Scottish Animal Welfare Commission - proximity of seals to farmed fish: response to Marine Scotland

Outcomes of the investigations

Literature review

As stated above, there was evidence from Scotland and other countries that direct attacks by seals can cause significant losses. However, while it was stated that seal presence was likely to cause stress, there was no evidence presented to quantify this or to quantify any possible down-stream effects such as increased disease prevalence or reductions in growth.

Survey

Respondents from the finfish farming industry provided strong evidence that seal attacks (direct predation) cause significant losses. Data were presented from the Farmed Fish Health Framework showing that up to 500,000 fish could be lost per year, with 80-92% of Scottish farms affected.

In terms of the effect of seal presence, it was suggested that this could cause reductions in feeding, reduced growth or compromise to the immune system leading to secondary disease. However, data directly linking seal presence with disease events or reductions in growth were not presented in the survey responses. It was explained that while feed consumption, growth and mortality are extensively monitored, seal presence could not be systematically monitored. Seals may also be present in the vicinity of the farm for an extended period of time rather than in a single defined ‘event’. Additionally, fluctuations in growth and disease occurrence can also occur due to other factors. This means that while fluctuations in feeding and growth occur regularly and can be quantified, it is difficult to link any particular disease event or perturbation in growth or feeding to the presence of seals at that particular time.

However, the opinion was strongly expressed that seal presence does cause stress to the fish, and that this has adverse effects on the health and welfare of the fish. The SSPO (Scottish Salmon Producer Organisation – now Salmon Scotland) stated that it was universally accepted among fish farmers that seals attacks (the SSPO categorised both ‘direct attacks’ and ‘presence’ as ‘attacks’) as causing reductions in feeding and growth. It was noted that these effects were more marked in sea pens with more seal presence/attack, which provides indirect evidence of a link. Further indirect evidence comes from observation of the video camera footage that is used to monitor feeding. It was stated that changes in fish behaviour are seen in the presence of seals and/or seal attacks.

The SSPO Prescribing Vets Group also presented a separate response. The members of this group are an independent group of experienced fish veterinarians. Their submission stated that based on their professional expertise and experience, seal attacks and presence have significant negative impacts on salmon growth, health and the incidence of disease, and that seal presence causes changes in fish behaviour. Additionally, they stated that they have witnessed instances of disease outbreak where they considered that a seal attack was a primary or underpinning factor. 

Reductions in feeding, growth and increasing incidence of disease will have a financial impact on the fish farm, as feed conversion will be reduced, and animals will take longer to reach slaughter weights. Disease will also reduce growth, and increase time to slaughter, whilst also incurring costs associated with veterinary treatments. While poor growth carries an economic penalty, disease and the potential for chronic hunger in fish which are not feeding well are welfare issues.