All About Snakeheads

An angler competing in a bass fishing competition on Saturday pulled a 13-inch northern snakehead out of the Potomac River, marking the third time in nine days that the exotic species has been captured in or near the waterway and heightening fears that the Asian predators could become permanently established: Third Snakehead Taints the Potomac, (Post, May 18).

What are snakeheads and what makes them an undesirable addition to the local population?

Andrew Lazur, associate professor at the University of Maryland Center for Environmental Science and a Maryland Sea Grant Extension Specialist, was online Wednesday, May 19 at Noon ET, to take questions about the recent discovery of Snakehead fish in local waterways.

A member of Maryland's Snakehead Scientific Advisory Panel (2002), Lazur is considered an expert in fish biology and ecology, and has been working with finfish since 1981. During the summer of 2002, Lazur conducted the critical laboratory experiments that determined the effectiveness of a commonly used fish-control poison -- or rotenone -- on the snakeheads.

Editor's Note: Washingtonpost.com moderators retain editorial control over Live Online discussions and choose the most relevant questions for guests and hosts; guests and hosts can decline to answer questions.

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Dr. Andrew Lazur: Hello. I am Dr. Andrew Lazur with the Unviversity of Maryland Center for Environmental Sciences. I appreciate the opportunity to respond to the public regarding the important issue of introductions of invasive fish species. We should all be concerned with these introductions and the potential harm they may have on our native fish populations and aquatic ecosystems. I will look forward to addressing specific questions on the snakehead fish today.

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Centreville, Va.: Being a tropical fish, can the Snakehead adapt to the cold winters and survive during the colder months?

Dr. Andrew Lazur: The northern snakehead fish is actually a temperate species adapted to cooler waters tolerating 40-80 degrees. Many of the other snakhead fish species are tropical and prefer warmer water tempertatures

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St. Mary's City, Md.: How tolerant of varying salinity levels is this fish? Can we expect it in all the tributaries and throughout the Chesapeake soon?

Dr. Andrew Lazur: The northern snbakehead fish is native to freshwater rivers and streams in Asia and apparently does not tolerate salinity well which may prevent its migration to brackish or marine waters

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Washington, D.C.: How far can a snakehead "walk" before it needs to return to water?

Dr. Andrew Lazur: I am not aware of any documentation of the northern snakehead fish walking. Their fins are not shaped for "walking" and the fish may only be able to slide a short distance at best in wet locations

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Woodbridge, Va.: Is it true that they can survive on land for a period of time?

Dr. Andrew Lazur: The northern snakehead fish has been reprted to be able to survive out of water only in cool climates (50-60 degrees)and if kept moist

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Washington, D.C.: Good afternoon, Dr. Lazur. With these three snakeheads found recently in the Potomac River, can you give us the worst case scenario at this point, based on their size and age? How soon are they able to reproduce and what's the typical (snake)head count of a typical offspring cycle?

Dr. Andrew Lazur: The northern snakehead becomes capable of reproducing at 2 years of age and at that size can produce several thousand eggs. Like all fishes, eggs, larvae and juvenlies fish are subject to predation by other fishes, snakes, and water insects, so that the recruitment or number of surviving fish to adult stage is limited in a typical ecosystem. Snakehead fish may be even more susecptible to predation by game fish species. A report from Japan shows where introduced largemouth bass in lakes negativley impacted many established fish species including the northen snakehead

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Wheaton, Md.: Do the snakeheads have any natural enemies in local water systems, such as bass or snakes? If so, is it likely they will be killed off before establishing a permanent population?

Dr. Andrew Lazur: Yes, The norethen snakehead fish has many predators as do other fishes. In response to another question, I mentioned research from Japan where largemouth bass was shown to prey upon the snakehead fish to where populations declined significantly

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Alexandria, Va.: Dr. Lazur,

I appreciate your efforts in protecting the Potomac from the dreaded Snakehead fish, however if they are so dangerous to our ecosystem, why hasn't the U.S. made it illegal to import them from China? and How can we help to make it illegal to import them into the U.S.? Should we write our Congressmen or is there another avenue that we should follow.

Dr. Andrew Lazur: The United States Fish and Wildlife Service Has enacted a ban on all snakehead fishes in 2003. This makes it illegal to import live snakehead into the US and to transport live snakehead fish across statelines. This should result in a significant decline in the numbers of fish and eventual drying up of supply.

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Washington, D.C.: Has it been determined yet whether any of the recently caught fish were native-born/wild? Or are they all thought to be imported fish set free?

Dr. Andrew Lazur: It is not known at this time if the few fish caught were released directly or are from a spawn that occurred. Sampling resulting in the presence of all life stages will determine whether the fish have spawned in the river.

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Alexandria, Va.: If one were swimming in the Potomac or other bodies of water, is it possible that the Snakehead could bite? If so, what effects from the bite would one experience?

Dr. Andrew Lazur: It has been suggested in one case where a person may have been bit when disturbing the fishes' nest. The northern snakehead fish do show a tendency to guard their nest.

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Boston, Mass.: How big can the snakehead get, and what are some examples of large prey that they eat?

Dr. Andrew Lazur: The northern snakehead fish can reach up to 13 pounds and 33 inches in length. In their natural environmment, their main prey as adults is smaller fish. Juveniles will prey upon small crustaceans, insects and fish

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Herndon, Va.: If these snakehead fish aren't so bad, as you make it sound, then why the big ordeal and trying to rid our waters of them?

Dr. Andrew Lazur: Any non-native fish can complicate the food chain. Having the snakehead fish in the river adds another predator and may impact the balance of native predator/prey fishes.

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Silver Spring, Md.: Dr. Lazur:

If you're going to recommend killing of snakeheads, can you at least describe a humane method of doing so? After all, it isn't the snakehead's fault that some careless human being introduced it here. So, please, tell us: what is the least painful, most humane way to kill a snakehead?

Thanks!

Dr. Andrew Lazur: Freezing is a more humane method to kill exotic fish and if a snakehead fish is caught, it should be placed in a cooler with ice or in a freezer and reported to MD DNR.

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Washington, D.C.: I understand they are very edible. Are those catching them enjoying it other than catching a snakehead rather than a bass? Could they be a game fish?

Dr. Andrew Lazur: many snakehead species are cultured in Asia for food and they are a very popular food fish species there. Live snakehead fish were imported in to the US for food in many Asian food markets.

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Fairfax, Va.: How/why do you think the snakehead has managed to get into the Potomac?

Dr. Andrew Lazur: One explantion, as in the Crofton pond situation, is that fish were purchased from a live food market and taken home and used as a pet. If fed substanially, the fish may out grow small aquaria and someone decided to release the fish rather than euthanizing them by freezing which is recommended

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Holloman AFB, N.M.: Earlier, you mentioned that the snakehead can be protective of their nests. Where would these nests be located in lakes, streams and rivers?

Dr. Andrew Lazur: Nests are typically located in dense vegetation near the water surface

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Arlington, Va.: If memory serves, during the last snakehead scare I read that there the fish have even larger cousins in China. My question is, if we are scared about what these little ones will do to local fish-life, how can there be any other fish left in China? Do they have some natural defenses to protect themselves from the snakeheads?

Dr. Andrew Lazur: Again, snakehead fishes are another predator species nad may not be any more aggressive than native fishes. Reports in China state that it would take up to 14 years for a snakehead population to double in ideal conditions, which is very slow suggesting thatyoung fish life stages are very heavily preyed upon by other fish and other predators.

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Tampa, Fla.: Dr Andrew Lazur, would you say their presence here is permanent?

Dr. Andrew Lazur: Only consistent sampling will determine how the fish released will survive, reproduce or compete with our native fishes. It is importnat for us to montor the situation and prevent any other introductions.

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New York, N.Y.: Might it be more effective to conduct a series of dives (scuba) to survey the scope of the problem rather than rely soley on angler catch reports?

Dr. Andrew Lazur: Diving may not be a viable option due to many factors such as water clarity, and the fishes'preference towards vegetated areas. Angler catch can be an important indicator as well as strategic sampling by natural resource agency staff.

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Richmond, Va: I hear that Snakeheads are good to eat. Have you ever tried one?

Dr. Andrew Lazur: No, I have not, but it is a very popular fish in China, Thailand and Korea.

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Jacksonville, Fla.: Have these fish appeared in other parts of the U.S. outside of the D.C.-area?

Dr. Andrew Lazur: Florida has an introduced popoulation of the bulleye snakehead and there are reports that California has had an introductions as well.

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Washington, D.C.: You said earlier that you were not aware of the snakehead walking, but I recall many news articles and TV stories saying the fish can breathe out of the water and can walk short distances. Was this just an error repeated many times over?

For example, WRIC the Richmond TV station recently:
"It eats almost anything in the water, has no natural predators in the United States, and can live out of water for long periods of time."

I also remember an AP story recently mentioning it walking, and many stories mentioning walking when the pond in Maryland was discovered.

Dr. Andrew Lazur: Again, if you look at the fins, which are soft and flexible and therefore cannot support weight, it is not well adapted to walk. Living out of the water for long period is in question. The research shows a it capable of surviving for several days only st cooler temperatures and the gills and skin must remain moist for oxygen transfer to occur.

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Bethesda, Md.: My four-year-old daughter wants to know if a snakehead bites people?

Dr. Andrew Lazur: The northern Snakehead fish has only been reported in one case to bite someone, but it was when the person was disturbing the fishes' nest.

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New York, N.Y.: If it does turn out that the snakehead is spawning in the Potomac, how long will it be till they migrate to other rivers? Would they find living in water from Florida to Maine favorable?

Dr. Andrew Lazur: Again, because the northern snakehead does not tolerate elevated salinty, it is doubtful that they would migrate to other rivers, instead remaining in the freshwater areas.

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Washington, D.C.: Though the Northern Snakehead appears to be a very significant threat to existing native species, is this not just a more severe example than most of the adverse impact of introducing nonnative species? If so, why shouldn't all nonnative species of animals be banned from this country? What other measures might be taken?

Thanks!;!;

Dr. Andrew Lazur: The impact of these introdcutions remains to be seen. Sampling will need to be condsuted to assess the actual impact. In Florida whre the bulleys snakehead fish has been introdcued in the canals, it has not been shown to be any more aggressive preadtor than the native fishes and has not created a significant problem to native game and other fish species. We have very little information on what impact the snakehead fish has - assessment by sampling surveys is critical to understand the impact. Education is the key to preventing future releases! More effort should be taken to inform the public what may happen if non natives are released and what are alternatives. We are working with the MD pet industry and have developed a re-homing program where new homes can be found for unwanted exotic speices. This will be in operation soon.

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Seoul, Korea: This may just be me. But I can't help myself but rooting for this fish. It's a great story, and it seems that most people hate it because it's ugly.

What are the chances of this fish completely devastating the Potomac's ecosystem?

Dr. Andrew Lazur: Only sampling will tell what the impact of the snakehead fish will be, but information from the introducded fish in Florida and one research study in Japan suggests that the northern snakehead fish is one of several predatory fish species, not neccessarily more successful, and that they are suseptible to predation by native gamefish species. Time will tell.

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Anonymous: If the incursion can't be controlled, then how far up the Potomac could this species establish itself?

Dr. Andrew Lazur: Because of the fishes' low tolerance to salinity, if the fish were to successfully populate, it would be in the freshwater regions only.

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Charleston, S.C.: In what grades (salt, fresh; rivers, lakes) of water can snakeheads populate?

What risk do the pose to humans?

If their presence in Maryland waters is an isolated event on the eastern seaboard, how long could it take for them to travel to further southern regions?

Dr. Andrew Lazur: The northen snakehead fish is native to freshwater rivers and streams in Asia and does not tolerate salinty, therefore suggesting that it would not move out of the freshwater regions of the Potomac river. From the limited reports, the risk to humans appears to be minimal and only if a nest is disturbed where the adult fish are guarding their young.

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Accokeek, Md.: It is my understanding that there is a bill before Congress right now that would authorize upwards of $25 million for Rapid Response activities associated with the discovery of non-native species in watersheds. My questions to you is let's assume that money is available right now to impliment a response to the snakehead problem, what would/should we be doing?

Dr. Andrew Lazur: Assessing the extent of the introduction by planned sampling is essential to determine the impact. This will require natural resource agency staff to conduct regular sampling surveys and also educate anglers on the fish and what to do if another snakehead is caught. Bottomline is assessment and education!

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