Atlantic wolffish

Key signals

Biomass indices from stock surveys are high, fishable biomass peaked in 2022-23.
The recruitment index (<40 cm) dropped to low levels in SMB in 2011, but has been increasing since.
Fishing pressure on the stock is below F_msy and F_pa. Spawning-stock is above MGT B_trigger, B_pa and B_lim.
Data from surveys and fisheries indicate that Atlantic wolffish in 5a is currently in good condition. This is also confirmed by the stock assessment.
MFRI recommends a continued closure of the most important spawning area west of Iceland during the spawning and incubation season in autumn and winter.

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 been increasing, while it has declined in the west. Catches at the main spawning ground, Látragrunn (located west of Iceland), have been decreasing since 2008 (Figure 1 and 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 meters. The proportion of the catch from the 0–60 m depth range declined between 2003 and 2007 but has been increasing since. In the 61–120 m depth range, the catch proportion has remained relatively stable since 2000. At depths of 121–180 m—which includes the main spawning ground at Látragrunn—the catch proportion increased between 2003 and 2008 but has declined since then (Figure 3).

Atlantic wolffish in mainly caught by longliners, demersal trawlers and seiners (Figure 4). Proportions in each gear have been changing in most recent years with demersal seiners increasing their share, resulting in roughly one third of the Atlantic wolffish catch being caught by that fleet (Figure 4). Since 2001, the number of vessels reporting Atlantic wolffish catches of 10 tonnes/year or more has decreased. Most of the decrease is in the longline fleet, where the number of vessels has dropped from 198 in 2001, down to 39 in 2024. The number of trawlers has been variable but not changed much, and the number in 2024 is the same as in 2002. Number of demersal seiners has increased in the period 2000-2024 (Table 1).

In 1994 and 1995, more than 500 vessels accounted for 95% of the annual catch of Atlantic wolffish in Icelandic waters, but this number had dropped to 200 vessels in 2008 despite higher catches. Since 2010 the number of vessels accounting for 95% of the annual catch has remained relatively constant (about 150-200 vessels), despite catch reductions (Figure 5).

Figure 1: Atlantic wolffish. Geographical distribution of the Icelandic fishery over the past 9 years, based on reported logbook catch data.

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.

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	2 706	2 986	2 275	7 967
2023	36	49	20	0	3 154	2 756	2 388	8 298
2024	39	45	24	0	2 612	2 914	2 900	8 426

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.

Data available

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 7 and Figure 6).

Figure 6: 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 7: Atlantic wolffish. Spatial distribution of length samples (crosses) from commercial catches in Icelandic waters.

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, as well as in Norway. 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 reduce discards in mixed fisheries.

Sampling from commercial catches

The number of length and age samples from landed Atlantic wolffish was reduced in 2014 (Table 2 and Table 3). Prior to that, approximately 1600–3000 fish were sampled annually for age readings and about 6000–14000 were measured for length. Between 2015 and 2021, otoliths were collected annually from an average of just over 1200 wolffish. In 2024, a total of 10, 29 and 26 samples were collected from longline, bottom trawl and demersal seine catches, respectively (Table 3, Figure 7).

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	15	1 357	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	10	1 071

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	10	200	29	580	26	508

Length composition

The length distribution of landed Atlantic wolffish has been relatively stable since 2005 in all gears (Figure 8).

Figure 8: Atlantic wolffish. Length distribution from the Icelandic fishing fleet since 2005

Age composition

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 2024, 9-14 year old fish are most common in the catches (Figure 9 and Figure 10).

Figure 9: 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 10: 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

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 11). Catch by year and age is shown in Figure 12. The contribution of the plus group (16+) is often high.

Figure 12: Atlantic wolffish. Catch by year and age from the commercial fishery in Icelandic waters.

Catch and effort

CPUE estimates of Atlantic wolffish in Icelandic waters are not considered representative of stock abundance, as changes in fleet composition, technical improvements and differences in gear setup among other things have not been accounted for when estimating CPUE. Effort of demersal trawl is defined as the number hours towed, for longline number of hooks and demersal seine number of sets. CPUE is calculated based on sets or tows in which Atlantic wolffish was more than 10% of the total catch and sets where Atlantic wolffish was caught. CPUE index for each year and gear is then caught as the median CPUE for the selected sets for each gear and year.

CPUE in longline was relatively stable prior to 2018, fluctuating around 75 kg/1000 hooks but doubled between 2000 and 2023. CPUE of demersal trawl was at it highest in 2005 and 2015 with approximately 270-300 kg/h, between those years it dropped below 200 kg/h and has been around that level since. CPUE of demersal seine has been increasing since and is at it´s highest (Figure 13). In summary we see contrast between CPUE in bottom trawl and CPUE in demersal seine and long line in last 5 years where bottom trawl CPUE is stable but CPUE in the other gear increasing.