Iceland Scallop Chlamys islandica
Publication of Advice: 6. júní 2025. Published by Marine and Freshwater Research Institute.
Advice
MFRI advises in accordance with the MSY approach that catches in the fishing years 2025/2026 and 2026/2027 should be no more than 40 tonnes in Breiðasund and that no fishing for scallop in other areas in Breiðafjörður should be allowed.
Stock development
Stock size is below Itrigger and fishing pressure is below FMSY proxy.
Iceland scallop. Catch by area, fishing pressure proxy, and scallop survey fishable biomass (>60 mm) index. Fishing pressure proxy is less than that corresponding to FMSY proxy (LF=M) when the proxy is lower than 1 (shown by the horizontal dotted line). The shaded area in the biomass plot represents 95% CI.
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 scallop survey biomass indices |
Approach | Reference point | Value | Basis |
|---|---|---|---|
MSY approach | Itrigger | 8 413 | Iloss×1.4; Iloss defined as the lowest survey value |
FMSY_proxy | 1 | Relative value from LBI analysis, assuming M/K = 1.5 | |
Lc | 68 | Length at first capture, 50% modal abundance from catch length data | |
LInf | 108.1 | Asymptotic length, defined as maximum length from catch length data | |
K | 0.14 | Population growth rate | |
LF=M | 78.025 | 0.75 x Lc + 0.25 x LInf |
Prospects
The ICES framework for category 3 stocks, for which an analytical assessment is not possible but trends in biomass indicators are assumed to reflect changes in stock dynamics, was applied (ICES, 2025). A model (sdmTMB) was developed for Iceland scallop in Breiðafjörður based on data from the drop camera survey and biological sampling. Fishable biomass of Iceland scallop in Breiðafjörður is used an indicator of stock development. As sufficient data on life history in addition to length measurements from the survey, the advice is based on the rfb-rule for ICES category 3 data-limited stocks.
Iceland scallop. Advice calculation.
Ay: Catch advice for 2024/2025 | 75 |
Stock biomass trend | |
Index A (2024-2025) | 5 276 |
Index B (2021-2023) | 5 895 |
r: Stock biomass trend (index ratio A/B) | 0.895 |
Fishing pressure proxy | |
Mean catch length (Lmean = L2024) | 81 |
MSY proxy length (LF=M) | 78 |
f: Fishing pressure proxy (LF=M/Lmean) | 0.967 |
Biomass safeguard | |
Last index value (I2025) | 5 153 |
Index trigger value (Itrigger=Iloss*1.4) | 8 413 |
b: Index relative to trigger value, min{I2025/Itrigger, 1} | 0.612 |
Precautionary multiplier to maintain biomass above Blim with 95% probability | |
m: Multiplier (generic multiplier based on life history) | 0.95 |
Advice calculation1) | 40 |
Stability clause (+20% / -30% compared to Ay, only applied if b>1)2) | 0 |
Catch advice for 2025/2026 and 2026/2027 | 40 |
% advice change3) | -46 |
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 the fishing years 2025/2026 and 2026/2027 is lower than the advice for 2024/2025 because of new basis of the advice and the poor state of the stock.
Quality of the assessment
The data used in the model covers the depth range and geographical distribution of Iceland scallop experimental fishery in Breiðafjörður from 2014–2019 and the commercial fishery in 2024. No surveys were conducted in 2020–2023. Uncertainties in the biomass estimates are high. Inter-annual variation of survey indices are low.
Other information
The stock is at a critical stage as the biomass and recruitment have decreased year on year and are now at historical low levels. The stock is below biomass reference points (Itrigger). Therefore, the advised catch levels are expected to decline in the proceeding years, or potentially a fishing ban of Iceland scallops could be advised.
Fishing ground for Iceland scallop in Breiðasund is defined with the following coordinates:
65°03,60ˈN, 022°43,50ˈW
65°07,10ˈN, 022°43,50ˈW
65°07,10ˈN, 022°31,50ˈW
65°03,60ˈN, 022°31,50ˈW
Iceland scallop. Recommended fishing grounds in Breiðafjörður.
Advice, TAC and catch
Iceland scallop. Fishing year, area, recommended TAC, national TAC, and catches (tonnes).
Fishing year | Recommended TAC Breiðasund | Recommended TAC Hvammsfjörður | National TAC Breiðasund | National TAC Hvammsfjörður | Total catch Breiðasund | Total catch Hvammsfjörður |
|---|---|---|---|---|---|---|
2020/2021 | 62 | 31 | 62 | 31 | 40 | |
2021/2022 | 62 | 31 | 62 | 31 | 59 | |
2022/2023 | 62 | 25 | 50 | 25 | 43 | 11 |
2023/2024 | 50 | 25 | 50 | 25 | 44 | 16 |
2024/2025 | 50 | 25 | 50 | 25 | ||
2025/2026 | 40 |
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. Iceland scallop. Marine and Freshwater Research Institute, 6 June 2025.