Threats To Eels
There are strong concerns that the European eel population might be devastated by a new threat: Anguillicola crassus, a foreign parasitic nematode. This parasite from East Asia (the original host is Anguilla japonica) appeared in European eel populations in the early 1980s. Since 1995 it also appeared in the United States (Texas and South Carolina), most likely due to uncontrolled aquaculture eel shipments. In Europe, eel populations are already from 30% to 100% infected with the nematode. Recently it was shown that this parasite inhibits the function of the swimbladder as a hydrostatic organ (Wuertz et al. 1996). As an open ocean voyager, eels need the carrying capacity of the swimbladder (which makes up 3–6% of the eel's bodyweight) to cross the ocean on stored energy alone.
Because the eels are catadromous (living in fresh water but spawning in the sea), dams and other river obstructions can block their ability to reach inland feeding grounds. Since the 1970s an increasing number of eel ladders have been constructed in North America and Europe to help the fish bypass obstructions.
In New Jersey, an ongoing project monitors the glass eel migration with an online in situ microscope. As soon as more funding becomes available, it will be possible to log into the system via a Longterm Ecological Observatory (LEO) site.
Read more about this topic: Eel Life History
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