It is a finding that Popper says "should not be extrapolated to other fish species or the effects of other sound sources." Cause for Concern There is considerable concern that human-produced (anthropogenic) sounds added to the environment could have damaging effects on marine life. While much of the interest has focused on marine mammals, such as dolphins and whales, there is growing interest in the effects of these sounds on fish. "The effects of sound on fish could potentially include increased stress, damage to organs, the circulatory and nervous systems," says Popper. "Long-term effects may alter feeding and reproductive patterns in a way that could affect the fish population as a whole."