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21.11.11, 13:17 (comments: 0)

Greetings fellow scientists!

So this week I have been working to make an entry for an invasive species database and have found myself wrapped up in the endless reading of articles- very long scientific articles! It’s hard work and can be frustrating when you read a whole paper to realise that it contained no information relevant to what you’re looking for but when you do eventually find something, it’s almost like solving a mystery and feels very satisfying!

I am working on a notorious species, known for being highly invasive all over the world: the Pacific oyster, Crassostrea gigas. It was first introduced to Portugal by trading ships coming from Japan back in the 16th Century and is known as the Portuguese oyster, C. angulata, only being identified as being similar to C. gigas by genetic studies (Boudry, Heurtebise et al. 1998). C. gigas is now on every continent except Antarctica, as it is tolerant of wide ranges in both salinity and temperature and is capable of surviving for a number of days outside of water, making it easy to transport. A major reason behind introduction was for aquaculture purposes, as it grows to a good size and, apparently, tastes very good! Crassostrea sp. are very well established in the Ria Formosa Lagoon, South Portugal (Huvet, Fabioux et al. 2004) and comparing this environment to the Baltic Sea, we can see how excellent this species is at acclimatization. C. gigas has not yet invaded the East Baltic, such as the Curonian Lagoon, but it is established in Kattegat and the Belt Sea, the strait that leads into the Baltic. With a large network of freshwater inflow, it could likely occur in the future. Climate change could also be a factor in this as temperatures increase over the next few years, creating an environment ideal for invasive species originating from warmer climates.

Global distribution of C. gigas (Miossec, Le Deuff et al. 2009)


The image (shown above) shows just how widely spread this species is, stretching across both Northern and Southern Hemispheres, infiltrating tropical and cold-temperate environments. Some ecosystems are able to withstand the pressures it puts on native populations, but others, such as that of the European flat oyster, Ostrea edulis, are declining in response, especially with the introduction of diseases (FAO, 2005-2011).

So I shall carry on with my work now whilst revising for my upcoming exam in Coastal Zone & Sustainable Tourism – wish me luck!

[hard at work!]




Boudry, P., S. Heurtebise, et al. (1998). "Differentiation between populations of the Portuguese oyster, Crassostrea angulata (Lamark) and the Pacific oyster, Crassostrea gigas (Thunberg), revealed by mtDNA RFLP analysis." Journal of experimental marine biology and ecology 226(2): 279-291.

FAO. © 2005-2011. Cultured Aquatic Species Information Programme. Ostrea edulis. Cultured Aquatic Species Information Programme. Text by Goulletquer, P. In: FAO Fisheries and Aquaculture Department [online]. Rome. Updated 1 January 2004. [Cited 21 November 2011].

Huvet, A., C. Fabioux, et al. (2004). "Natural hybridization between genetically differentiated populations of Crassostrea gigas and C-angulata highlighted by sequence variation in flanking regions of a microsatellite locus." Marine Ecology Progress Series 272: 141-152.

Miossec, L., R. M. Le Deuff, et al. (2009). "Alien species alert: Crassostrea gigas (Pacific oyster)." ICES Cooperative Research Report 299.



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