Fish tissue samples are collected from many sites across the commonwealth to help determine if the fish are safe for human consumption. Fish are analyzed for metals, including mercury, PCBs, chlordane, pesticides and herbicides. Results are used to determine if there are potential problems with contaminants in fish tissue that require further sampling. The data from this analysis is then provided to state and local officials so consumption advisories may be issued when warranted. If results are not elevated, no further fish tissue sampling is conducted in that stream reach.