Due to pollution and overfishing, population of American, Asian and Europeans eels have declined up to 99%.

Overfishing is often argued as the worst way we are abusing the planet. Some even argue it is worse than global warming because of the extent we are doing it. Eels are not the only victims, as our overfishing is getting continually worse.  For example, according to a 2011 report, 40 fish populations, or 16% of them, are subject to being victims of overfishing, compared with 38 fish populations in 2009.

Additionally, in 2009 there were 46 fish populations that were already overfished, but in 2010 it had gone up to 48. Though the numbers move around because of environmental changes in fish, they are steadily increasing. Overfishing is hard to enforce because much of the oceans are considered open territory and not owned by anyone. 

The United States Department of Commerce has an administration called the National Oceanic and Atmospheric Administration that attempts to limit overfishing. Currently, there are 528 federally managed fishing stocks, 203 of which have limits and measures in place to try and prevent what is happening to the eels from happening to other species. 

(Source)