TUSK in ICES Division 5.a and Subarea 14

Brosme brosme


Technical report
Published by

Marine and Freshwater Research Institute, Iceland

Published

6 June 2025

Key signals

  • Total stock biomass observed in the spring survey declined steadily from 1985 to 2001. It subsequently increased and remained at relatively high levels until 2020, when it reached its lowest point in the time series. Since then, biomass has increased again and is currently at the highest level observed.

  • Abundance of small tusk (<30 cm) in the, spring survey peaked in 2007, followed by a sharp decline until 2012. Since then, abundance has increased steadily and is now at its highest level in the time series. This increase is also evident in the length distribution from the SMB survey, where smaller tusk have become more frequent.

  • Spawning stock biomass (SSB) declined from 1981 to 2021 but has since shown a sharp increase.

  • Fishing mortality (F, ages 7–10) has been decreasing since 2010 and is now below the reference points FMGT, FPA and Flim since.

  • Recruitment has been increasing since 2011 and is currently at its highest observed level.

General information

Tusk, also commonly called cusk, is a slow-moving demersal species that lives solitary or in small aggregations in offshore stony or pebbly habitats, mainly at depths less than 400 m. It feeds on crustaceans, shellfish, and other demersal fish. In Icelandic waters it grows to sizes close to 100 cm and may attain ages close to 20 years, but age determination of individuals over 10 years old is highly uncertain.

The fishery

Landings trends

Tusk in 5.a is caught in a mixed longline fishery, conducted in order of importance by Icelandic, Faroese, and Norwegian boats. Between 90 and 370 Icelandic longliners report catches of tusk, but ~100 more vessels have small amounts of bycatch landings (Table 1). Far fewer gillnetters and trawlers participate in the fishery. The number of longliners reporting tusk catches has been continually decreasing in the last decade (Table 1). Most of tusk in 5.a, around 96% of catch, is caught by longlines, and this proportion has been relatively stable since 2000 (Table 1).

Figure 1: Tusk. Annual landings in ICES area 5.a and 14 since 1906
Table 1: Tusk. Number of Icelandic boats with tusk landings, catch by gear (tonnes) and total catches in ICES area 5.a since 2000.
Year nr. bottom trawl nr. nets nr. longlines Bottom trawls Net Longlines Other Total catch
2000 121 175 370 101 44 4 564 404 5 114
2001 108 224 350 87 63 3 248 1 439 4 838
2002 105 174 304 88 93 3 722 1 659 5 563
2003 97 148 305 65 41 3 941 1 549 5 598
2004 90 130 303 92 28 3 007 1 703 4 830
2005 88 101 324 116 19 3 398 1 510 5 044
2006 86 82 338 100 40 4 912 1 549 6 601
2007 74 65 308 104 38 5 834 1 560 7 537
2008 75 59 255 126 42 6 762 1 699 8 629
2009 75 65 239 115 72 6 757 1 524 8 469
2010 70 62 228 97 52 6 761 1 803 8 713
2011 63 54 221 72 24 5 742 1 862 7 701
2012 65 68 228 64 13 6 255 1 540 7 872
2013 66 43 233 76 15 4 911 1 300 6 302
2014 62 43 249 87 18 6 045 13 6 163
2015 55 32 228 71 7 4 745 13 4 835
2016 59 32 206 61 6 3 420 7 3 494
2017 52 31 180 48 5 2 481 6 2 540
2018 55 27 158 83 8 2 841 7 2 940
2019 49 23 154 103 7 3 323 11 3 445
2020 55 23 126 108 31 3 037 10 3 187
2021 51 18 123 112 12 2 649 6 2 779
2022 51 26 109 110 17 2 446 3 2 577
2023 53 32 94 91 10 2 940 5 3 047
2024 53 18 91 81 8 2 055 4 2 149

The main fishing grounds for tusk in 5.a as observed from logbooks are on the southeast, southwestern and western part of the Icelandic shelf (Figure 4 and Figure 5). The spatial distribution of catches in 5.a show a decreasing trend in the southeast until 2015, but this proportion has been increasing in the last 5 years (Figure 1 and Figure 5). The proportional catch in the northwest has also increased over the years. Most of the tusk caught in 5.a by Icelandic longliners is caught at depths less than 300 meters (Figure 3). Around 50–60% of tusk is caught on the southern and western parts of the shelf (Figure 3). Tusk in 14 is caught mainly as a bycatch by longliners and trawlers. The main area where tusk is caught in 14 is 63°–66°N and 32°–40°W (Figure 2).

Figure 2: Tusk. Distribution of catches in ICES area 14 from 1999-2023
Figure 3: Tusk. Depth distribution of catches in ICES area 5.a since 2000, as reported in logbooks by the Icelandic fleet. All gears combined.
Figure 4: Tusk. Catch distribution and proportions by region in ICES area 5.a since 2000, according to logbooks. All gears combined.
Figure 5: Tusk. Geographical distribution (tonnes) of the Icelandic longline fishery since 2004, as reported in logbooks by the Icelandic fleet.

Landings and discards

Total annual landings from ICES Division 5.a were 2149 tonnes in 2024 (Table 2). Since 2010, landings have steadily declined, dropping by 76%. This is contrary to the trend in landings from year 2000 to 2010 when annual landings gradually increased from approximately 5000 tonnes to 9000 tonnes (Figure 1). The foreign catch (mostly vessels from the Faroe Islands, but also from Norway) of tusk in Icelandic waters has always been considerable. Until 1990, between 40-70% of the total annual catch from ICES Division 5.a was caught by foreign vessels, mainly vessels from the Faroe Islands. This proportion has reduced since and has been 10-30% since 1991 (Table 2).

Landings in area 14 have always been low compared to 5.a, and before 2010 they rarely exceeded 100 t (Table 3). However, 1598 tonnes were caught in 2015, after which catches have been consistently substantial. In the fishing year 2015/2016, landings in 5.a were 900 tonnes and as the Icelandic TACs were relatively low during this period, this constituted over 25% of TAC. Landings data from section 14 reported by the Greenland Institute of Natural Resources also reflect this trend. In 2019, around 566 tonnes were caught in the 14.b mainly by Norwegian, Faroese and Greenlandic vessels (Table 3). This has however increased in 2024 to about 939 tonnes.

Discarding is banned in the Icelandic fishery. There is no available information on discarding of tusk in ICES area 14.

Table 2: Tusk. Nominal landings (tonnes) by country in ICES area 5.a since 1980
Year Iceland Faroe Islands Germany Norway United Kingdom Total landings
1980 3 109 2 873 0 928 0 6 910
1981 2 864 2 624 0 1 025 0 6 513
1982 2 801 2 410 0 666 0 5 877
1983 3 468 4 046 0 772 0 8 286
1984 3 430 2 008 0 254 0 5 692
1985 3 064 1 885 0 111 0 5 060
1986 2 549 2 811 0 21 0 5 381
1987 2 987 2 638 0 19 0 5 644
1988 3 087 3 757 0 20 0 6 864
1989 3 158 3 908 0 10 0 7 076
1990 4 821 2 475 0 0 0 7 296
1991 6 449 2 286 0 0 0 8 735
1992 6 432 1 567 0 0 0 7 999
1993 4 086 1 333 0 0 0 5 419
1994 4 065 1 217 0 0 0 5 282
1995 5 151 1 168 1 0 0 6 320
1996 5 548 907 1 3 0 6 470
1997 4 816 579 0 0 0 5 395
1998 4 130 1 080 1 0 0 5 211
1999 5 821 1 041 2 391 2 7 257
2000 4 727 10 0 374 3 5 114
2001 3 397 1 150 1 285 5 4 838
2002 3 910 1 279 0 372 2 5 563
2003 4 024 1 198 1 373 2 5 598
2004 3 135 1 478 1 214 2 4 830
2005 3 539 1 157 4 303 41 5 044
2006 5 054 1 244 2 299 2 6 601
2007 5 987 1 250 0 300 1 7 538
2008 6 934 1 398 0 298 0 8 630
2009 6 953 1 516 0 210 0 8 679
2010 6 919 1 794 0 263 0 8 976
2011 5 847 1 655 0 198 0 7 700
2012 6 344 1 310 0 217 0 7 871
2013 4 992 1 118 0 192 0 6 302
2014 5 057 681 0 425 0 6 163
2015 4 059 578 0 198 0 4 835
2016 2 704 488 0 302 0 3 494
2017 1 887 438 0 216 0 2 541
2018 2 160 454 0 326 0 2 940
2019 2 622 506 0 316 0 3 444
2020 2 380 536 0 271 0 3 187
2021 2 109 283 0 388 0 2 780
2022 1 956 264 0 357 0 2 577
2023 2 414 322 0 311 0 3 047
2024 1 539 287 0 123 0 2 148
Table 3: Tusk. Nominal landings (tonnes) by country in ICES area 14 since 1978.
Year Faroe Islands Norway Iceland Russia Spain Greenland Germany United kingdom Total landings
1978 0 38 0 0 0 0 47 0 85
1979 0 0 0 0 0 0 27 0 27
1980 0 0 0 0 0 0 13 0 13
1981 110 0 0 0 0 0 10 0 120
1982 0 0 0 0 0 0 10 0 10
1983 74 0 0 0 0 0 11 0 85
1984 0 58 0 0 0 0 5 0 63
1985 0 0 0 0 0 0 4 0 4
1986 33 0 0 0 0 0 2 0 35
1987 13 0 0 0 0 0 2 0 15
1988 19 0 0 0 0 0 2 0 21
1989 13 0 0 0 0 0 1 0 14
1990 0 7 0 0 0 0 2 0 9
1991 0 68 0 0 0 0 2 1 71
1992 0 120 3 0 0 0 0 0 123
1993 0 39 1 0 0 0 0 0 40
1994 0 16 0 0 0 0 0 0 16
1995 0 30 0 0 0 0 0 0 30
1996 0 157 0 0 0 0 0 0 157
1997 0 9 10 0 0 0 0 0 19
1998 0 12 0 0 0 0 0 0 12
1999 0 8 0 0 0 0 0 0 8
2000 0 11 11 0 3 0 0 0 25
2001 3 69 20 0 0 0 0 0 92
2002 4 30 86 0 0 0 0 0 120
2003 0 88 2 0 0 0 0 0 90
2004 0 40 0 0 0 0 0 0 40
2005 7 41 0 8 0 0 0 0 56
2006 3 19 0 51 0 0 0 0 73
2007 0 40 0 6 0 0 0 0 46
2008 0 7 0 0 0 33 0 0 40
2009 12 5 0 11 0 15 0 0 43
2010 7 5 0 0 0 0 0 0 12
2011 20 24 131 0 0 0 0 0 175
2012 33 46 174 0 0 0 0 0 253
2013 2 24 401 0 0 0 0 0 427
2014 145 35 0 0 0 74 0 0 254
2015 759 55 0 0 0 784 0 0 1 598
2016 243 178 0 0 0 182 3 0 606
2017 281 141 0 0 0 358 0 0 780
2018 345 228 0 0 0 108 0 0 681
2019 41 458 0 0 0 66 1 0 566
2020 64 114 0 0 0 45 2 0 225
2021 260 380 0 0 0 59 2 0 701
2022 35 558 0 0 0 87 1 0 681
2023 170 479 0 0 0 115 0 0 764
2024 287 477 0 0 0 174 1 0 939

Data available

In general sampling is considered appropriate from commercial catches from the main gear (longlines), although the quantity of samples has decreased substantially in the last decade (Table 5). The sampling does seem to cover the spatial distribution of catches for longlines and trawls. Similarly, sampling does seem to follow the temporal distribution of catches (ICES (2012)). The sampling coverage in 2024 is shown in Figure 6.

Figure 6: Tusk. Ratio of catch samples by month (bars) compared with proportion landings by month (black line) split by year and main gear types. Numbers above the bars indicate number of samples by year, month and gear from commercial catches of Icelandic vessels fishing in ICES area 5.a from 2021-2024

Length compositions

An overview of available length measurements from 5.a is given in Table 4. Most of the measurements are from longlines; number of available length measurements increased in 2007 from around 5000 to around 12000 and were close to that until 2015 when they decreased and in 2024, the number of length measurements from longlines were 1748. Length distributions from the longline fishery is shown in Figure 7.

No length composition data from commercial catches in Greenlandic waters are available.