1. Introduction
Exotic species are referred to the species of living organisms when discovered in an alien habitat. These exotic species when harms the ecological balance in their introduced habitat, then they are called invasive species. Channa argus commonly known as northern snakehead are native of China, Korea and Russia (Courtenay and Williams 143). In United States, it was first discovered by a fisherman in a pond in Crofton, Maryland in the year 2002 (Fields 1). It is considered highly invasive due to its harmful impacts on the aquatic ecosystem in the United States. Firstly, these fishes are voracious creatures feeding on smaller fishes, frogs, small aquatic insects, small reptiles and also aquatic fauna when they are young. In short, they eat anything that is caught in between their teeth. Thus they compete with other large predator fishes resulting in the depleting numbers of the desired fishes. It creates a negative influence on the food chains, hence, destroying the balance of ecosystem. They can survive in low oxygenated areas also, thus making them more skilful in adaption in comparison to the fishes like Pike and Bass that are in need of more oxygen as mentioned in the article Channa argus (fish) by Global Invasive Species Database. Channa argus or northern snakeheads grow very large in size and have high survival ability. It has been found that they can stay alive outside water for nearly four days in cold temperature. So, eradicating them from the aquatic world of United States is proving to be difficult. Another injurious effect of this fish is that it carries different kinds of parasites that harm other fishes like crucian carp, salmonids, etc. as mentioned in Channa argus (fish) by Global Invasive Species Database. All these facts when considered together Channa argus steps out as an extremely invasive species.
The Channa argus was found in lower Potomac River in 2004 and after that incident, many snakeheads have been found in ponds of FDR Park, Philadelphia, and Flushing, Queens, in New York, etc. as listed in Northern Snakehead in fishwild.vt.edu. Recent studies have shown that snakeheads has adapted itself in California, Hawaii, Florida, Maine, Maryland, Massachusetts, Rhode Island and Lake Michigan, Chicago as illustrated in the article Injurious Wildlife Species; Snakeheads from Environmental Protection Agency. In order to stop this invasive fish from permanently establishing itself in the introduced water bodies, various equipment and schemes have been launched. Promotion of hunting snakehead fish in Potomac River, or in some places like Ontario, complete ban of live possession or sale of this fish as can be referred in Northern Snakehead in Ontario’s Invading Species Awareness Program are some of the measures taken to check its growth rate. Electrofishing and netting may help in removing a few of these invasive fishes but cannot eliminate their existence completely. The most effective method that has been introduced is the usage of rotenone, an effective piscicide which is found in many plants of bean family like Jicama vine plant available in North America as cited from article Yam Bean or Jicama- A tasty and versatile Permaculture Crop by Lachy. This rotenone is mixed with other chemicals to produce piscicides like CFT Legumine or Nusyn Noxfish (Ott 6). Generally, CFT Legumine is used to eradicate Channa argus completely from a water body. But, this piscicide is toxic to other aquatic habitants as well. Rotenone stops the conversion of NADH to ATP and thus cellular oxygen depletes resulting in mortality (Hayes 144). And an air breather fish like Channa argus can escape the situation if this treatment is done in open environment like Potomac River. Hence, the result will be that the targeted fish survived but non- targeted ones were killed. So, I propose the increase of salinity in water can eliminate this invasive fish from American water.
2. Significance
Rotenone which is established as the only means to diminish the growth of this fish, is very expensive and toxic to other organisms. Therefore, usage of rotenone becomes very complicated. Firstly, this is effective only in closed water body like pond and secondly, there has to be provision to transfer the desired fishes in other place otherwise, most of the fishes will die. Now, instead of rotenone, if simple salt or sodium chloride (NaCl) is used all these drawbacks will be eliminated and it is not a toxic element. The fact is that Channa argus is a fresh water fish and it cannot tolerate salinity as can be referred in All about Snakeheads by Dr. Andrew Lazur in washingtonpost.com. So using salt if salinity of water is increased, then it will result in the death of Channa argus. However, if this is to perform in an open water body, then first the river has to be sectioned and by part the area has to be treated.
Common salt is very cheap and so it will also reduce all the expenses behind the removal of this invasive species. And the water body will remain free of any toxic chemicals. The salinity of open water body will flush automatically so it will not be a problem. Hence, it can be regarded as the safe, cheap and effective means to eliminate this invasive species. If this method can be successfully implemented in a river, then this will help the ecosystem to a great extent. The mass killing of all the aquatic organisms in order to eradicate only one targeted invasive species can be stopped. From many years, an alternative to rotenone that will be less expensive and less toxic to other organisms is being ferreted. And this may turn to be that alternative. This is effective in closed water body but its proper implementation in the open water surface needs to be tested. Although one notable point is that the impact of the salinity of water on Channa argus depends on the temperature also.
3. Hypothesis
Northern Snakeheads or Channa argus is a fresh water fish, hence it cannot tolerate salinity in water. My aim is to show that this invasive creature can be removed by adding common salt in water instead of using any toxic piscicide or any other complicated method. Rotenone is most commonly used piscicide. In comparison to rotenone, the availability of common salt is more and toxicity is negligible. Hence, only the targeted species can be destroyed while ensuring the safety of the rest species. In this method, the temperature plays an important role. At lower temperatures, approximately below 20 C, this fish develops a resistant against salinity in water. Along with that the amount of salinity in water will also influence on the time required for the death of this fish. This fish has very efficient survival tactics and always appears immune to most of the adverse conditions. May be this is one of the reasons that it was able to grow and reproduce in a different habitat also despite all the challenges. These fishes remain a little bit sensitive during the breeding period and that time may be the perfect time to implement this hypothesis into action. The salt content in different water bodies varies and according to the percentage of salt in water, the type of water is determined. A list of the percentage of salt in varieties of water bodies is displayed below in the table.
