north or south they live. They live up to 60 years in Canada, but likely only 25 to 30 years in the southeast. Southern populations typically grow faster and reach sexual maturity earlier than northern populations. For example, Atlantic sturgeon mature in South Carolina rivers at 5 to 19 years of age, in the Hudson River at 11 to 21 years, and in the Saint Lawrence River at 22 to 34 years.
Atlantic sturgeon spawning intervals range from 1 to 5 years for males and 2 to 5 years for females, with males returning almost every year and females usually returning every other year or every third year. Female egg production correlates with age and body size, and ranges from , to 1. In the Hudson River, females reach 50 percent of their maximum lifetime egg production at approximately 29 years.
Fish from more southern rivers reach this production earlier and fish from Maine and Canada later. Atlantic sturgeon take approximately 3 to 10 times longer than other bony fish species to reach 50 percent of maximum lifetime egg production.
The most significant threats to Atlantic sturgeon are unintended catch in some commercial fisheries, dams that block access to spawning areas, poor water quality which harms development of sturgeon offspring , dredging of spawning areas, water withdrawals from rivers, and vessel strikes.
Atlantic sturgeon are sometimes accidentally caught by fishermen trying to catch something else. This is called bycatch. Bycatch occurs primarily in gillnet and trawl fisheries. The prevalence and likelihood of bycatch varies by fishing season.
The fishing season also impacts the likelihood of sturgeon survival, which is more likely in cooler waters. Adults can be captured when moving into rivers to spawn. Juveniles can be captured in rivers and estuaries when moving from their nursery habitat or year-round while swimming and feeding.
Fisheries conducted within rivers and estuaries may intercept any life stage, while fisheries conducted in the nearshore and ocean waters are more likely to capture migrating juveniles and adults. Learn more about fishing gear and risks to protected species. Atlantic sturgeon habitat can be disrupted or lost because of various human activities, such as dredging, dams, water withdrawals, saltwater intrusion often caused by groundwater pumping from freshwater wells or drought , chemical contamination of sediments in rearing areas, and other development.
Sturgeon need hard bottom substrates in freshwater reaches for spawning, so any activity that destroys those locations directly e. To support all life stages, Atlantic sturgeon also require sufficient water quantities and water qualities sufficient to support all life stages, which are often impacted by the activities above. Recent dam removal projects on the Penobscot River, Maine and Rappahannock River, Virginia, have increased accessibility to upstream habitats.
Atlantic sturgeon can be struck by the blades of a propeller as a boat is passing, or struck by the boat itself.
The risk of injury and mortality can be high in areas with high ship traffic, including the Hudson, Delaware, and James rivers.
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