Friday, September 22, 2006

Snakehead Terror!!!!

Invasive species have become a commonplace event in any exploration of the outside world. They take many forms; for example the plants Purple Loosestrife, Hogweed, and Japanese Knotweed, the insects Africanized Honeybees and Red Fire Ant, and the aquatic ecosystem destructors like Zebra Mussels and Chinese Mitten Crab. However, no other introduced species has garnered as much hype as the Snakehead fish (Channa argus).

Snakeheads were introduced either intentionally, by people who wish to use them for a food source (they are supposed to be very tasty), or unintentionally by aquarists whose fish had outgrown their aquarium and they set them free. The snakehead rapidly became a fish of legend, mainly because of it's ability to exist outside the realm of water, it has retained a plesiomorphic lung allowing it to breathe air out of an aqueous environment, and also can move on land (if the ground is wet) although how far they can "walk" is unknown. Other caveats to the snakehead is it's voracious appetite ( it can rapidly become the top predator of any freshwater body directly affecting the sportfishing industry), and amazing fecundity (50,000 eggs per female/breeding season). Other interesting facts are, despite what the Sci-Fi channel says, they can only reach lengths of 3-4 feet maximum, and they can eat birds and small mammals. The snakehead also protects its eggs and young (a rarity in native fishes), allowing for a higher survival rate. Once, they are present they are there to stay. The snakehead reproductive population is centered in three states Florida, Hawaii and Maryland. Although, snakeheads have been found in many other states including Massachusetts.

Why I selected this topic is that there is still much to be learned from the snakehead, and there is research going on right now that I have had the opportunity to assist in. The Potomac River has a significant population of snakeheads and the U.S. Fish and Wildlife (headed by John Odenkirk) has begun research on snakehead migration patterns using radio tagging and telemetry (of which I trained the crew). They have already discovered that the snakeheads have a distinct home range, they travel out to feed but return to a home base. The research team has also discovered a mass exodus of the fish during times of high water levels after a storm event. There is other research performed by the Smithsonian National Zoological Park involving tracking the genetic line of captured snakeheads to determine the reproduction line and spread of snakehead populations in the Potomac, as well as their genetic diversity.

There is still much to learn about these fish including studying their amazing ability to make sounds (very few freshwater species do this) when foraging for food, and perhaps at other times such as breeding and socializing. Invasive species, once established, will become a significant threat to the delicate balance of the ecosystem, and the only seminal control of such a threat will be through detailed knowledge of the behaviors and biological activities. There is a need for scientists to pursue research on any number of invasive species across the US.

Submitted by BEK

6 Comments:

At 10:05 PM, Blogger PWH said...

It pleases me to no end that you mentioned the SciFi Channel's uhh... "film" on the subject. I like that you mentioned that in some cases Snakeheads were introduced intentionally. While we hear of the trouble caused by invasive species quite often, it is not often mentioned that these species were often introduced intentionally. There used to be government funded programs to introduce non-native fish species that were thought to be beneficial either as sport or food fish. An example of the problems this has caused would be Brown Trout and their subsequent displacement of native North American Salmonids. It is important to remember that when dealing with complex systems, good intentions are not enough. Your post does a good job of reminding us of that.

Posted by RWS

 
At 4:17 PM, Blogger PWH said...

I found it interesting to learn about a new invasive species. For how long has this snake been recognized as an invasive species? I'd like to know what type of wildlife this species poses a threat to, especially in Massachusetts. Is it a common prey of any predator and if not then possibly one should be found to balance out the population of this invasive species. I also find it a bit troubling to have to discern between what to do about a species that is posing threats because then we have to pose threats onto that species in response. Your post was very informative and showed us that we need to keep an eye on these types of threats.

Posted by EZP

 
At 11:43 AM, Blogger PWH said...

Your article was very informative and flowed quite well while touching upon the characteristics of the snakehead, as well as the global threats that could be caused by these same adaptive characteristics. Although the snakehead has not ruined any ecosystems in the US, one must always take precautions when a new voracious predator is introduced in a new environment. I watched a film called Darwin's Nightmare in which the Nile Perch was introduced into Lake Victoria, where it there reproduced with amazingly rapidity and is virtually destroying the lake and its ecosystem by predation and dropping the oxygen levels.
Importation of the snakehead fish into the US was banned in 2003, and fisherman who catch any snakeheads are suppose to report to the local fish and wildlife authorities. Australia has also put a ban on the fish, already suffering from similar incidents before. Some measures to destroy the fish include putting herbicides in the pond to drop oxygen levels so low as to kill the vegetation and kill the fish. But if the fish were smart enough, all it had to do was crawl into a next pond, seeing that it can survive on land for up to 4 days. Very good article.

Posted by TSK

 
At 5:29 PM, Blogger PWH said...

Very cool post! A central-place foraging fish; how common is that for fish that aren't guarding a nest? I hope you comment on this when we cover foraging in class.

It would be great if you could embed an image of a radio-tagged fish in your post.

Great example of the applied aspects of animal behavior. We can't control these fish unless we know what they are up to.

(BEK, you need to append the week you were assigned to post to your signature.)

Posted by PWH.

 
At 8:24 PM, Blogger catherineS said...

I recently read an article about snakehead fish in Maryland. That state's Department of Natural Resources has asked for federal help because the snakehead has no known natural predators in US waters. The characteristics of this fish are simply amazing. I am curious to know more about it's physiology and find the ability to vocalize astounding. But this begs the question..If they can make noise can they hear noise? Also, without predators to worry about and armed with all of these enhanced survival mechanisms...how long will they live? Will older fish become food for younger fish as other populations of fish and amphibians dwindle? This post has been on my mind sice I read it, great fuel for thought!

 
At 8:25 PM, Blogger catherineS said...

I recently read an article about snakehead fish in Maryland. That state's Department of Natural Resources has asked for federal help because the snakehead has no known natural predators in US waters. The characteristics of this fish are simply amazing. I am curious to know more about it's physiology and find the ability to vocalize astounding. But this begs the question..If they can make noise can they hear noise? Also, without predators to worry about and armed with all of these enhanced survival mechanisms...how long will they live? Will older fish become food for younger fish as other populations of fish and amphibians dwindle? This post has been on my mind since I read it, great fuel for thought!

 

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