The northern snakehead (Channa argus) is a delicacy in its Asian homeland. In the United States however, it is a highly feared invasive species whose spread has not been successfully slowed. When the snakehead first emerged as an ecological threat in 2002, media reports first described the fish as being capable of surviving weeks out of water and walking miles from one body of water to the next. In reality, the snakehead’s unusual physiology allows it to survive approximately one day on dry land, possibly up to four in moist muddy areas. Furthermore, it is the more mundane aspects of this species’ life history, and not the biological rarity of being able to breathe both underwater and on land, that make it such a nuisance species.
Snakehead are efficient carnivores whose group hunting tactics can rapidly deplete native fish populations. However, more important to their spread throughout the United states is their ability to tolerate a wide range of water temperatures. This general diet and wide thermal tolerance have led some experts to estimate that the northern snakehead could invade all of the lower 48 states.
Current efforts at controlling snakehead populations focus on the use of piscicides (poisons designed to eradicate fish) to wipe out the invasive species. The current piscicide of choice is the toxin rotenone, which is derived from the jicama plant. Rotenone is 100% lethal to the northern snakehead; however it also kills all other fish in the target area and is rather expensive. This combination of collateral environmental damage and high cost is what led Duke University research Evan Schwartz to try and develop alternative piscicides for use in slowing the spread of the northern snakehead.
Schwartz and his team of researchers are looking at three new toxins obtained from other plants with known poisonous properties (Nerium oleander, Canabium sativum, and Strychros nux vomica) to determine if a cheaper, and greener, piscicide can be produced. Their research will include expansive field testing that compares the efficacy of these newly derived poisons to that of rotenone as well as other control techniques such as electro-shocking and netting. Schwartz says that his research should pose little threat to surrounding populations because rotenone decomposes in sunlight and is also inherently less toxic to humans and other mammals.
From these field experiments, Schwartz hopes to assemble data on how each of the new plant-based toxins compares to rotenone in terms of both snakehead mortality as well as the effect on the native fish populations. Ideally, one of the tested poisons would retain the same high lethality towards the snakehead as rotenone, but would cause much less collateral damage to the native species. Yet, this is unlikely and so a more realistic outcome would be to find a plant based poison with both positive and negative effects similar to rotenone that can be more cheaply produced. This would allow for the broader implementation of snakehead control policies throughout the contiguous United States, hopefully leading to a halt of the spread of this aquatic invader.