|Northern snakehead, Channa argus|
The snakeheads are members of the freshwater perciform fish family Channidae, native to parts of Africa and Asia. These elongated, predatory fish are distinguished by their long dorsal fins, large mouths, and shiny teeth. They breathe air with gills, which allows them to migrate short distances over land. They have suprabranchial organs developing when they grow older, which is a primitive form of a labyrinth organ. The two extant genera are Channa in Asia and Parachanna in Africa, consisting of about 40 species.
They are valuable as a food source and have become notorious as an intentionally released invasive species.
The various species of snakeheads differ greatly in size. Dwarf snakeheads, such as Channa gachua, do not surpass 25 cm (10 in) in length. Most other snakeheads reach between 30 and 90 cm (12 and 35 in). Five species (C. argus, C. barca, C. marulius, C. micropeltes and C. striata) can reach 1 m (3 ft 3 in) or more.
Snakeheads are thrust-feeders that consume plankton, aquatic insects and mollusks when small. As adults, they mostly feed on other fish (such as carp) or on frogs. In rare cases, small mammals such as rats are eaten.
The Channidae are well represented in the fossil record and known from numerous specimens. Research indicates snakeheads likely originated in the south Himalayan region of the Indian Subcontinent (modern-day northern India and eastern Pakistan) at least 50 million years ago (Mya), during the Early Eocene epoch. Two of the earliest known species, Eochanna chorlakkiensis Roe 1991 and Anchichanna kuldanensis Murray & Thewissen, 2008, have both been found in the Middle Eocene of Pakistan. By 17 Mya, during the Early Miocene, Channidae had spread into western and central Eurasia, and by 8 Mya, during the late Tortonian, they could be found throughout Africa and East Asia. As Channidae are adapted to climates of high precipitation with mean temperatures of 20 °C (68 °F), their migrations into Europe and Asia correspond to the development of the Intertropical Convergence Zone, which increased air humidity, and the intensification of the East Asian monsoon, respectively. Both weather patterns emerged due to greater vertical growth of the Alps, Pyrenees, and Himalayas, which affected Eurasian climatic patterns.
Snakeheads can become invasive species and cause ecological damage because in many areas to which they are not native the absence of natural enemies gives them apex predator status. Not only can they breathe air, but they can also survive on land for up to four days, provided they are wet, and are known to migrate up to 400 metres (1/4 mile) on wet land to other bodies of water by wriggling with their body 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 "introduc[tion]" of snakeheads into the state without specific authorization, although the relevant statute does not explain whether mere importation is sufficient to constitute "introduc[tion] into the Commonwealth" or whether instead release into the environment is required.
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, and is produced in aquacultures (fisheries motivation) or by ignorance (as was the case in Crofton, Maryland). Some examples of the introduction of snakeheads to nonindigenous waters include:
Snakeheads became a national news topic in the United States because of the appearance of Channa 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; and possibly established in Florida. in approximately 120 miles (190 km) of river, the population has surpassed 21,000 individuals.
According to the United States Environmental Protection Agency, snakeheads have also been spotted in California, Delaware, Florida, Hawaii, Maine, Maryland, Massachusetts,Virginia, and Rhode Island. In particular, the bullseye snakehead (Channa marulius) has become a major problem throughout South Florida, growing larger than 14 pounds (6.4 kg).
According to the International Game Fish Association, Caleb Newton, a Spotsylvania County, Virginia resident, caught a world record 17 pound, 6 ounce northern snakehead at the junction of Aquia Creek and the Potomac River on June 1, 2013. The previous record, two ounces smaller, had been caught in 2004 in Miki, Kagawa, Japan.
Snakeheads are considered valuable food fish. Called nga yant in Burmese, it is a prized fish eaten in a variety of ways. In Vietnam, they are called ca loc, ca qua, or ca chuoi; it is prized in clay pot dishes and pickled preparations. Larger species, such as Channa striata, Channa maculata, and Parachanna obscura, are farmed in aquaculture. In the United States, chefs have suggested controlling the snakehead invasion by serving them in restaurants. In Indonesia, snakehead fish are called ikan gabus, served as the main parts of traditional dishes such as Betawi's pucung gabus, and considered to be a delicacy due to their rarity in wild and aquaculture, as they are harder to raise than other popular freshwater fish such as catfish and carp.
The snakeheads comprise two extant genera:
Two other genera are only known from fossils:
After its release in non-native North American waters, either accidentally or intentionally, the aggressive and predator-free snakehead's reputation as a "Frankenfish" or "monster fish" has become part of the culture Besides mentions on TV shows such as The Sopranos and The Office, the snakehead has been featured in three Sci-fi Channel original pictures entitled Snakehead Terror, Frankenfish, and Swarm of the Snakehead. In the Animal Planet TV series River Monsters, Jeremy Wade shows a dramatization of a snakehead, "the fish from hell", stalking an unsuspecting baby and Chihuahua. With the help of a snakehead researcher, however, Wade shows that although it is capable of living outside of water and is able to move on land, its weak pectoral muscles make movement difficult and render the snakehead an unlikely "stalker" on land.
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