How'd that get into the pond?

The face that accompanies this blog posting is that of a Northern Snakehead, a fish native to East Asia and that’s now swimming in some North American waters.

How might it have gotten here? First, some background:

Humans, being mobile creatures, tend to move fauna and flora around, not always intentionally and not always anticipating every consequence.

One example is Eurasian watermilfoil, an aquatic weed that’s native to northern Europe and Asia. It arrived in the United States sometime between the late 1800s and 1940 either in the ballasts of ships or as decorative foliage in aquariums.

At some point milfoil got into public waters, after which boaters began inadvertently moving it from lake to lake on their trailered craft.

The book that’s behind this blog says the following about milfoil: “The feathery plant forms mats of vegetation and tangled growths in lakes and ponds that can crowd out native plants, inconvenience swimmers, clog the propellers of motorboats, provide habitat for mosquitoes, reduce the value of lakeside properties, and turn off tourists.”

 Milfoil is now in the waters of most states and every Canadian province. Millions of dollars are spent each year trying to get rid of the weed and also to prevent it from getting into new waters.

But note, please: Not everything that humans move from here to there, inadvertently or by intent, is bad.

“Water Connections” also describes an American minnow named Gambusia affinis that, by having been moved around the planet, has done good things. The tiny fish dines on mosquito larvae, hence its nickname “mosquitofish.” The minnow was native to central and southern parts of the United States where its appetite for mosquitoes was discovered, and at one point in the 20th century it was the most widely distributed freshwater fish in the world. It’s credited with having helped eradicate malaria in South America, and today it’s being enlisted to go after mosquitos that carry the Zika virus.

Not everybody has good feelings about the mosquitofish, however. In Australia where the minnows were imported in 1925 to battle malaria, they’re now considered a nuisance for their tendencies to attack other fish, plus eat the tadpoles of various frogs, plus consume plankton that otherwise can help keep algae blooms in check. Rather coldly, Australia’s Biosecurity Act of 2014 lists Gambusia affinis as “a noxious fish.”

So, with that background, where in the order of things is the Northern Snakehead fish whose face is pictured with this blog?

Here’s what New York State’s Department of Environmental Conservation has to say about the fish, which on this continent was first noticed swimming in a Maryland pond in 2002 and has since turned up in other Eastern waters:

Northern snakeheads (Channa argus) are predatory fish native to Asia. They were most likely introduced to New York through aquarium dumpings and both accidental and intentional releases from fish markets. It is crucial that we stop the spread of this invasive predator to protect the health of our waters, wildlife and fishing industry.

“Northern snakeheads are long, thin fish with a single fin running the length of the back. They are generally brown with large, dark blotches along their sides and can grow up to three feet long. They have a somewhat flattened head and a large mouth with many teeth…

“Northern snakehead juveniles feed on a wide variety of microscopic organisms, insect larvae, and crustaceans on which native fish rely. As adults, they feed mostly on other fish species, but also eat crustaceans, reptiles, mammals and small birds. Snakeheads have the potential to reduce or even eliminate native fish populations and alter aquatic communities. Municipalities which rely on tourist dollars from recreational fishing may suffer losses should northern snakeheads continue to invade New York waters.”

As it is with the mosquitofish, however, not everyone is of the same mind about the Northern Snakehead. A few months ago an outdoors columnist for the Associated Press penned a defense of the fish that in one Pennsylvania newspaper was headlined “Fish Commission wrong again on ‘invasive’ species.”

So, there are differences over the fish, which is remarkable enough in ability and appearance to be nicknamed “Frankenfish” in some quarters. Among other things, its breathing mechanism is such that the fish can move short distances over dry land.

Concerns about the Northern Snakehead come at a time of heightened worries in the United States about invasives generally.

Last year a new law went into effect that calls for a federal strategic plan to deal with invasive fauna and flora. It’s the John D. Dingell, Jr. Conservation, Management, and Recreation Act. A draft of the plan is available here; the public comment period ends on Oct. 9.


 For more reading on the general subject, I strongly recommend “The Ecology of Invasions by Animals and Plants,” a landmark study by British zoologist Charles S. Elton in 1950 that for the first time catalogued the many ways that humans had shifted nature around for their own purposes. It’s a fascinating book for its accounts of human impact on the natural world.


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