Atlantic wolffish

Key signals

Biomass indices have declined across all survey parameters following a peak in 2022–23, and fishing mortality now exceeds F_msy, F_pa, and F_mgt.
Recruitment index (≤40 cm) declined to a historical minimum in 2011, recovered through 2023, and has since declined again toward critically low levels.
Spawning stock biomass still remains above B_lim, B_pa, and MGT B_trigger, though current exploitation levels are slightly above reference points.
Although survey indices are declining, commercial catch data suggest that the wolffish stock remains in balance, which is confirmed by the stock assessment.
Continued closure of the Látragrunn spawning area during the spawning and incubation season is recommended.

General information

The Atlantic wolffish is a long-bodied species with a large head, characterized by prominent canine teeth for seizing prey and powerful molars for crushing it. Most individuals caught measure between 50 and 80 cm in length, although the largest specimen recorded in Icelandic waters reached 125 cm. The species is most commonly found on the continental shelf northwest of Iceland. Its feeding grounds are typically located on muddy or sandy bottoms at depths shallower than 100 meters. In contrast, spawning grounds are found on coarser substrates featuring crevices or cavities, generally at depths greater than 100 meters.

Fishery

The primary fishing grounds for Atlantic wolffish are located on the western and northwestern parts of the Icelandic continental shelf. Since 2010, the proportion of the catch taken in the northwest has increased, while it has declined in the west. Catches at the main spawning ground, Látragrunn (west of Iceland), have decreased since 2008 (Figure 1; Figure 2). Notably, part of this area has been closed to trawling during the spawning and incubation period since 2010. Approximately 80% of the Atlantic wolffish catch is taken at depths shallower than 120 m. The proportion of the catch from the 0–60 m depth range increased in 2017 and has remained stable since. In the 61–120 m depth range, the catch proportion has remained relatively stable since 2000. At depths of 121–180 m, which include the main spawning ground at Látragrunn, the catch proportion has been declining over the past decade (Figure 3). Atlantic wolffish are primarily caught by longliners, demersal trawlers, and demersal seiners (Figure 4). The relative contributions of these fleets have changed in recent years, with demersal seiners increasing their share to approximately one-third of the total catch (Figure 4). Since 2001, the number of vessels reporting annual Atlantic wolffish catches of 10 tonnes or more has declined. This reduction is mainly attributable to the longline fleet, where the number of vessels decreased from 195 in 2001 to 29 in 2025, representing the lowest level since 2000. The number of trawlers and demersal seiners has varied over time but without marked long-term trends (Table 1). In 1994 and 1995, more than 500 vessels accounted for 95% of the annual Atlantic wolffish catch in Icelandic waters. This number declined to approximately 200 vessels by 2008, despite higher catch levels. Since 2010, the number of vessels accounting for 95% of the annual catch has remained relatively stable (approximately 150–200 vessels), despite reductions in total catch (Figure 5).

Figure 2: Atlantic wolffish. Spatial distribution of the Icelandic fishery by fishing area since 2000 according to logbooks. All gears combined.

Figure 3: Atlantic wolffish. Depth distribution of demersal trawl, longline and demersal seine catches according to logbooks.

Figure 4: Atlantic wolffish. Total catch (landings) by fishing gear since 1994, according to statistics from the Directorate of Fisheries.

Figure 5: Atlantic wolffish. Number of vessels (all gear types) accounting for 95% of the total catch annually since 1994. Left: Plotted against year. Right: Plotted against total catch. Data from the Directorate of Fisheries.

Table 1: Atlantic wolffish. Number of Icelandic boats and catches by fleet segment participating in the Atlantic wolffish fishery from logbooks.

Year	nr. longlines	nr. trawlers	nr. demersal seiners	nr. other	Longline	Demersal trawl	Demersal seine	Total catch
2000	161	53	16	0	8 687	3 380	528	12 595
2001	195	59	14	1	11 267	3 391	513	15 182
2002	140	44	13	0	7 773	3 735	601	12 110
2003	138	45	19	0	7 785	5 463	1 066	14 313
2004	103	34	29	0	4 670	4 773	1 609	11 052
2005	91	47	24	1	5 445	6 893	1 140	13 508
2006	120	48	25	0	6 626	6 286	1 149	14 061
2007	105	60	24	0	5 259	7 566	1 338	14 163
2008	87	60	22	3	4 663	6 960	1 427	13 093
2009	114	55	28	1	6 708	5 468	1 205	13 391
2010	74	46	20	3	5 916	4 436	842	11 286
2011	64	37	18	0	5 344	3 565	1 010	9 918
2012	66	24	22	1	5 328	2 827	895	9 091
2013	73	30	18	2	4 652	2 341	647	7 662
2014	70	23	13	1	3 681	1 637	891	6 220
2015	56	34	17	2	3 989	1 905	926	6 848
2016	61	37	18	2	4 848	1 662	1 127	7 661
2017	59	28	18	2	3 829	1 102	1 095	6 049
2018	60	37	27	6	4 923	1 587	2 186	8 770
2019	64	34	21	1	4 595	1 630	2 168	8 404
2020	46	38	24	1	2 491	2 046	2 040	6 588
2021	45	48	22	0	3 343	3 021	2 086	8 451
2022	40	48	23	0	2 506	2 981	2 223	7 710
2023	34	49	20	0	2 899	2 755	2 346	8 000
2024	37	45	24	0	2 405	2 914	2 826	8 145
2025	29	46	24	0	2 096	3 460	3 056	8 612

Catch per unit of effort from commercial fisheries

CPUE estimates of Atlantic wolffish in Icelandic waters are not considered representative of stock abundance, as changes in fleet composition, technological improvements and differences in gear setup, among other factors, have not been accounted for in the estimation of CPUE. Non-standardized estimates of CPUE for longline (kg/1000 hooks), demersal trawl (kg/hour) and demersal seine (kg/set) are calculated as the total catch weight from sets or tows in which Atlantic wolffish constituted more than 10% of the catch, according to logbook records.

CPUE for longline vessels was relatively stable prior to 2018, fluctuating around 75 kg/1000 hooks; however, it doubled between 2020 and 2025 and has remained high since. CPUE of demersal trawl was highest in 2005 and 2015, at approximately 270-300 kg/hour. Between these years, it dropped below 200 kg/hour and has remained around that level since. CPUE of demersal seine increased from just under 400 kg/set to around 650 kg/set during 2020-2023 and is currently at its highest level (Figure 6).

In summary, there is a contrast in recent trends among gear types: over the past five years, CPUE for bottom trawl has remained stable, while CPUE for demersal seine and longline has increased.

CPUE data are not used in the stock assessment, as they do not reliably reflect trends in stock abundance.

Figure 6: Atlantic wolffish. Non-standardized estimates of CPUE for demersal trawl (left, kg/h), demersal seine (middle, kg/sets) and longline (right, kg/1000 hooks).

Landings and discards

Landings by Icelandic vessels are obtained from the Icelandic Directorate of Fisheries. Landings of Norwegian and Faroese vessels are given by the Icelandic Coast Guard. Discarding is banned by law in the Icelandic demersal fishery. Measures in the Icelandic management system such as converting quota from one species to another are used by the Icelandic fleet to a large extent, and is thought to discourage discards in mixed fisheries.

Data and sampling

Commercial data

The commercial catch samples taken should be representative of the landings with most number of samples taken in areas of high catch intensity. In general, sampling from commercial catches is considered acceptable from the main gears (demersal seines and trawls). The sampling seems to follow the spatial and seasonal distribution of catches (Figure 8 and Figure 7).

Figure 7: Ratio of samples by month (bars) compared with proportion landings by month (solid black line) split by year and main gear types. Numbers of above the bars indicate number of samples by year, month and gear.

Figure 8: Atlantic wolffish. Spatial distribution of length samples (crosses) from commercial catches in Icelandic waters.

In 1969-1997, on average 500 otoliths were sampled annually, except in 1970, 1973, and 1974 when no otoliths were sampled. In 1999, the effort of sampling Atlantic wolffish from commercial catch was increased. The number of length and age samples from landed Atlantic wolffish was reduced in 2014 (Table 2 and Table 3). In the years 1999-2014 annual sampling of aged fish was 1600-3000 or on average 2200, but since 2015 this average has been around 1200 fish. In 2025, a total of 4, 29 and 32 samples were collected from longline, bottom trawl and demersal seine catches, respectively (Table 3, Figure 8).

Table 2: Atlantic wolfish. Number of samples and length measured fish from landed catch of Atlantic wolffish.

Year	Bottom Trawl		Demersal Seine		Long Line
Year	Num. samples	Num. lengths	Num. samples	Num. lengths	Num. samples	Num. lengths
2000	22	2 852	4	468	29	3 698
2001	13	1 806	3	376	33	4 147
2002	37	4 912	2	281	44	5 151
2003	36	4 270	7	1 251	42	6 433
2004	33	3 932	12	1 505	23	3 241
2005	57	7 732	16	1 684	33	5 089
2006	43	5 829	7	754	44	5 882
2007	44	5 935	17	1 839	33	3 963
2008	64	9 903	13	1 355	24	3 351
2009	52	8 470	14	1 674	33	4 464
2010	54	9 640	13	1 666	30	3 911
2011	20	3 015	12	1 391	17	2 524
2012	41	9 684	12	1 206	26	3 574
2013	20	3 175	5	671	26	3 711
2014	31	4 296	31	3 623	30	3 748
2015	20	2 358	20	1 984	26	3 168
2016	13	1 596	10	970	26	2 806
2017	9	956	6	633	24	2 973
2018	9	817	17	1 687	22	2 654
2019	12	1 128	23	2 349	23	2 677
2020	18	1 833	17	1 652	9	1 007
2021	25	2 987	15	1 070	14	1 277
2022	23	2 420	17	1 235	3	269
2023	22	2 365	25	2 203	12	1 039
2024	33	3 646	26	2 075	11	1 174
2025	40	4 725	32	2 972	4	354

Table 3: Atlantic wolffish. Number of samples and aged fish from landed catch of Atlantic wolffish.

Year	Longline		Bottom trawl		Demersal seine
Year	num. samples	num. otoliths.	num. samples	num. otoliths.	num. samples	num. otoliths.
2000	29	1 395	18	752	4	200
2001	27	1 343	11	509	3	150
2002	25	1 240	16	645	2	100
2003	31	1 525	20	899	6	300
2004	19	950	23	1 060	8	400
2005	15	746	25	1 202	6	292
2006	23	1 110	21	1 029	5	250
2007	18	900	25	1 250	10	451
2008	19	950	25	1 248	4	200
2009	16	800	20	999	4	200
2010	29	1 669	19	1 090	5	285
2011	14	750	15	778	9	550
2012	26	1 300	14	700	7	350
2013	25	1 249	14	691	4	200
2014	30	800	26	675	28	700
2015	25	625	19	479	19	474
2016	25	625	13	325	9	225
2017	23	575	9	220	6	150
2018	22	550	9	225	17	425
2019	22	550	11	276	20	500
2020	9	225	14	350	16	400
2021	14	350	25	625	15	375
2022	3	60	23	465	17	338
2023	12	240	21	420	25	499
2024	11	220	29	580	26	508
2025	4	80	29	580	32	632

Length compositions

The length distribution of landed Atlantic wolffish has been relatively stable since 2005 in all gears (Figure 9).

Figure 9: Atlantic wolffish. Length distribution from the Icelandic fishing fleet since 2005

Age compositions

Commercial age data is available since 1980s. In samples from commercial landings, the mean age of Atlantic wolffish was around 10.7 years in 1999. Since then, mean age from commercial catches has generally been increasing to around 12 years in recent years. In 2025, 9-14 year old fish are most common in the catches (Figure 10 and Figure 11).

Figure 10: Atlantic wolffish. Catch at age from the commercial fishery in Iceland waters. Bar size is indicative of the catch in numbers and bars are coloured by cohort. Scale of the y-axis varies between plots.

Figure 11: Atlantic wolffish. Catch at age from the commercial fishery in Iceland waters. Biomass caught by year and age; bars are coloured by cohort.

Weight at age in the catch

Mean weight at age in commercial catches in Icelandic waters are available from 1996. Weight of the oldest year classes has been above average for the past years (Figure 12).

Survey data

The Icelandic spring groundfish survey (hereafter spring survey, IGFS), conducted annually in March since 1985, covers the principal distribution area of Atlantic wolffish in Icelandic waters. In addition, the Icelandic autumn groundfish survey (hereafter autumn survey, IAGS) was initiated in 1996 and expanded in 2000. A full autumn survey was not conducted in 2011 due to a labour strike. Both surveys cover the main distribution areas of Atlantic wolffish; however, the spring survey includes approximately three times as many stations within the core distribution area. Furthermore, the trawl used in the spring survey is heavier and better suited for catching wolffish. Diurnal variation in survey catches is substantial, with lower catches observed during daytime.

Total biomass and harvestable biomass indices declined during 1985–1995. The biomass index increased from 1996 to 1998, then declined to a historical low during 2010–2012. Since then, it has shown an increasing trend, although a marked decline is observed in the most recent survey (Figure 13). The harvestable biomass index has generally increased since 1995, with considerable interannual variability, but also shows a decline in the most recent year. The recruitment index was high during 1992–2003 but has generally declined since 1999. This decline coincides with increased trawling effort and catches at the main spawning ground west of Iceland (Látragrunn) during the spawning and incubation period. Recruitment reached a historical low in 2011 and subsequently increased, albeit with fluctuations. More recently, it has declined again and is approaching historically low levels. The post-2011 increase coincides with the expansion of the closed spawning and incubation area at Látragrunn from 500 km² (established in 2002) to 1,000 km² in October 2010. However, the marked decline in the most recent spring survey warrants further investigation. Although spring survey indices appear more precise (i.e. narrower confidence intervals), they exhibit greater variability than expected based on their estimated uncertainty or plausible changes in stock size.

During the spring survey, Atlantic wolffish are primarily located on their feeding grounds, typically in relatively shallow waters. The highest abundance has consistently been observed in the northwest (NW) area (Figure 14; Figure 15). In contrast to the catch distribution (Figure 2), a larger proportion of the stock is observed in the northeast (NE) area in the survey data, particularly during the late 1990s (Figure 14).

Length distributions from the surveys have remained relatively stable in recent years. The spring survey exhibits a bimodal distribution, likely reflecting differences in growth among areas around Iceland (Figure 16). Mean lengths have increased since 2000 in both surveys (Figure 16).

Figure 13: Atlantic wolffish. Total biomass indices (upper left) and harvestable biomass indices (≥60 cm, upper right), large fish biomass indices (≥80 cm, lower left) and juvenile abundance indices (≤40 cm, lower right), from the spring survey (blue) and the autumn survey (red), along with the standard deviation.

Figure 14: Atlantic wolffish. Spatial distribution of biomass index from the spring and autumn survey.

Figure 15: Atlantic wolffish. Location and abundance in the most recent spring survey (SMB) and the autumn survey (SMH).

Figure 16: Atlantic wolffish. Length distribution from the spring and autumn survey.

Figure 17: Atlantic wolffish. Age disaggregated indices in the autumn survey and the spring survey. Fill colours indicate cohorts. Note different scales on y-axes.

Stock weight at age

Mean weight at age in the survey is shown in Figure 18. Stock weights are obtained from the groundfish survey in March and are also used as mean weight at age in the spawning stock. Stock weights show considerable positive trend from 2013-2025.

Figure 18: Atlantic wolffish. Stock weights from the spring survey in Icelandic waters. Bars are coloured by cohort.

Stock maturity and natural mortality

Females have more reliable maturity designations; a maturation scale for males is unavailable. Therefore, spawning stock is only based on mature females caught in the autumn survey and in commercial catches from June – December. From these data, maturation occurs close to 60 cm and around age 10 but is highly variable and difficult to measure. Proportion mature at age has increased for the past 20 years for most age groups (Figure 19 and Figure 20). No information is available on natural mortality. For assessment and advisory purposes, the natural mortality is set to 0.15 for all age groups.

Figure 19: Atlantic wolffish. Maturity at age in the autumn survey and commercial catches in June-December. The values are used to calculate the spawning stock.

Figure 20: Atlantic wolffish. Maturity at age in the autumn survey and commercial catches in June-December. The values are used to calculate the spawning stock.

Stock assessment

Model and data inputs

Atlantic wolffish in 5a became part of the ICES assessment process after an MoU between Iceland and ICES was signed in December 1st 2019. Assessment method for Atlantic wolffish was established during benchmark in April 2022 and SAM model (state-space stock assessment model) was agreed upon as an assessment tool.

The new assessment model is a statistical catch at age model based on:

commercial catch-at-age and landings data from 1979 onwards, in the period 1981-1997 the age disaggregated catches are not available but total landings are used (Figure 10),
the Icelandic spring groundfish survey from 1985 (Figure 17),
the Icelandic autumn groundfish survey in Iceland from 2000 (Figure 17).

The model runs from 1979 onwards and ages 4 to 16 are tracked by the model, treating age 16 as a plus group. Natural mortality of 0.15 was chosen for all age groups. During the workshop, a wide range of estimates for natural mortality were tested and none showed a significant improvement in terms of model fit. It was therefore decided to use a M of 0.15.

Diagnostics and fit

Figure 21 illustrates the overall fit to the survey indices and catch. The model generally reproduces historical stock trends, with a closer fit to catch and SMB than to SMH. Furthermore, terminal estimates exhibit no substantial deviation from observed values across most age groups. The overall model fit is further assessed in Figure 24, which presents a comparison of observed and predicted survey biomass. Neither observation nor process residuals exhibit systematic patterns (Figure 22 and Figure 23).

Figure 21: Atlantic wolffish. Model fit to indices from the spring survey, autumn survey and catch. Black dots are observed values and the black line is the model fit.

Figure 22: Atlantic wolffish. Observation error residuals of the SAM model.

Figure 23: Atlantic wolffish. Process error residuals of the SAM model.

Figure 24: Atlantic wolffish. Aggregated model fit to the total biomass indices. Note that residual correlation is estimated (see text for further details).

Results

Model results indicate that Atlantic wolffish spawning stock biomass (SSB) has increased overall since 1992, with a temporary decline around 2014, and remains at a relatively high level. This trend partly reflects increases in weight and maturity at age. Survey biomass indices for fish >60 cm and >80 cm have also increased over this period (last 30 years; Figure 13), indicating that the increase in SSB is not solely driven by changes in maturity or stock weight. Recruitment declined to a low level in 2011, increased thereafter, and declined again in 2025. The post-2011 increase is likely associated with the larger spawning stock and the closure of key spawning areas. Landings decreased from the high levels observed during 1990–2009 and have remained relatively stable since 2014 (Figure 25).

The results of an analytical retrospective analysis are presented in Figure 26. The analysis indicates relatively stable estimate, except in the earliest peel. Mohn’s rho was estimated to be -0.0251 for SSB, -0.0132 for F, and 0.0273 for recruitment. Mohn’s \(\rho\) values for spawning stock biomass, fishing mortality, and recruitment are low and fall well within the acceptable range recommended by Carvalho et al. (2021).

Figure 26: Atlantic wolffish. Retrospective plots illustrating stability in model estimates over a 5-year “peel” in data. Results of spawning stock biomass, fishing mortality F, and recruitment (age 4) are shown.

Short-term projections

Short-term projections are carried out using the standard procedure in SAM via the forecast function. Three-year averages are applied for stock weights, catch weights, and maturity. The projections form the basis for the catch advice (Table 4).

Table 4: Atlantic wolffish. Results from the short term prognosis

Year	F(10-15)	Recruitment	SSB	Catch
2026	0.214	11986	31265	8639
2027	0.200	13340	33495	8926
2028	0.200	13340	34704	9249

The advice is aligned with the Icelandic fishing year, which begins in September, whereas the assessment model operates on a calendar-year basis. This mismatch requires adaptation of the standard SAM projection procedure to accommodate the offset between assessment and advisory years.

Given the assessment in year \(y\), interim year catches are based on the following fishing mortality:

\[ F_{y} = \left(\frac{8}{12}F_{sq} + \frac{4}{12} F_{mgt}\right) \]

and therefore the total catches for year \(y\) will be:

\[ C_{y} = \frac{F_{y}}{F_{y} + M} \left(1 - e^{-(F_{y} + M)}\right)B_{y} \]

and the part of the catch in the fishing year y-1/y will be

\[ \frac{\frac{8}{12}F_{sq}}{\left(\frac{8}{12}F_{sq} + \frac{4}{12} F_{mgt}\right)} C_y \]

and the catch in fishing year y/y+1 will be:

\[ C_{y/y+1} = \frac{\frac{4}{12}F_{mgt}}{\left(\frac{8}{12}F_{sq} + \frac{4}{12} F_{mgt}\right)} C_y + \frac{8}{12}C_{y+1} \]

where

\[ C_{y+1} = \frac{F_{mgt}}{F_{mgt} + M} \left(1 - e^{-(F_{mgt} + M)}\right)B_{y} \]

Reference points and advice basis

History

The Ministry of Industries and Innovation is responsible for management of the Icelandic fisheries and implementation of legislation. Atlantic wolffish was included in the ITQ system in the 1996/1997 quota year and as such subjected to TAC limitations. From that time to the fishing year 2004/2005, the catch was on average 5% more than recommended by the MRI (Marine Research Institute), although in some years it was lower than advised TAC. In the fishing years 2005/2006 to 2011/2012, the catch was on average around 34% above the advised TAC (Figure 27). The main reasons were that national TAC was set higher than the advised TAC, and quota of other species were being transferred to Atlantic wolffish quota (Figure 28). Net transfer of Atlantic wolffish quota for each fishing year is usually less than 15%.

Figure 27: Atlantic wolffish. Comparison of advice, quota, and total catch.

Figure 28: Atlantic wolffish. Net transfer of quota to and from Atlantic wolffish in the Icelandic ITQ system by fishing year. Between species (upper): Positive values indicate a transfer of other species to Atlantic wolffish, but negative values indicate a transfer of Atlantic wolffish quota to other species. Between years (lower): Transfer of quota from given quota year to the next quota year.

Harvest control rule

As part of the WKICEMP 2022 HCR evaluations (ICES 2022a), the following reference points were defined. This resulted in an estimate of \(B_{pa}\) of 21 000 t, based on the lowest observed SSB following the 2001 shift in recruitment (observed in 2002). The limit reference point was defined as \(B_{lim} = B_{pa} e^{-1.645\sigma_B}\), yielding 18 500 t, where \(\sigma_B\) was set to the ICES default value of 0.2. Fishing pressure, defined as the fishing mortality applied to ages 10–15, was estimated in accordance with ICES guidelines. This resulted in estimates of \(F_{lim} = 0.33\), \(F_{p05} = 0.20\), and \(F_{msy} = 0.20\). The MSY \(B_{trigger}\) was set equal to \(B_{pa}\).

A Management Strategy Evaluation (MSE) was conducted for Atlantic wolffish in 5a. The operating model, which generates the “true” future populations in the simulations, was based on equilibrium simulations (eqsim). Selection, maturity and stock weights were based on the resampling of estimates by age from previous 10 years. Recruitment was projected using a log-normal distribution based on the distribution of CVs and autocorrelations estimated by the assessment model with MCMC resampling with a break point in B\(_{lim}\). Advice error in the simulations was implemented as auto-correlated log-normal variations in F, with a CV of 0.212 and \(\rho\) of 0.423.

The proposed HCR for the Icelandic Atlantic wolffish fishery, which sets a TAC for the fishing year y/y+1 (September 1 of year y to August 31 of year y+1) based on a fishing mortality \(F_{mgt}\) of 0.20 applied to ages 10 to 15, modified by the ratio SSB\(_{y}\)/MGT B\(_{trigger}\) when SSB\(_y\) < MGT B\(_{trigger}\), maintains a high yield while being precautionary as it results in lower than 5% probability of SSB < B\(_{lim}\) in the medium and long term.

Table 5: Atlantic wolffish. Reference points adopted from ICES WKICEMP 2022

Framework	Reference_point	Value	Technical_basis
MSY Approach	MSY Btrigger	21000	Bpa
	FMSY	0.2	F that produces MSY in the long term

Precautionary Approach	Blim	18500	Bloss (SSB in 2002)
	Bpa	21000	Blim x e1.645 * σB
	Flim	0.33	Fishing mortality that in stochastic equilibrium will result in median SSB at Blim.
	Fpa	0.2	Maximum F at which the probability of SSB falling below Blim is <5%
Management plan	MGT Btrigger	21000	According to the harvest control rule
	FMGT	0.2	According to the harvest control rule

Management considerations

A reduction in fishing mortality has led to harvestable biomass and SSB slowly increasing. Atlantic wolffish is a slow-growing late-maturing species, therefore closures of known spawning areas should be maintained and expanded if needed. Similarly, closed areas where there is high juvenile abundance, both in the fishery and surveys, should also be maintained and expanded if needed. Survey indicators are suggesting decline in all indices in the last three years, fishing mortality is above \(F_{lim}\) and \(F_{mgt}\). The results of this year analytical assessment follows the drop in most recent indicators.

Ecosystem considerations

Most fishing for Atlantic wolffish occurs in the northwest and west of Iceland, where the fastest growing Atlantic wolffish are found. A likely cause for differences in growth is environmental differences between the relatively warm southwestern waters versus colder northeastern waters. The surveys indicate that 25-50% of the stock is in the NE area while less than 10% of the catch is taken there (Figure 14) and (Figure 1)

However, Atlantic wolffish are also highly sedentary, especially while guarding nests during spawning and rearing season, and therefore additional metapopulation structure cannot be excluded. Therefore, it is possible that local depletion may occur in more heavily fished areas despite a stable overall biomass level.

References

Carvalho, Felipe, Henning Winker, Dean Courtney, Maia Kapur, Laurence Kell, Massimili-ano Cardinale, Michael Schirripa, et al. 2021. “A Cookbook for Using Model Diagnostics in Integrated Stock Assessments.” Fisheries Research 240: 105959.

Gunnarsson, Á., Hjörleifsson, E., Thórarinsson, K., Marteinsdóttir, G., 2006. Growth, maturity and fecundity of wolffish Anarhichas lupus L. in Icelandic waters. Journal of Fish Biology, 68, 1158-1176. doi: 10.1111/j.1095- 8649.2006.00990.

Gunnarsson, Á., Sólmundsson, J., Björnsson, H., Sigurðsson, G., Pampoulie, C., 2019. Migration pattern and evidence of homing in Atlantic wolffish (Anarhichas lupus). Fisheries Research, 215. https://doi.org/10.1016/j.fishres.2019.03.001

ICES. 2022a. Workshop on the evaluation of assessments and management plans for ling, tusk, plaice and Atlantic wolffish in Icelandic waters (WKICEMP). ICES Scientific Reports. 4:37. 271 pp. http://doi.org/10.17895/ices.pub.19663971

ICES. 2022b. Stock Annex: Atlantic wolffish (Anarhichas lupus) in Division 5.a (Iceland grounds). ICES Stock Annexes. 32 pp. https://doi.org/10.17895/ices.pub.22819988