Sea cucumber

Commercial fishing

An experimental fishery for sea cucumber started in Breiðafjörður in 2003, but landings were minimal until the fishery expanded into Faxaflói (area E, Figure 1) in 2008, yielding a catch of around 800 t. In August 2019, a new regulation was implemented, and fishing was permitted only within the eight designated areas (A-H, Figure 1). An experimental licence was required for fishing activity outside those areas.

Fishing is generally dispersed throughout the year except for when no fishing is permitted in May and June in the western areas (A-E, Figure 5, Figure 6) and in June and July in other areas (Figure 7) due to spawning of sea cucumber. Sea cucumbers are fished by a dredge, 250 cm in width and with minimum mesh size of 80 mm. The number of dredges used (one or two) is not reliably registered in the logbooks, although most vessels have operated with two dredges in recent years (in calculations the effort of those boats was raised by the factor of 1.8).

Figure 1: Sea cucumber. Fishing grounds (A-H) according to regulation from August 2019.

Through the years, annual catches of sea cucumber have fluctuated. The annual catch in Faxaflói (E) ranged from 128-1175 t, off the east coast (areas F & G) from 0 to 1760 t and 0-559 t in Aðalvík (A). There was an increase in the catches during 2016-2019, but a considerable drop in catches in 2020 and 2021. Maximum landings were 5985 t in 2018; an almost twofold increase from 2017, but catches declined to 5605 t in 2019 and to 1465 t in 2020. The low landings in 2020 can partly be explained by the TAC for the 2019/2020 fishing year having been almost fully taken during the autumn of 2019, together with a slower start to the autumn fishery in 2020. According to stakeholders, the slow start followed a mutual agreement to even out the fishing effort over the full fishing year of 2020/2021. Difficult markets due to the COVID-19 pandemic could also explain the decreased effort. The majority of the 1429 t landed in 2021 were fished during the summer. Catches increased considerably in 2022, to 2823 t, and in 2023 the catch was around 2400 t, most of it taken in area G (1056 t). In 2024 the catch was markedly lower than in the two preceding years, at 1353 t, and lower still in 2025 at 1160 t. Throughout the years, catches in area G have been the highest (Figure 2).

In 2025, landings from the Westfjord areas were 8 t from Aðalvík (area A), 48 t from area B and 17 t from area C. Landings from area D in outer Breiðafjörður were 43 t and 18 t in inner Breiðafjörður (area DI.). Landings from Faxaflói (area E) were 152 t. In Eastern Iceland, 43 t was fished from the Northern area (F), 742 t from the middle area (G) and 87 t from the Southern area (H).

Figure 2: Sea cucumber. Total catch (t) by area during 2008-2025.

Figure 3: Sea cucumber. Distribution of catch by year, from 2008 to 2025.

An overall declining trend in raw catch per unit effort (CPUE) has been evident throughout the history of the sea cucumber fishery, although a slight increase was observed on all grounds in 2021 (Figure 4). The CPUE estimates may be biased, as some tows are entered in the database as a single long tow (up to two days) rather than as several shorter tows. CPUE has remained relatively stable in recent years, and in 2025 it was 452 kg/hour. CPUE in area D is highly variable, most likely because only one vessel operates there; in 2025 that vessel reported large catches per tow, resulting in a correspondingly high CPUE (Figure 4).

Figure 4: Sea cucumber. CPUE by area during during 2008-2025.

Figure 5: Sea cucumber. Distribution of catch in the Westfjords and Breiðafjörður (areas A, B, C and D) by month in 2025. Grey shaded months mark closure of fishing due to spawning.

Figure 6: Sea cucumber. Distribution of catch in Faxaflói (area E) by month in 2025. Grey shaded months mark closure of fishing due to spawning.

Figure 7: Sea cucumber. Distribution of catch in Eastern Iceland (areas F, G and H) by month in 2025. Grey shaded months mark closure of fishing due to spawning.

Catch (Figure 5, Figure 6, Figure 7) and CPUE vary between years, with catches generally higher in spring and summer, largely reflecting weather conditions. In recent years, fishing has been conducted almost continuously throughout the year. Catchability is lower in poorer autumn and winter weather, which may partly account for the low CPUE observed. The composition of the fleet has also changed, with larger vessels — able to operate in poorer weather — entering the fishery. To reduce bias in the raw CPUE index, CPUE trends were standardised for areas with a sufficiently long catch history (areas A, E, F and G) using a generalized linear model (GLM):

$$ log(catch) = towtime + year + month + ship $$

The model results indicated that catches are on average lower during the winter months (December – March, Figure 8). The recent trend in the year effect fluctuated in a similar manner to the raw CPUE index. In area A, the GLM year effect increased sharply over 2020-2022 and then declined again, most likely because few vessels, several of them new to the fishery, participated in 2021. In recent years the CPUE has been going downward since 2020 in area A until this year when there was a slight increase. In area E the CPUE has remained relatively unstable throughout the years. For the eastern areas, CPUE has stayed relatively stable in area F but in area G there has been a steady decrease since 2020 (Figure 9).

Figure 8: Sea cucumber. Standardized CPUE index by month for areas A, E, F and G, estimated with a GLM (area A without the vessel term)

Figure 9: Sea cucumber. Standardized CPUE index by year for areas A, E, F and G, estimated with a GLM (area A without the vessel term)

Experimental fishing

An experimental license is required for fishing activity outside the defined fishing areas (Figure 1). Within the experimental framework, limited fishing took place in July 2021 in northwestern Húnaflói (east of area A) with no landed catch. Similarly, in August 2021 and March-May 2024, 7 and 29 t, respectively, were fished in Northeast Iceland around Glettinganes, Kögur and Vopnafjörður north of area F (Figure 2, Figure 3).

Surveys

Older surveys

From 2008-2010 several surveys were carried out on commercial fishing boats in Aðalvík (A) and Faxaflói (E). Based on 100% gear efficiency biomass was estimated to be 0.3 kg/m² in Aðalvík (A) in 2008. In Faxaflói (E) during 2008, biomass was estimated to be 0.13 kg/m² at Vestrahraun and 0.18 kg/m² at Syðrahraun sub-locations.

In September 2017, a five-day drop-frame camera survey was conducted in area G off the east coast of Iceland. In total, 55 stations (ten images per station) were sampled on two grounds in the southern part of the area. The densities of sea cucumbers were 0.6 and 0.7 individuals/m², respectively. The mean whole wet weight (from fish processing) of sea cucumber from this area during the autumn of 2017 was 198 g, which yields a biomass of 0.119 and 0.139 kg/m², respectively (mean 0.13 kg/m²).

Surveys in 2020-2026

Sea cucumber areas A, B, E, F, G and H were surveyed during a beam trawl survey in autumn 2020. The gear used was a 4 m wide beam trawl, lined with a 40 mm mesh size in the cod end. The beam trawl was towed between 0.5 to 1.2 nautical miles at each station (µ = 0.89) at a speed of 4 nm/h. Start position of each tow and towing direction were randomly generated. Overlapping tows and tows that ended outside known fishing areas based on VMS data were excluded. The second survey was carried out in 2021 and the tows from 2020 were repeated; one tow was added in area A and two tows were skipped in area E owing to hard, untowable bottom. Three tows in area D were added in the survey of 2022. In subsequent years, 52 tows from the previous years were repeated (Figure 10, Figure 11, Figure 12). All of the cruises have taken place at the same time of year within the timeframe August 07 to September 11, most occurring before the end of August.

Average density per nautical mile ranged from 606 in area H in 2026 to 3056 in area D in 2022. In general, small changes were observed within areas between years. Average gutted catch per nautical mile ranged from 121 kg in area H in 2026 to 394 kg in area D in 2022 (Table 1 & Figure 10 - 12). Biomass estimates for each area were based on spatial modelling of the average gutted weight and size of known fishing areas (a GLMM implemented in the sdmTMB R package; Anderson et al., 2022). Biomass estimates ranged from 798 t in area B to 7086 t in area G, both in 2024 (Figure 4). Biomass in the Eastern areas (F,G,H) has fluctuated over the past three years with an all-time low in areas F and H in 2026 (Table 1 & Figure 10 - 12).

Table 1: Sea cucumber. Summary of the 2020-2026 beam trawl surveys. Number of tows in each area, average number of sea cucumber per towed nautical mile (±SE), average catch of gutted sea cucumbers (kg±SE), biomass index (t) with 95% confidence interval.

Figure 10: Sea cucumber. Density (n/nm) in the 2020-2026 beam trawl surveys in areas A (top right) and B (lower left). Blue lines are tows, red lines define the fishing areas and red polygons represent fishing grounds based on VMS.

Figure 11: Sea cucumber. Density (n/nm) in the 2020-2026 beam trawl surveys in area E. Blue lines are tows, red lines define the fishing areas and red polygons represent fishing grounds based on VMS.

Figure 12: Sea cucumber. Density (n/nm) in the 2020-2026 beam trawl surveys in areas F (top), G (middle) and H (lowest). Blue lines are tows, red lines define the fishing areas and red polygons represent fishing grounds based on VMS.

The density of sea cucumber (number per nautical mile) in the areas has decreased in the Eastern areas since the beam trawl survey started (Figure 13). In the Western areas, the density remains relatively constant (Figure 14).

Figure 13: Sea cucumber. Density of sea cucumbers in the Western areas (A, B and E). The shaded area shows the 95% confidence interval.

Figure 14: Sea cucumber. Density of sea cucumbers in the Eastern areas (F, G and H). The shaded area shows the 95% confidence interval.

It can be difficult to properly measure the length of the sea cucumbers, as the animal often contracts and assumes a rounded shape. To estimate changes, size frequency (both length and circumference) was used, and the resulting metric is referred to as “adjusted length”. The surface area of the animals was calculated as a cylinder, but without the top and the bottom area (as they are contracted at the ends), and the square root of that number calculated $L_a = \sqrt{2*\pi*r*L}$. The length–weight relationship was stronger for the adjusted length than for either length or circumference.

In general, sea cucumbers are heavier in eastern Iceland (areas F-H) than in western Iceland (areas A, B and E; Figure 15). The average adjusted length was also greater in the east, where individuals generally had thinner body walls and a higher water content (Figure 15).

Figure 15: Sea cucumber. Adjusted length (cm), weight (g) and gutted weight (g) distributions in the 2020-2026 beam trawl surveys. The line in each ridge represents the mean.

Weather and sea conditions

Weather and sea conditions have always been registered in the cruises (Figure 16). To test whether these conditions affect the sea cucumber catch, a linear model was fitted with density (scaled catch per standard tow) as the response and seafloor temperature, wind speed and wave height as covariates, controlling for area and year. None of the three weather/sea variables had a statistically significant effect on density (linear model, p > 0.05 in all three cases), indicating that same-day weather doesn’t affect the catch of sea cucumber. However, weather can affect the distribution of sea cucumbers several days before the sample is taken as well, making it generally hard to estimate the effect on weather on the catch.

Figure 16: Sea cucumber. Seafloor temperature (°C), wind speed (m/s) and wave height (m) by year and area in the beam trawl survey.

Management

The Ministry of Industries is responsible for management of the Icelandic fisheries and implementation of legislation. The sea cucumber stocks were included in the ITQ system in 2022, but prior to that when the issued TAC had been reached the area was closed with a regulation issued by the Ministry.

In 2009 three fishing zones were marked by the Ministry: 1) Western area: Reykjanes to Skagatá, 2) Northern area: Skagatá to Glettinganes and 3) Southern and eastern area: Glettinganes to Reykjanes. For each of these zones three fishing licenses were issued and vessels were not permitted to move between zones. However, no fishing was conducted in the Northern area as limited fishing trials did not give positive results. In 2013, the Ministry abolished the area restriction. Initially, the main fishing areas were in Faxaflói and Aðalvík in the Western area, and since 2009 also off the east coast belonging to the Southern and eastern area. In 2013, the main fishing areas were defined by coordinates (Regulation 795/2013, Figure 1).

In 2009, the stock status in Faxaflói and Aðalvík were estimated, the fishing areas defined, and total allowable catch (TAC) advice issued for the first time. In 2012, the stock status off the east coast was estimated, which resulted in advice for that area during the fishing year 2013/2014. Total TAC was given for the eastern area even though it was divided into two areas, until 2018/2019 when the TAC was divided (area F and G). When the maximum allowable catch had been reached within an area, the area was closed, but further fishing could be continued outside the defined areas.

In a letter in February 2019, the Ministry of Industries and Innovation requested advice on fishing opportunities for sea cucumber by increasing number of sea cucumber management areas built on fishing ventures outside the previously managed areas (A, E, F & G). The new (mostly adjacent) areas were granted, and the management areas are now eight (A-H) (Anon, 2019, Figure 1). A national TAC has been issued from the fishing year 2022/2023 and onward. Before that a recommended TAC was issued and fishing was closed by regulation issued by the Ministry when the TAC was reached. The catch has mainly followed the TAC since the new areas were implemented in 2019 (Figure 17).

Figure 17: Sea cucumber. Development of advice by year and area. Blue bars show catch and the red line shows the advice. The light blue part of the bars in area D shows catch from area DI (no advice given).

The catch advice for sea cucumber is now given for each calendar year rather than for each fishing year, because the stock assessment survey takes place late in the fishing year, which makes it impractical to publish advice before the start of each new fishing year.

Stock assessment

The catch advice for the year of 2027 follows the ICES framework for stocks where analytical stock assessment can’t be implemented but biomass indices and information on life history are available (areas A, B, E-H). The advice follows the $rfb$ rule of ICES:

\[ A_{y+1} = A_{y-1} r f b m \]

where $A_{y+1}$ is recommended catch, $A_{y-1}$ is the recommendation of the previous year, $r$ is the biomass ratio of the last two years (Index A) vs. the three previous years (Index B):

\[ r = \frac{\frac {\sum_{i_y-2}^{y-1}I_1} {2}} {\frac{\sum_{i=y-3}^{y-5}}{3}} \]

This year, the ratio of the last two years survey biomass index compared to the previous three years was used.

𝑓 is a fishing proxy for the exploitation (mean catch length divided by an MSY reference length):

\[ f=\frac{\bar{L}_{y-1}} {L_{F=M}} \]

where $\bar{L}$ is the mean catch length above $L_c$ (the length at which the frequency is at least half that of the modal length, see Figure 18). For the sea cucumber, adjusted length from the surveys was used (Figure 19).

$L_{F=M}$ is calculated as:

\[ L_{F=M} = 0.75L_c + 0.25L_\infty \]

where $L_c$ is the length at which the frequency is at least half that of the modal length, and $L_\infty$ is the von Bertalanffy $L_\infty$.

$b$ is the biomass safeguard and is used to reduce catch advice when index falls below trigger, but that value has not yet been defined for the sea cucumber stocks.

$m$ is a multiplier based on stock growth. For slow-growing species such as sea cucumber (Hamel & Mercier, 1996), m = 0.95, whereas for fast-growing species m = 0.9. In general, advice according to the $rfb$ rule is applied for two years (ICES, 2023), but due to the short biomass time series and declining biomass in the eastern areas, the advice is currently given for one year.

Figure 18: Sea cucumber. Adjusted length frequency distribution from surveys on areas A, B, E, F, G & H. Red bars indicate lengths at which the frequency is at least half that of the modal length; the smallest such length is $L_c$ (broken line indicates the 50% frequency). The red vertical line denotes the von Bertalanffy $L_\infty$.

Figure 19: Sea cucumber. Mean adjusted length higher $L_c$ , from surveys in fishing areas A, B, E, F, G & H. Broken blue lines shows MSY reference length ($L_{F=M}$).

References

Anon, 2019. MFRI Assessment Reports 2019. Sea cucumber – New areas. Marine and Freshwater Research Institute, 22 March 2019.

Anderson, S.C., E.J. Ward, P.A. English, L.A.K. Barnett. 2022. sdmTMB: an R package for fast, flexible, and user-friendly generalized linear mixed effects models with spatial and spatiotemporal random fields. bioRxiv 2022.03.24.485545.

Hamel, J.-F., and A. Mercier. 1996. Early development, settlement, growth and spatial distribution of the sea cucumber Cucumaria frondosa (Echinodermata: Holothuroidea). Canadian Journal of Fisheries and Aquatic Sciences, 53, 253–271.

ICES. 2012. Implementation of Advice for Data-limited Stocks in 2012 in its 2012 Advice. ICES CM 2012/ACOM 68. http://www.ices.dk/sites/pub/Publication%20Reports/Expert%20Group%20Report/acom/2012/ADHOC/DLS%20Guidance%20Report%202012.pdf

ICES. 2021. Tenth Workshop on the Development of Quantitative Assessment Methodologies based on LIFE-history traits, exploitation characteristics, and other relevant parameters for data-limited stocks (WKLIFE X). ICES Scientific Reports. Report. https://doi.org/10.17895/ices.pub.5985

ICES, 2023. Eleventh Workshop on the Development of Quantitative Assessment Methodologies based on LIFE-history traits, exploitation characteristics, and other relevant parameters for data-limited stocks (WKLIFE XI). ICES Scientific Reports. Report. https://doi.org/10.17895/ices.pub.22140260.v1