Aquatic Invasive Species

Reading the four articles, especially the Mute Swans article, got me thinking about the definition of invasive species. While the ecological definition of invasive species is relatively well defined (“non-native species of plants or animals that out-compete native species in a specific habitat” from http://www.floridasprings.org/glossary.html), I feel that that the qualities that label a species as “invasive” and offensive by the public are much more vague.

The Mute Swans, for example, are scientifically an invasive species. The species was first introduced to the East Coast from Europe and Asia in the early 1900’s, when they were imported as decorative birds for parks and estates. Wild Mute Swan populations increased drastically in the Chesapeake Bay in the 1980’s and 90’s, as they out-competed native species for food and habitat. Legislation was passed in 2000 to control the swan population. There has, however, been public opposition to killing the mute swans. The article from class mentioned the “deeply divided” state panel, and the opposition from animal rights groups.

Mute swans pose just as great a threat to native species as snakeheads or didymo, but the opposition to swan population control in the Chesapeake made me wonder why there were no similar movements for these species. I guess the fact that swans are more aesthetically pleasing (as opposed to http://www.mountainmurmur.com/wp-content/uploads/2008/11/didymo-mararoa_s1.jpg) does influence public opinion on how comparatively “invasive” species seem, since noone wants didymo in their water. I’m sure there are many other invasive species that drastically disrupt native ecosystems and completely drive away certain species, but we don’t make a big deal about them because we are okay with having the invasive species around. There are factors (economic or aesthetic) other than endangering native ecosystems that the public takes into account when we decide whether a species is “invasive” and should be eliminated, or if nature should be allowed to run its course.

http://news.nationalgeographic.com/news/2003/06/0605_030605_muteswan.html

http://www.chesapeakebay.net/muteswan.aspx?menuitem=16930

The Muting of the Swans (SW1)

By: David Lung

Cygnus olor, or commonly known as the mute swan, originally came from much of Europe and Asia, but was introduced into North America where it was presented for its ornamental value in parks, zoos and private estates. A few escaped in New Jersey and New York in 1916 and 1919 respectively. They can grow up from 4-5 feet tall and weigh up to 30 lbs. Adult swans are white with orange bills that have a characteristic black basal knob. They lay up to 10 eggs and guard their young vigorously. There are few natural predators of mute swans and only attack cygnets. They often avoid attacking when adults are present, leaving many mute swans to grow to adulthood. The mute swan can be seen from Southern Ontario all the way to North Carolina and has been a symbol of love, grace and beauty for many people in the United States. However, its aesthetic appearance does not coincide with the mute swan’s image. The mute swan feeds heavily on submerged aquatic vegetation (SAVs), which causes many problems for the survival of these SAVs as well as the survival of young animals such as crabs and fish that use the SAVs as shelters before they can live on their own., The Rhode Island Department of Environmental Management (RIDEM) and the University of Rhode Island have observed that areas where mute swans feed have a 95% decrease in the biomass of SAVs. The mute swan also is aggressive towards native species such as the loon and tundra swan, driving many of these birds away from their original nesting grounds, resulting in a decline in these native species’ breeding frequency and ultimately a decline in their population. The mute swans also affect humans. Mute swans also will attack humans who get close to their breeding grounds as well as potentially contaminate our drinking water supplies when they defecate into the water. The contamination will also add excess nutrients into the water, causing algal blooms which will result in problems for many organisms in that aquatic ecosystem such as a decline in the rate of photosynthesis and oxygen reduction in the water (suffocation of fish and other aquatic organisms).

There are many methods employed today to control the mute swan’s rapid population growth such as egg addling (coating eggs with oil to prevent their hatching), relocation, and killing of adult birds. Most states allow the mute swans to be hunted. Animal rights groups have tried to limit the killing of adult birds by trying to get state governments or the federal government to protect the birds, but they have not been successful because of a general agreement that mute swans have a deleterious effect on aquatic ecosystems that impact the organisms in them and also humans. In the article Maryland panel members John Grandy and Joseph Lamp asked for proof that the elimination of mute swans would help the recovery of SAVs, but with the RIDEM and University of Rhode Island’s findings on the effect of mute swans on the population of SAVs, it is clear that the mute swan population must be controlled.

The mute swans, despite my own personal admiration of swans, are detrimental to aquatic environments in North America. They disrupt the breeding patterns in these aquatic ecosystems by driving out native waterfowl, damaging their breeding grounds and leaving young organisms vulnerable by consuming large amounts of SAVs that provide shelter for them before they fully mature. They also might potentially disrupt the food chain of these ecosystems as they reduce the SAVs and other vegetation drastically and harm other organisms. Mute swans are also a danger to humans by contaminating our water supplies and attacking humans whenever we are around their breeding grounds. I support most measures to reduce the population of mute swans. The claims in the article concerning breaking the necks of mute swans is too drastic, but continuing to coat their eggs with oil and shooting them is acceptable since both are effective methods to managing the mute swan population. However, should the swans be completely eliminated or just be controlled? Humans brought the mute swans to North America, hence it is not natural for them to be here and natural selection does not apply since it only works in a population, not in an entire ecosystem. In the controlling of populations, why are animal rights groups not on board with the process? Although systematic elimination of mute swans is unfortunate, it is for the greater good since many other organisms would benefit from it. Animal rights groups seem to be more of a hindrance and blind to the fact that many organisms are also being harmed as long as the mute swans are present. Because there is so much admiration for the mute swans, should the federal government also get involved in the efforts to relocate the swans rather than killing them? Relocation is expensive, but the federal government could provide substantial aid in helping to reduce the costs, even though there may be opposition from voters who do not want to see their tax money being used for it.

Sources:

http://www.bioone.org/doi/abs/10.1656/1092-6194%282003%29010%5B0305%3AMSCOIO%5D2.0.CO%3B2

http://www.dem.ri.gov/programs/bnatres/fishwild/pdf/muteswan.pdf

http://www.mdsg.umd.edu/issues/restoration/non-natives/workshop/mute_swan.html

http://www.dnr.state.mn.us/invasives/terrestrialanimals/muteswan/index.html

http://www.washingtonpost.com/wp-dyn/content/article/2009/05/15/AR2009051501258.html