Sturgeon

Sturgeons are very old fish.

They have hard plates on their skin. These plates act like armor.

Their bodies are long and smooth. They have tails like sharks.

Many sturgeons live in rivers. Some also live in the sea. They swim upstream to lay eggs.

These fish can live a long time. Some kinds are in danger now.

Sturgeons are a special group of fish. There are 27 different species in this family.

These fish are very old. Their ancestors lived a long time ago. Some fossils date back 174 to 201 million years. Because they have changed very little, people call them living fossils.

Sturgeons have a unique look. Their bodies are long and smooth. They do not have scales. Instead, they have bony plates called scutes. These scutes act like armor. They also have a tail like a shark.

Many sturgeons are anadromous. This means they spend most of their lives in salt water. Then, they swim upstream to rivers to spawn, or lay eggs.

Some sturgeons grow to be very large. A female beluga caught in 1827 was huge. People often harvest sturgeons for roe. This is the eggs inside the fish. It is made into a food called caviar. This has put many species in danger of extinction.

Sturgeons are a fascinating group of fish. There are 27 different species in this family.

These fish are found in many places. They live in rivers, lakes, and coastlines. They inhabit areas from temperate zones to sub-Arctic regions. Some live only in freshwater. Others live in the salty ocean. They are also native to Eurasia and North America.

Most sturgeons have a very special way of living. They are often anadromous bottom-feeders. This means they spend most of their lives in river deltas or estuaries. They feed along the bottom of the water. When it is time to spawn, they migrate upstream. This journey is part of their natural life cycle.

Some species even venture into the open ocean.

These fish have a unique look. They have long, spindle-like bodies. Their skin is smooth and has no scales. Instead, they are armored with five rows of bony plates. These plates are called scutes. They also have a heterocercal caudal fin. This is a tail shape that is similar to a shark's tail.

Sturgeons are very old. Their ancestors lived during the Early Jurassic period. This was about 174 to 201 million years ago. Because they have changed so little, people call them living fossils. The oldest known sturgeon fossil is a partial skull from Alberta, Canada. This fossil is from the Cenomanian age.

Some sturgeons can grow to be huge. The largest on record was a female beluga. She was caught in the Volga Delta in 1827.

Many people harvest sturgeons for their roe. This is the fish eggs. It is processed into a luxury food called caviar. This harvesting has caused serious overexploitation. Now, most species are critically endangered. They are very close to extinction.

Sturgeons are a unique group of fish belonging to the family Acipenseridae. There are 27 known species within this family.

They are found in various environments across Eurasia and North America. These fish inhabit subtropical, temperate, and sub-Arctic waters. They live in rivers, lakes, and along coastlines. Some species live only in freshwater. Others live in marine environments and can even venture into the open ocean.

Most sturgeons follow a life cycle known as anadromous behavior. This means they spend most of their lives feeding in river deltas and estuaries. These areas are where rivers meet the sea. When it is time to spawn, or lay eggs, they migrate upstream into rivers.

As bottom-feeders, they search for food along the floor of their habitat. This specific way of living connects different water systems through their migrations.

Physically, sturgeons look very different from most modern fish. They have elongated, spindle-like bodies. Instead of having scales, their skin is smooth and armored. They possess five lateral rows of bony plates called scutes.

Their tail is a heterocercal caudal fin. This means the tail is shaped similarly to the tails seen on sharks. These physical traits have remained mostly unchanged for millions of years.

Because they have changed so little, scientists often call them living fossils. Their ancestors, known as acipenseriform fish, date back to the Early Jurassic period. This was approximately 174 to 201 million years ago.

True sturgeons appear in the fossil record during the Upper Cretaceous. The oldest known remains are a partial skull found in Alberta, Canada. This fossil dates to the Cenomanian age, between 100 and 94 million years ago. They likely survived because of their size, their bony scutes, and a wide tolerance for different temperatures and salt levels.

Taxonomy, or the science of classifying living things, is difficult with sturgeons. This is because individuals can vary greatly in shape and size. They can also produce viable hybrids between different species. This makes it hard to group them perfectly.

Currently, the family is divided into five main genera: Acipenser, Huso, Scaphirhynchus, Pseudoscaphirhynchus, and Sinosturio. Recent studies using molecular phylogenetics, which looks at DNA, help scientists understand these relationships better than looking at bones alone.

Some species within these groups are much larger than others. The beluga sturgeon is one of the largest.

The largest sturgeon ever recorded was a female beluga caught in the Volga Delta in 1827. While some species are thriving, others are in danger. Two species, H. naccarii and S. dabryanus, may be extinct in the wild. Another species, P. fedtschenkoi, may be entirely extinct.

Human activity has a major impact on sturgeon populations. Many species are harvested for their roe, which are the fish eggs. When processed, this roe becomes a luxury food called caviar. This trade has led to serious overexploitation.

Because of this and other conservation threats, most sturgeon species are now listed as critically endangered. They are currently living at the very edge of extinction. Protecting these ancient fish is a major goal for modern conservation science.