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Texas by Nature

Invasive Species Watch: Snakehead

Menacing fish poses a serious threat to America's rivers

By Buddy Gough

Beware the snakehead, an Asian fish that is rapidly spreading through America’s rivers. According to local lore in Thailand, certain specimens of the aggressive fish have grown large enough to even attack humans.

While the snakehead poses no physical threat to people in the United States, the fish is an ecological monster capable of altering the balance of freshwater ecosystems throughout much of the country.

Bearing a superficial resemblance to common North American bowfins with elongated dorsal and anal fins, snakeheads are striking in appearance, with pale-colored bodies overlaid with extensive dark mottling and mouths full of sharp teeth.

Most were imported live into the country for sale as a food fish in Asian markets and were either intentionally or accidently released into local waters. Others were imported for aquariums and released after growing too large.

While importation of snakeheads has been banned in many states, the species has nevertheless spread throughout nine states along the East, West and Gulf coasts. In 2008, the snakehead was discovered in Arkansas, putting the species dangerously close to Texas.

The most common of the 28 species of snakeheads is the northern snakehead, which has established reproducing populations in Maryland and Virginia and which is capable of growing to 47 inches and weighing 15 pounds. Larger species like giant snakeheads and great snakeheads can reach weights of up to 60 pounds. 

Wherever they occur, the voracious and aggressive fish feed almost exclusively other fish, crustaceans and amphibians, asserting themselves as apex predators with no natural enemies.

Besides being able to filter oxygen from the water through gills, snakeheads can breathe air to survive in the most stagnant waters. They can also live out of the water for several days and can wriggle their way overland for short distances.

They can survive extremes ranging from winters in the icy waters of New England to summers in tropical waters of Florida, putting much of the country under threat of invasion.

They are also prolific spawners, with mature females producing up to 100,000 eggs. Survival of their fry and fingerlings is high because both the males and females aggressively guard their young.

The Nature Conservancy, of course, joins with state and federal conservation agencies in encouraging fishermen to report and retain any snakehead showing up in Texas waters.  

For more information about The Nature Conservancy's work in Texas, including other invasive species we help control, visit nature.org/texas.

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