Scientists from the UK's University of Exeter have found that heavy metal pollution from mining has dramatically reduced genetic diversity of brown trout in south-west England.
Human activity, according to the latest findings, may also alter the genetic patterns of wild populations.
Researchers said that occurrence of metal contaminants in rivers across England is directly linked to mining activities that dated back many years.
Exposure to high-concentrations of metals can disturb fishes' health and negatively impact their genetic diversity and population structure.
University of Exeter lead author and postgraduate researcher Josephine Paris said: "Our research shows that brown trout populations have been severely affected by both historical and contemporary mining practices.
"The effects of both metal contamination and changes in environmental geochemistry have driven dramatic changes in the genetic architecture of these fish."
When DNA samples from 15 brown trout populations from heavily-polluted and 'clean' rivers were compared, it was found that all populations from metal contaminated rivers derived from a single common ancestor 960 years ago.
During the industrial revolution around 150 years ago, further genetic separation occurred when rivers were again polluted with increased levels of metal contaminants at a time when trout numbers slipped substantially in heavily polluted areas such as the River Hayle.
University of Exeter research fellow in Biosciences co-author Dr Andrew King said: "The metal contaminated populations are genetically distinct from one another and we think this is a response to the unique cocktail of metals found in each river."
Image: Brown trout (Salmo trutta fario). Photo: courtesy of US Fish and Wildlife Service.