Question: Can fish pollute the ocean/lake if so how do they?

Lauren Laing answered on 11 Mar 2016:

They do not create any pollution themselves, but small marine organisms living on the bottom of the ocean in sediments have been shown to accumulate pollutants in their tissues. These creatures are then eaten by bigger fish, who in turn are eaten by bigger fish, marine mammal or even birds. It is thought that in this way pollutants can be transferred up the food chain and into larger species. Some scientists have found evidence to suggest these chemicals can then be stored and accumulate in the tissues of fish we may eat as humans.