Sturgeon - Ancient Freshwater Fish - Animal Corner (2024)

Sturgeons are a group of paddlefish belonging to the family Acipenseridae, that have been around for a very long time. Often referred to as ‘living fossils,’ these remarkable fish have been around for approximately 200 million years! They have been around long enough to witness the fall of the dinosaurs, and they retain a prehistorical, primitive appearance.

With 25 distinct species and 3 subspecies spread across 4 different genera, sturgeons are a modest family. They are primarily found in the temperate salt and fresh waters of the Northern Hemisphere, particularly around North America and Eurasia. They are known for their elongated bodies, rows of bony plates, and their prized roe, which is processed into caviar – a delicacy enjoyed worldwide.

Despite their ancient lineage and once-abundant populations, most sturgeon species today face threats from overfishing, habitat loss, and pollution. There isn’t a single species that has a stable population today.

Appearance & Characteristics of Sturgeon

Imagine a fish that can grow up to a whopping 18 feet long and tip the scales at a massive 2,200 pounds. That’s the sturgeon for you! They are a bit smaller than this on average though and it does vary by species. Most usually grow to between 2 – 3.5meters (7–12feet) in length, but dwarf species in the Pseudoscaphirhynchus genus are lucky to grow as much as a meter (3feet) in length.

On the other end of the scale is the White Sturgeon and the Beluga Sturgeon which average between 5 to 6 meters long. The largest beluga sturgeon females can even reach over 7 meters (23 feet)!

The sturgeons elongated bodies are adorned with bony plates called scutes instead of the typical scales we see on most fish. Their long snouts and shark-like tails make them easily distinguishable from other fish, especially in freshwater environments.

Despite their massive, somewhat intimidating size, these giants have toothless mouths, relying on a suction mechanism to feed. Their barbels, which are a kind of whisker-like sensory organ, dangle near their mouths. They are super sensitive and help them detect food.

One feature that makes them quite unique amongst all the other bony fish, is that their skeletons are almost completely made out of cartilage.

5 Of The Most Common Sturgeon Species

Beluga Sturgeon (Huso huso)

Physical Dimensions: Can grow up to a whopping 7.2 meters in length and weigh well over 1 ton.

Appearance: The Beluga sturgeon is the largest of all sturgeon species. It has a torpedo-shaped body, smooth skin, and a pointed snout. Its color varies from dark gray to light gray.

Habitat: Primarily found in the Caspian and Black Sea basins, but they can also be found in the Adriatic Sea.

Atlantic Sturgeon (Acipenser oxyrinchus)

Physical Dimensions: Typically grows up to 2-3 meters in length and can weigh up to 140 kg.

Appearance: It has a brownish-black color on its upper body with a white belly. The body is covered with five rows of bony plates.

Habitat: Found along the east coast of North America, from Labrador to Florida, primarily in coastal and estuarine waters.

Lake Sturgeon (Acipenser fulvescens)

Physical Dimensions: Typically grows up to 1.5-2 meters in length and can weigh up to 90 kg.

Appearance: It has a shark-like tail and its body color ranges from olive to brown, with a lighter belly. The body is covered in bony plates instead of scales.

Habitat: Found in freshwater lakes, rivers, and streams of North America, primarily in the Hudson Bay and Mississippi River basins.

Russian Sturgeon (Acipenser gueldenstaedtii)

Physical Dimensions: Typically grows up to 2-2.3 meters in length and can weigh up to 115 kg.

Appearance: It has a short snout with a rounded tip. The body color is grayish-green with a white belly.

Habitat: Native to the Black Sea, Azov Sea, and the Caspian Sea. They are also found in the rivers feeding into these seas.

Green Sturgeon (Acipenser medirostris)

Physical Dimensions: Typically grows up to 2.1 meters in length and can weigh up to 159 kg.

Appearance: It has a more streamlined body compared to other sturgeons and is olive-green in color. The snout is more tapered and the mouth is more ventral than other species.

Habitat: Found along the west coast of North America, from Alaska to Baja California, primarily in coastal waters, bays, and estuaries.

Distribution – Location and Habitat

Sturgeons have a vast range, predominantly in the Northern Hemisphere. There are no species that occur naturally any further south than the equator.

They are versatile, thriving in both freshwater and saltwater environments. From the temperate waters of North America including the Gulf of Mexico and the Great Lakes, to the rivers of Eurasia, Russia and Central Asia, these fish have made their mark.

Each species has its unique preference and I’ve put an overview of each one in the table at the bottom of this post. For instance, while the Beluga sturgeon is a fan of the Caspian Sea, the Lake sturgeon prefers freshwater habitats like the Mississippi River basin.

The Lifestyle & Behaviour of Sturgeon

Despite being slow swimmers, sturgeons are known for their impressive migratory patterns. Some journey thousands of miles to find the perfect breeding ground. Their ancient lineage means they’ve developed unique behaviours that have allowed them to survive for so long in various environments.

These fish have a variety of features that help them navigate and interact with their environment. The most impressive are the variety of electroreceptors that they have. These electroreceptors, located on their head, allow them to feed by sense rather than sight. They help the sturgeon to pick up signals from their environment and from other fish, providing valuable data for both migration and for mating, not just feeding!

Though no one really knows why, many species of sturgeon like to leap out of the water. There are many theories, and much speculation but the true nature of this behaviour is not entirely understood. These are massive fish, and the noise of them re-entering the water with a slap can be heard over quite a distance.

Diet & Nutrition of Sturgeon

One feature that Sturgeon have in common, is that they are all bottom feeders. They use their tube-like, toothless mouths to suck up food from the bed of their aquatic home. Their diet mainly consists of small animals like worms, crustaceans, clams, sea snails and small fish. The exception to this are two species of the Husogenus – thewhite sturgeonand thepallid sturgeon which, as adults, both prefer a diet of other fish including salmon.

They rely heavily on their barbels to sense and locate their meals. They rely on these electroreceptors as they don’t feed by sight. In their early lives, small Sturgeon ‘Fry’ dine mostly on insect larvae and crustaceans.

Sturgeon Reproduction

Sturgeons are oviparous, meaning they lay eggs. A single female can lay thousands, even millions, of eggs at once. However, not all of these eggs will be fertilized and only a fraction of these eggs survive to adulthood. The journey from egg to adult is fraught with challenges, but those that make it can live for a very long time.

From the egg, they will hatch into larval fish, and then into fry. In their first year, they will grow to around 20 cm long, and when they get to this stage they will usually leave their nursing areas, back into the main, freshwater rivers or lakes with the rest of the population.

It takes them around 15 to 20 years until they reach sexual maturity, but even when they reach this, they require specific environmental conditions to be able to spawn their eggs. These conditions don’t happen every year, so the regularity of reproducing is somewhat obscure for these fish, relying on many external factors all meeting their needs.

The eggs of many sturgeon, particularly the beluga, are seen as an elitist delicacy. They once were a food for paupers, but are now a very expensive luxury item often filling canapes in boardrooms and corporate events. Industries like this, and overfishing are a real threat to these ancient fish.

Lifespan of Sturgeon

Sturgeons are among the longest-living fish. Some species can live for over 100 years, but most can expect to live around 50-60 years given the chance. They don’t mature for many years, even after they are fully grown. Their life stages include juvenile, sub-adult, and adult phases, with each phase lasting varying durations depending on the species.

Predators & Threats to Sturgeon

Given their size, adult sturgeons have few natural predators. However, birds of prey, sharks, and sea lions might occasionally target them, particularly younger fish that are smaller and easier to target.

The most significant threat to these ancient fish is, unfortunately, humans. Overfishing, habitat destruction, and pollution have severely impacted their populations. The demand for caviar, which comes from sturgeon eggs, has also led to their decline.

Population and Conservation

The sturgeon’s story is a somber one. Over 85% of sturgeon species are classified as Critically Endangered, making them the most critically endangered species listed by the IUCN. Their numbers have dwindled due to various threats, primarily human-induced, and even in the last few years the rating of many species have been downgraded as the populations collapse.

However, organizations like WWF are at the forefront, championing their cause, establishing protected areas, and advocating for sustainable fishing practices. They have a sturgeon initiative to try and promote policy and educate to protect these ancient fish.

5 Fun Sturgeon Facts for Kids

• Sturgeons have been around since the age of the dinosaurs!
• Some people love to eat sturgeon eggs, which are turned into a food called caviar.
• Some sturgeons can jump fully out of the water, just like dolphins!
• They have an amazing sense of smell, which helps them find food.
• Sturgeons have whisker-like structures called barbels. It’s like they have a built-in food detector!

The 28 Extant Species & Subspecies Of Sturgeon