During the late spring and summer of 2019 the Fish Health Inspectorate received and investigated reports of moribund wild adult Atlantic salmon being observed or caught in Scottish rivers. Clinical signs of disease included skin damage, such as petechial haemorrhaging on the ventral surface and ulcer like lesions. Fungal-like infections were also reported in addition to inflamed red vents. Observations were reported from eight Scottish rivers, a summary document can be found here:
Since May 2020, the FHI have started to receive notifications of wild adult Atlantic salmon displaying similar clinical signs of disease to those observed during 2019. Due to the current COVID-19 restrictions on travel and social distancing, no sampling has been conducted by the FHI to date in relation to these reports.
For the time being we are recording incidents to allow us to monitor the situation. Please submit any reports of clinical disease, moribund fish, abnormal mortality or unusual fish behaviour to the Duty Inspector (email@example.com) and the local DSFB. In particular please include the following information:
- Date observed/caught;
- Size and weight estimate;
- One sea winter or multi sea winter;
- Location caught (OS grid ref if known);
- Clinical signs of disease;
- Water temperature;
- Any other observations.
Whilst Inspectors are restricted in conducting investigations at this time, the laboratory is still operational so samples can be processed if delivered to the Marine Laboratory, Aberdeen. We can issue a sampling kit, with guidance, to allow for a diagnostic sample, of up to five fish, to be taken. This would include taking histology, bacteriology, molecular and parasitology samples.
It is recommended that this is completed by someone with a biology background (preferably a fisheries biologist) as the process is fairly technical however, the guidance is comprehensive.
If there were no moribund fish to sample on receipt of the diagnostic kit a fridge would be required to store some of the sample media to maintain its viability for use.
Please consider the following points before removing fish and undertaking sampling:
- Wild adult Atlantic salmon returning to rivers to spawn can naturally present with some physical damage due to a number of environmental factors;
- There is no general requirement at this stage to remove fish with damage for disease control purposes;
- Fish should not be removed from rivers where retention is prohibited, for example under the conservation of salmon regulations, except under the appropriate licence;
- Moribund or lethargic fish should be targeted where sampling is considered appropriate;
- Moribund fish should be maintained alive until sampling can be completed as the tissue samples need to be fresh;
- Moribund fish that cannot be maintained alive should have details recorded and photographs taken, where possible, before being returned to rivers. Details should be sent to local DSFBs and FHI;
- If local wild fishery interests determine that moribund fish are not to be returned to the river, they should be percussion stunned or suitably dispatched and maintained in a refrigerator at 4°C, until a determination on sampling is undertaken;
- Good biosecurity practice should be followed when handling affected fish with hands, clothing and equipment being suitably cleaned and disinfected, where appropriate.
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