Some of the fish in New York’s Hudson River have evolved resistance to several of the waterway’s toxic pollutants. Instead of getting sick from dioxins and related compounds including some polychlorinated biphenyls, Atlantic tomcod harmlessly store these poisons in fat.  However, it may not be so good for the higher-ups in the food chain.

http://www.wired.com/wiredscience/2011/02/fish-toxins-environment/

http://www.wired.com/wiredscience/2011/02/fish-toxins-environment/