Metal tolerance in trout (Salmo trutta) in southwest England

Humans have exploited the earth’s metal resources for thousands of years leaving behind alegacy of toxic metal contamination and poor water quality. The Cornwall and West Devon Mining Landscape, a UNESCO World Heritage Site in the southwest of England, provides a well-defined example of such activity, with a rich history of metal mining dating to the Bronze Age (2500 BC). Mine water wash-out continues to negatively impact water quality across the region where trout (Salmo trutta L.) populations exist in both metal-impacted (see photo) and relatively clean rivers. 

Our analyses demonstrate that metal-impacted trout populations have characteristically low genetic diversity and have experienced severe population declines. Investigation of trout population structure showed that populations in metal impacted rivers are genetically distinct from trout populations in relatively clean rivers, and also from one another, despite being geographically proximate. Using approximate Bayesian computation (ABC), we were able to date the appearance of these genetic patterns to periods of intensive mining activity. The divergence of contemporary metal-impacted trout populations from those inhabiting clean rivers dated to the Medieval period, a time characterized by the development of sophisticated, yet environmentally damaging, mining practices. Moreover, we observed two distinct genetic populations of trout within a single catchment (the river Hayle) and dated the split of these populations to a time when local mining activity peaked at the end of the Industrial Revolution (c. 1860). 

These anthropogenic actions have left a clear genetic footprint on modern trout populations. Our investigation thus provides an evaluation of the use of contemporary genetics in inferring demographic history and, importantly, the influence of human-altered landscapes to change the genetic make-up of a species.  

Further details of this work can be found in: 

• Paris, J.R., King, R.A. and Stevens J.R. (2015) Human mining activity across the ages determines the genetic structure of modern brown trout (Salmo trutta L.) populations. Evolutionary Applications, 8: 573-585.

• Durrant, C.J., Stevens, J.R., Hogstrand, C. and Bury, N.R. (2011) The effect of metal pollution on the population genetic structure of brown trout (Salmo trutta L.) residing in the River Hayle, Cornwall, UK.  Environmental Pollution, 159: 3595-3603.