The kaluga (Huso dauricus), also known as the river beluga, is a large predatory sturgeon found in the Amur River basin. With a maximum size of at least 1,000 kg (2,205 lb) and 5.6 m (18.6 ft), the kaluga is one of the biggest of the sturgeon family. Like the slightly larger beluga, it spends part of its life in salt water. Unlike the beluga, this fish has 5 major rows of dermal scutes and feeds on salmon and other fish in the Amur. They have gray-green to black backs with a yellowish green-white underbelly. The kaluga has been hunted to near extinction for its valuable roe. Despite constant anti-poaching patrols, poachers still continue to catch the fish. In Russia, illegally fishing for kaluga anywhere in the Amur River is felony punishable by law. However, kalugas are known to have an aggressive nature, and instances of them toppling fishing boats and drowning fishermen have been reported, although no concrete evidence exists of them assaulting or hunting people. Habitat Kaluga sturgeon are semi-anadromous, spending some of its life in salt water but most of its life in freshwater. Kalugas are one of the four species of sturgeons to exist in the Amur River. The Amur River is one of the largest rivers in East Asia and lies between the borders of China and Russia. There are two types of Kaluga that exist in this river. One group of Kalugas spawn in the main stem of the river, while others spawn downstream and work their way to the middle of the river. In the early life of a Kaluga, the offspring prefer to live in a clear habitat setting. They prefer the point of the river where there is an illuminated white bottom and open space for them to swim way above the bottom of the river. The Kaluga also prefers to avoid any cover from the river. Observations suggest that the Kaluga embryos might do this to avoid predators near the bottom of the river. The Kaluga sturgeon are currently endangered now because of human interaction. However, environmental factors such as warm water temperatures pose risk for fungus over free embryos and could be a cause of death also. The migration intensity of Kaluga is also a big factor in the life of a Kaluga. Water velocity in the stream has a great effect on the migration of the free embryos,