Battle of the invasive species!

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Who wins when you pit two of the world's two most invasive freshwater species against each other? This was the subject of a study published in a recent issue of the online journal PLoS ONE.

Michelle Jackson and colleagues studied the system in Lake Naivasha, Kenya. Red swamp crayfish (Procambarus clarkii) were introduced to the lake in the late 1970s and the Common carp (Cyprinus carpio) followed in 1998.

Using stable isotope and eight years’ worth of concurrent ecological data, the authors examined the trophic interactions occurring between the carp and the crayfish.

They found that the carp was proliferating at the expense of the crayfish. Both species were utilising the same food source, but the significant increase in the carp population caused the crayfish to feed on lower quality food such as hippo dung.

The carp became so successful at forcing the crayfish into such a narrow dietary niche that the crayfish population may have been eliminated from the lake (as sampling carried out since 2009 failed to catch any crayfish).

For more information, see the paper: Jackson, MC, I Donohue, AL Jackson, JR Britton, DM Harper, J Grey (2012) Population-level metrics of trophic structure based on stable isotopes and their application to invasion ecology. PLoS ONE 7, e31757.

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