North American Journal of Fisheries Management dio: 10.1577/M05-074.1 (2006)
In an attempt to eradicate the invasive Northern Snakehead from Maryland waters, state and local government agencies have been adding the toxin rotenone to the invaded waters. This practice is outline in Andrew Lazur’s study, titled Acute Toxicity f 5% Rotenone to Nothern Snakeheads. After adding rotenone into local ponds to levels at low as .075mg per liter of water, there was a 100% mortality rate among the Northern Snakehead within 1 hour. Ultimately, 8 adult and 834 juvenile dead Snakheads were collected from the lake. However, this effective solution has a severe downside: nearly 500 kg of native fish were also collected. This study concluded that the use of the toxic rotenone is an extremely effective solution to ending the ecological threat that the Northern Snakehead presents.
The Flathead Catfish, native to the Mississippi and Ohio River watersheds, is known to significantly disrupt the balance of aquatic ecosystems when released into a non-native habitat. The fish prefers deep lakes and rivers where it can cover itself with submerged logs and protect the eggs deposited by female flatheads. Due to its sheer size (record is 124 lbs.), its frenzied feeding habits, and its ability to swim long distances in a short period of time, the Flathead Catfish has quickly become known to cause severe problems to its foreign habitats such as threats to biodiversity, human health risks and negative economic impacts.
First sighted in the Delaware River watershed in a reservoir in 1991, the species rapidly spread to the greater Delaware River near towns of Roebling, NJ and Philadelphia, PA. The fish has greatly multiplied its populations, especially in the Schuylkill River basin, which bisects Philadelphia. Due to its rabid eating habits, the flathead has severely decreased food supplies and forced the native fish species to starve or find new habitats. In recorded instances in Georgia and North Carolina, the flathead has totally wiped out the native catfish, as well as turned its appetites towards crayfish, crabs and shad.
The flathead’s feeding habits directly relates to the economic problems it creates, such as negatively affecting the blue crab industry predominate in the Chesapeake Bay area by preying heavily on the coveted crabs. In addition, the aquatic invasive species is known to accumulate toxins like PCBs to such an extreme that Pennsylvania strongly advises its residents to not consume more than one flathead meal per month. In order to prevent further proliferation of the flathead problem, states affected by the intruder like Pennsylvania, New Jersey, Delaware and Maryland have advised fishermen to not release flathead catfish caught in the Delaware or Susquehanna river watersheds.
I believe these states are approaching the problem of the flathead positively by commanding fisherman to not release the fish back into the waters. However, I wonder if there are even more aggressive means to which the flathead could be eradicated from the Delaware River watershed. Perhaps if there was a massive, synchronized movement to take nets throughout the Delaware River watershed and separate native fish from the flatheads caught, and then turn over the flatheads to the state’s Division of Wildlife, a large portion of the invasive species could be removed from the rivers and streams. This leads me to my question of what would happen to the fish once the Division of Wildlife would acquire the fish—would they release them back into their native waters? Or simply dispose of the flathead catfish?
The Northern Snakehead, or Channa argus is an exotic fish native to China and other parts of Asia. It is speculated that this breed of fish was introduced to the Chesapeake Bay area and other waterways along the East Coast through release from the fish market or pet aquariums. For ordinary fish, this would not be an overwhelming problem; they would probably succumb to their surroundings. But, the C. argus species is clearly dominant over all other fish. With its sharp teeth and growth up to 47 inches and 15 pounds, the Snakehead has been described as a “voracious top-level predator.” This means that it is at the top of the food chain in bays, ponds, and lakes, thus posing a serious threat to local fish populations. On top of this, the Northern Snakehead apparently has the ability to move short distances on land to other bodies of water.
The species was first caught in Crofton Pond, USA near Washington D.C. in 2002. Since the pond was in Maryland territory, the state government took action to poison the pond to prevent the uprising of this foreign fish. Even after this isolated incident, there have still been finds of the fish. 2 years later, in Wheaton Regional Park, Maryland, a very surprised fisherman landed a 19 inch Snakehead. The lake that it was caught in was soon drained. Still, another was caught in 2007 in Lake Wylie, North Carolina. I think that the Northern Snakehead is a serious threat to the water ecosystems of North America. More action should be taken in preventing them from entering our waters in the first place. Zoos, aquariums and wildlife agencies could buy overgrown fish from owners. Preventative measures are one possible solution to reducing Snakehead finds and protect indigenous ecosystems in the future.
image obtained from http://www.rivervalleynwc.com
The Chinese Mitten Crab first arrived on the shores of North America in 1965. One crab, found in Ontario, resulted in widespread discussion throughout the country because no one wanted to see it spread. Unfortunately, it spread and they can be found in California, Maryland, New York, and most recently, New Jersey. In these states the crabs have caused many problems, i.e. clogging San Francisco’s water system, and now that New Jersey has become the next victim, fisherman have begun to panic. According to Gregory Ruiz “40 crabs have been caught, reported and confirmed in New Jersey alone, making that state ground zero right now for mitten crabs.” The state is trying to do whatever it can to contain the population, asking all residents to try and capture any specimen they encounter to prevent reproduction. New Jersey Division of Fish and Wildlife is trying to stop the spread now because the females can produce up to 1 million eggs per reproductive cycle, and that would not end well for New Jersey’s aquatic and marine ecosystems.
The urgency with which the state is trying to address the issue is completely rational. Hopefully New Jersey can manage the situation without it getting too out of hand. These crabs can cause serious issues to ecosystems because they are omnivores, and therefore prey on a multitude of organisms. Aside from the organisms, the crabs have destroyed the physical ecosystems in their previous homes when they burrowed into the walls of riverbanks, causing erosion. Despite Jew Jersey’s efforts, its plan is flawed because it relies so heavily on assistance from civilians. To many people the idea of seeing a live crab disturbs them, but to capture one is in a league of its own. Therefore, I believe that New Jersey should continue to encourage people, but try to unite with other states that have this problem so there can be a joint effort. Also, some people tend to work harder if there is some sort of incentive. Perhaps if a small reward were offered per crab, more people would try to catch them in hopes of profiting. In general, I just want this problem to be handled so that my home, New Jersey does not face any irreversible repercussions.