Aquatic Invasive Species

Myriophyllum, more commonly known as “water milfoil”, is an aquatic invasive species originating in Eurasia. This species has recently been discovered in some of the rivers that run through the Adirondacks, very popular spots for fly-fishermen. The most reasonable explanation for the migration of this species from the Eastern to the Western hemisphere is that of ballast-water transportation. Before embarking on a journey, large ships take in a certain amount of water called “ballast water”. This water is used as a type of counterweight – the addition of it to the ship’s weight helps to stabilize the ship and provide proper buoyancy. Upon reaching their destination, these ships release this water into the surrounding bay, dock, inlet, etc. Biologists have concluded that this is the most justifiable reason for the discovery of water milfoil in the United States – particularly the New York area, as it is such an epicenter of the coming and going of ships. One way environmentalists are attempting to reduce the water milfoil population in upstate New York water parks is with devices called “benthic barriers”. This form of eradication is fairly simple – gigantic plastic sheets are taken to the bottom of the lakes and pinned down, covering water milfoil colonies. This prevents sunlight from reaching the plants, and eventually leads to their death. Another method is called “biocontrol”, where certain fish and small marine life are introduced to these ecosystems in order to feed on the watermilfoil population and keep it under control. A curious fact about these plants is that it is seen as a valuable source of biofuel, especially in our day and age where everybody is struggling to “go green”. The battle of whether to kill off milfoil or to try and control it for human use is currently underway.

The mute swan – generally seen as a majestic creature and one that inspires peace and tranquility, this large waterfowl is not understood to be an aquatic invasive species by most of the general public. What makes this bird so destructive? It is typically known as one of the most aggressive species of waterfowl, and it consumes large amounts of underwater vegetation. This vegetation is important to the rest of the ecosystem in that it helps to hide baby crabs, fish, etc. who need the protection of the grass before they are big enough to make it alone in open water. This over consumption of underwater grasses is leading to a decline in those native populations, and a 10% increase in mute swan populations every year (meaning that the population doubles every 7 to 8 years). Right now, officials in the Maryland/Chesapeake Bay area are considering several methods for the reduction of the mute swan population. The least violent of these methods is a process where mute swan eggs are covered with oil which prevents them from hatching. Although reluctant to resort to such a measure, killing the swans (either by shooting or breaking their necks) is provided for as a last resort option. While animal rights activists claim that the mute swans do not have a great effect on bay grasses, studies have shown that the average adult mute swan eats up to 8 lbs of bay grass every day.

Although I could not find any direct information on aquatic invasive species in Texas, I did find this interesting website that lists many of the invasive species found in the state. Some of the more unique ones are electric eels, freshwater sting rays, and piranhas.

http://www.tpwd.state.tx.us/huntwild/wild/species/exotic/

http://en.wikipedia.org/wiki/Mute_Swan#Distribution_and_habitat

http://en.wikipedia.org/wiki/Myriophyllum

Rusty Crayfish

First discovered in 1960 in a Minnesota lake, Rusty Crayfish have since spread to lakes in over seventeen states in the United States Midwest and parts of Canada. The fact that these Rusty Crayfish are not originally native to these Midwestern lakes creates quite an unsavory predicament for the native marine life, mostly due to the Rusty Crawfish’ aggressive invasion tendencies. Rusty Crayfish tend to displace other native crayfish species, but they also harm native fish populations by feeding on their unhatched eggs which lie at the bottom of the lakes. Finally, these pesky crustaceans also severely reduce the amount of aquatic vegetation in lakes.

Although not confirmed, the spread of Rusty Crayfish is believed to be linked with careless anglers who dump their bait buckets or do not pay attention to what live bait they are using. Even transferring only a few Rusty Crayfish can be detrimental to a lake’s ecosystem, since females can carry both fertilized eggs and male sperm. This means that feasibly all that is needed to start a new population of Rusty crawfish is a single female. There have been attempts however, to regulate this spread stemming from when the species was declared a regulated invasive species, simply meaning that the spread of Rusty Crayfish into the wild is illegal.

Although Rusty Crayfish are very harmful to native Midwestern lake ecosystems, many strides have been made in legislature to control the population. Starting with declaring Rusty Crayfish to be an official regulated invasive species, it is now illegal to spread Rusty Crayfish into the wild and even simply sell them as live bait. Of course, some penny-pinching fisherman will still inevitably opt to use live Rusty Crawfish as bait, which is why it would probably be a good idea to start cracking down on the bait industry to make sure all live bait is regulated and Rusty Crawfish-free. In terms of getting rid of the current infestation of Rusty Crawfish inhabiting lakes, a few options are available. Some suggest the use of chemicals to kill the invader, but nothing has yet been discovered that kills the Rusty Crayfish that doesn’t also kill native crawfish as well. Interestingly enough, it was once actually proposed to use the invasive Rusty Crawfish to regulate the population of the also invasive Eurasian Watermillfoil, but this idea was swiftly turned down. The best option, it seems, would be to ask fishermen to use Rusty Crawfish in lakes where they have already established a home in as bait whenever possible. While this method will definitely not eradicate the population, it will surely prove to be damage-control at the very least, most likely protecting many native aquatic plants and animals.

Sources

http://www.dnr.state.mn.us/invasives/aquaticanimals/rustycrayfish/index.html

http://www.seagrant.umn.edu/ais/rustycrayfish

http://www.seagrant.umn.edu/ais/rustycrayfish_invader

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

Eurasian Watermilfoil has been crowding out species native to the Americas for some time now; its estimated introduction to our continent is 1900. Its introduction may have been caused by its survival in a boats ballast water or the aquarium trade, and its spread is significant due to its reproduction through stem fragmentation. A colony of watermilfoil gets tangled on boat, and stems of the plant are consequently transported.

This invasive species out competes native flora, causing an imbalance in the natural lake ecosystems throughout America. Specifically, watermilfoil tends to dominate nutrient-rich lakes, having less of an impact on ones lower in nutrients. Watermilfoil threatens such ecosystems by dominating the lake surface and encroaching its shallows. This is certainly concern for the native flora, but as for us, the nuisance of thick, ugly vegetation is its only imposition. Therefore, the question is whether the removal or containment of eurasian watermilfoil is worth the money it costs, whether it is our duty to protect the native species.

http://www.invasivespeciesinfo.gov/aquatics/watermilfoil.shtml

http://www.great-lakes.net/envt/flora-fauna/invasive/milfoil.html

WATER PRIMROSE

Although the yellow flowers and green leaves of the water primrose (Ludwigia hexapetala) seem harmless, the native of South America has become a growing problem within the waterways of South Carolina, and is now included on the state’s list of aquatic plants illegal to own, import, or sell within the state. Distinguished by showy its yellow flowers and a tendency to form dense mats along the edges of bodies of water, the plant spreads both through fragmentation and transport and through the production of seeds. The former method, coupled with its fast growth, adds to its threat as an invasive species. If a piece of water primrose breaks and attaches to a boat or animal, it can then be transported to other bodies of water that were previously uninfected. In its new environment, the plant can spread and form a new mat, which often out competes native species for sunlight and space and can sometimes quickly destroy the ecological diversity of a lake or stream.

Similar to some other aquatic invasive plant species, water primrose can spread from place to place relatively easily through human and animal activity and is difficult to control. However, according to the State of Washington Noxious Weed Control Board, physically removing the plant or covering it with material that prevents sunlight from reaching the plant may be effective ways of slowing its growth and controlling populations. However, physical solutions are costly and not always effective, since the plant grows quickly and can reclaim a body of water within weeks if specimens are left behind. Chemical methods could potentially harm native plants as well as the target species, despite their attractiveness and apparent ease of use. Prevention is therefore the best method of controlling water primrose’s spread. Encouraging (or even requiring) boaters and fishermen to remove the plant from their boats, ballast water, and lines could spread non-animal transport of plant fragments to places that were previously not infested.

The problems of the water primrose are similar to other problematic species. It is aggressive, and spreads easily from one habit to another. Based on the states of Washington and South Carolina, the best method of preventing the plant from taking over native habitats seems to be preventing its spread and establishment. Once it takes over, the plant is nearly impossible to control. Although use of herbicide seems like a simple solution, it is fraught with problems. A herbicide (like Rodeo) effects not only non native plants like water primrose, but also native plants that are already being out competed by invasive species. Also, plants can form a resistance to herbicides over time, leaving the ineffective. This leads to a series of questions. First, is it possible to tailor an herbicide to specifically target water primrose? This is probable, but leaves other questions. Would a tailor-made herbicide be both economically feasible and non harmful to other parts of the aquatic environment? This second question is improbable. New herbicides often have unforeseen effects on the environment as a whole, and may or may not be effective. Means of preventing the spread of water primrose are also problematic. Although the plant is classified as illegal to possess in the state of South Carolina, departments like Natural Resources are often under funded, leading to problems with enforcement. Without enforcement, the law means little. The plant will still spread regardless of regulations. Voluntary measures like cleaning the bottoms and ballast areas of boats are also encouraged, but have the same problem. There is no extrinsic incentive for most boaters and fishermen to go to the trouble of removing the plant. Until there is more of an incentive to comply with these suggestions, there will be little hope in controlling the spread of water primrose.

http://www.ecy.wa.gov/programs/wq/plants/weeds/waterprimrose.html

http://www.dnr.sc.gov/invasiveweeds/primrose.html

http://plants.usda.gov/java/profile?symbol=LUGRH

http://www.ecy.wa.gov/Programs/wq/plants/plantid2/descriptions/ludhex.html

http://www.nwcb.wa.gov/weed_info/Written_findings/Ludwigia_hexapetala.html

The Chinese Mitten Crab (Eriocheir sinensi) is a textbook example of an invasive species that has a presence much more appreciated in it’s native habitat. Originally introduced to North America in the early 90′s, this species had slowly spread across the California region of the Pacific coast and the San Francisco Bay area. Speculation is that these crabs were first introduced on purpose. This is likely considering the actual value of these crabs in certain areas. There is also the possibility that the crab was introduced via ballast water from it’s native region, eastern Asia. The Chinese mitten crab acts as an invasive species by competing with the local fauna for resources. Being a burrowing species, they can also cause property damage, weaken embankments and clog infrastructural systems. The presence of these crabs could also interfere with the native crab fisheries, lowering income and posing pecuniary problems to the companies involved. There is no conclusive evidence that shows the crab will impact these fisheries negatively, but people are still concerned. In most of the areas in the US, owning, transporting or dealing in live mitten crabs is illegal. In California, mitten crabs are fair game fish, but under strict regulation.

While it is illegal in the US, people in China usually can’t possess this crab for an entirely different reason: it is prohibitively expensive. The Chinese mitten crab is considered a delicacy in Shanghainese cuisine and ordinary citizens shell out ridiculous sums of money in order to get their hands on a tiny, palm-sized specimen. Seeing as how this crab is one of foods that Anthony Bourdain sampled when he traveled to Shanghai for No Reservations, one can easily imagine the regard to which it is held by the native population. Perhaps the greatest irony is that the most prized part of the crab is the roe and the ovary. In the United States, the roe and ovaries of the crab are why we detest it. Across the ocean, the roe and ovaries are instead the reason for its lofty price. Considering this, I think the solution to the invasion is to develop a taste for the crab, like the Chinese have. With a market behind it, seafood companies will have more reason to invest time and money in catching and selling the delicious crab. The American public gets exposure to something new and the crab will no longer have a rampaging population. A rare instance of capitalism working in tandem with environmentalism.

http://www.dfg.ca.gov/delta/mittencrab/life_hist.asp

http://www.wsg.washington.edu/mas/ecohealth/invasive_crabs/mitten_crab.html

http://www.iisgcp.org/exoticsp/Chinese_Mitten_Crab.htm

The Eurasian watermilfoil has spread far and wide since its initial introduction to the United States. This non-native species can now be found in forty-six out of fifty states, and carries with it effects ranging from undesirable to ecologically threatening. The most prominent of these problems is the “crowding out” caused the watermilfoil’s overgrowth in an area. The plant will block sunlight and otherwise compete with native species in a given body of water, using its ability to create densely infested areas to its advantage. Other issues are related to human use of the water in question, as watermilfoil can make boating, swimming, or fishing nearly impossible.

While it may sound selfish, the effects on human recreation are what interest me the most. As a lifeguard in a pond with a watermilfoil problem, (there is water chestnut as well, but this problem is under control) I have seen the impacts of watermilfoil first hand. The effects on pond use are twofold. First, there are the obvious problems related to human use of the water. Children who may be scared of the water already will refuse to swim because they are scared to touch the watermilfoil under water. Canoeing and kayaking is severely limited in certain areas where boats become ensnared and paddling becomes difficult. Even the fishing population is effected, as fishermen cannot cast a line in large portions of the pond without hooking a watermilfoil stem.

The second set of issues are concerned with the economics of limiting an invasive species. Even considering the above problems, the watermilfoil infestation could be much worse in this pond. It is limited by constant and expensive vigilance on the part of the town, which devotes a large amount of resources to pond maintenance. First, they must pay for the daily operation and maintenance of a weed harvester, essentially a large boat that serves as an underwater lawn mower. Also, netting is laid down in shallow areas each year to try and restrict growth of the watermilfoil. Finally, lifeguards spend a significant amount of time manually uprooting the plant in swimming areas. As a consequence, the town pond runs each summer in the red, losing money in order to preserve the use of the water while it still can. In today’s economy, this level of spending does not look good to town officials, and accordingly the pond is facing budget cuts in the upcoming summer.

NOTE: the last link below is an old version of the pond’s contingency plan for the watermilfoil if you are interested in learning more.

http://el.erdc.usace.army.mil/aqua/apis/PlantInfo/plantinfo.aspx?plantid=33

http://www.lakegeorgeassociation.org/html/eurasian_watermilfoil.htm

http://www.morsespond.org/studies/2005_weed_harvesting_wagner.htm

The green porcelain crab (Petrolisthes armatus) is a small tropical crustacean that has advanced up the eastern seaboard of the United States since 1990.  Commonly found in the oyster reefs of the South Atlantic Bight, the porcelain crabs appear to be having mixed effects on native species.  Recent research at the Georgia Institute of Technology has demonstrated that the porcelain crabs do not directly prey upon oysters, in fact, they seem to promote the survival of juvenile oysters.  This is due to the fact that the native predators of juvenile oysters appear to prefer porcelain crabs, thus possibly simultaneously increasing the predator population and reducing the predation of juvenile oysters.  However, this positive effect for the oyster population is at least somewhat mitigated by the fact that the researchers also found that the presence of porcelain crabs suppressed the growth of juvenile oysters, supposedly through competition for food as both species are filter feeders.  In light of these conflicting effects, further monitoring and research of the porcelain crab is necessary to ascertain the long term effects its arrival will have for the ecosystems of the southeastern United States.

Due to their roles as nurseries for many species, oyster reefs serve as the foundation of the marine ecosystems of the southeastern United States and so any threat to this valuable habitat warrants serious investigation.  One source of danger is that the green porcelain crab appears to be a preferred prey option to many common native predators of oysters. This could lead to an ecological disaster if the porcelain crab suddenly died out and the increased predator population reverted to its traditional prey.  Also, if the green porcelain crab is truly slowly the development of juvenile oysters, this will have important ramifications for the commercial fishermen who harvest oysters.  As noted in the article, too little is presently known about the long term effects of the green porcelain crab to determine if it poses a significant threat.  However it should be noted that despite the heavy predation, green porcelain crab populations in its new range exist in densities far in excess of what has been observed in its native habitat.  This suggests that ecological management of the green porcelain crab will be costly and difficult should it become necessary to protect the valuable oyster reef ecosystems of the southeast.

Weblink: http://newswise.com/articles/view/533029/

Eli Wilber

With their elegant-shaped necks, and snowy white feathers, mute swans are arguably one of the most beautiful birds in America. Especially in the Chesapeake Bay, they have become a common vista for travelers and the inhabitants of that area. It is therefore surprising to find that the mute swans are an invasive species to the area and are on a warpath of destruction that is reaping havoc on the habitats of indigenous species. Mute swans were introduced to eastern United States when five “lawn-ornament” swans escaped from an estate. Since then, the population has bloomed from the original five to a peak of four thousand. The swans feed on shallow-root grasses that are the safe-haven for young crabs and fishes. Each swan can consume up to 8 pounds of bay grass each day, accumulating to 10.5 million pounds for the entire population. Also, mute swans are extremely territorial, and will trample over nests of endangered native bird species, e.g. least terns (Sterna antillarum) and black skimmers (Rynchops niger), etc.

Currently, measures are being taken to shoot down a quota of swans and addle their eggs with vegetable oil so that the eggs won’t be able to hatch. Though such dealings to appear to be a bit severe, they do appear to be necessary to control the mute swan’s exponentially expanding population. I think because of the extent to which muted swans have already disrupted the environment of native species, it is necessary to shoot down swans in attempts to control the population. However, because of how much mute swans have become part of the milieu in the Chesapeake Bay area, we should take caution from killing too many swans and from wiping them completely out of the area.

After all, what is an invasive species? All animals eventually will migrate from one place to another; the world is in a constant flux. Humans are merely facilitating the process. What difference is human-introduction of a species to a new area and natural migration? Over time, according to Darwin’s theory of evolution, the newly introduced will eventually adapt to the environment and become the indigenous. Therefore, though this isn’t what I actually believe, given Darwin’s theory of natural selection, is it even necessary to attempt to control the mute swans’ population? Maybe the endangered indigenous species are too evolutionarily weak and the swans are there to place a stressor on them so that they can evolve into a stronger species. But then that question doubts the concept that endangered species need saving.

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

http://www.njaudubon.org/SectionConservation/ThreatenedandEndangeredSpecies.aspx

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

http://somd.com/news/headlines/2009/10085.shtml

With their striped coats and long yet poisonous fins, Red Lionfish make an exotic aquarium specimen. However, they have recently been spotted in record numbers in the Caribbean Sea and as far up the Atlantic coast as New York. They are tenacious creatures, constantly swimming and feeding off the smaller fish that keep seaweed growth in check. They have few, if any, predators. Sharks appear to be reluctant to eat them, and although Red Lionfish move slowly, they usually swim just deep enough so that they can’t be caught using nets. In short, Red Lionfish can be extremely disruptive to the reef ecology along the Atlantic coast.

Red Lionfish were originally found in southeastern Asian waters, but it is believed that they were accidentally released into the Atlantic Ocean after a hurricane destroyed part of a Florida aquarium in the early nineties. They were spotted swimming in nearby waters a few days later. What I do not understand is why they did not initially recapture the fish when they were spotted. The aquarium officials even knew that they were only missing six fish. In any case, I think it is fascinating to see how such an exotic fish can be so adaptive in a new environment literally half a world away.

My parents used to take me to Asian farmers’ markets when I was little, and while most children press their noses on the windows of candy stores, I vividly recall pressing my nose on the glass of the seafood tanks at these farmers’ markets in Georgia. There were so many unusual creatures: squids, frogs, and sharks. I am not absolutely sure, but I think I might have also seen Red Lionfish on display in one of the tanks. I remember the same peacock-like fan of reddish brown spikes.

I think that one way to control the Red Lionfish would be to eat it. They are a delicacy in their native homeland and people in the Huffington Post article claimed that Red Lionfish taste a bit like halibut. If Americans could develop a taste for Red Lionfish, this would be a viable and not to mention delicious solution.

Frank Chang

Sources:

http://www.huffingtonpost.com/2008/08/18/red-lionfish-invade-carib_n_119521.html

http://www.shellfish.uga.edu/invasive%20webitems/Educational%20materials/Booklet%20Proof%20minus%20blank%20pages.pdf