ATLANTIC HALIBUT

Key signals

• Halibut fisheries peaked early in the 20th century, declining significantly since 1960; since 2012, targeted fishing is banned, and release of all viable individuals is mandatory.

• Atlantic halibut stock indices have remained low since 1990 but slightly improved recently, with the 2024 recruitment being the highest since 1988; indices indicate growth in spawning stock since 2020.

General information

Atlantic halibut is the largest of all flatfish species and the largest bony fish caught around Iceland. The largest recorded halibut caught in Icelandic waters measured 365 cm and weighed 266 kg, captured north of Iceland in 1935. Halibut matures slowly; approximately half of males mature at around 80 cm and half of females at 103 cm. Halibut is found all around Iceland but is most prominent west and south of the country. It is a bottom-dwelling species inhabiting sandy, muddy, rocky, and even hard bottoms down to depths of 2000 m. Juveniles occupy shallow waters until 3–5 years of age, after which halibut gradually moves deeper and farther offshore. Halibut is known for extensive migrations; individuals tagged in Icelandic waters have been recaptured near the Faroe Islands, East and West Greenland, and Newfoundland. Likewise, halibut recovered in Icelandic waters have previously been tagged in the Faroes and Canada.

Fishery

Halibut fisheries were intensive in the 20th century, and catch data from Icelandic waters indicate that the species is sensitive to heavy fishing pressure (Figure 1). After peaks in catches were reached, often within very short periods, catches quickly declined. For example, the halibut stock recovered during the fishing ban of the war years when fishing activity around Iceland was limited. When fisheries resumed, catches rapidly peaked within a few years but declined sharply thereafter.

The highest halibut catches in Icelandic waters occurred in 1907, reaching nearly 8 000 tonnes, and in several other instances ranged between 6 000 and 7 000 tonnes (Figure 1). Since about 1960, annual halibut catches have steadily declined. Between 2004 and 2007, annual catches ranged from 527 to 683 tonnes, mainly caught by bottom trawls and longlines. Annual catches from 2008 to 2011 were slightly under 600 tonnes, with an increasing proportion caught by longlines due to intensified targeted fishing efforts. Since 2012, when a ban on targeted fishing was enacted and requirements to release all viable halibut were introduced, reported catches have ranged between 36 and 200 tonnes. Catches from 2022–2024 have been approximately 200 tonnes annually, mostly taken by bottom trawls.

The distribution of halibut fishing effort has changed over the past r tyr-2012 years due to the 2011 ban on targeted fishing and directives to release all viable halibut (Figure 2). Between 2000 and 2011, halibut were mainly caught west of Iceland, according to logbook data (Figure 3). After the ban, halibut fishing shifted from the western continental shelf to bottom trawl grounds northwest of Iceland.

Targeted fishing for halibut using longlines with hooks occurred at depths greater than 300 meters (Figure 4). Halibut are now caught at shallower depths, mostly by bottom trawls.

Historically, halibut was primarily caught using longlines with hooks and bottom trawls, accounting for approximately 85% of landed halibut catches (Figure 5, Table 1). Since 2011, almost no halibut has been landed from longlines (Table 1), mainly because most halibut caught by this method are viable and thus released. The number of released viable halibut increased from 2018 until 2021, when approximately 7 800 individuals were released (Table 2). Since then, releases have decreased, particularly from longline fisheries.

Figure 1: Atlantic halibut. Landed catch 1903–2024.

Table 1: Atlantic halibut. Number of Icelandic vessels landing Atlantic halibut, and all landed catch divided by gear type 1993–2024.

Year	Catch (tonnes)					Vessels (numbers)
	Bottom trawl	Demersal sein	Longline	Other gears	Total catch	Bottom trawlers	Demersal seiners	Longliners	Other vessels	Total
1993	340	96	248	75	759	265	78	420	466	1229
1994	306	151	279	96	831	257	101	491	476	1325
1995	243	116	206	45	609	225	100	460	404	1189
1996	309	173	253	50	785	187	113	411	401	1112
1997	275	104	194	45	619	169	107	314	347	937
1998	197	74	214	32	517	161	98	329	314	902
1999	199	110	222	29	561	155	87	347	272	861
2000	202	85	171	38	496	137	79	349	283	848
2001	216	95	255	62	628	136	85	348	346	915
2002	245	116	272	48	681	129	81	309	323	842
2003	215	141	202	72	631	126	88	320	304	838
2004	215	94	218	42	569	118	84	331	287	820
2005	221	54	205	41	521	119	79	327	213	738
2006	176	38	228	21	464	107	73	319	162	661
2007	177	39	187	26	429	107	68	295	122	592
2008	191	46	242	19	498	97	63	252	97	509
2009	164	47	298	19	529	92	61	235	120	508
2010	126	34	386	14	559	84	50	207	154	495
2011	88	24	423	12	548	79	47	195	174	495
2012	33	0	1	1	35	54	9	33	26	122
2013	34	1	2	3	41	67	21	46	28	162
2014	33	4	6	3	45	60	17	61	32	170
2015	72	9	0	2	84	63	18	33	18	132
2016	113	4	0	2	119	70	17	11	23	121
2017	84	16	0	1	102	67	25	8	22	122
2018	115	16	0	3	133	64	29	8	27	128
2019	103	22	0	2	128	59	30	12	24	125
2020	120	17	1	3	142	64	29	11	22	126
2021	134	16	0	3	153	63	30	6	31	130
2022	152	17	23	3	194	62	27	14	29	132
2023	137	17	19	3	176	55	25	12	37	129
2024	154	22	16	5	197	58	28	12	25	123

Figure 2: Atlantic halibut. Spatial distribution of catches by all gears according to Icelandic logbooks 2005–2024.

Figure 3: Atlantic halibut. Changes in spatial distribution of Atlantic halibut catches as recorded in Icelandic logbooks.

Figure 4: Atlantic halibut. Depth distribution of Atlantic halibut from longline, demersal trawl and seine according to Icelandic logbooks.

Figure 5: Atlantic halibut. Landed catch by fishing gear since 1994, according to the Directorate of Fisheries.

Table 2: Atlantic halibut. Number of released Atlantic halibut by year and fishing gear, and number of Icelandic vessels that reported released halibut.

	Bottom trawl		Longlines		Gillnets		Demersal seine		Total released
	Vessels	Number released	Vessels	Number released	Vessels	Number released	Vessels	Number released
2017	1	1	7	472	0	0	0	0	473
2018	0	0	13	2044	3	7	0	0	2051
2019	1	3	12	2214	0	0	1	95	2312
2020	1	2	5	2480	1	1	1	33	2516
2021	1	10	14	7723	0	0	2	66	7799
2022	1	1	8	2536	2	8	1	5	2550
2023	6	43	22	882	8	13	2	242	1180
2024	12	64	20	1046	4	15	3	164	1289

Sampling overview

Sampling of biological information of Atlantic halibut from the commercial catch is not considered good (Table 3). Few samples are taken each years and in some years no samples have been taken. Samples have not been taken since 2021.

Table 3: Atlantic halibut. Number of samples and length measurements from landed catch.

	Bottom trawl		Demersal seine		Longline
	Samples	Length measured	Samples	Length measured	Samples	Length measured
1994	0	0	1	122	0	0
1995	0	0	0	0	2	63
1996	1	27	2	249	0	0
1997	1	2	1	57	1	1
1998	51	215	2	199	8	104
1999	63	309	1	83	1	26
2000	24	86	2	168	2	31
2001	2	30	1	76	0	0
2002	1	17	0	0	0	0
2003	1	5	1	4	0	0
2004	0	0	1	27	0	0
2007	3	63	0	0	1	1
2008	0	0	0	0	1	65
2009	0	0	0	0	2	16
2011	1	3	0	0	0	0
2012	5	9	0	0	0	0
2013	3	21	0	0	0	0
2017	0	0	0	0	2	5
2019	11	60	2	3	0	0
2020	6	26	0	0	0	0

Icelandic survey data

Atlantic halibut is monitored in the Icelandic Groundfish Surveys both in spring and autumn. The spring groundfish survey (IS-SMB), conducted primarily within 500 m depth, has been ongoing since 1985. Juvenile halibut are common in this area, and catches in the IS-SMB mostly comprise immature individuals aged 3–6 years. In contrast, the autumn groundfish survey (IS-SMH), running since 1996, tends to capture larger halibut, as towing occurs at greater depths. IS-SMB captures fluctuations in numbers and biomass of immature halibut more effectively than IS-SMH due to its longer time series and lower uncertainty in index estimates. Therefore, advisory provided by the Marine and Freshwater Research Institute (MFRI) primarily relies on IS-SMB data. However, neither survey adequately covers areas inhabited by mature halibut, making them insufficient for accurately assessing spawning stock size.

Results from IS-SMB show that the total stock index (by weight) declined sharply from 1985 to 1990 and has remained low since then (Figure 6). Between 2008–2014, this index was at its lowest recorded level but has since increased. The 2025 index is about one-third of the peak observed in 1985. On the other hand, the index for large halibut (>86 cm) has increased significantly since 2020 in both IS-SMB and IS-SMH, suggesting growth in the spawning stock.

The total index by number provides a clearer picture of stock development than biomass indices (Figure 6), mainly due to the influence of large halibut on biomass calculations, especially in IS-SMH. In IS-SMB, the total index by number in 2025 was only about 5% of the 1985 value. The number index from IS-SMH has remained low and aligns well with IS-SMB observations.

As previously mentioned, halibut caught in IS-SMB mainly comprises immature individuals aged 3–6 years. These age groups have been in a prolonged decline for over three decades. The last significant recruitment wave, with several large year classes in succession, occurred from 1980 to 1984, implying that the spawning stock was above the minimum size until 1980. The last notably abundant year class on the continental shelf was from 1990 (Figure 6). In 2024, the recruitment index (<30 cm) recorded in IS-SMB was the highest since 1988.

Figure 7 shows relative indices from IS-SMB and IS-SMH, indicating little difference between the two surveys in terms of total biomass and total numbers.

Small halibut (30–60 cm) dominates in IS-SMB, whereas length distribution in IS-SMH is broader and without clear patterns (Figure 8).

Halibut is mainly found northwest and west of Iceland in IS-SMB (Figure 9). From 2002 to 2010, halibut was also notably present in southeastern areas. In IS-SMH, catches of halibut are generally sparse but, when they occur, are usually northwest and west of Iceland (Figure 9).

Figure 6: Atlantic halibut. Indices in the spring survey (blue line) 1985–2025 and the autumn survey (black line). Shaded areas are the 95% confidence intervals.

Figure 7: Atlantic halibut. Relative biomass and abundance indices in IS-SMB (blue line) IS-SMH (black line). Shaded areas are the 95% confidence intervals.