Invasive Species

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Invasive species is the term used to describe plants and animals introduced to new areas where these same species do not belong.  The introduction of invasive species has been a problem for as long as ships have been traveling the seas.  Both plants and animals from land and sea are moved in, on and under ships from their existing habitat to new areas where they can become an invasive species. When these foreign species are introduced into a new habitat and environmental conditions are favorable, these non-indigenous species become established. They, in turn, can compete with or prey upon native species of plants, fish, and wildlife. They may also carry diseases or parasites that affect native species because they have no resistance. This can disrupt the aquatic environment and economy of affected near-shore areas.

Most of the invasive species are introduced from shipping ballast tanks which provides balance and weight to ships when they are not carrying full cargo loads. It can contain a wide variety of microscopic marine life including eggs, cysts, larvae, and bacteria. Global shipping now moves about 80 percent of the worlds' commodities, making this phenomenon a grave threat to all marine environments. "Every assessment indicates that the rate of marine introductions in U.S. waters has increased exponentially over the past 200 years and there are no signs that these introductions are leveling off. New introductions are occurring regularly on all coasts, producing immediate and damaging impacts, and leading to millions of dollars in expenditures for research, control, and management efforts. In the San Francisco Bay alone, for example, an average of one new introduction was established every 14 weeks between 1961 and 1995" (Carlton, J. T., 2001, abstract)

It is estimated that there are hundreds of invasive species within U.S. coastal waters and that they may cost the U.S. hundreds of millions of dollars each year. On average, some two million gallons of ballast are released into U.S. waters alone each hour, resulting in the introduction of potential invasive species. "It has been estimated that exotic species that become invasive cost the United States $137 billion annually… more than earthquakes, floods and fires combined." (Goldsborough, William J., 2003).

Shipping is not the only way in which invasive species are introduced. Marine debris can also allow non-native species to travel great distances where they can eventually be introduced into a new area. The slow rate of travel associated with slower environmental changes can allow the transplanted plants and animals to have a high survival rate. In a survey of some 30 remote islands, David Barnes of the British Antarctic Survey in Cambridge, UK, found that human debris and litter had more than doubled as a vehicle for marine organisms to transport themselves to remote lands. Barnes is further quoted as saying "I estimate that rubbish of human origin in the sea has roughly doubled the propagation of fauna in the subtropics and more than tripled it at high (> 50°) latitudes, increasing the potential for alien invasion and adding to the problems already created by sea-borne plastic materials in the form of injuries and mortality among marine mammals and birds." (Barnes, D. K. A., 2002)

A more recent cause of invasive species problem has been practices within the Aquaculture industry.


The Aquaculture industry

During the last generation as the human population increased, our demand for fish has grown tremendously.  The commercial fishing industry has been able to meet this demand by creating better fishing techniques. We have now reached a point when the demand is so high and the technique so effective that many ocean areas have been over-fished and are now depleted of the fish quantities that are sufficient to meet the growing demand (more information). 

One potential solution to this problem is aquaculture (see picture below courtesy NOAA). Aquaculture is quite simply the production of fish and other aquatic species by using farming techniques. This method of supplying fish has, in recent years, been growing at a tremendous pace.  "Aquaculture is now one of the fastest growing sources of protein, expanding at 10 percent per year. Output more than tripled between 1984 (the first year global aquaculture statistics were compiled by FAO) and 1996, from 7 million tons worth $10 billion, to 23 million tons valued at $36 billion. Today, one out of every five fish consumed comes from the farm." (The Worldwatch Institute, 1998). 


While this could be a sustainable method of meeting the seafood demands of the exploding human population, it to date has shown to have some serious problems;


    • There have been many large scale escapes introducing hundreds of thousands of farm- raised fish into the wild. In one single incident in 2000, the population of salmon in Maine was elevated by 1000 times when approximately 100,000 fish escaped (National Marine Fisheries Service and U.S. Fish and Wildlife Service, 2004). Contrary to what some people may think this is not beneficial to the marine environment, as it does not "just replace the natural number of fish".

      • The farmed fish are often not native to the areas in which they are farmed.  This practice often displaces the native species.

      • Many fish farms use antibiotics and genetically altered fish, known as transgenic fish. They are altered to grow fast to a large size while consuming less food.  They often are not permitted to even live to sexual maturity.

      • Farmed fish may have diseases not found in the wild.  The wild fish have no natural resistance to these diseases. 

      • There have been studies which show that farm raised fish are more aggressive breeders than their wild counterparts (Ananthaswamy, Anil, 2003).

      • Farmed fish now outnumber wild fish 48 to 1 in the North Atlantic. (World Wildlife Federation Scotland, 2003)


    • Thousands of acres of mangroves are altered to make room for shrimp farms, displacing those species which naturally exist there, thus forever altering the ecologically important mangrove areas. 

    • To provide food for the farmed fish, trawlers vacuum the sea for anchovies and mackerel to make fish meal, effectively removing these fish from the ocean's food chain.

    • The genetically altered farmed fish pose a risk to the genetic quality of wild fish, as escaped farmed fish are now interbreeding with wild fish.

    • Rotting, uneaten food pellets from fish pens pollute surrounding areas. These pellets, combined with the concentrated excrement from the farmed fish, often contain antibiotics and dioxins which contribute to ecosystem destruction and, in some cases, "Dead Zones". 

    • Sea lice infestations from high concentrations of farmed salmon have caused health problems to wild salmon.


    • "Analysis of Fish Consumption Data Shows 800,000 U.S. Adults Eat Enough PCBs From Farmed Salmon to Exceed Allowable Lifetime Cancer Risk 100 Times Over". "The Environmental Working Group bought the salmon from local grocery stores and found seven of 10 fish were so contaminated with PCBs that they raise cancer-risk concerns, relative to health standards of the US Environmental Protection Agency (EPA)". (Environmental Working Group, 2003) The toxin levels are believed to be higher as farmed fish are often fed ground-up junk fish (fish with little other commercial value) captured close to shore where these toxins levels are higher. 

    • "There's no doubt that fish is good for you, but these data suggest if you're going to eat farmed salmon then eating it a little less frequently would be a good idea." (CBS News, 2004)


    • To produce one pound of farmed salmon, 2.4 to 4 pounds of wild sardines, anchovies, mackerel, herring and other fish must be ground up to render the oil and meal that is compressed into pellets of salmon chow. (George Meteljan Foundation, 2005)  Resulting in a 58 percent to 75 percent loss of protein and food energy. 


What can you do about it?

  • If you are a boater, do not  carry your ballast or bilge water into new environments.

  • After boating, carefully clean the boat's hull and propellers before introducing the boat to a new area.

  • If you fish, dump your bait buckets in the trash, not local waterways.

  • Do not release aquarium contents into local waterways.

  • Choose seafood safe for your family and the environment. This is one issue over which consumers have the power make change. There is a lot of information available on the web to guide you. One site we find easy to use is Seafood Watch by The Monterey Bay Aquarium. They provide a downloadable/printable wallet-sized card to help you buy the seafood that is healthy for consumption and  the environment as well as more information about the issues surrounding sustainable fishing methods.
  • Your Voice counts. Use our letter writing area to make sure your opinions and concerns are heard by government and industry leaders. 


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