Following reports of salmon returning to Norway and Scotland with a skin disease in spring 2019, Inland Fisheries Ireland (IFI) have been proactive in relation to this issue as regards Irish rivers and waters.
IFI issued an alert on 17th June 2019, informing anglers that small numbers of salmon showing signs of bleeding and skin ulceration were also being observed returning to Irish rivers and appealed to anglers and fishery owners to report any incidences of affected salmon encountered. Anglers and fishery owners were asked to report incidences of salmon with rash like symptom to help determine the scale of the problem nationally.
I am advised by IFI that salmon first began appearing in Irish rivers with these symptoms in early June and by mid-June, there were reports of fish with ulceration in at least six rivers, both on the east and west coast of Ireland.
The affected salmon show signs of bleeding, ulceration and haemorrhaging mainly along the area on the belly of the fish and on the head and the tail. Secondary fungal infection can set in and be fatal. IFI advised that until the cause of the disease was determined and the risk of spreading the disease established, affected salmon should not be removed from the water. Anglers who captured salmon with these symptoms were advised to follow normal biosecurity procedures and disinfect tackle, waders and equipment.
IFI set up a dedicated email (email@example.com) for anglers to report any incidence of diseased salmon encountered in Irish rivers and provide photographs. Anglers were also advised to contact Inland Fisheries Ireland’s 24 hour confidential hotline number on 1890 34 74 24 or 1890 FISH 24 in this regard. Inland Fisheries Ireland collaborated with the Fish Health Unit in the Marine Institute in Galway and provided, for disease testing, a live salmon with symptoms of the disease captured in the upstream trap from the National Salmonid Index Catchment on the river Erriff.
A freshly caught salmon with disease symptoms was also provided from the river Lee for disease testing. Salmon were also collected from the River Boyne by IFI staff and given to specialist fish veterinary group in Galway for examination. No responsible disease was identified in any of these samples that could explain the symptoms observed in Irish and other salmon.
The vast majority of reports of disease salmon were from June and July with small numbers of reported incidences since that time. Analysis also suggests that the number of fish which died from the disease was small with east coast rivers such as those in the North East appearing to be most affected.
Given the international dimension to the issue, IFI scientists consulted with their colleagues in Norway and Scotland since early June in an effort to establish the cause of the disease. To date no laboratory in Europe has definitively identified the cause of the disease symptoms observed although it is thought that there may be some link to a change in salmon diet at sea and a related vitamin deficiency which is being investigated further as a possible contributing factor.
In this context, an IFI scientist will attend an international workshop in Norway shortly and present the available information on the disease outbreak in Ireland. The workshop will cover exchange of observations and knowledge about the disease between countries, results of disease testing and the identification of knowledge gaps and potential future collaboration.