|Home||Archived April 13, 2016||(i)|
Southeast Ecological Science Center
Snakeheads (family Channidae) are airbreathing freshwater fishes containing two genera, Channa, native to Asia, Malaysia, and Indonesia, and Parachanna, endemic to tropical Africa. Taxonomy of these fishes is in flux, but leading authorities on snakehead systematics currently recognize 26 species of Channa and 3 of Parachanna. A few snakeheads are small, reaching about 17 centimeters; most, however, are much larger, the largest reported to be 1.8 meters in length. All are considered thrust predators with most being piscivorous as adults.
Within parts of their native ranges, some species of snakeheads are highly valued as food fishes, particularly in India, southeastern Asia, China, and to a lesser extent in Africa. They have long been an important part of capture fisheries and, in recent decades, some species have been utilized in aquaculture and a few used as predators to control density of tilapiine fishes in culture.
Because of its popularity as a food fish in southern China and adjacent southeastern Asia, the chevron snakehead (Channa striata) has been reported as widely introduced into islands from the western Indian Ocean eastward to Hawaii. The northern snakehead (C. argus) has been a market leader, and is cultured in China and Korea. This species has been exported to other nations, including Canada and the United States where it has been sold alive in certain ethnic markets and restaurants. Although purposefully introduced and established in Japan in the early 1900s, its introduction and subsequent establishment in ponds, rivers, and reservoirs of Kazakhstan, Turkmenistan, and Uzbekistan (formerly part of the Soviet Union) in the early 1960s appear to have been accidental.
Other snakeheads utilized as food fishes include the Chinese snakehead (Channa asiatica), blotched snakehead (C. maculata), and spotted snakehead (C. punctata). The bullseye snakehead (C. marulius), found in the live-food and aquarium fish trades, is now established in Broward County, Florida, and the blotched snakehead has been established in Oahu, Hawaii, prior to 1900.
Snakeheads used in the aquarium fish trade include a few small species and brightly colored juveniles of several large snakeheads. They are moderately popular with hobbyists in Japan and Europe. Several species are marketed in Canada and have been sold in the U.S., even in states where possession of live snakeheads has been illegal for decades. Hobbyists and importers can purchase snakeheads through a variety of sites on the Internet. Because of their highly predacious nature, however, snakeheads have not had a large following of interested hobbyists in the U.S. Those who purchased attractively colored juveniles of the larger species typically found that snakeheads became incompatible with other fishes (even killing others of their own kind), required expensive food (preferably live), and quickly outgrew their aquaria. This apparently has led to releases of “pet” snakeheads. As a result of these habits and their prohibition in several states, snakeheads have had a limited market in the U.S. aquarium fish trade. The fact remains, however, that they have been available for purchase.
The earliest known record of snakehead imports into the contiguous U.S. was published by Brind (1914). The importation consisted of about 60 juvenile fish that we believe were blotched snakeheads. Their progeny are thought to have been consumed by parent fish (Brind, 1914). Klee (1987) noted that a snakehead species, the chevron snakehead, probably a misidentification of the Chinese snakehead, was in the U.S. aquarium fish trade by 1912. Ross B. Socolof (personal commun., 2003) said that the Chinese snakehead was the first snakehead imported for the U.S. aquarium fish trade in the very late 1800s or early 1900s. Innes (1917) mentioned snakeheads as aquarium fishes, but did not include individual species. Innes (1920) reported on his having received a “breeding pair” of what he cited as Channa fasciata from a colleague who brought the fish to him from San Francisco. He indicated that a “single adult pair and a few young” of this snakehead had been “recently imported into California from Southern Asia.” The photograph of this fish in Innes (1920) is clearly that of the Chinese snakehead, and the same photograph appeared in the account of the Chinese snakehead by Innes (1955). Armstrong (1923) purchased four progeny of Innes snakehead in 1922, and included his failures and success in breeding these fish and their care under aquarium conditions. Stoye (1935) and Axelrod and Schultz (1955) provided descriptions, illustrations, and information on the care and breeding of Chinese snakehead, leading us to believe that it was available for sale to aquarium hobbyists through at least the 1950s.
The Chinese snakehead is one of a few species known to crawl short distances overland references to this snakehead in the aquarium fish literature may have played a role in creation of an information “strip” on this species, published by Walt Disney Productions in 1959 (fig. 1), and brought to our attention by Robert Howells of the Texas Department of Parks and Wildlife.
Figure 1 Perhaps due to its availability in the aquarium fish hobby through the 1950s, Walt Disney Productions published this depiction of the Chinese snakehead, Channa asiatica, in 1959. This is a species of snakehead known to crawl overland for short distances. Reprinted with permission of Disney Publishing Worldwide. Disney Enterprises, Inc. - click to enlarge
A comprehensive snakehead fish study, including a biological synopsis, risk assessment, and accounts for each species, was conducted between September 2001 and September 2002 by the U.S. Geological Survey, with support provided by the Division of Scientific Authority and Fisheries Management of the U.S. Fish and Wildlife Service. This study was prompted for several reasons--
A limited number of snakeheads have been available for sale through the aquarium fish trade for several decades, but a new pathway--introduction of these fishes in live-food fish markets--had been largely overlooked.
Because snakeheads are highly predatory, some having the ability to travel overland to new water bodies, the inevitable release of these fishes by hobbyists, escapes from aquaculture, and liberation of live-food fish into U.S. waters threatens aquatic ecosystems. This report provides a comprehensive assessment of the risks involved with introductions of potentially invasive snakeheads into non-native waters.
|Home||Archived April 13, 2016|