Water Environment and Water Services (Scotland) Act 2003 implementation: environmental standards - consultation

6. Loch fish

We are proposing a new loch fish assessment procedure using environmental DNA (eDNA) monitoring. It is a completely new method and would be the first WFD assessment procedure based on environmental DNA (eDNA) sampling and analysis. Further technical details about this new assessment method are available from UKTAG^[6].

Gill netting has traditionally been the sampling method used to describe lake fish communities across the globe. However, for a number of reasons there has not been a tradition of lake gill netting in Great Britain. This has meant that we have lacked the basic data to develop a loch fish assessment procedure. With the development of eDNA based monitoring methods an opportunity has arisen to develop a loch fish sampling procedure using this new method.

Field and laboratory investigations have identified that eDNA analysis provides a description of the contemporary fish communities. Studies have shown that fish eDNA rapidly declines after fish have been removed from the study environment, indicating that eDNA in water samples is representative of the fish population at the time of sampling.

Implications of the proposal

As there is no pre-existing loch fish assessment procedure, it is not possible to make comparisons and Table 6.1, below, only shows the effect of applying the new loch fish (eDNA) classification method.

Only one of the four waterbodies classified as moderate for loch fish (eDNA) would downgrade the overall classification of that waterbody from good to moderate status. Given the high level of symmetry between the new lake fish tool and other methods for assessing nutrient enrichment the need for any regulatory action as a result of this change is unlikely.