Ratio of the number of Salmon smolts put to sea: EIR release

Information requested

Clarification regarding Table 19 of the Scottish Fish Farm Production Survey 2024. Specifically, you requested: Clarification on whether the ratio of ova laid down to salmon smolts produced compares figures from the same calendar year or from different years. If different, which year’s ova are used to calculate the ratio for smolts put to sea in a given year. An explanation of how the ratio is calculated.

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.

The ratio presented in Table 19 compares the total number of smolts put to sea in a given year with the total number of ova laid down to hatch during the winter of the previous year and the given year. For 2024, producers were asked to report the total number of ova laid down to hatch in winter 2023–2024. This figure is then used  tocalculate the ratio by dividing the total number of smolts produced in 2024 by the total number of ova laid down to hatch in the 2023-2024 winter period.

The survey does not report a direct comparison between ova hatched in a specific year and the smolts subsequently produced from those ova. Instead, the ratio in Table 19 is calculated using two separate totals for the same reporting year.

This approach has been used consistently across all previous surveys to maintain comparability and ensure continuity in reporting of these official statistics. The ratio is therefore an indicative measure of production scale rather than a biological conversion rate for a single cohort, as smolts transferred in any given year may originate from ova laid down in different years depending on whether they are S½ (out-of-season smolts produced by photoperiod and/or temperature manipulation to accelerate development) or S1 smolts (standard smolts that spend approximately one year in freshwater before seawater transfer).

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