Lake Sturgeon
| Scientific Name | Acipenser fulvescens |
| Survival Strategy | Active All Winter |
| Conservation status | Least Concern |
Spring
The timing of the lake sturgeon spawning run is dependent on the water temperature in the river, typically taking place in late April and early May when river temperatures reach 12°C (53°F) to 15°C (59°F). Females will lay between 50,000 to 700,000 sticky eggs on rocky riverbeds. After the eggs hatch in about six days, the lake sturgeon larvae (newly hatched fish still feeding on their yolk sacs) begin their fight for survival. After spawning, adult sturgeon swim rapidly back downstream, with most not returning for several years.
Summer
Adult lake sturgeon forage within their home range throughout the summer, preferring water depths of 6 m (20ft) to 9 m (30ft) and water temperatures between 10°C (50°F) and 18°C (60°F).
Fall
Sturgeon spend the fall as they did the summer, swimming and looking for food.
Winter
Lake sturgeon continue foraging during winter, although feeding may slow. By early March, spawning sturgeon will begin moving towards their natal streams.
Behavior
Reproduction
Female sturgeon will reach their breeding age at 25 years and spawn every 4 to 6 years, while males reach sexual maturity around 15 years and spawn almost every year. The timing of the spring spawning run is linked to water temperature and river flow. If the spring river flow is high, spawning will begin at lower temperatures, and during lower river flows, spawning will occur at higher temperatures. Spawning occurs in shallow rocky portions of the stream where several males compete to get closest to a single female. The males vibrate their bodies against the female and release sperm as she releases her eggs. Sturgeon are broadcast spawners, releasing such incredibly high numbers of sperm and eggs into the water that the probability of egg fertilization is high.
The lake sturgeon spawning runs have become eco-tourism attractions, offering the public a fantastic wildlife viewing opportunity. Wisconsin’s prime spots include New London’s Sturgeon Trail Park and Shawano’s Sturgeon Park. Both locations are accessible to strollers and wheelchairs. Eco-tourism brings the public closer to nature and helps support local businesses.
Porpoising
In the weeks before spawning begins, when water temperatures reach 6°C (43°F) to 16°C (61°F), lake sturgeon can be seen jumping vertically out of the water and landing with a splash. This behavior looks much like leaping porpoises.
Feeding with a Vacuum
Lake sturgeon are bottom-feeding omnivores that locate their food using four taste-sensitive barbels that hang down from their snout (these are the same as the “whiskers” found on bullhead and catfish). Sturgeon have no teeth and feed by vacuuming up potential food from the lake bottom and spitting out inedible bits through their gills.
Physiology
Water Temperature and Available Oxygen
Unlike many living things in the upper Midwest, low winter temperatures are not a threat to lake sturgeon. This prehistoric fish can survive for months in water temperatures near 0°C (32°). Excessively warm water, on the other hand, can be lethal. Warm water holds less oxygen, so fish need to pump more water across their gills to make up for the lower oxygen content of the water. At the same time, warm water speeds up the fish’s metabolism, requiring it to use more oxygen. In a limnological Catch-22, warmer water increases a fish’s need for oxygen while at the same time making less oxygen available to it. Lake sturgeon exposed to extended periods of water temperatures above 26°C (78°F) will die from a lack of oxygen (hypoxia).
Diet
The diet of the lake sturgeon includes midges, insect larvae, crayfish, snails, clams, leeches, fish eggs, and algae.
Lifespan and Mortality
Male lake sturgeon can live for 55 years or more, while females often live for more than 80 years. The first year of life is the riskiest for lake sturgeon. Less than 0.01% survive their first year. By the time they reach adulthood, survival increases to 83%.
Predators
Sturgeon eggs are an easy meal for crayfish and small fish. Fingerling sturgeon can be prey for herons. Invasive sea lamprey will parasitize adult sturgeon.
The biggest threats to lake sturgeon come from the loss of spawning beds due to river silt and power dams that are barriers to migration.
Climate Vulnerability
A warming climate will likely impact lake sturgeon in several ways. Earlier spring temperatures will alter the timing of spawning runs, although biologists do not yet understand how this will affect reproduction.
As increases in summer water temperatures reduce the concentration of oxygen in the water, the runoff from more frequent heavy rains will increase the nutrient load of lakes and rivers. The additional nutrients encourage the growth of algae. Decomposing algae use oxygen from the water, further reducing the amount of oxygen available for fish and increasing the frequency of hypoxia.
Never Stop Learning
First Nations: The Ojibwe word for lake sturgeon is “Namé.”
Anatomy: Sturgeon have very little true bone. Most of their internal skeleton is composed of cartilage, as in sharks.
References
| Sturgeon, D. 2001. “Acipenser fulvescens” (On-line), Animal Diversity Web. Accessed November 18, 2021 at https://animaldiversity.org/accounts/Acipenser_fulvescens/ |
| How and Why Lakes Stratify and Turn Over: We explain the science behind the phenomena https://www.iisd.org/ela/blog/commentary/lakes-stratify-turn-explain-science-behind-phenomena/ |
| How Fish React to Changing Water Conditions, Lisa Ballard, Outdoor America Article, 2020 Issue 1 https://www.iwla.org/publications/outdoor-america/articles/outdoor-america-2020-issue-1/how-fish-react-to-changing-water-conditions |
| Ojibwe People’s Dictionary: Sturgeon https://ojibwe.lib.umn.edu/main-entry/name-na |