Megrim Lepidorhombus whiffiagonis
Publication of Advice: 6 June 2025. Published by Marine and Freshwater Research Institute.
Advice
MFRI advises that when the MSY approach is applied, catches in each of the fishing years 2025/2026 and 2026/2027 should be no more than 110 tonnes.
Stock development
Stock size is above Itrigger and the fishing pressure is below FMSY proxy.
Megrim. Catch by gear type, IS-SMB juvenile index (<20 cm), fishing pressure proxy and IS-SMB biomass (≥30 cm) index. IS-SMB juvenile index: the error bars show 95% confidence intervals. IS-SMB biomass index: the red horizontal lines indicate average biomass indices for 2021–2023 and for 2024–2025 used in the advice calculations; the shaded area shows 95% confidence intervals.
Basis of the assessment and reference points
Basis of the advice | MSY approach |
Management plan | There is no management plan for this stock |
Assessment type | Trends in biomass indicators |
Input data | Commercial catch and survey biomass indices (IS-SMB) |
Approach | Reference point | Value | Basis |
|---|---|---|---|
MSY approach | Itrigger | 167 | Iloss×1.4, Iloss defined as the lowest survey value |
FMSY_proxy | 1 | Relative value from LBI analysis, assuming M/K = 1.5. | |
Lc | 43 | Length at first capture, 50% modal abundance from catch length data | |
LInf | 62 | Asymptotic length, defined as maximum length from catch length data | |
K | 0.19 | Population growth rate | |
LF=M | 47.75 | 0.75 x Lc + 0.25 x LInf |
The ICES framework for category 3 stocks, for which analytical assessment is not possible but trends in biomass indicators are assumed to reflect changes in stock dynamics, was applied (ICES, 2025). IS-SMB biomass index of megrim ≥30 cm is used as an indicator of stock development. As sufficient data on life history is available in addition to length measurements from catches, the advice is based on the new rfb-rule for ICES category 3 data-limited stocks and is valid for each of the fishing years 2025/2026 and 2026/2027.
Prospects
Megrim. Advice calculation.
Ay: Catch advice for 2024/2025 | 92 |
Stock biomass trend | |
Index A (2024-2025) | 473 |
Index B (2021-2023) | 324 |
r: Stock biomass trend (index ratio A/B) | 1.462 |
Fishing pressure proxy | |
Mean catch length (Lmean = L2024) | 56 |
MSY proxy length (LF=M) | 48 |
f: Fishing pressure proxy (LF=M/Lmean) | 0.854 |
Biomass safeguard | |
Last index value (I2025) | 563 |
Index trigger value (Itrigger=Iloss*1.4) | 167 |
b: Index relative to trigger value, min{I2025/Itrigger, 1} | 1 |
Precautionary multiplier to maintain biomass above Blim with 95% probability | |
m: Multiplier (generic multiplier based on life history) | 0.95 |
Advice calculation1) | 150 |
Stability clause (+20% / -30% compared to Ay, only applied if b>1)2) | 1 |
Catch advice for 2025/2026 and 2026/2027 | 110 |
% advice change3) | 20 |
1) Ay × r × 1/f × b × m | |
2) min{max(0.7Ay, Ay+1), 1.2Ay} | |
3) The figures in the table are rounded. Calculations were done with unrounded inputs, and compared values may not match exactly when calculated using the rounded figures in the table. | |
The advice for each of the fishing years 2025/2026 and 2026/2027 is higher than the advice for 2024/2025 because the stock size indicator has increased.
Quality of the assessment
IS-SMB is considered to cover the geographic distribution of the stock.
Other information
Recruitment in the IS-SMB in 2025 was the highest recorded since the survey began in 1985. However, the stock is expected to remain at a low level in the coming years due to poor recruitment from 2012 to 2023.
Advice, tac and catch
Megrim. Recommended TAC, national TAC, and landings (tonnes)
Fishing year | Recommended TAC | National TAC | Total catch |
|---|---|---|---|
2010/2011 | 270 | ||
2011/2012 | 429 | ||
2012/2013 | 380 | ||
2013/2014 | 369 | ||
2014/2015 | 429 | ||
2015/2016 | 498 | ||
2016/2017 | 467 | ||
2017/2018 | 387 | ||
2018/2019 | 341 | ||
2019/2020 | 289 | ||
2020/2021 | 194 | ||
2021/2022 | 206 | 86 | |
2022/2023 | 132 | 91 | |
2023/2024 | 92 | 48 | |
2024/2025 | 92 | ||
2025/2026 | 110 | ||
2026/2027 | 110 |
References and further reading
ICES. 2025. ICES Guidelines - Advice rules for stocks in category 2 and 3. Version 3. ICES Guidelines and Policies - Advice Technical Guidelines. 31 pp. https://doi.org/10.17895/ices.pub.28506179
MFRI Assessment Reports 2025. Megrim. Marine and Freshwater Research Institute, 6 June 2025.