TUSK

Brosme brosme


Technical report
Published by

Marine and Freshwater Research Institute, Iceland

Published

7 June 2024

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 and discards

Total annual landings from ICES Division 5.a were 3046 tonnes in 2023 (Table 2), signifying a continuous decrease in landings from 2010. This is contrary to the trend in landings from year 2000 in which the annual landings gradually increased in 5.a to around 9000 tonnes in 2010 (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 1).

Landings in area 14 have always been low compared to 5.a, rarely exceeding 100 t (Table 3). However, 1598 tonnes were caught in 2015, after which catches have been consistently substantial. Catch data from section 14 reported by the Greenland Institute of Natural Resources (WGDEEP, 2019:WD06) also reflect this trend. Around 566 tonnes in 2019 were caught in the 14.b mainly by Norwegian, Faroese and Greenlandic vessels (Table 3). This has however increased in 2023 to about 1528 tonnes. As the Icelandic TACs were relatively low during this period, this constituted over 25% of the annual catch.

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

Table 2: Tusk. Nominal landings by nations in 5.a
Year Faroe Islands Germany Iceland Norway UK Total catch
1980 2873 0 3089 928 0 6890
1981 2624 0 2827 1025 0 6476
1982 2410 0 2804 666 0 5880
1983 4046 0 3469 772 0 8287
1984 2008 0 3430 254 0 5692
1985 1885 0 3068 111 0 5064
1986 2811 0 2549 21 0 5381
1987 2638 0 2984 19 0 5641
1988 3757 0 3078 20 0 6855
1989 3908 0 3131 10 0 7049
1990 2475 0 4813 0 0 7288
1991 2286 0 6439 0 0 8725
1992 1567 0 6437 0 0 8004
1993 1329 0 4746 0 0 6075
1994 1212 0 4612 0 0 5824
1995 979 1 5245 0 0 6225
1996 872 1 5226 3 0 6102
1997 575 0 4819 0 0 5394
1998 1052 1 4118 0 0 5171
1999 1035 2 5794 391 2 7224
2000 1154 0 4714 374 2 6244
2001 1125 1 3392 285 5 4808
2002 1269 0 3840 372 2 5483
2003 1163 1 4028 373 2 5567
2004 1478 1 3126 214 2 4821
2005 1157 3 3539 303 41 5043
2006 1239 2 5054 299 2 6596
2007 1250 0 5984 300 1 7535
2008 959 0 6932 284 0 8175
2009 997 0 6955 300 0 8252
2010 1794 0 6919 263 0 8976
2011 1347 0 5845 198 0 7390
2012 1203 0 6341 217 0 7761
2013 1092 0 4973 192 0 6257
2014 728 0 4995 306 0 6029
2015 625 0 4000 198 0 4823
2016 543 0 2649 302 0 3494
2017 492 0 1833 216 0 2540
2018 517 0 2097 326 0 2940
2019 549 0 2579 316 0 3444
2020 558 0 2590 272 0 3420
2021 341 0 2049 389 0 2780
2022 288 0 1932 357 0 2577
2023 336 0 2399 311 0 3046
Table 3: Tusk. Nominal landings by nations in 14.
Year Faroe Islands Norway Iceland Russia Spain Greenland Germany United kingdom total
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 1598
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

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 recent years. 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 2023 is shown in Figure 5.

Figure 5: Tusk. Ratio of 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.

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 2016 when they decreased and in 2023, the number of length measurements from longlines were 2671. Length distributions from the longline fishery is shown in Figure 6.

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

Figure 6: Tusk. Length distributions from Icelandic commercial longline catches.

Table 4: Tusk. Number of available length measurements from Icelandic (5.a) commercial catches.
Year Bottom trawl Demersal seine Gill nets Longlines Other
2000 0 0 0 2995 0
2001 0 0 0 3097 151
2002 0 0 0 2843 0
2003 0 0 0 8444 0
2004 150 0 0 3809 0
2005 21 0 0 5820 0
2006 472 0 0 4861 0
2007 150 0 167 11936 0
2008 0 0 0 20963 0
2009 0 0 0 21451 0
2010 0 0 0 9084 0
2011 0 0 0 8158 0
2012 150 0 0 11867 0
2013 0 150 0 6469 0
2014 0 0 0 11748 0
2015 0 0 0 4821 0
2016 0 0 0 4844 0
2017 0 0 0 1710 0
2018 0 0 0 2781 0
2019 0 0 0 2952 0
2020 1 0 0 2336 0
2021 0 0 0 1499 26
2022 83 0 0 682 461
2023 0 0 0 2671 0

Age composition

Table 5 gives an overview of otolith sampling intensity by gear types from 2008 to 2023 in 5.a. Since 2010, considerable effort has been put into ageing tusk otoliths, so now aged otoliths are available from 1984–1995, 2008–2023. The age data are used as input for the SAM assessment. It is expected that the effort in ageing of tusk will continue. Catch at age is shown in Figure 7 and Figure 8.

Figure 7: Tusk. 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.

Figure 8: Tusk. Catch at age from the commercial fishery in Iceland waters. Biomass caught by year and age; bars are coloured by cohort.

Table 5: Tusk. Number of available otoliths from Icelandic (5.a) commercial catches and the Icelandic Spring survey and the number of aged otoliths.
Year No. samples catch No. otoliths (catch) No. samples (survey) No. aged (survey)
2008 32 1600 282 475
2009 27 1350 277 434
2010 29 1449 241 363
2011 28 1400 270 728
2012 35 1750 285 750
2013 23 1150 275 536
2014 28 620 241 559
2015 26 555 260 573
2016 14 290 259 676
2017 8 160 245 571
2018 9 180 247 549
2019 15 330 251 704
2020 14 290 250 647
2021 15 291 278 811
2022 14 287 313 897
2023 18 355 302 954

Weight at age

Weight-at-age from catch from 5.a is shown in Figure 9. No data are available from 14. Catch weights of three year old is stable and around the average, whereas the other age groups show more variability between years. The three oldest year classes are the most common in the catch, and recently, younger tusk has become less common in catch (Figure 10).

Figure 9: Tusk. Mean weight at age in the catch from the commercial fishery in Icelandic waters. Bars are coloured by cohort..

Figure 10: Tusk. Catch weights by age from the commercial fishery in Icelandic waters

Icelandic survey data (ICES Subarea 27.5a)

Information on abundance and biological parameters from tusk in Icelandic waters is available from the Icelandic groundfish survey in the spring (SMB) and the Icelandic autumn survey (SMH). In addition, a gillnet survey is conducted in areas closer inshore every April during cod spawning periods, designed to sample the cod spawning stock. A detailed description of the Icelandic spring, autumn groundfish surveys and the gillnet surveys are given in the stock annex (ICES 2022c). The Icelandic spring groundfish survey, which has been conducted annually in March since 1985, covers the most important distribution area of the tusk fishery. In 2011 the ‘Faroe Ridge’ survey area was included in the estimation of survey indices. In addition, the autumn survey commenced in 1996 and expanded in 2000; however, a full autumn survey was not conducted in 2011 and therefore the results for 2011 are not presented. A detailed description of the Icelandic spring and autumn groundfish surveys is given in the Stock Annex (ICES (2017b)). Figure 11 shows a recruitment index and the trends in various biomass indices. Length distribution from the autumn and spring survey is shown in Figure 13 and the survey index at age from the spring survey in Figure 14. Since 2014, the survey indices of younger tusk have been increasing. This is also apparent in the length distribution from the spring survey, where smaller tusk have become more frequent.

Figure 11: Tusk. a) Total biomass indices, b) biomass indices larger than and including 40 cm, c) biomass indices larger than and including 60 cm and d) abundance indices smaller than and including 30 cm. The lines with shaded areas show the spring survey index from 1985 and the points with the vertical lines show the autumn survey from 1997. The shaded area and vertical lines indicate +/- standard error. The dark green line without a shaded area is the index excluding the Iceland-Faroe Ridge.

Figure 12: Tusk. Estimated survey biomass in the spring survey by year from different parts of the continental shelf (upper figure) and as proportions of the total (lower figure)

Figure 13: Tusk. Length distributions from the spring survey (SMB) since 1985.

Figure 14: Tusk. 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 15. Stock weights are obtained from the groundfish survey in March and are also used as mean weight at age in the spawning stock. Mean weight of the oldest year classes has been gradually increasing since the early 2000s, whereas the mean weight at age of younger tusk is more variable between years.

Figure 15: Tusk. Stock weights from the spring survey in Icelandic waters. Bars are coloured by cohort

Stock maturity at age

Maturity at age data is taken from the autumn groundfish survey and calculated based on maturity at length each year and length distributions of fish assigned to each age. The spring survey data is not used because maturation patterns appeared to occur at larger fish and differed between sexes. From 1994 to 2000, the proportion mature at age increased gradually in age groups 5 to 10, but steadily declined after until the year 2015. Since then, there has been an upward trend in the proportion of individuals reaching maturity at older ages, with maturity approaching the mean (Figure 16 and Figure 17)

Figure 16: Tusk. Maturity at age in the autumn survey. Bars are coloured by cohort. The values are used to calculate the spawning stock.

Figure 17: Tusk. Proportion mature at age from the autumn survey.

Other surveys

German survey data (ICES Subarea 27.14)

The German groundfish survey was started in 1982 and is conducted in autumn. It is primarily designed for cod but covers the entire groundfish fauna down to 400 m. The survey is designed as a stratified random survey; the hauls are allocated to strata off West and East Greenland both according to the area and the mean historical cod abundance at equal weights. Towing time was 30 minutes at 4.5 kn. (Ratz, 1999). Data from the German survey in 14 were available at the meeting up to 2015. The trend in the German survey catches is similar to those observed in surveys in 5.a. It should, however, be noted that the data presented in Figure 18 is based on total number caught each year so it can’t be used directly as an index from East Greenland. Length distributions from the survey in recent years are shown in Figure 19.

Figure 18: Tusk. Biomass and abundance estimates from the Walter Herwig survey in 14. The data are just the total number caught and then converted to weight.

Figure 19: Tusk. Length distributions from the Walter Herwig survey in 14.

Greenland survey data (ICES Subarea 27.14)

The Greenland Institute of Natural Resources conducted a stratified bottom trawl survey in East Greenland (ICES 14b) from 1998 to 2016 at depths between 400 to 1500 m (ICES 2019:WD05). Survey results for tusk show a highly variable but increasing trend over recent years, so results from this survey will be monitored after it resumes in the future as a potential biomass index to be included in the tusk assessment.

Data analyses

There have been no marked changes in the number of boats or the composition of the fleet participating in the tusk fishery in 5.a (Table 1). Catches decreased from around 9000 tons in 2010 to 3046 tonnes in 2023. This decrease is mainly because of reductions in landings by the Icelandic longline fleet and to a lesser extent Faroese and Norwegian landings (Table 2 and Table 3). This has resulted in less overshoot of landings relative to set TAC, except in the last two years when the stock has experienced an all-time low. As this all-time low is more likely due to the low recruitment during 2010–2011 rather than overexploitation, so is expected to increase as subsequent higher recruitment levels grow to fishable sizes. There are no marked changes in the length compositions since 2004, mean length in the catch ranges between 52 and 58 (Figure 6). Length distributions from the spring survey show a distinct large cohort, or series of consecutive cohorts, appearing in 2014, growing through time, and just beginning to reach fished sizes approximately this year. This recruitment peak appears to follow a recruitment low that can also be traced through the length distribution from 2014 and can still be observed this year as slightly lower-than-average frequencies of tusk in the 45-50 cm range. According to the available length distributions and information on maturity only around 29% of catches in abundance and 44% in biomass are mature. The reason for this is unknown but given the lack of distinctive cohort structure in the data the first explanation might be a lack of consistency in ageing. Also, tusk have experienced a reduction in fishing mortality over the latter half of this range. Reasons such as difference in sampling, temporal or spatial are highly unlikely.

At WGDEEP 2011 the Iceland-Faroe Ridge was included in the survey index when presenting the results from the Icelandic spring survey for tusk in 5.a. The total biomass index and the biomass index for tusk larger than 40 cm (reference biomass) decreased substantially but increased again and has remained at relatively high similar level as in 2011 (Figure 7). The same holds for the index of tusk larger than 60 cm (spawning–stock biomass index). The index of juvenile abundance (<30 cm) decreased by a factor of six between the 2005 survey when it peaked and the 2013 survey when it was at its lowest observed value. Since 2013 juvenile index has increased year on year in the 2014–2017 surveys. The index excluding the Iceland-Faroe Ridge shows similar trends as described above. The results from the shorter autumn survey are similar to those observed from the spring survey except for the juvenile abundance index that is more or less at a constant level compared to the spring survey juvenile index. Due to a labour strike, the autumn survey did not take place in 2011.

When looking at the spatial distribution from the spring survey, around 25% of the index is from the SE area. However only around 4% of the catches are caught in this area (Figure 3 and Figure 4). The change in juvenile abundance between 2006 and recent years can be seen in Figure 7.

Catch, effort and research vessel data

The CPUE estimates of tusk in 5.a are not considered representative of stock abundance.

CPUE estimations have not been attempted on available data from 14.

Analytical assessment using SAM

From 2010-2021, s Gadget model (Globally applicable Area Disaggregated General Ecosystem Toolbox, see www.hafro.is/gadget) was used for the assessment of tusk in 5.a (See stock annex for details, ICES 2022c). In 2022, Tusk in 5.a and 14 was re-assessed as the previously benchmarked Gadget model had begun to show great instability in retrospective patterns in recent years. As a part of a Harvest Control Evaluation requested by Iceland, the stock was benchmarked (WKICEMSE 2022b) which resulted in changes in the assessment method and updated reference points. Model setup and settings are described in the stock annex (ICES 2022c).

Data used by the assessment and model settings

Data used for tuning and the model configuration are given in the stock annex (ICES 2022b).

Model fit

Model results are shown in Table 7. The model fit to survey indices are shown in Figure 12 and Figure 13. Generally, the model closely follows the spring survey data, which are in good agreeance. The autumn survey is noisier but generally follows the same pattern. Fits to the April gillnet survey (age 10 abundance) are much noisier. An overview of model parameter estimates are shown in ?@fig-fig19.

Figure 18: Tusk. Model fit to spring survey and autumn survey indices.

Figure 19: Tusk. Model fit to gillnet survey indices.

Model results

The spawning stock biomass has shown a gradual decline prior to 1995, although prior to 1985 the model is informed by very little data, so uncertainty is high. The period 1995-2015 was steady, with a gradual decline thereafter that continued until 2021, when biomass levels have started to increase again. This pattern is likely due to a distinctive low point in recruitment in 2011-2012, which has since then increased to relatively high levels. Therefore, given moderate fishing levels, spawning stock biomass is expected to increase over the next several years as the newest higher recruitment levels grow into the fishable population. The previous peak in recruitment (2004-2005) likely did not increase spawning stock biomass levels substantially during this period due to higher fishing rates and catch values during 2008-2010, when these fish would have been entering the fishery (Figure 20).

Figure 20: Tusk. Model results of population dynamics overview: estimated catch, average fishing mortality over ages 7 - 10 (Fbar), recruitment (age 1), and spawning stock biomass (SSB). Catch and Fbar in 2024 are projections.

Retrospective analysis

The results of an analytical retrospective analysis are presented (Figure 21). The analysis indicates generally consistent model results over the 5-year peel. Mohn’s ρ was estimated to be 0.0219224 for SSB, 0.0316901 for F, and 0.0865775 for recruitment. Recruitment indices generally tend to be uncertain as there are few repeated observations at larger sizes with which this influence can be tempered. However, the good fit to survey indices at age 1, (Figure 18), suggests that recent recruitment estimates from this peak are reliable. In addition, a peak in these sizes of tusk followed by a sharp decline in 2020 are reflected in length distribution data as a rather large but steep peak in proportions of fish that have begun to shift right (to larger sizes) with no obvious new peaks of small sizes taking its place (Figure 7). Therefore, it is likely that the increase in biomass observed this year will continue in the next year or so.

Figure 21: Tusk. 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 3) are shown

Observation and process residuals show slight trends in autocorrelation and some blocks of time where the model was consistently over- or underestimating the model. (Figure 22 and Figure 23). However, a better model configuration could not be found in the benchmark that would remove these patterns, and similar model configurations gave similar model results (WKICEMP, ICES 2022c). Process variance is therefore rather high in this model, indicating high uncertainty in true population dynamics, due to greater uncertainty in input data (Figure 25).

Figure 22: Tusk. Observation error residuals of the SAM model.

Figure 23: Tusk. Process error residuals of the SAM model.

Figure 24: Tusk. Overview of the SAM model parameter estimates. Error bars indicate 95% confidence intervals.

Management

The Icelandic Ministry of Food, Agriculture and Fisheries is responsible for management of the Icelandic fisheries and implementation of legislation. Tusk was included in the ITQ system in the 2001/2002 quota year and as such subjected to TAC limitations. At the beginning, the TAC was set as recommended by MFRI but thereafter had often been set higher than the advice. One reason is that no formal harvest advisory rule existed for this stock. Up until the fishing year 2011/2012, the landings, by quota year had always exceeded the advised and set TAC by 30-40%. However, since then the overshoot in landings has decreased substantially, apart from 2014/2015 when the overshoot was 34%. In recent years the TACs were not filled, until the past two years when the TAC has been exceptionally low (Table 6).

The reasons for the large difference between annual landings and both advised and set TACs are threefold: 1) It is possible to transfer unfished quota between fishing years; 2) It is possible to convert quota shares in one species to another; 3) The national TAC is only allocated to Icelandic vessels. All foreign catches are therefore outside the quota system. However, in recent years managers have to some extent taken into account the foreign catches when setting the national TAC (see below).

There are bilateral agreements between Iceland, Norway and the Faroe Islands related to fishing activity of foreign vessels in restricted areas within the Icelandic EEZ. Faroese vessels are allowed to fish 5600 t of demersal fish species in Icelandic waters which includes a maximum 1200 tonnes of cod and 40 t of Atlantic halibut. The rest of the Faroese demersal fishery in Icelandic waters is mainly directed at tusk, ling, and blue ling. The tusk advice given by MFRI and ICES for each quota year is, however, for all catches, including foreign catches.

Figure 25 shows the net transfers in the Icelandic ITQ-system. During the 2005/2006–2010/2011 fishing years there was a net transfer of other species quota being converted to tusk quota, this however reversed during the following three fishing years. In the 2015/2016 and 2016/2017 fishing years there was again a small net transfer of other species being changed to tusk quota. In the last four out of five fishing years, 2017/2018-2019/2020 fishing years, net transfers were negative again with tusk quota being converted to other species, while 2020/2021 and 2021/2022 shows an overshoot of the quota. In 2023/2024, tusk quota was transferred to other species (Figure 25).

Table 6: Tusk. Recommended TAC, national TAC, and catches (tonnes)
Fishing year MFRI advice National TAC Catch Iceland Catch other Total catch
2010/2011 6000 6000 6235 1898 6235
2011/2012 6900 6900 5983 1606 5983
2012/2013 6700 6700 5555 1314 5569
2013/2014 6300 6300 4850 487 5438
2014/2015 4000 4000 4136 1304 5440
2015/2016 3440 3440 3221 900 4121
2016/2017 3780 3780 1689 729 2418
2017/2018 4370 4370 2200 885 3085
2018/2019 3776 3776 2453 778 3231
2019/2020 3856 3856 2460 781 3241
2020/2021 2289 2289 2192 757 2949
2021/2022 2172 2172 1918 503 2421
2022/2023 4464 4464 2420 640 3060
2023/2024 5139 5139
2024/2025 5914

Figure 25: Tusk. Net transfer of quota in the Icelandic ITQ system by fishing year. Between species (upper): Positive values indicate a transfer of other species to tusk, but negative values indicate a transfer of tusk quota to other species. Between years (lower): Net transfer of quota for a given fishing year (may include unused quota).

Management considerations

Increased catches in 14.b, and now 14.a also, from less than 100 tons in previous years to around 900 tons in 2015 are of concern. Catches reduced after but have been around 150-800 tons since. In 2023, catches were also substantial, close to 800 tonnes. However, the signs from commercial catch data and surveys indicate that the total biomass of tusk in 5.a is stable. This is confirmed in the assessment. Recruitment in 5.a shown high levels after a low in 2011. A reduction in fishing mortality has also led to harvestable biomass and SSB that seem to be either stable or slowly increasing. Due to the selectivity of the longline fleet catching tusk in 5.a and the species relatively slow maturation rate, a large proportion of the catches is immature (60% in biomass, 70% in abundance). The spatial distribution of the fishery in relation to the spatial distribution of tusk in 5.a as observed in the Icelandic spring survey may result in decreased catch rates and local depletions of tusk in the main fishing areas. Tusk is a slow growing late maturing species, therefore closures of known spawning areas should be maintained and expanded if needed. Similarly, closed areas to longline fishing where there is high juvenile abundance should also be maintained and expanded if needed.

Table 7: Tusk. Estimates of biomass, biomass spawning–stock biomass (SSB) in thousands of tonnes and recruitment at age 1 (millions) and fishing mortality from the SAM model
YEAR BIOMASS SSB REC1 CATCH F
1979 39055 16360 11896 6711 0.089
1980 39785 17573 10942 6706 0.103
1981 39931 19179 9327 6663 0.107
1982 38946 19099 7741 6370 0.113
1983 38793 18908 6464 6918 0.154
1984 31853 13821 6952 6032 0.138
1985 28982 11473 8708 5129 0.136
1986 29518 12040 8990 5541 0.138
1987 29824 12565 9085 5709 0.150
1988 29818 12388 7538 6722 0.170
1989 30118 12230 5728 7267 0.185
1990 27260 10606 5125 7323 0.211
1991 24750 8850 4690 8960 0.228
1992 23664 8007 4640 8414 0.247
1993 19324 6268 6165 5950 0.246
1994 17584 5478 7838 5979 0.278
1995 19457 5504 11580 6054 0.372
1996 18452 5446 14651 5815 0.391
1997 19078 5805 15101 5306 0.349
1998 19432 6312 14042 5069 0.341
1999 20808 7254 14101 6093 0.383
2000 19801 6993 19019 5304 0.332
2001 19850 5917 20646 4817 0.350
2002 20867 5847 22284 5192 0.373
2003 22341 5983 24861 5423 0.336
2004 24230 6344 25054 4999 0.287
2005 27463 6574 24838 5510 0.279
2006 30786 7595 22679 6715 0.316
2007 32707 7556 18519 8130 0.360
2008 36110 7134 11594 8932 0.426
2009 34826 6679 7735 8998 0.451
2010 30833 6186 6205 8686 0.462
2011 29829 6122 4476 8202 0.399
2012 29961 6735 4218 7909 0.425
2013 27831 5342 6642 6421 0.411
2014 27374 4857 13326 6409 0.334
2015 22954 4874 17458 5945 0.325
2016 23470 4757 16906 4175 0.239
2017 22966 5011 21931 3333 0.208
2018 21181 4572 16110 3581 0.242
2019 20886 4039 17551 3784 0.247
2020 20486 3934 19733 2769 0.274
2021 22751 3918 24355 3144 0.219
2022 29213 5308 28568 3310 0.158
2023 35801 7086 38064 3606 0.145
2024 40987 8749 43736 3502 0.146

References

ICES. 2011. “Report of the Working Group on the Biology and Assessment of Deep-Sea Fisheries Resources (WGDEEP), 2 March–8 March, 2011, Copenhagen, Denmark. ICES Cm 2011/Acom:17.” International Council for the Exploration of the Seas; ICES publishing.

2012. “Report of the Working Group on the Biology and Assessment of Deep-Sea Fisheries Resources (WGDEEP), 28 March–5 April, 2012, Copenhagen, Denmark. ICES Cm 2012/Acom:17.” International Council for the Exploration of the Seas; ICES publishing.

2017. “Report of the Workshop on Evaluation of the Adopted Harvest Control Rules for Icelandic Summer Spawning Herring, Tusk and Tusk (WKICEMSE), 21–25 April 2017, Copenhagen, Denmark. ICES CM 2017/ACOM:45.” International Council for the Exploration of the Seas; ICES publishing.

2022a. “11.2 Icelandic Waters ecoregion – Fisheries overview.” International Council for the Exploration of the Seas; ICES publishing. https://doi.org/10.17895/ices.advice.21487635.v1

2022b. Iceland request for evaluation of a harvest control rule for tusk in Icelandic waters. In Report of the ICES Advisory Committee, 2022. ICES Advice 2022, sr.2022.6d, https://doi.org/10.17895/ices.advice.19625823

2022c. “Stock Annex: Tusk (Molva molva) in Division 5.a (Icelandic grounds).” International Council for the Exploration of the Seas; ICES publishing. Unpublished

2022d. Workshop on the evaluation of assessments and management plans for Tusk, tusk, plaice and Atlantic wolffish in Icelandic waters (WKICEMP). ICES Scientific Reports. Report. https://doi.org/10.17895/ices.pub.19663971.v1