Friday, October 14, 2011

Red King Crab

This is an interesting invasive species case. Red king crab, normally found in the Pacific Ocean, was brought into Norway’s seas by scientists in hopes of establishing a population for fishing in the 1960s and 1970s. In 2009, there were more than 2 million adult red king crabs found in this area.

The red king crab is destroying the ecosystem in the Varanger area, though. The scientists that introduced it did not realize how drastic this crab species could alter its environment. Not only do the crabs prey on larger individual organisms, but they also dig and scoop up the sediments looking for soft-bodied organisms to eat. Therefore, other species are being directly preyed upon, and the benthic zone is subject to destruction by these crabs.

location of the Voranger area

The article reports the decrease in numbers for other species. Specifically, more sedimentary species, such as echinoderms and large mollusks, decreased drastically in numbers. Because each species has a role in this ecosystem, their decrease is devastating. For example, some organisms’ function, like water pumping, helps maintain a healthy level of oxygen in the benthic zone. So because the crab is harming other species, the ecosystem as a whole is also being harmed.

The authors note that research on this species is vital as it can spread to other areas. Also, the affects of the red king crab are not fully studied. But, conservation ecology is a crisis science, as we learned in the first few lectures, so it is hard to decide how much time we should spend studying the crabs before we decide to take action, if at all.

But even if scientists decided on an exit plan for the red king crab from this area, would the local human population be okay with that? Now this is a commercial crab, with the government regulating its fishing. In 2009, quotas were set for 1,300 tons! How can scientists get people on their side if their economy is going to be hurt by saving the environment? Can another industry be developed by restoring the ecosystem?

The second article I listed studies the effects of loss of limbs on crabs. They found that if males lose their chelipeds (pincers), they cannot successfully mate with females. Males need to hold the females up, and without these appendages, they cannot reproduce. Also, if any crab loses its main appendages, it cannot feed as well, thus lowering its survival rate. As I read this article, I just imagined people picking off the claws of crabs as a way of decreasing the population size, which seemed silly to me.

From these two articles, the only way of removing these crabs semi-reasonably is by overfishing, in my opinion. But will the Norwegians be okay with that? And will the ecosystem return to what it was?

Oug, E., Cochrane, S. K. J., Sundet, J. H., Norling, K., & Nilsson, H. C. (2010). Effects of the invasive red king crab (paralithodes camtschaticus) on soft-bottom fauna in varangerfjorden, northern norway . Marine Biodiversity under Change, 41(3), 467-479.

Dvoretsky, A. G., & Dvoretsky, V. G. (2009). limb autotomy patterns in paralithodes camtschaticus (tilesius, 1815), an invasive crab, in the coastal barents sea. Journal of experimental marine biology and ecology, 377(1), 20-27.

Images found on Wikipedia.


John Latto said...

Interesting example. As a thought experiment, would your opinion on what is the 'right thing to do' differ if this was a poorer country where the crabs provided valuable food security for local people?

James Proffitt said...


Adam Eshraghi-Johnston said...

It’s sad to see a single invasive organism having such a huge negative effect on an ecosystem. Although this post covered the physical problems caused by the introduction of the Red King Crab, I also think that the accidental introduction of parasites that have a symbiotic relationship with the crustaceans could also cause large amounts of damage to the existing ecosystem. As if the introduction of an invasive species wasn’t detrimental in itself, I think that there is a high chance that parasites such as polychaetes, hydrozoans and nemerteans could also be introduced via the crabs as vectors and have severe effects on the native species. Fortunately this didn’t seem to be the case in Norway, but another paper by Dvoretsky et al, went into further detail analyzing the risk of spreading parasites from Red King Crabs in Russia:

Dvoretsky, Alexander G., and Vladimir G. Dvoretsky. "Distribution of Amphipods Ischyrocerus on the Red King Crab, Paralithodes Camtschaticus: Possible Interactions with the Host in the Barents Sea." Estuarine, Coastal and Shelf Science 82.3 (2009): 390-96. Print.