Information in relation to Moritella viscosa in Scottish Aquaculture: EIR release

Information requested

I am writing to request information under the Freedom of Information (Scotland) Act 2002 relating to the occurrence of winter ulcer disease (Moritella viscosa) in Scottish aquaculture.

Specifically, I am after:

1. The number of salmon farming sites at which Moritella viscosa was detected or diagnosed per year, for each of the last five calendar years (or most recent years available).

2. Where available, the number of inspection cases or investigations in which Moritella viscosa was identified as a primary or contributing cause of disease.

3. Any annual summary reports or internal surveillance summaries held by Marine Scotland or the Fish Health Inspectorate that reference Moritella viscosa or winter ulcer disease incidence.

Response

As the information you have requested is ‘environmental information’ for the Purposes of the Environmental Information (Scotland) Regulations 2004 (EIRs), we are required to deal with your request under those Regulations. We are applying the exemption at section 39(2) of the Freedom of Information (Scotland) Act 2002 (FOISA), so that we do not also have to deal with your request under FOISA.

This exemption is subject to the ‘public interest test’. Therefore, taking account of all the circumstances of this case, we have considered if the public interest in disclosing the information outweighs the public interest in applying the exemption. We have found that, on balance, the public interest lies in favour of upholding the exemption, because there is no public interest in dealing with the same request under two different regimes. This is essentially a technical point and has no material effect on the outcome of your request.

Request for information in relation to Moritella viscosa in Scottish Aquaculture

Question 1

I have provided a breakdown below of available data held by the Scottish Government detailing the number(s) of salmon fishing sites where instances of Moritella viscosa were detected for each of the last 5 calendar years (2021 to 2025):

Year	Number of sites where Moritella viscosa was detected
2021	1
2022	5
2023	4
2024	5
2025	2

I wish to highlight that the Scottish Government does not hold a full dataset on the occurrence of Moritella viscosa or Winter Ulcers in Scottish aquaculture. The information we do hold is primarily sourced from case visits conducted by officials from the Scottish Government’s Fish Health Inspectorate (FHI) or from mortality events reported by industry to FHI. I would also note that Moritella viscosa is not a listed disease and therefore does not require to be reported to the competent authority.

Additionally, under Regulation 6(1)(b) of the EIRs, we do not have to give you information which is already publicly available and easily accessible to you in another form or format. If, however, you do not have internet access to obtain this information from the website(s) listed, then please contact me again and I will send you a paper copy.

FHI case visit information that you may wish to review is published on the Scottish Government website via the following: Publication of Fish Health Inspectorate information

Question 2

Under Regulation 6(1)(b) of the EIRs, we do not have to give you information which is already publicly available and easily accessible to you in another form or format. If, however, you do not have internet access to obtain this information from the website(s) listed, then please contact me again and I will send you a paper copy.

I have provided a list below of cases for the last five calendar years (2021 to 2025) where tests conducted by FHI officials detected (or ruled out) instances of Moritella viscosa. You may wish to review the associated case report documents for said cases which are available via the FHI case visit information link provided in my response for Question 1 above as these provide further information on site visits that you may find helpful.

Date of visit	Case number
14/05/2021	20210132
13/10/2021	20210385
27/04/2022	20220110
11/05/2022	20220146
31/08/2022	20220368
05/10/2022	20220469
08/11/2022	20220541
25/01/2023	20230009
07/02/2023	20230015
07/06/2023	20230240
21/11/2023	20230076
28/11/2023	20230528
07/02/2024	20240024
21/02/2024	20240041
17/04/2024	20240092
27/03/2024	20240097
28/05/2024	20240165
28/01/2025	20250021
13/03/2025	20250062
16/12/2025	20250501

Please note that case visit information is published approximately one month in arrears with the December 2025 information currently due to be published in February 2026, this will be published via the FHI publications page linked above when available.

The Scottish Government also publishes fish mortality statistics via the Fish Health Inspectorate: Mortality Information publication which contains data voluntarily provided by industry stakeholders along with further background information that you may find helpful.

Question 3

I have provided an extract below of summarised information held by the Scottish Government, broken down by year and number of recorded incidences per month, of Moritella viscosa and/or Winter Ulcer Disease from January 2021 up to and including June 2025 (the date when the latest available summary was collated).

Year	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
2021	0	0	0	0	0	0	0	0	0	1	0	0
2022	0	0	0	1	1	0	0	1	0	1	1	0
2023	1	0	0	0	0	1	0	0	0	0	2	0
2024	0	2	1	1	1	0	0	0	0	0	0	0
2025	1	0	1	0	0	0	N/A	N/A	N/A	N/A	N/A	N/A

About FOI

The Scottish Government is committed to publishing all information released in response to Freedom of Information requests. View all FOI responses at https://www.gov.scot/foi-responses.