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Eels were among the first species to recolonize the Thames river after it was cleaned up in the 1960s and 70s. But scientists are sounding an alarm that the populations have crashed over the last five years, and they aren't sure what the problem is. The Guardian writes that scientists are unsure if the decline is happening because eels aren't returning to the Thames any longer, or if they're facing problems once entering the waters. Either way, in 2005, 1,500 eels were captured in traps, and only 50 were captured in 2009. And other European rivers are also seeing a decline in eel numbers.
Dr Matthew Gollock, tidal Thames conservation project manager, said: "Eels are mysterious creatures at the best of times but we are very concerned about the rapid disappearance in the Thames. It is difficult to say what is going on - it could be due to a number of potential factors including changes in oceanic currents due to climate change, man-made structures such as dams and the presence of certain diseases and parasites."
The eels - like everything in the river's ecosystem - are an important component in the food web, and their rapid disappearance will impact the other flora and fauna living in a river that has been trying hard over the last 50 years to recover from rampant pollution. There's little time for scientists to not only discover the cause, but also a solution to bring the eel populations back up.
European eels are considered critically endangered, and some of the potential causes for their population decline include overfishing, parasites, hydroelectric plants blocking river entrances, PCBs, and changes in the North Atlantic oscillation, Gulf Stream and the North Atlantic drift.
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