GREATER SILVER SMELT

Argentina silus


Technical report
Published by

Marine and Freshwater Research Institute, Iceland

Published

7 June 2024

General information

Greater silver smelt is a rather small silvery bathypelagic species that can form large schools close to the seafloor mainly at depths >500 m. In Icelandic waters it can live to around 26 years old. Juveniles tend to aggregate in shallower depths. Greater silver smelt mainly feed on zooplankton (e.g., euphausiids, amphipods, and copepods) or small nekton (e.g., squids, jellyfish, or fish).

The Fishery

Fleets

Since 1996 between 20 and 40 trawlers have annually reported catches of greater silver smelt in Icelandic waters (Table 1). The trawlers participating in the greater silver smelt fishery also target redfish (Sebastes norvegicus and S. mentella) and to lesser extent Greenland halibut and blue ling. Number of hauls peaked in 2010, but the number of hauls has decreased since then in line with lower total catches. In most years over 50% of the greater silver smelt catches are taken in hauls where the species is more than 50% of the catch (Table 1).

Targeting and mixed fisheries issues in the fishery in Icelandic waters

Mixed fisheries issues: species composition in the fishery

Redfish spp. (golden redfish (Sebastes norvegicus) and deepwater redfish (S. mentella)) are the main bycatch species in the mixed fishery encompassing greater silver smelt. Other species of lesser importance are Greenland halibut, blue ling and ling. Other species than these rarely exceed 10% of the bycatch in the greater silver smelt fishery in Icelandic waters (Table 2).

Table 2: Greater silver smelt in Icelandic waters. Proportional bycatch species composition where greater silver smelt was more than 50% of the total catch in a haul.
Year Golden redfish Deepwater redfish Greenland halibut Ling Blue ling Other
1997 1.41 79.28 0.00 6.80 7 5.39
1998 5.23 77.49 0.00 3.51 7 6.65
1999 4.09 79.80 0.00 2.72 6 7.55
2000 4.92 70.88 0.16 0.34 10 13.74
2001 22.69 55.05 4.50 0.52 1 16.10
2002 17.32 73.92 0.44 1.19 4 3.13
2003 38.44 51.24 0.44 0.05 5 4.83
2004 24.87 68.68 0.68 0.12 1 4.80
2005 15.40 69.88 4.22 1.42 3 6.08
2006 28.80 59.79 1.44 0.88 1 8.14
2007 11.90 71.20 5.93 0.32 6 4.63
2008 26.66 60.84 2.76 1.21 5 3.30
2009 20.14 64.62 3.20 0.19 8 3.99
2010 15.96 63.74 2.03 0.87 6 11.05
2011 13.20 66.41 2.18 0.36 5 13.01
2012 8.79 67.30 1.33 0.24 8 14.82
2013 9.54 63.91 4.61 0.15 9 12.63
2014 2.46 78.28 2.83 0.26 5 10.68
2015 12.58 64.07 4.67 0.23 4 14.53
2016 10.88 73.54 5.45 0.22 3 7.14
2017 2.93 85.63 1.57 0.24 3 6.77
2018 4.68 87.66 2.05 0.05 2 3.99
2019 7.77 81.15 1.84 0.55 2 7.03
2020 5.58 87.46 1.69 0.12 1 4.20
2021 11.55 72.26 5.80 0.28 1 8.66
2022 5.68 83.95 3.95 0.22 3 2.90
2023 10.64 58.88 21.43 0.28 2 6.83

Spatial distribution of catches through time

Spatial distribution of catches in 1995–2022 is presented in Figure 3 and Figure 4. Most of the catches have been from the southern edge of the Icelandic shelf. In the period, a gradual relative increase is seen in the western area and a gradual decrease in the southeastern area (Figure 3).

Figure 3: Greater silver smelt. Catch distribution and proportions by area according to logbooks.

Figure 4: Greater silver smelt. Spatial distribution of catches as reported in logbooks.

Table 3: Greater silver smelt. Landings (tonnes) records from the Icelandic directorate of Fisheries and Greenland.
Year Section 5.a Section 14.b Total
1988 241 0 241
1989 8 0 8
1990 113 0 113
1991 246 0 246
1992 657 0 657
1993 1526 0 1526
1994 756 0 756
1995 586 0 586
1996 881 0 881
1997 3935 0 3935
1998 15242 0 15242
1999 6681 0 6681
2000 5657 0 5657
2001 3043 0 3043
2002 4960 0 4960
2003 2680 0 2680
2004 3645 0 3645
2005 4482 0 4482
2006 4769 0 4769
2007 4227 0 4227
2008 8778 0 8778
2009 10828 0 10828
2010 16428 0 16428
2011 10516 0 10516
2012 9289 0 9289
2013 7155 0 7155
2014 6344 4 6348
2015 6058 23 6081
2016 5646 16 5662
2017 4344 666 5010
2018 4035 425 4460
2019 3209 2 3211
2020 3775 27 3802
2021 4140 15 4155
2022 6886 28 6914
2023 5268 0 5268

Data available

In general, sampling from commercial catches is considered representative of the stock, as one of the requirements of owning a fishing license for greater silver smelt is the retention of scientific samples (Table 4). Samples were only obtained from bottom trawls. The sampling does seem to cover the spatial and temporal distribution of catches. The sampling coverage in 2023 is shown in Figure 5, but in recent years there has been a large decline in sampling with an increase in 2023.

Figure 5: Greater silver smelt. Fishing grounds in 2023 as reported in logbooks and positions of samples taken from landings (asterisks).

Landings and discards

Landings by Icelandic vessels are given by the Icelandic Directorate of Fisheries. Discarding is banned in Icelandic waters, and currently there is no available information on greater silver smelt discards. It is however likely that unknown quantities of greater silver smelt were discarded prior to 1996.

Length compositions

Table 4 gives the number of samples and measurements available for calculations of catch in numbers of greater silver smelt in Icelandic waters. Length distributions from autumn survey and commercial samples are presented in Figure 6 and Figure 7, respectively. Length distributions from the autumn survey are rather stable, with 2023 being close to the long-term average (Figure 6).

Figure 6: Greater silver smelt. Length distribution from the autumn survey (grey area) and mean length distribution (black line).

Figure 7: Greater silver smelt. Relative length distributions from Icelandic commercial bottom trawl catches.

Age compositions

Table 4 gives the number of samples and measurements available for calculations of catch in numbers of greater silver smelt in Icelandic waters. Age distributions from the autumn survey in Figure 8 and estimated as catch in numbers are given in Figure 9.

Table 4: Greater silver smelt. Summary of sampling intensity and overview of available data.
Year No. length samples No. length measurements No. otolith samples No. aged otoliths
1997 48 4992 1447 1059
1998 148 15559 6964 889
1999 58 4163 2180 82
2000 27 2968 1011 113
2001 10 489 245 17
2002 21 2270 360 127
2003 63 5095 425 0
2004 34 997 225 84
2005 49 3708 772 0
2006 29 4186 616 525
2007 14 2158 285 272
2008 44 3726 1768 1387
2009 53 5702 1746 1574
2010 134 16353 3370 3120
2011 63 6866 1953 1774
2012 43 4440 1492 603
2013 47 4977 710 704
2014 39 4709 350 340
2015 11 1275 221 217
2016 45 5879 285 283
2017 29 3466 430 416
2018 12 1437 185 181
2019 10 1250 40 40
2020 12 1905 130 130
2021 14 1301 215 214
2022 8 603 165 165
2023 26 2598 439 436

Figure 8: Greater silver smelt. Age distributions in proportions from the Icelandic autumn survey.

Figure 9: Greater silver smelt. Greater silver smelt. Catch in numbers by age (proportion).

Weight at age

Biological data from the spring survey, autumn survey, and commercial catches were combined to analyse growth. Von Bertalanffy growth curves were fitted and plotted within a series of time periods, including 2016-2019, 2011-2015, 2006-2010, 2001-2005, 1994-2000, and prior to 1994 to increase sample sizes for estimating each curve. The exponential length-weight relationship is extremely consistent across periods. In general, there is very little variation between periods, although females can be seen to grow larger sizes than males.

Maturity at age and natural mortality

Estimates of maturity ogives of greater silver smelt in 5.a were presented at the ICES 2020 meeting for both age and length (ICES 2020) using data collected in the Icelandic autumn survey (See stock annex for details). Males tend on average to mature at a slightly higher age or at 6.5 compared to 5.6 for females but at a similar length as females 35.3 cm. Most of the greater silver smelt caught in commercial catches in Icelandic waters are mature.

No information exists on natural mortality of greater silver smelt in Icelandic waters.

Catch, effort and Survey Data

Catch per unit of effort and effort data from commercial fisheries

At WKDEEP 2010 a glm cpue series was presented (WKDEEP 2010, GSS-05), however because of strong residual patterns the group concluded that the glm-cpue series was not suitable to use as an indicator of stock trends. The cpue is not considered to represent changes in stock abundance as the fishery is mostly controlled by market factors, oil prices and quota status in other species, mainly redfish.

Icelandic survey data

The Icelandic spring groundfish survey, which has been conducted annually in March since 1985, gives trends on fishable biomass of many exploited stocks on the Icelandic fishing grounds. In total, about 550 stations are taken annually at depths down to 500 m. The survey area does not cover the most important distribution area of the greater silver smelt fishery in Icelandic waters and is therefore not considered representative of stock biomass. The survey may be indicative of recruitment; however, the data have not been explored in sufficient detail to be used for this purpose.

The Icelandic groundfish autumn survey was commenced in 1996 and expanded in 2000. A detailed description of the autumn groundfish survey is given in the stock annex (ICES 2020) for greater silver smelt in Icelandic waters. The survey is considered representative of stock biomass of greater silver smelt since it was expanded in 2000. Figure 11 gives the most recent catch quantities and locations of surveys. Due to a strike in 2011 the autumn survey was cancelled after about one week of survey time. Greater silver smelt is among the most difficult demersal fish stocks to get reliable information on from bottom-trawl surveys. This is in large part because most of the greater silver smelt caught in the survey is taken in few but relatively large hauls. This can result in very high indices with large variances particularly if the tow-station in question happens to be in a large stratum with relatively few tow-stations. For example, survey indices in 1999, 2014, and 2021 are especially high in comparison with survey indices from adjacent years (Figure 10). No substantial changes in spatial distribution are seen in general in Figure 12 & Figure 13.

Figure 10: Greater silver smelt. Indices calculated from the Icelandic spring survey (lines and shaded area) and from the autumn survey (dots). Vertical lines and shaded area represent +/- 1 standard error.

Figure 11: Greater silver smelt. Abundance and distribution of greater silver smelt in the spring survey (SMB) in 2024 and in the autumn survey (SMH) in 2023.

Figure 12: Greater silver smelt. Estimated survey biomass in the autumn survey by year from different areas (upper figure) and as proportions of the total (lower figure).

Data analyses

Landings and sampling

Spatial distribution of catches in Icelandic waters has not changed markedly in recent years and fishing for greater silver smelt in the NW area seems to have reduced (Figure 2 and Figure 3). Landings of greater silver smelt increased rapidly from 2007 to 2010 when they peaked at around 16 000 tonnes, since then they have decreased to around 5430 tonnes in 2023 (Figure 4 and Table 3). The decrease in catches is the result of increased vigilance by the managers to constrain catches to those advised and also lesser interest by the fleet in the stock. Mean length of greater silver smelt in catches has been rather stable from 2005 in the range of 37 – 43 cm (Figure 7). However, there was a slight increase in mean length in 2012 which can also be seen in recent years (Figure 7 and Figure 8). A similar continuous downward trend in mean age in the commercial catches is also observed. Mean ages from catches have been variable from 2000 in the range 8 – 14 years, with relatively high mean ages recently. The reason for these changes is not known as there is no marked difference in the spatial distribution of the fishery; however, reduced fishing pressure may be a factor.

Surveys

As mentioned above, greater silver smelt is a difficult species to survey in trawl surveys and the indices derived from the both the spring and autumn surveys have high CVs. Occasional spikes in the indices without any clear trend characterize the spring survey biomass indices. The only thing that can be derived from the spring survey is that the biomass indices (total and >25 cm), in 1985–1993 and again from 2002 to 2023 are at a higher level than in 1994–2001. The juvenile index (spring survey) has a very high peak in 1986 but then hardly any juveniles are detected in the survey in 1987 to 1995. Since 1998 there have been several small spikes in the recruitment index (Figure 10).

The observed trends in the biomass indices from the autumn survey have a considerably different trend than those observed in the spring survey (Figure 10). According to the autumn survey, biomass increased more or less year on year from 2000 to 2008 but then decreased in 2009 and 2010. The total biomass index in the autumn survey showed slight variations until 2014 when the index increased to the highest value observed, and thereafter has been relatively stable but with high variability. In 2023, the index reached the highest value in the timeseries.

There is a clear gradient in mean length of greater silver smelt with depth, larger fish being in deeper water, and therefore the spring survey, which is conducted at shallower depths, is not considered representative of the stock.

Analytical assessment

In 2020 a model of greater silver smelt in Icelandic and Greenlandic waters (ICES areas 5.a and 14) developed in the Gadget framework (Globally applicable Area Disaggregated General Ecosystem Toolbox, see http://www.hafro.is/gadget for further details) was benchmarked for the use in assessment (ICES 2020). This year, Gadget 3 was used instead of Gadget 2. Gadget 3 is the same model except that it uses template model builder (TMB) which allows it to utilize TMB’s automatic differentiation procedures producing models that can be optimized faster and that can use R optimizers (rather than Gadget 2’s inbuilt optimizers).

Data used and model settings

Data used for tuning and model settings used in the Gadget model are described in more detail in the stock annex (ICES 2020).

Diagnostics

Observed and predicted proportions by fleet

Overall fit to the predicted proportional length and age–length distributions is close to the observed distributions, except for a small peak of small-sized fish (Figures 13-16). This peak does not shift from year to year and therefore is considered due to high catchability in aggregations of small fish rather than cohorts in recruitment peaks. These peaks are likely absent from commercial data due to the requirement of fishing at >400 m depth.

Figure 13: Greater silver smelt. Fitted proportions-at-length from the Gadget model (black lines) compared to observed proportions in the autumn survey (vertical lines and points).

Figure 14: Greater silver smelt. Fitted proportions-at-age from the Gadget model (black lines) compared to observed proportions in the autumn survey catches.

Figure 15: Greater silver smelt. Fitted proportions-at-length from the Gadget model (black lines) compared to observed proportions from commercial catches.

Figure 16: Greater silver smelt. Greater silver smelt. Fitted proportions-at-age from the Gadget model (black lines) compared to observed proportions in commercial catches.

Model fit

Figure 17 shows the overall fit to the survey indices described in the stock annex. In general, the model appears to follow the stock trends historically. In previous category 3 assessments of this stock, the autumn survey was Winsorized due to high variability in the survey index, which can also be seen here, as survey indices are not Winsorized or standardized before being used. The survey indices for the smallest tow size classes (10-25 and 25-30 cm) due to generally low selectivity the peak on small-sized fish that likely results from aggregation rather than cohort dynamics (see previous section).

This year’s indices for large-sized fish are at an historical high, indicating that the last two year’s values were more likely to be relatively accurate. These high values may be the result of high variability in the survey index numbers in general, however. If survey indices are lower again next year, the model fit is likely to experience a correction to lower predicted index values.

Figure 17: Greater silver smelt. Fitted autumn survey index by length group from the Gadget model (black line) and the observed number of greater silver smelt caught in the survey (points). The green line indicates the difference between the terminal fit and the observations.

Results

The results are presented in Table 5 and Figure 18. Recruitment has been increasing over the past decade. But the high estimates of age 5 recruitment in 2021 may have been the result of recent high variability in survey indices and have been revised downwards in the last two years. Spawning–stock biomass has increased since 2012 and reached the highest SSB estimate in the time-series in 2023. Fishing mortality for greater silver smelt (age 6–14) has decreased from 0.2 in 2010 to less than 0.04 over the past several years due to greater regulation of the fishery as well as reduced commercial interest. Uncertainty was estimated by spatially bootstrapping the data and refitting the assessment model to resampled data. The spatial bootstrap entails refitting the model to 100 sets of data resampled by spatial areas to maintain spatial correlation in the data (see the stock annex). The base model assessment results appear unbiased as it corresponds well with the median of results (Figure 18). Asymmetry in the confidence intervals is likely to be the result of a small number of model runs with a set of resampled data that are a poor representation of the actual data. For this reason, it was suggested by WGDEEP to improve the spatial bootstrap methods so that they better represent variation in the data.

Figure 18: Greater silver smelt. Estimated biomass, spawning stock biomass (SSB), fishing mortality for fully selected fish, recruitment, and total catches. The black solid line in the SSB plot represents Bpa and the solid red line indicates Blim. The horizontal solid line in the fishing mortality plot indicates the fishing mortality used in the ICES MSY advice rule, whereas the horizontal dashed lines indicate the bounds of the realized fishing mortality resulting from the advice rule given the uncertainty in the assessment. Uncertainty was estimated by spatially bootstrapping the data and refitting the assessment model to resampled data. Outer yellow ribbons with red borders indicate 95% interquantile ranges, whereas inner yellow ribbons indicate 50% interquantile ranges. The central red line indicates the median, and the dashed red line is the base model run for the assessment upon which advice is based.

In comparison with last year’s assessment, there has been a slight upward revision of biomass levels and downward revision of fishing mortality (Figure 19), but within the range expected according to benchmark uncertainty estimates (ICES 2020).

Figure 19: Greater silver smelt. This year’s assessment compared with previous assessments. Spawning stock biomass (SSB), fishing mortality for fully selected fish and recruitment.

Table 5: Greater silver smelt. Gadget assessment model results including input catch values (tonnes),. estimated spawning stock biomass (SSB, tonnes), recruitment (Rec., age 5 in millions, and fishing mortality (age 6-14). Projections are given in the last year. Projections are given in the last year and also the second to last year for catch and F.
Year Total biomass Catch SSB REC F
2000 50435.94 5.657 19833.15 20.02472 0.131
2001 53142.90 3.043 19100.31 33.21761 0.068
2002 60148.04 4.961 19732.45 37.84657 0.094
2003 66713.92 2.680 16534.91 37.86023 0.045
2004 73688.23 3.645 32409.75 21.86167 0.055
2005 80193.98 4.482 45184.55 18.70857 0.063
2006 85410.44 4.769 46541.19 29.77400 0.062
2007 88539.04 4.227 57162.44 23.28200 0.049
2008 93580.01 8.778 56732.35 29.97845 0.101
2009 93896.90 10.828 51011.24 32.30500 0.125
2010 90992.27 16.428 56264.24 19.73749 0.205
2011 83725.74 10.516 44571.31 28.43445 0.145
2012 82904.93 9.289 38069.51 42.88490 0.128
2013 83753.73 7.155 40775.75 32.44244 0.092
2014 89085.70 6.348 40899.34 34.64067 0.079
2015 96396.51 6.070 42917.42 38.94335 0.071
2016 104086.56 5.662 45303.26 42.43918 0.061
2017 111833.30 5.011 48624.44 58.93554 0.050
2018 122989.98 4.460 56313.61 57.66196 0.038
2019 133669.17 3.210 64432.82 47.96406 0.024
2020 143291.26 3.797 76958.01 42.20321 0.027
2021 151828.27 4.156 77580.31 73.13467 0.027
2022 154697.71 6.914 88730.26 56.07708 0.041
2023 166633.12 5.268 94874.00 36.52668 0.030
2024 168681.20 6.572 100195.67 41.27439 0.038

Retrospective analysis

An analytical retrospective analysis is presented (Figure 20). The analysis indicates that there were downward revisions of biomass from the second to fourth years of the 5-year peel followed by an upward revision of biomass (SSB) over the last year. As a result, there was slight upward then downward revision of \(F\). Estimates of recruitment are decently stable, though less so in the most recent years.

Mohn’s rho was estimated to be -0.017 for SSB, 0.063 for F, and -0.109 for recruitment.

Figure 20: Greater silver smelt. Retrospective plots illustrating stability in mod-el estimates over a 5-year ‘peel’ in data. Results of spawning stock biomass, fishing mortality F, and recruitment (age 5) are shown.

Comments on the assessment

In 2020 this stock was benchmarked (ICES 2020) and a length- and age-based assessment was accepted as a category 1 assessment method. The ICES MSY advice rule is applied for this stock in 2024/2025 advice. The decision which allocates catches to the fleets requires 1) an expected quantity of catch to be removed that will complete total catch removals for the current fishing season, 2) a 1-year projection to determine the amount of biomass available to fish, and 3) application of projected fishing effort according to Fmsy to determine the expected catch from fishing at this level. Advised catch is set to this value while SSBy>Btrigger, scaled by (SSBy)/Btrigger while Blim≤SSBy<Btrigger, and set to 0 while SSBy≤Blim.

Management

The Icelandic Ministry of Food, Agriculture and Fisheries is responsible for management of the Icelandic fisheries and implementation of legislation. The Ministry issues regulations for commercial fishing for each fishing year (1 September–31 August), including an allocation of the TAC for each stock subject to such limitations. Before the 2013/2014 fishing year the Icelandic fishery was managed as an exploratory fishery subject to licensing since 1997. A detailed description of regulations on the fishery of greater silver smelt in Icelandic waters is given in the stock annex (ICES 2020). Fishing for greater silver smelt is banned at depths less than 400 m to avoid catching younger fish.

The TAC for the 2013/2014 fishing year was set at 8000 t based on the recommendations of MRI using a preliminary Gadget model and the 2014/2015 fishing year the recommendation was to maintain the catches at 8000 t. For the fishing year 2015/2016 it was also maintained at 8000 t, but varied between 7600 and 12273 since then, the most recent being the highest (Table 6).

Figure 21 illustrates the difference between national TAC and landed catch in Icelandic waters. Flexibility is built into the Icelandic fisheries management system in which quota is automatically transformed for use for constraining species when it is available. As this stock is consistently caught at levels lower than the TAC in recent years, it has been a source of quota that may be used to fish other species.

Table 6: Greater silver smelt. TAC recommended by the Marine and Freshwater Research Institute, national TAC set by the Ministry, and total landings (tonnes).

Fishing year

Recommended TAC

National TAC1)

Catches other nations2)

Catches Iceland

2010/2011

8  000

8  000

12  091

2011/2012

6  000

6  000

0

8  410

2012/2013

8  000

8  000

11  039

2013/2014

8  000

8  000

7  243

2014/2015

8  000

8  000

4

6  849

2015/2016

8  000

8  000

12

6  019

2016/2017

7  885

7  885

16

3  570

2017/2018

9  310

9  310

666

5  159

2018/2019

7  603

7  603

425

2  807

2019/2020

9  124

9  124

2

3  775

2020/2021

8  729

8  729

27

4  282

2021/2022

8  717

8  717

15

6  550

2021/2022

9  244

9  244

28

6  550

2022/2023

11  520

11  520

0

5  430

2023/2024

10  9203)

12  080

2024/2025

12  273

1) Icelandic TAC

2) Calendar year catches in East Greenland

3) Corrected advice in 2024

Figure 21: Greater silver smelt. Net transfer of quota in the Icelandic ITQ system by fishing year. Between species (upper): Positive values indicate a transfer of other species to greater silver smelt, but negative values indicate a transfer of greater silver smelt quota to other species. Between years (lower): Net transfer of quota from a given fishing year (may include unused quota).

Current advisory framework

Reference points defined for the stock are shown in Table 7.

Table 7: Greater silver smelt. Reference points.

Approach

Reference point

Value

Basis

MSY approach

MSY Btrigger

25 437

Bpa

FMSY

0.07

Fishing mortality that leads to MSY; estimated using stochastic simulations

Precautionary approach

Blim

18 300

Bloss (SSB in 2010)

Bpa

25 437

Blim * 1.4

Flim

0.24

Equilimbrium F which will maintain the stock above Blim with a 50% probability

Fpa

0.16

F that leads to a < 5% risk of SSB < Blim in equilibrium

Information on how these reference points were generated and the model setting for short-term projections can be found in ICES 2020 report (ICES 2020). The current intermediate year assumption regarding catch is set equal to the expected status quo fishing level during the fishing season (last quarter of year y and quarters 1–3 in year y+1) and projections for the following year run at a selected harvest rate. The status quo fishing level was calculated as the mean landings over the previous three fishing seasons.

Age 1 recruitment estimates are highly uncertain from the most recent three years. Therefore, in forecasts, it is proposed to use the geometric mean of the three years before these values (e.g., for 2020, this would be the geometric mean of age 1 recruitment estimates from years 2014–2016). The projected recruitment reported from the model output is for age 5 because recruitment estimated for ages 1-4 are highly uncertain.

Management considerations

Exploitation of greater silver smelt in Icelandic waters has been reduced in recent years, coming down from a relatively high level in 2010, to levels lower than the average exploitation rate in the reference period.

Ecosystem considerations for management

Shorter periods of reduced biomass due to high fishing rates are observed in the history of greater silver smelt fishing in Iceland. However, there has been a general trend since the mid-1990s of a decrease in biomass levels from the mid-1980s to the mid-1990s, during which catch records are unreliable so the general reduction cannot directly be attributed to fishing, followed by a general increase in biomass in the past two decades. It is likely that a combination of lower fishing rates and favourable environmental conditions have led to high recruitment levels over the past decade.

REFERENCES

ICES. 2010. Report of the Benchmark Workshop on Deep‐water Species (WKDEEP), 17–24 February 2010, Copenhagen, Denmark. ICESCM2010/ACOM: 38. 247pp. http://www.ices.dk/sites/pub/Publication%20Reports/Expert%20Group%20Report/acom/2010/WKDEEP/wkdeep_final_2010.pdf

ICES. 2014. “Report of the Working Group on the Biology and Assessment of Deep-Sea Fisheries Resources (WGDEEP). ICES Scientific Reports. 1:21., Copenhagen, Denmark. ICES Cm 2014/Acom:17.” International Council for the Exploration of the Seas; ICES publishing. https://doi.org/10.17895/ices.pub.5262.

ICES. 2020. “Stock Annex: Greater silver smelt (Argentina silus) in Subarea 14 and Division 5.a (East Greenland and Iceland grounds).” International Council for the Exploration of the Seas; ICES publishing. https://doi.org/10.17895/ices.pub.20037254

ICES. 2021. Benchmark Workshop of Greater silver smelt (WKGSS; Outputs from 2020 meeting). ICES Scientific Reports, 3:5. 485 pp. https://doi.org/10.17895/ices.pub.5986.