Sturgeon family Dachshund sturgeon (scientific name: Huso dauricus), commonly known as koji, sturgeon and koji, from Northeast Asia, Heilongjiang, Ussuri River and other waterways, the largest existing freshwater fish, but also the second largest cartilaginous, hard-scaled fish after its close relative, the European koji, up to 5.6 meters long, 1 ton weight. The European sturgeon, on the other hand, can reach 6 meters long and weigh 1.5 tons, but is not a purely freshwater fish, but lives mainly in brackish water.

Beavers

Beavers are known as "nature's dam engineers". They are found mainly in the northern Americas, with very few in Europe and Asia. They can use twigs, shrubs, rocks, dirt and other materials to build dams and cabins for living. The wetlands they create provide ideal habitat for other organisms, so beavers are considered a keystone species in the ecosystem. Male and female beavers can form ongoing mating relationships where they live with their offspring. Older offspring can help their parents build dams and cabins, and will even help care for younger siblings. Beavers use mud, crushed earth, and beaver scent (a substance secreted by the beaver's pyriform glandular sacs and excreted in urine) to mark territory boundaries. Beavers can recognize relatives by the scent secreted by their anal glands, and they are more tolerant of related beavers living around them.