Aquatic Invasive Species

Aquatic invasive species are a large threat to our marine ecosystems in the Pacific Northwest. These invasive species are often spread through common human activities, such as recreational boating. Boating is a popular past-time in the Pacific Northwest and is considered an largely unregulated vector for the spread of invasive species.

http://www.kiriwina.com/log2011/files/1305foul.jpg

In a study that was performed off the coast of British Columbia, it was found that recreational boating is a major vector that is contributing to the spread of marine invasive species and the researchers suggested that boats should be subject to more regulation (Murray, 2011). The study showed that recreational boats can "represent a high-risk vector for both primary introduction and secondary spread (Murray, 2011)" of marine invasive species. A total of nine invasive species were found in hull fouling communities in the waters of British Columbia and were even found on active and relatively clean boats. Ideal vectors are small boats that can travel long distances and at relatively slow speeds. Although there are preventative measures that can be taken, such as using anti-fouling paint, there are also certain aquatic species of invaders, such as Waterispora subtorquata and Bugula neritina, that have a tolerance to anti-fouling paint compounds. Their ability to grow over these chemicals facilitates the growth of other invaders that cannot grow on the paint but can grow on top of these paint-tolerant species, thus avoiding the harmful chemicals.

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One species that has been particularly troublesome in the Pacific Northwest area is Styela clava, a clubbed tunicate. This tunicate is native to the Pacific coasts of Korea and Japan and has made its way to the coasts of the Pacific Northwest on the hulls of boats. They are able to "breed rapidly in water temperatures above 15 degrees Celsius and form highly dense populations that crowd out other forms of marine life" (REEF, 2011). S. clava is usually found on artificial surfaces and survives best in areas protected from strong wave actions, such as harbors and marinas.

Cordell, 2012
The number of tunicates per 100 cm^2 found on different hull materials after 
exposure for 8 and 12 weeks. Aluminum is most susceptible to tunicate fouling. 

One study showed that untreated hulls made of fiberglass, painted wood, and bare aluminum are very susceptible to colonization, with bare aluminum attracting the greatest amount of tunicates (Darbyson, 2009). Anti-fouling paints were found to be very effective in reducing hull fouling. However, by week 12 of the study, a low level of tunicate infestation was observed. Unpainted boats were very vulnerable to infestation because invaders can establish themselves more easily in the grooves of unpainted wood.

Recreational boats serve as suitable infestation sites because they are usually used only once or twice a week and then are left docked for a few days at a time, giving the tunicate plenty of time to establish itself on the hull. Darbyson et al. also found that these tunicates are capable of withstanding temporary exposure to air by closing its siphons, a structure on molluscs that functions in feeding and respiration, to create a suitable microhabitat, making this species an even more dangerous invader and greatly increasing their potential range and rate of spread. The main factor that makes recreational boating such a dangerous vector is the fact that this activity lacks proper management and regulations in terms of controlling the spread of invasive species. In order to control this issue, recreational boating should be put under more regulations and owners of boats should take precautions to prevent fouling of their boats and the spread of invasives, such as using anti-fouling paints and regularly checking their boat for signs of fouling.