Fish are sensitive indicators of water quality and their assessment is an important part of water management. 
However traditional methods of surveying by netting are costly and can cause the fish harm. The Environment Agency has just published the results of a project, a DNA based monitoring method for fish in lakes (SC140018), which seems to have found an effective solution to this problem. This project appears to revolutionise the way fish species can been monitored in freshwater lakes with 14 out of the 16 key fish species known to be present in Lake Windermere being detected through eDNA compared with the four species found by conventional survey techniques.
However traditional methods of surveying by netting are costly and can cause the fish harm. The Environment Agency has just published the results of a project, a DNA based monitoring method for fish in lakes (SC140018), which seems to have found an effective solution to this problem. This project appears to revolutionise the way fish species can been monitored in freshwater lakes with 14 out of the 16 key fish species known to be present in Lake Windermere being detected through eDNA compared with the four species found by conventional survey techniques.Fish leave behind traces of DNA from their skin urine or faeces and it is this matter which makes up the eDNA which is used to provide information on the fish living in the lake. From the results of this project only 10 -20 samples are needed to show which species are present but to estimate fish populations more comprehensive sampling is likely to be required. Interestingly the 6no shoreline samples taken over a relatively short stretch of shoreline of Lake Windermere also gave better results than the traditional survey technique where 12 species of fish were identified.
Whilst these results are really encouraging the project summary does draw attention to the need to demonstrate that the findings can be repeated at different times of the year and whether this approach would also have wider applicability in water bodies with greater chemical and physical variability. For more information on this project please go to https://www.gov.uk/government/publications/a-dna-based-monitoring-method-for-fish-in-lakes.
