Prehistoric Animals
Sturgeon appeared in the fossil record approximately 200 million years ago, and managed to survive the extinction of the dinosaurs. Since that time, sturgeon have undergone little morphological change, meaning that sturgeon alive today look very similar to those that were alive when dinosaurs walked the Earth. Their persistence and apparent slow rate of evolution is partly due to their long life span, ability to tolerate a wide range of environmental conditions (namely temperature and salinity), and lack of predators (due to the large size of the adults, and the bony plated armour (or scutes) on the young).
Primitive Characteristics
Sturgeon still retain several primitive characteristics, such as a heterocercal tail (meaning shaped like a shark), lack of distinct scales, and a unique jaw suspension. Sturgeon have four barbels (whiskers) that precede their toothless wide mouths. Most species of sturgeon are at least partially anadromous (tolerant of fresh and salt water), spawning in fresh water and feeding in nutrient-rich, brackish waters of estuaries or undertaking significant migrations along coastlines. However, some species, such as the Lake Sturgeon, have evolved primarily freshwater existences. They navigate their riverine habitats traveling just off the bottom with their barbels dragging along the substrate.
Sturgeon Are Vulnerable Everywhere
Throughout their extensive range, almost all sturgeon species have become highly threatened or vulnerable to extinction due to a combination of habitat destruction and fragmentation, overfishing, and pollution. The International Union for Conservation of Nature (IUCN) has listed 16 species as “critically endangered”, two as “endangered”, two as “near threatened”, three as “vulnerable”, and two of “least concern” (ICUN 2015).