Inshore waters - regulated commercial use of traps/pots to catch wrasse: fisheries assessment

8. Minimum landing size of ballan wrasse

Recent UK studies provide conflicting recommendations for wrasse minimum landing sizes in relation to harvestable proportion.

The current ballan wrasse landing sizes imposed by the Scottish Government are calculated to target 30% of the total wrasse population, ensuring that 70% of the ballan wrasse population is outwith the landing range sizes and is unexploited (SlotLim/SlotLim). Rules-of-thumb for Maximum Sustainable Yield (MSY) theory suggest that MSY lies within 30-40% (Pauly & Froese 2021). Here instead of depleting 30%-40% of the stock, the Scottish ballan wrasse fishery only targets 30% of the stock.

Scottish data suggests 12-24 cm may be adequate for limiting the ballan wrasse population to 30% which are targeted by the fishery whilst reports of English wrasse fisheries recommend increasing the MLS for ballan wrasse to 18cm based on literature reviews and stakeholder consultation as opposed to biological inference of maturation or population sustainability (SlotLim/SlotLim; Henly, 2022).

Many of the estimates of length at maturity estimates (16-25cm) are based on lower latitude populations drawn from literature relating to Portugal (Costa, 2007), Galicia (Villegas-Ríos et al., 2013a), Turkey (Artüz, 2005) and France (Quignard, 1966). Northern European estimates from gonad histological reading is limited to work from the Isle of Man, however the work did not provide a length estimate, only ages (Dipper, 1976). Similarly, a gonad staging observations paper for Norwegian samples, omit such detail of the size of the fish the gonads are extracted from (Muncaster et al., 2010).

Whilst noting the limitations of applying the findings to a wild fishery, hatchery raised ballan wrasse in Scotland have been found to start to maturate at around 11cm (Palma et al., 2023).

The Scottish Government considers that there are several methodological, geographical and scientific limitations to the publication Darwall et. al., 1992 and do not consider that it should be used as the primary evidence source to determine minimum maturation size for ballan wrasse in Scotland. The Scottish Government also notes that some of the more recent academic studies relating to ballan wrasse CRS are based, to differing extents, on the same cited literature (Pritchard et al., 2025; Henly, 2023).

The Scottish Government has been undertaking modelling work to determine potential sizes of maturation to inform minimum landing sizes, given the absence of empirical gonad histological observations. We anticipate that work continuing through summer 2025. Whilst that work is being undertaken, Marine Directorate’s Science, Evidence, Data and Digital (SEDD) portfolio have recommended it would be a sensible approach to increase the minimum landing size at this time, with the understanding that there is a requirement for further work.

Until the modelling work is completed, the MLS for ballan wrasse in Scotland will be increased from 12cm to 14cm.