Science Evidence Data and Digital Portfolio Annual Report 2024 - 2025

Aquaculture, Fish Health and Biosecurity (AFHB)

Headlines

• The Fish Health Inspectors conducted risk-based inspections of 359 aquaculture and related facilities; 197 of these have been to finfish farms, 160 to shellfish farms, 1 fishery and 1 processing site.
• The Fish Health Inspectorate carried out 34 investigative samples, ruling out the presence of listed diseases. Our Diagnostic Laboratories analysed the samples from those investigations and provided a similar analysis of 14 cases for other government agencies and universities.
• The Fish Health Inspectorate collected 760 muscle samples from farmed fish for analysis for veterinary medicine residues and environmental contaminants on behalf of the Veterinary Medicines Directorate.
• Our National Reference Laboratory demonstrated its capacity to identify listed pathogens by participation in a number of proficiency tests.
• Thirteen scientific trials were conducted in the Ellis Building high biosecurity containment aquarium.
• Thirteen new authorisations and registrations were concluded for aquaculture production businesses, specialist transporters, fisheries and non-commercial businesses.
• AFHB acts as a statutory consultee to planning authorities consenting aquaculture facilities. Eight applications for sites or facilities, ten modifications to sites, seven prior notifications / prior approvals under permitted development rights and seven screening / scoping opinions were considered and comments passed to planning authorities.

Key Work in 2024 - 25

1. Scientific support, research, evidence and advice on aquaculture and aquatic animal health.

Contributes to:

Authorisation, inspection, sampling, certification and disease control ensures compliance with Scottish regulation, and provides the evidence base to maintain approved zone status, allowing UK borders to be protected and maintains the ability to identify and control listed disease as well as supporting trade and a viable aquaculture sector. Provides evidence on the state of Scottish Aquaculture with regards to sea lice and containment.

Collects samples for the Veterinary Medicines Directorate for veterinary medicine and environmental contaminant analysis. Specialist advice to planning authorities on specific aspects of aquaculture and contributes to consenting improvements as they apply to aquaculture.

2. Scientific support, research, evidence, policy and advice on biosecurity and Invasive Non- Native Species.

Contributes to:

Advice on border control matters relating to fish health, biosecurity and contingency planning. Working with the UK Office for Sanitary and Phytosanitary allows for practical measures to protect UK borders from the ingress of pathogens, pests and non-native species.

3. Scientific support, research, evidence and advice on diseases of fish, molluscs and crustaceans

Contributes to:

Provision of the National Reference Laboratory (NRL) for Scotland – to support the Fish Health Inspectorate in their surveillance for, and diagnosis of, listed and emerging diseases where they occur. Provision of commercial disease and pathogen testing for

fish veterinarians and sector health specialists, whilst maintaining and increasing internal expertise, methods and knowledge.

4. Provision of scientific and aquarium services to internal and external contracts.

Contributes to:

Provision of serviced aquarium facilities to researchers in pursuit of improved knowledge regarding, for example, fishing gear technology, the interactions of fish with pathogens, parasites and other aquatic animals and improved treatments for pathogens and parasites of fish. Participation in the Animal Welfare Ethical Review Body (AWERB) and the provision of services to the AWERB.

Case study: An investigation of unexplained mortality in European native oysters, Ostrea edulis

In August 2023, unexplained mortalities occurred in a cohort of native oysters on a site located on the west coast mainland of Scotland, which were being farmed for habitat restoration purposes. The mortalities were reported to the Fish Health Inspectorate (FHI) who initiated an investigation.

Approximately 800 individual oysters were reported to have died in a 3-week period, representing 8% of the stock being held. Predation was highlighted as a potential cause as many green shore crabs (Carcinus maenas) had been observed in the holding bags alongside the oysters. In addition, environmental data showed that there had been a significant drop in salinity the week prior to the rise in mortality observed due to heavy rainfall in the local area. Samples were taken from thirty survivors of the cohort for histological and molecular genetic analysis.

Histological examination was negative for pathogenic protists but revealed a possible viral infection with enlarged nuclei and possible viral inclusions in 7 of 30 oysters. Samples tested negative for OsHV-1 PCR, the known herpesvirus. The National Reference Laboratory at Cefas in Weymouth were contacted to discuss the case and to investigate whether they had seen similar occurrences in England or Wales. Cefas had already observed identical pathology in native oysters and provided their specific QPCR for testing our samples. The samples tested positive with varied CT values.

Similar observations have been previously reported in flat oysters in Spain and England but the identity of the virus remains undetermined. According to Cefas, electron microscopy and metagenomic analyses indicated the presence of a herpes-like virus. The extent to which this virus is a direct or indirect cause of mortality is unknown. Further investigation would be required to better understand the virus dynamics and to develop new diagnostic methods.