they breathe air, but they can also survive on land for up to 4 days, provided they are wet, and are known to migrate up to 400 m (1/4 mi) on wet land to other bodies of water by wriggling with their bodies and fins. National Geographic has referred to snakeheads as "fishzilla" and the National Geographic Channel reported the "northern snakehead reaches sexual maturity by age two or three. Each spawning-age female can release up to 15,000 eggs at once. Snakeheads can mate as often as five times a year. This means in just two years, a single female can release up to 150,000 eggs." "Since 2002, it has been illegal to possess a live snakehead in many US states, where they are considered a destructive invasive species." Virginia has criminalized the "introduction" of snakeheads into the state without specific authorization, although the relevant statute does not explain whether mere importation is sufficient to constitute "introduction into the Commonwealth" or whether instead release into the environment is required. Intentional introductions Humans have been introducing snakeheads to nonindigenous waters for over 100 years. In parts of Asia and Africa, the snakehead is considered a valuable food fish since the flesh is very tender, and is produced in aquacultures (fisheries motivation) or by accidental release (as was the case in Crofton, Maryland). Examples of the introduction of snakeheads to nonindigenous waters include: Channa maculata was introduced to Madagascar and to Hawaii around the end of the 19th century. It can still be found there today. Channa striata was introduced to islands east of the Wallace line by governmental programs in the latter half of the 20th century. In Fiji, the introduction failed. Channa asiatica, which is native to southern China, was introduced to Taiwan and southern Japan; the origin of and reason for the introduction are unknown. Channa argus, which is native to northern China's Amur River, was introduced to central Asia (Kazakhstan, Turkmenistan, and Uzbekistan). It was introduced from the Korean Peninsula to Japan about 100 years ago due to fisheries' motivations. Its introduction to Czechoslovakia by its government in the 1960s failed. Reported sightings In the United States Snakeheads became a national news topic in the United States because of the appearance of C. argus, commonly known as northern snakeheads, spawning in a Crofton, Maryland, pond in 2002. Northern snakeheads became permanently established in the Potomac River around 2004;