The northern snakehead also known as Chesapeake Channa (Channa argus) is a species of snakehead fish native to temperate East Asia, in China, Russia, North Korea, and South Korea. Their natural range goes from the Amur River watershed in Siberia and Manchuria down to Hainan. It is an important food fish and one of the most cultivated in its native region, with 510,000 tonnes annual production worldwide. Due to this, the northern snakehead has been exported throughout the world and has managed to establish non-native populations in Central Asia and North America. In the United States, it is found in Pennsylvania, Virginia, West Virginia, Delaware, Maryland, North Carolina, Arkansas, Missouri, and Mississippi.
Appearance
The distinguishing features of a northern snakehead include a long dorsal fin with 49–50 rays, an anal fin with 31–32 rays, a small, anteriorly depressed head, the eyes above the middle part of the upper jaw, a large mouth extending well beyond the eye, and villiform teeth in bands, with large canines on the lower jaw and palatines. It is generally reported to reach a length up to 100 cm (3 ft 3 in), but specimens approaching 150 cm (4 ft 11 in) are known according to Russian ichthyologists. The largest registered by the International Game Fish Association weighs 9.53 kg (21 lb 0 oz). Its coloration is a golden tan to pale brown, with dark blotches on the sides and saddle-like blotches across the back. Blotches toward the front tend to separate between top and bottom sections, while rear blotches are more likely to be contiguous. Coloration is nearly the same between juveniles and adults, which is unusual among snakeheads, and is similar to Channa maculata, but can be distinguished by two bar-like marks on the caudal peduncle (where the tail attaches); in C. maculata, the rear bar is usually complete, with pale bar-like areas before and after, while in C. argus, the rear bar is irregular and blotched, with no pale areas around it.
Fish similar in appearance The eyespot bowfin (Amia ocellicauda) and northern snakehead can be found in the same waters on the swampy tidal coastal plain of the mid-Atlantic United States, such as the Potomac and Delaware River, and are commonly confused with each other. Some contrasting differences in northern snakehead include the lack of a black eyespot on their caudal peduncle, a golden tan to brown coloration with dark splotches, a longer anal fin, a more elongated head, and an upper jaw that is shorter than its lower jaw. Another noticeable difference is that the northern snakehead has scales that continue uniformly from the body through to their head, whereas bowfin heads are smooth and free of scales.
Behavior The northern snakehead is a freshwater fish and cannot tolerate salinity in excess of 10 parts per million. It is a facultative air breather, using a suprabranchial organ and a bifurcated ventral aorta that permit both aquatic and aeria respiration. This unusual respiratory system allows it to live outside of water for several days. As an amphibious fish, it can wriggle its way between bodies of water or survive being transported by humans. Only young members of this species (not adults) may be able to move overland for short distances using wriggling motions. The preferred habitats of this species are stagnant water with mud substrate and aquatic vegetation, or slow, murky, swampy streams; it is primarily piscivorous, but is known to eat crustaceans, other invertebrates, and amphibians.
Reproduction
The northern snakehead can double its population in as little as 15 years. It reaches sexual maturity at age three or four, when it will be about 30 to 35 cm (1 ft 0 in – 1 ft 2 in) long. The eggs are fertilized externally; a female can lay 100,000 eggs a year. Fertilization occurs in shallow water in the early morning. The eggs are yellow and spherical, about 2 mm (0.079 in) in diameter. Eggs hatch after about 1–2 days, but they can take much longer at lower temperatures. The eggs are guarded by the parents until egg absorption, when the eggs are about 8 mm (0.31 in) long.
Subspecies Two subspecies have been recognized:
C. a. argus (Cantor, 1842) (Northern snakehead) China and Korea C. a. warpachowskii Berg, 1909 (Amur snakehead) eastern Russia.
As an invasive species In its native Asia, the snakehead fish is considered to be an important food fish and for this reason they have been exported to many other regions around the world. They were first introduced to Japan from mainland Asia in the early 1900s, where they have since become a sport fish. The USSR experimented with aquaculture of snakeheads during the mid 20th century in both Europe and Central Asia. In the United States, snakeheads were only cultured in Arkansas, but have managed to establish populations there and several states in the Mid-Atlantic.
Japan Snakeheads of Korean stock were first introduced to Japan in the 1920s, and since then have spread to about every suitable body of water on the Japanese mainland.
Europe During the Cold War, the USSR imported several different species of fish from eastern Eurasia into Europe for new prospects in aquaculture. Among these fish was the northern snakehead, which came from the Amur River basin and were stocked in various ponds of the Moscow region starting in 1949. These initial experiments were successful and it was recommended that snakehead be stocked into various other waterbodies. However, only one shipment to Czechoslovakia was ever made in 1955, and nothing else after. The snakehead was also introduced to the Volga Delta and various ponds in Yekaterinburg, but are presumed to have failed due to no reports since then. While the snakeheads were reported to have been breeding in Moscow in the 1950s, they have since disappeared. There are no known populations in Europe in this moment. In the European Union, it is included in the list of invasive alien species of Union concern and hence cannot be imported, bred, transported, commercialized, or intentionally released into the environment in any of its member states.
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