Sturgeon Life Cycle and Migration

A sturgeon begins life clinging to a river bed. Its fertilised egg sticks to rock, cobble or gravel; inside, an embryo develops before hatching into a fish sustained by its own yolk reserve. From that small freshwater beginning, the paths diverge. Some sturgeon eventually feed at sea and return upriver to spawn. Others spend their entire lives in freshwater. Many take years or decades to mature, and females generally leave several years between breeding attempts.

The sturgeon life cycle, stage by stage

The first transformation happens inside the egg. An embryo is the developing fish within a fertilised egg, not a separate animal or a later arrival. After hatching, the young sturgeon lives initially on stored yolk before finding food for itself. Atlantic sturgeon provide the worked example below, following NOAA's life-stage descriptions. Other sturgeon follow different timetables.

A sub-adult here is a fish that has begun coastal migrations but cannot yet breed. The term helps describe Atlantic sturgeon; freshwater species have no corresponding sea-going stage to complete. For the wider anatomy and physiology, start with sturgeon biology.

The first meal comes from within

A newly hatched sturgeon does not immediately hunt. During the yolk-sac phase, stored nutrients support its development as it shelters in spaces in the river bed. When that reserve runs out, the fish must find suitable food. This is its first essential change of diet.

Water temperature strongly influences the pace of development. Minnesota's fisheries agency gives a lake sturgeon hatching period of 5 to 8 days under the conditions it describes, with favourable incubation temperatures around 15 to 18°C (59 to 64°F). Egg development before the eggs leave the female is an earlier chapter, covered in oocyte stages and atresia.

Sea migrants and freshwater travellers

For Atlantic sturgeon, the journey to sea eventually leads back to the river where life began. They are anadromous: they grow and feed at sea, then return to freshwater to reproduce. The ocean does not follow immediately after hatching, however. Their early years include residence in rivers and estuaries, and they generally return to their natal river to spawn.

Lake sturgeon live in lakes and rivers, with no necessary marine phase. Yet freshwater residence can involve substantial journeys. Canadian assessments describe movements of hundreds of kilometres between spawning, feeding and overwintering areas in some river systems. Whether the route reaches the coast or stays inland, migration connects the habitats a sturgeon needs at different times of life.

Why the spawning journey leads upriver

Spawning adults seek a river bed where their eggs can hold fast. They need freshwater, flowing and oxygenated, over hard substrate: the material forming the bottom. Once fertilised, the eggs become adhesive and attach to rock, cobble and gravel. These are very different requirements from those of an adult feeding ground.

Temperature and river flow help organise the journey, with different patterns between seasons. In South Carolina's Great Pee Dee River, researchers implanted acoustic transmitters in 147 Atlantic sturgeon and modelled their movements against environmental conditions. Spring migration was associated with rising temperatures and high discharge; autumn migration with falling temperatures and lower discharge.

Michigan Sea Grant describes lake sturgeon females living 80 to 150 years, compared with an average around 55 years for males.

The spawning calendar also changes with geography. NOAA describes spring and early summer spawning from Delaware northwards. Farther south, rivers can support late summer and autumn spawning, sometimes alongside a separate spring run. Wild runs and farming seasons explains why these river calendars do not translate directly into a single caviar season.

How often do adults breed?

A mature sturgeon can breed repeatedly, but maturity does not mean spawning every year. Nor does an adult population spawn all together. Females generally leave longer intervals than males: Canada's 2017 lake sturgeon assessment reports males typically spawning every 1 to 3 years and females every 2 to 7 years.

NOAA's 2023 Atlantic sturgeon consultation framework gives broader intervals of 1 to 5 years for males and 2 to 5 years for females. These species-level summaries sit alongside more local findings. A York River system study combining capture records and telemetry found spawning return intervals of 1 to 3 years for males and 1 to 4 years for females.

A return visit does not necessarily mean eggs are released. The York study recorded females carrying advanced eggs in consecutive years, while recognising that retained eggs could complicate interpretation of those observations.

Slow maturity, long adult lives

An Atlantic sturgeon may reach maturity at 5 to 19 years in South Carolina, yet take 22 to 34 years in the Saint Lawrence River population, according to NOAA. Its account links colder northern waters with slower growth, later maturity and longer life. Becoming an adult is a very different prospect in those two settings.

The contrast continues into old age. NOAA gives an expected 25 to 30 years for South Carolina Atlantic sturgeon and records lives up to 60 years farther north. Michigan Sea Grant describes lake sturgeon females living 80 to 150 years, compared with an average around 55 years for males. These figures describe differences between populations and sexes, rather than a fixed lifespan for each fish.

Growth changes pace along the way. Minnesota's lake sturgeon account describes rapid early length growth, followed by slowing growth towards maturity. Farm harvest schedules involve different conditions and are covered separately in how long sturgeon take to produce caviar.

What sturgeon eat as they grow

Yolk is the first food. After that comes prey. Once Atlantic sturgeon larvae begin feeding independently, they take aquatic insects, insect larvae and other small invertebrates. Sub-adults and adults move on to larger bottom-dwelling prey, including molluscs, crustaceans, worms and small fish.

Lake sturgeon also feed mainly near the bottom. Their downward-facing mouths suck in insect larvae, snails, mussels and other animals. A larger body opens up a wider range of usable prey, making suitable feeding habitat an essential part of the life cycle. It is much more than somewhere to wait until the next spawning migration.

The precarious first year

Producing many eggs is only the beginning. Canada's lake sturgeon assessment describes low survival to the first birthday, followed by potentially high annual survival once that threshold has been passed. The greatest natural losses come early, long before those young fish can become breeding adults.

Predators can take their toll before hatching. During 2006 and 2007, researchers working on Wisconsin's Peshtigo River used experimental egg bags and examined predator stomach contents. Crayfish and several fish species ate sturgeon eggs. Yet among 862 predator stomachs, researchers found only one sturgeon larva.

The study reveals a clear egg-stage risk in that river; it does not establish how much larval predation occurs elsewhere. Young fish must also survive the switch to external food and reach suitable nursery habitat. Successful spawning is one achievement. Successful recruitment, the addition of surviving young to the population, is another.

How a connected cycle gets broken

A dam can stop adults reaching their spawning grounds. But opening a route is only part of restoring a life cycle. Altered flows, sediment-covered spawning beds and lost nursery habitat can disrupt incubation, downstream dispersal or feeding, even where adults are still present.

Late maturity and intermittent breeding make the loss of established breeders especially consequential. Each loss removes reproductive opportunities that younger fish cannot quickly replace. The mechanisms and conservation responses are covered in dams, pollution, bycatch and lost habitat.

How researchers follow the journey

A sturgeon's movements emerge from several kinds of evidence: tagging and recapture, egg and larval sampling, and telemetry, which tracks signals from transmitters carried by fish. Together, these methods help researchers piece together the journeys between habitats. How scientists track wild sturgeon explains how they work.