Monitoring the Effects of Fish Farms on Wild Salmonids

The Intervention

Underwater cameras will be used to live stream videos of these rivers so that the condition of migrating fish can be assessed by anyone online. The Camera system utilises Go Pro Hero 9 technology with underwater WiFi extension cabling allowing the footage to be viewed remotely on an overwater monitor. This technology allows the operator to film at the most opportune periods. Initially, the project will focus on four distinct regions in the southwest of Ireland. Two of them are adjacent to aquaculture farms while the other two are not and will provide a simple means of comparison.

Other than making the videos available online, the levels of infestation with sea lice will also be categorised and reported to Inland Fisheries Ireland and the Marine Institute to allow further inspection and research. This should help prioritise coastal areas for environmental DNA sampling and subsequent quantification of sea lice density.

The project is funded through our business membership with Arctic Stone.

But populations have declined

Unfortunately Atlantic salmon and sea trout populations have been declining in Ireland over the last few decades. One important contributor appears to have been the expansion of artificial salmon aquaculture facilities along the west coast of Ireland. By keeping individuals at high densities these facilities often face problems with sea lice infestations which can spread to adjacent wild fish populations. These parasites feed on the mucus, skin and muscle of the fish and the tissue damage they create leads to physiological stress, a lower feeding rate and a reduced ability to deal with changing water salinity and ultimately can lead to increased mortality. One way sea trout try to cope with this is by migrating to their native rivers prematurely - it is easier for them to cope with freshwater when their skin is damaged and to rid themselves of the lice. This premature return does come with a cost, less time spen feeding at sea means the fish are often small and weak and less capable of making their return journey successfully.

The evidence that sea lice can impact wild salmon populations is also clear. For example, a study published last year shows that salmon in this region are 19 – 46% less likely to return upstream in years with high levels of sea lice in nearby farms.