I forbindelse med metoderevisjonsarbeidet i ICES på kysttorsk nord for 62°N høsten 2020-våren 2021, ble det utarbeidet nye mengdeindeks-serier basert på faste trålstasjoner og akustikk under kysttoktet om høsten. Akustikkserien dekker perioden 1995-2019, mens trålindeksen dekker perioden 2003-2019. Denne rapporten beskriver metodikken brukt og presenterer kort resultatene i form av tabeller og grafer.
Summary
In connection with the benchmark processes within ICES on Norwegian Coastal Cod north of 62°N during autumn 2020-spring 2021, new abundance index series based on bottom trawl stations and acoustics at the autumn coastal survey were made. The acoustic index covers the period 1995-2019 while the trawl index covers the period 2003-2019. This report describes the methods used and briefly presents the results.
April 30th 2021: Some updates in Appendix.
1 - Introduction
New abundance index series for Norwegian coastal cod north of 62° were produced using the software StoX (Johnsen et al. 2019). Indices were calculated by applying trawl swept area and acoustic methods, using data collected during the Norwegian annual coastal survey in autumn NOcoast-Aco-4Q.
Time series of indices for the period 1995 to 2019 in numbers and biomass (2003-2019 for the swept-area index), their coefficient of variation, length- and weight-at-age are tabulated for three subareas and the total area in Appendix A (acoustic indices) and Appendix B (swept-area trawl indices).
2 - Biology, stock structure, and management of coastal cod
Coastal cod occurs in fjords and coastal areas along the entire coast of Norway. The management area for this species is divided into two areas south and north of 62 ° N. Genetic studies indicate a genetic cline along the coast from eastern Finnmark to inner Skagerrak (Dahle et al., 2018). Coastal cod north of 62 ° N is somewhat related to Northeast Arctic (NEA) cod, while coastal cod south of 62 ° N showing some similarities to North Sea and Skagerrak cod.
Compared to NEA cod the immature coastal cod has faster individual growth and earlier age of maturation (Berg and Albert, 2003). Since individual growth is reduced after the age of first maturation, the weight at age for old fish is somewhat lower for coastal cod than for Northeast Arctic cod at the same age.
Spawning areas for coastal cod have been mapped by egg sampling and classified according to their relative value (Gytefelt Torsk MB at www.fiskeridirektoratet.no ). See also Figures 18-23 in Aglen et al. (2020). Some of these coastal cod spawning areas are close to spawning areas for NEA cod. Probably due to rather small-scale differences in currents and egg buoyancy, the coastal cod eggs and larvae tend to be retained near the spawning areas, while NEA cod eggs and larvae are transported by currents northward into the Barents Sea.
Annual total allowable catches (TAC) were set for coastal cod at 40 kt in the years 1987-2003, 20 kt in 2004, and 21kt in later years. A large proportion of the annual landings of coastal cod is by-catches in the fishery for NEA cod. A rebuilding plan was established 2011 and several technical regulations were introduced to reduce “bycatches” of coastal cod, including gear restrictions and restrictions on vessel size, and closures of spawning areas in the spawning season (Henningsværstraumen and Inner Lofoten).
3 - The autumn coastal survey
3.1 - The history of the survey and how it has developed over the years
The Institute of Marine Research (IMR) has since 1985 conducted an annual acoustic survey of coastal areas and offshore banks north of 62°N with the objective of obtaining abundance indices of commercially important fish species (Skants, 2019). The annual coverage (in October and November) of coastal areas and fjords, as well as open ocean banks, between Stad (62°N) and Varanger (71.3 °N) has since 1995 included measurements of coastal cod ( Gadus morhua ).
The trawl gear used during the first years was a Campelen 1800 standard shrimp trawl with rock hopper gear and 35 mm mesh size in the cod end. Scanmar sensors provided information about the trawl opening (height in meters), door spread and bottom contact. Since 2003 a Campelen 1800 standard shrimp trawl with rock hopper gear, 20 mm mesh size in the cod end and 80mm (stretched) in the front part is the standard fishing gear, combined with Scanmar trawl and door sensors (Aglen et al., 2005). Additional stations were added in 2017, which was done as it was considered necessary to gather more information on deep water shrimps and redfish (Mehl et al., 2018a). Standard trawl duration is 30 minutes at a speed of 3 knots, with preferred doorspread of 49-52m and trawl opening of 3.5-4.5m. Data were collected with several vessels, which are listed in Table 1.
The survey consists of a stratified grid for acoustic measurements, with fixed bottom trawl stations and additional bottom and pelagic stations on acoustic registrations within each of the strata.
During the surveys hydrographic stations were sampled semi-regularly. CTD-measurements were taken at some of the fixed bottom trawl stations or with a set distance of 30 nautical miles between each station (Staby et al., 2020).
The surveyed area was initially divided into 23 strata, and these were grouped into three subareas: North of 67°N (Area “A”), 65°-67°N (Area “B”), and 62°-65°N (Area “C”) (Figure 1). The stratum “Vestfjorden East” was, however, removed from all years, since this stratum had no acoustic coverage and no trawl hauls in most years.
Acoustic transects and bottom trawl hauls are standardized since 2003. In 2017 additional acoustic transects were added to selected strata in order to improve the accuracy of saithe biomass estimates in those strata that contributed a significantly to the total estimate. Figure 2 shows the acoustic transects and trawl hauls made during the coastal survey in 2019.
Trawl catches are sorted and weighed by species according to standard procedures (Mjanger et al., 2020). Length measurements (e.g. total length; from snout to end of the caudal fin) are done for most species, either of all sorted individuals or of a subsample from large catches. Additional information such as age and type from otoliths, sex and gonad maturity stage are collected from cod.
3.2 - Previous attempts to extract abundance indices from the survey data
As described in chapter 1.2, the autumn coastal survey has a long history and has undergone various changes over the years. It started out as an acoustic survey primarily targeting coastal cod in the Troms and Finnmark counties in the 1980s. These surveys were conducted by the former “Fiskeriforskning” marine research institute in Tromsø. IMR in Bergen started a survey at approximately the same time of the year, but targeting mainly saithe in the outer coastal areas, partly overlapping the areas of the former survey. A third survey, covering overwintering herring in the fjords was aslo conducted by IMR. “Fiskeriforskning” was discontinued and the department responsible for resource surveys was included in IMR. From 2003 these surveys were combined and standardized to be a combined acoustic and trawl survey mainly targeting coastal cod and saithe. When the surveys were merged and standardized in 2003, attempts were made to construct an acoustic index for coastal cod based on the original coastal cod survey and the saithe survey, covering also more southern parts of the coast north of 62 ° N. Due to partly different procedures, working protocols, and data format at the two responsible institutes, and since the surveys partly overlapped in space and time, this combination was difficult. The series was started in 1995, but for the years prior to 2003, only some of the acoustic transects, mostly those that had been standardized during the “Fiskeriforskning” survey, were used in index calculations.
3.3 - Description of the survey data
Table 1 lists the surveys from 1995-2019, which vessels took part, the number of stations taken etc.
Year
Vessel
Cruise ID
For swept area index
For acoustic index
N BT
N aged
N length
N BT (with cod)
N aged
N length
N miles scrutinized
Total
With cod
Total
With cod
1995
Michael Sars
1995111
2515
497
3869
3575
Johan Hjort
1995211
80
1845
3952
2158
Volstad
1995810
0
54
0
0
1996
Johan Hjort
1996214
171
2727
3285
1905
Michael Sars
4-1996
2393
5376
6186
1552
1997
Johan Hjort
1997213
432
3656
3687
2650
Michael Sars
4-1997
1670
4653
4180
0
1998
G.O.Sars
1998016
493
2237
3030
1808
Jan Mayen
4-1998
2476
4060
3175
0
1999
Johan Hjort
1999215
399
1083
3813
1653
Jan Mayen
4-1999
2780
4444
3420
0
2000
Johan Hjort
2000214
414
1202
3766
1816
Jan Mayen
4-2000
4240
5276
3090
0
2001
Johan Hjort
2001213
267
844
4523
1229
Jan Mayen
4-2001
3181
3815
2614
0
2002
Johan Hjort
2002214
362
1173
4655
2128
Jan Mayen
4-2002
2048
2511
3164
0
2003
Johan Hjort
2003211
58
50
1381
2520
72
1580
2808
3695
2012
Jan Mayen
2003706
78
68
1367
1734
109
1635
2077
4007
3130
2004
Johan Hjort
2004212
50
41
981
1714
67
1159
2010
3502
1989
Jan Mayen
2004704
81
69
1270
1814
88
1345
1942
3469
2824
2005
Johan Hjort
2005212
42
36
759
1345
51
949
1625
3013
1768
Jan Mayen
2005704
82
66
695
863
80
689
870
3794
3180
2006
Johan Hjort
2006213
51
42
543
821
48
677
1047
3851
2165
Håkon Mosby
2006623
0
0
0
0
7
33
51
4479
34
Jan Mayen
2006705
90
71
865
995
87
886
1021
4013
3260
2007
Johan Hjort
2007212
39
25
179
296
39
327
489
3550
1042
Håkon Mosby
2007623
0
0
0
0
8
0
103
3778
0
Jan Mayen
2007703
107
87
834
1040
85
829
1036
4670
3860
2008
Johan Hjort
2008210
86
81
1197
1773
103
1381
2012
6275
5831
Håkon Mosby
2008623
31
16
233
329
24
308
439
1875
0
Jan Mayen
2008705
4
4
73
127
10
73
192
214
193
2009
Johan Hjort
2009209
49
41
760
1240
46
818
1306
2860
1696
Håkon Mosby
2009629
17
6
11
11
5
29
29
1127
180
Jan Mayen
2009703
66
57
1263
2345
75
1299
2466
2819
2680
Jan Mayen
2009704
4
4
140
382
14
166
544
524
524
2010
Johan Hjort
2010211
114
90
1957
3847
120
2284
4841
6175
4284
Jan Mayen
2010704
6
6
149
489
12
168
518
380
380
2011
Johan Hjort
2011214
38
32
536
839
31
561
880
2450
1796
Helmer Hanssen
2011722
81
71
1246
2075
80
1292
2158
4074
2875
Helmer Hanssen
2011723
6
6
114
177
18
184
290
240
222
2012
Johan Hjort
2012210
64
55
834
1496
64
974
1701
3760
2552
Håkon Mosby
2012620
65
51
1129
1878
50
1202
2123
2663
1402
2013
Johan Hjort
2013210
54
51
932
1638
72
1020
1836
3018
1602
Håkon Mosby
2013623
59
50
1160
2288
65
1249
2451
2339
1227
Helmer Hanssen
2013851
8
8
124
317
21
124
492
436
432
2014
Helmer Hanssen
2014011
8
8
209
717
21
222
736
455
449
Johan Hjort
2014213
61
54
928
1601
81
1046
1767
4036
2680
Håkon Mosby
2014621
74
61
1292
2555
94
1344
2623
2718
1837
2015
Johan Hjort
2015211
64
53
901
1272
65
992
1797
3880
2289
Håkon Mosby
2015621
74
58
1180
1798
59
1183
2580
2447
1578
Helmer Hanssen
2015854
8
7
181
566
21
229
613
395
390
2016
Johan Hjort
2016210
70
61
1451
2336
91
1545
2580
4594
4429
Håkon Mosby
2016620
69
53
976
1463
59
1012
1522
2978
1567
2017
Johan Hjort
2017210
99
89
1616
2822
94
1656
2887
4696
2322
Kristine Bonnevie
2017620
87
70
917
1854
97
957
1931
3760
1567
2018
Johan Hjort
2018210
110
90
1713
3282
134
1747
3316
4141
1527
Kristine Bonnevie
2018623
86
66
1301
2365
94
1389
2523
3983
2146
2019
Johan Hjort
2019210
128
100
1516
2059
108
1598
2164
4832
2411
Kristine Bonnevie
2019629
87
70
1191
2409
117
1196
2499
3345
2371
Table 1. Description of survey data. The number of bottom trawl (BT) stations for swept area and acoustic indices differ because different data filters are applied (see sections 4.1.3 and 4.2.6).
4 - Software used
StoX is a software developed by the Institute of Marine Research for survey analysis and index calculation. StoX is freely available (ftp://ftp.imr.no/StoX/Download/ ) and is relatively well documented (Johnsen et al., 2019). StoX is currently used for the calculation of bottom trawl indices from the Barents Sea winter survey (Mehl et al., 2018b) and from the Barents Sea ecosystem survey in the autumn (BESS) (Johannesen et al., 2019).
The data was mainly downloaded from: https://datasetexplorer.hi.no/apps/datasetexplorer/v2/navigation and the folder “Varanger Stad NOR coastal cruise in autumn». However, for some research vessels, especially in the early part of the period, data was lacking in the relevant folders and had to be retrieved from the original data files and reformatted to the current xml format used by StoX (https://www.hi.no/hi/forskning/prosjekter/stox). Steps have been taken to have these data stored in the “Varanger Stad NOR coastal cruise in autumn” folder structure and quality assure for later use.
5 - Acoustic indices
A stock abundance index series based on acoustic data from the annual autumn coastal survey ( NOcoast-Aco-4Q ) was calculated using the StoX software (Johnsen et al., 2019). Acoustic data covering the coastline from 62°N to the Russian border are available back to 1995, although the coverage in various parts of this area varied somewhat due to various reasons, see chapter 3.1 and 3.2 for details. For some early years in the series, acoustic data was only available from parts of the survey area. The area was split into 23 strata (see above) and the stock abundance index was calculated for each stratum separately. For various reasons, it was decided to split the total area into three subareas: The coast north of 67°N (A, consisting of 18 strata), between 65° and 67°N (B, consisting of 2 strata), and between 62°N and 65°N (C, consisting of 2 strata) (Fig 1). The spatial coverage during most of the time series is much better in subarea A than in B and C.
To estimate the uncertainty, 500 bootstrap runs were performed, and the indices are the average index from these runs.
5.1 - Acoustic indices by length
The conversion of mean nautical area scattering coefficient (NASC, m 2 nmi −2 ) to fish density was carried out using a standard procedure, where trawl stations (with a catch of more than 1 cod individual) were assigned to each PSU. As a rule, all stations within a stratum were assigned to the PSUs in the same stratum. However, if less than three trawl stations were carried out in a stratum, stations in neighbouring strata were assigned to the PSUs so that at least three stations were assigned to each PSU.
The combined length distribution (d), calculated for each transect (PSU, j), is given by
, (eqn 1)
where d l,s,j is fish density (number by 1 nmi tow distance) by station (s) and length group (l, cm), and n is the total number of stations.
The fish density (ρ, individuals nmi -2 ) by length group and transect was calculated using
(eqn 2)
where NASC j,l is the mean nautical area scattering coefficient by transect and length group and σ bs,l (m2) is the acoustic backscattering cross-section for a fish of length l.
NASC j,l is given by
(eqn 3)
where σ bs,l is the acoustic backscattering cross-section for a fish of length l multiplied by the proportion (p) of a fish of length l in d l,j , and NASC j is the mean nautical area scattering coefficient over a given transect.
The acoustic backscattering cross-section for a fish of length l is calculated using
, (eqn 4)
where the target strength, TS (dB re 1m 2 ), for a fish of length l is calculated using
, (eqn 5)
where m and a are constants, set at 20 and -68.0 respectively.
The abundance (N, inds) of cod by length group l and stratum k is given by
, (eqn 6)
where A (nmi 2 ) is the stratum area, and the mean density of cod by l and k is given by
(eqn 7)
where is the transect weight, is the total number of sample transects and and are the distance of each transect by stratum and the mean transect distance over each stratum respectively.
5.2 - Acoustic indices by age
Only a subsample of the length-measured individuals (j) is aged. A two-stage conversion process is used to convert the abundance of fish by length group to abundance of fish by age group.
First, the abundance ( Nk,l ) by l and k is distributed the length-measured individuals to generate so-called super-individuals, each representing an abundance estimated as:
, (eqn 8)
where
, (eqn 9)
and m is the number of length-measured individuals.
Second, in instances where a super-individual is not aged, the missing age is filled in by a random data imputation. The imputation of missing age is principally carried out at the station level, randomly selecting the value from aged super-individuals within the same length group. If no aged super-individual is available at station level, the imputation is attempted at strata level, or lastly on survey level. In instances, where no age information is available at any level for a specific length group, the abundance estimate is presented with unknown age. As the imputation of missing age values in both examples also imputes associated biological parameters, abundance can be estimated for any combination of classifications assigned to the super-individuals e.g. sex, maturity, age etc. In our case the otolith type was used to classify the super-individuals, see below.
5.3 - Length and weight at age
Length and weight at age was calculated using the weighting factors defined in eqn 8 (the “super -individuals”).
5.4 - Uncertainty of abundance indices
Uncertainty was estimated as the coefficient of variation (ratio of standard deviation to the mean, CV). StoX calculates CV using bootstrap runs by stratum, treating each trawl station as the primary sampling unit. Here we used 500 bootstrap runs.
5.5 - Extracting coastal cod from total cod
Since the discrimination of coastal cod and other cod caught at the coastal survey is based on otolith types (see above), this poses a special challenge to producing abundance index series with uncertainty for coastal cod. Running a StoX project on the acoustical and biological data to produce an acoustic index series will primarily produce indices for all cod present in these data sources. However, when running the bootstrap process in StoX, it is possible to group the superindividuals by several categories, for instance age and otolith type. There is no facility inside StoX to present those “two-dimensional” bootstrap data but using an R-script manipulating the bootstrap files generated by StoX it is possible to extract relevant data. Thus, this was done after the whole time series was made by ordinary StoX-runs, by selecting only those entries in the bootstrap data that contained superindividuals with otolith types “1” and “2”. All tables and figures in the appendices were produced with this R-script. The R-script itself is documented in appendix C. Since the growth pattern can only be distinguished with certainty in otoliths from two-year old and older fish (although an otolith type is in some cases noted also for younger fish), the indices of age 0 and age 1 were excluded from the index series suggested for use in stock assessment.
5.6 - Acoustic indices - settings in StoX
The processes included and the settings of parameters when running StoX for acoustic indices are given in Tables 2-5:
Table 2. Baseline processes:
Process
Parameters
Values
ReadProcessData
ReadAcousticXML
FileName1, FileName2, …
Relevant data files
FilterAcoustic
AcousticData
ReadAcousticXML
DistanceExpr
N/A
FreqExpr
N/A
NASCExpr
acocat == 31
NASC
LayerType
WaterColumn
ReadBioticXML
FileName1, FileName2, …
Relevant file names
FilterBiotic
FishStationExpr
fs.getLengthSampleCount(‘TORSK’)>1
CatchExpr
species == ‘164712’
SampleExpr
N/A
IndExpr
N/A
StationLengthDist
LengthDistType
NormLengthDist
RegroupLenghDist
LengthInverval
1.0
Catchability
CatchabilityMethod
LengthDependentSweepWidth
LengthDist
RegroupLengthDist
ParLenfthDependentSweepWidth
SpecCat=;Alpha=5.91;Beta=0.43;LMin=15.0;LMax=62.0
RelLengthDist
LengthDist
Catchability
DefineStrata
UseProcessData
“ True”
StratumArea
AreaMethod
Accurate
DefineAcousticTransect
DefinitionMethod
UseProcessData
MeanNASC
NASC
NASC
SampleUnitType
PSU
BioStationAssignment
BioticData
FilterBiotic
AssignmentMethod
Stratum (first time, then UseProcessData)
EstLayers
1~PELBOT
BioStationWeigting
WeightingMethod
SumWeightCount
TotalLengthDist
LengthDist
RelLengthDist
AcousticDensity
LengthDist
TotalLengthDist
NASC
MeanNASC
m
20
a
-68
MeanDensity_Stratum
Density
AcousticDensity
SampleUnitType
Stratum
SumDensity_Stratum
Density
MeanDensity_Stratum
Abundance
Density
SumDensity_Stratum
PolygonArea
StratumArea
IndividualDataStations
Abundance
Abundance
IndividualData
IndividualDataStations
IndividualDataStations
SuperIndAbundance
Abundance
Abundance
IndividualData
IndividualData
AbundWeightMethod
StationDensity
LengthDist
RegroupLengthDist
Table 3. Baseline report processes:
Process
Parameters
Values
FillMissingData
Superindividuals
SuperIndAbundance
FillVariables
ImputeByAge
Seed
1
FillWeight
Mean
EstimateByPopulationCategory
Superindividuals
FillMissingData
Lengthinterval
5.0
Scale
1000
Dim1
olotithtype
Dim2
age
Dim3
SpecCat
Table 4. R processes:
Process
Parameters
Values
runBootstrap
bootstrapMethod
AcousticTrawl
acousticMethod
PSU~Stratum
bioticMethod
PSU~Stratum
startProcess
TotalLengtDist
endProcess
SuperIndAbundance
nboot
500
seed
1
cores
4
imputeByAge
seed
1
cores
4
SaveProjectData
“ Enabled”
Table 5 R report processes:
Process
Parameters
Values
getReports
out
all
options
grp1=”age”, grp2=”otolithtype”
getPlots
out
all
options
grp1=”age”, grp2=”otolithtype”
5.7 - Resulting time series
The annual abundance indices and biomass indices by age groups and for age group 2+, their coefficient of variation, and mean length and weight by age groups are shown in Appendix A for the total area and for the subareas A, B and C.
The abundance indices for age 2+ are depicted in Figures 3 to 6. The series for the total area (Fig 3) is characterized by high indices at the beginning of the time series, but rapidly decreasing from 1997 to a level of 10-20 million, without any clear trends. In general, the uncertainties are larger during the first part of the time series compared to more recent years.
The series for subarea A (the northern part of the survey area, Figure 4) resembles that for the total area, because this area contains most of the coastal cod.
The indices for subareas B (Figure 5) and C (Figure 6) are lower than for subarea A. The uncertainties are also more variable from year to year.
To assess whether the indices can describe the stock dynamics over time, plots on how year classes (cohorts) could be traced from year to year were constructed (Figure 7-10). The progression of year classes through the stock is reasonably well described for the total area and for subarea A (Figures 7-8). A year effect is visible for instance in 1998, when all age groups where recorded lower than expected. In other years, single age groups, in particular among older fish, show unexpected patterns. This seems to be a problem for age groups above 10 years. As expected, the plot for Subarea A (Figure 8) resembles that for the total area, while those for Subarea B (Figure 9) and Subarea C (Figure 10) show a much less consistent picture, where strong year effects are visible .
5.8 - Internal consistency in the acoustic series for subarea A
The internal consistency plots (number at age n in year n plotted versus number at age n+1 in year y+1) for age groups 1-6 are shown in Figure 11 and for age groups 7-12 in Figure 12. In most cases the fit is rather poor. Exceptions are age 1-2 and age 2-3, with rather high correlation, but the regressions are highly affected by the large indices during the first part of the period.
5.9 - Comparison with acoustic index series calculated with previous methods
An acoustic index has been calculated for this stock since 1995 (see chapter 1.3). Because this approach used a somewhat more detailed strata system and a method based on the SAS software platform, it is difficult to compare that series with the new acoustic index developed in StoX. Nonetheless, a comparison made for the sum over ages 2+ (Figure 13) shows that there are large differences between the series before 2002. For the period after 2002 the indices are much more similar, with the new series estimates being somewhat lower in most years. A part of the large discrepancies found in the early years of the series can be explained by poor data quality of the acoustic data. When the series was rerun in StoX and the acoustic data checked in detail, some few enormous NASC values were detected, indicating that parts of the bottom signal had been integrated. In small strata containing few transects and few values, such erroneous values may have a big impact on the total index. For instance, in 2000, taking out a NASC value of 4718 from a small stratum (Sørøya Indre) made the index in that stratum change from 46 000 tonnes to 1400 tonnes. In 1996, 1999 and in 2000 six extremely high values were found and removed from the transects, which had profound effects on the index values from these years. It is unknown whether these erroneous values were in fact included in the old acoustic series or not. In the remaining years before 2002, no extreme values could be found and also in these years the new index is substantially lower than the old index, indicating that there are other reasons for the differences. Despite this we argue that the new indices should be accepted on the grounds that they are developed in one go, using a more quality assured software with identical settings from year to year, and with a more thorough quality assurance of the acoustic data.
6 - Swept area indices
A stock abundance index series based on bottom trawl hauls at the annual autumn coastal survey ( NOcoast-Aco-4Q ) was calculated using the StoX software. Trawl data covering the coastline from 62°N to the Russian border were available back to 1995, although the coverage in various parts of this area varied somewhat due to ship availability, weather conditions etc. However, the survey was designed as an acoustic survey before 2003, and trawls were done on acoustic registrations in order to supply biological data for the acoustic observations. Consequently, we did use trawl data prior to 2003 when calculating the swept-area indices for coastal cod. The area is split into 22 strata (Figure 1) and the stock abundance index is calculated for each stratum separately. It was decided to split the total area into three subareas: The coast north of 67°N (A, consisting of 18 strata), between 65° and 67°N (B, consisting of 2 strata), and between 62°N and 65°N (C, consisting of 2 strata). The coverage during most of the time series is much better in subarea A than in B and C.
The coastal cod was split from the NEA cod using the same methods as described for the acoustic index, see above.
To estimate the uncertainty of the estimate, 500 bootstrap runs were performed, and the indices are the average index from these runs.
6.1 - Swept area indices by length
The following description is taken from Johannesen et al. (2019):
The swept area density ( ρ , individuals per square nautical mile, inds nmi -2 ) by stratum (k), station (s) and length group l (1 cm), is given by
, (eqn 10)
where fk,s,l is the number of individuals standardized over a towing distance of 1 nmi by k, s and l, and swl is the adjusted swept width in nmi’s by length group calculated using
, (eqn 11)
where EW l is the length dependent effective swept width. The length dependency of swept width is taken from (Dickson, 1993)
The abundance ( N , inds) by l and k is calculated using
, (eqn 12)
where A is stratum area (nmi 2 ), and ρk,l is the average swept area density by l and k, given by
, (eqn 13)
where n is number of stations.
6.2 - Swept area indices by age
The sampling protocol for the survey is to sample one individual from each 5 cm length group at each trawl station for aging and individual weights. A two-stage conversion process is used to convert the abundance of fish by length group to abundance of fish by age group.
Firstly, the abundance ( Nk,l ) by length group l (5 cm) and stratum k is distributed by the length-measured individuals (j) to generate so-called “Super-individuals” (super-individuals represent fractions of a total, our use corresponds to a probability based design where is the inverse of the inclusion probability for a single fish sample), each representing an abundance estimated as:
, (eqn 14)
where
, (eqn 15)
and m is the number of length-measured individuals
Secondly, in instances where a super-individual is not aged, the missing age is filled in by a random data imputation. The imputation of missing age is principally carried out at the station level, randomly selecting the value from aged super-individuals within the same length group. If no aged super-individual is available at the station level, the imputation is attempted at strata level, or lastly on survey level. In instances where no age information is available at any level for a specific length group, the abundance estimate is presented with unknown age (Johnsen et al., 2019).
6.3 - Length and weight at age
Length and weight at age was calculated using the weighting factors defined in eqn 15 (the “super -individuals”).
6.4 - Uncertainty of abundance indices
Uncertainty was estimated as the coefficient of variation (ratio of standard deviation to the mean, CV). StoX calculates CV using bootstrap runs by stratum, treating each trawl station as the primary sampling unit. Here we used 500 bootstrap runs.
6.5 - Extracting coastal cod from total cod
Since the discrimination of coastal cod and other cod caught at the coastal survey is based on otolith types (see above) this poses a special challenge to producing abundance index series with uncertainty for coastal cod. Running a StoX project on the biological data to produce a swept-area index series will primarily produce indices for all cod present in this data source. However, when running the bootstrap process in StoX, it is possible to group the superindividuals by several categories, for instance age and otolith type. There is no facility inside StoX to present those “two-dimensional” bootstrap data but using an R-script manipulating the bootstrap files generated by StoX it is possible to extract relevant data. Thus, this was done after the whole time series were made by ordinary StoX-runs, by selecting only those entries in the bootstrap data that contained superindividuals with otolith types “1” and “2”. Alle tables and figures in the appendices to this document were produced by this R-script. The R-script itself is documented in appendix “C”.
6.6 - Swept area indices – settings in StoX
The processes included and the settings of parameters when running StoX for swept area indices are given in tables 6-9:
Table 6. Baseline processes:
Process
Parameters
Values
ReadProcessData
ReadBioticXML
FileName1, FileName2, …
Relevant file names
FilterBiotic
FishStationExpr*
gear =~[‘3270’,’3271’] and
gearcondition < 3 and
tawlquality =~[‘1’,’3’] and
fishstationtype !=[‘2’] and
CatchExpr
species == ‘164712’
SampleExpr
N/A
IndExpr
N/A
DefineSweptAreaPSU
Method
Station
StationLengthDist
LengthDistType
NormLengthDist
RegroupLenghDist
LengthInverval
5.0
Catchability
CatchabilityMethod
LengthDependentSweepWidth
LengthDist
RegroupLengthDist
ParLenfthDependentSweepWidth
SpecCat=;Alpha=5.91;Beta=0.43;LMin=15.0;LMax=62.0
RelLengthDist
LengthDist
Catchability
DefineStrata
UseProcessData
“ True”
StratumArea
AreaMethod
Accurate
TotalLengthDist
LengthDist
RegroupLengthDist
SweptAreaDensity
SweptAreaMethod
LengthDependent
BioticData
FilterBiotic
LengthDist
TotalLengthDist
DistanceMethod
FullDistance
SweepwidthMethod
Predetermined
MeanDensity_Stratum
Density
SweptAreaDensity
SampleUnitType
Stratum
PolygonArea
StratumArea
AbundanceByLength
Density
MeanDensity_Stratum
IndividualDataStations
Abundance
AbundanceByLength
IndividualData
IndividualDataStations
IndividualDataStations
SuperIndAbundance
Abundance
AbundanceByLength
IndividualData
IndividualData
AbundWeightMethod
StationDensity
LengthDist
RegroupLengthDist
* In the period 2017-2019 this filter was changed to allow for inclusion of stations coded with StationType = C and trawlQuality = 2
Table 7. Baseline report processes:
Process
Parameters
Values
FillMissingData
Superindividuals
SuperIndAbundance
FillVariables
ImputeByAge
Seed
1
FillWeight
Mean
EstimateByPopulationCategory
Superindividuals
FillMissingData
Lengthinterval
5.0
Scale
1000
Dim1
otolithtype
Dim2
age
Dim3
SpecCat
Table 8. R processes:
Process
Parameters
Values
runBootstrap
bootstrapMethod
AcousticTrawl
acousticMethod
PSU~Stratum
bioticMethod
PSU~Stratum
startProcess
TotalLengtDist
endProcess
SuperIndAbundance
nboot
500
seed
1
cores
4
imputeByAge
seed
1
cores
4
SaveRImage
“ Enabled”
Table 9. R report processes:
Process
Parameters
Values
getReports
out
all
options
grp1=”age”, grp2=”otolithtype”
getPlots
out
all
options
grp1=”age”, grp2=”otolithtype”
6.7 - Resulting time series
Index series for the total area (Figure 14) and for the three subareas A (Figure 15), B (Figure 16) and C (Figure 17) are shown below. The abundance indices for the total area is rather flat but one year, 1997, stands out from the rest having a three times as high index and much wider confidence limits than the rest of the years in the series.
The amount of coastal cod in subarea A (Figure 15) is much higher than in the more southern subareas B and C, and the index series in subarea A therefore resembles the total index to a high degree. While the index for subarea A (and therefore also the total area) shows peaks in 2003 and in 2014-2015, the series for subareas B and C are without conspicuous trends. The relative uncertainty is much higher for the two southern subareas than for the northern (subarea A). The uncertainty in the last four years is smaller than for the earlier part of the index series, for all subareas.
Consistency among cohorts are illustrated on Figures 18-21. The cohorts can be followed in subarea A (and in the total area) without conspicuous year effects, except in 2005 and 2007. For the two subareas B (Figure 20) and C (Figure 21) it is not possible to follow the year classes except for short periods, indicating that the indices for these subareas do not reflect the total abundance of coastal cod during the period 2002 to 2019.
6.8 - Consistency within the trawl index series for area A
The internal consistency plots (number at age n in year n plotted versus number at age n+1 in year y+1) for age groups 1-6 are shown in Figure 22 and for age groups 7-12 in Figure 23. In most cases the fit is poor.
7 - Comparison of the trawl and acoustic index series
The acoustic index series and the trawl index series give a partly independent view of the stock situation over time. They are not totally independent, since the length information used to translate the acoustic backscatter into fish abundance comes by and large from the same trawl hauls that are used for calculation of swept area indices, and the age information used to break the acoustic index down to age groups partly comes from the same trawl hauls that are used to calculate the swept area indices. However, the total backscatter, mainly determining the acoustic index, is totally independent of the catch rates in the trawl hauls, so in this respect the two series give independent information about the amount of fish. There are numerous reasons that these indices differ. Trawling on the bottom is only possible were the bottom is trawlable, that is soft and smooth and not to steep. In many areas of the coast it is not possible to trawl, and consequently the trawl hauls may not be representative of areas with hard and/or steep bottom. On the other hand, even though the acoustic method will cover all navigable waters, the acoustic backscatter signal is difficult to interpret where the bottom is steep, and in all areas the dead zone near the bottom will not be covered. Also, the allocation of acoustic backscattering by species can be challenging, and in particular in areas where it is not possible to trawl.
In Figure 24 the new acoustic index series and the swept-area series are compared, and also the landings statistics are included on the figure for comparison.
The acoustic series, going back to 1995, shows a decrease in the last part of the 1990s with a simultaneous decrease in catches during that period, from a record high catch in 1995 to a level at about half of that total during the next decades. The acoustic index and the trawl index fluctuate without clear trends after 2003, in some years the acoustic index is higher than the trawl index and vice versa. These index series are compared on age-group basis in figure 25 and 26. The consistency is quite good for many of the age groups, with r 2 in the range 0.2-0.6. However, for some age groups (mainly 3-6) the fit is poorer, with r 2 in the range 0.0-0.1.
8 - Conclusions by the data evaluation workshop regarding inclusion of these time series in the assessment of Norwegian Coastal Cod north of 62°N
Based on an evaluation of what is presented in this document concerning data quality, survey coverage, and year-to-year consistency, the data evaluation workshop held in December 2020 concluded that
The acoustic abundance index series from 1995 to 2019, for age groups 2-10+, may be used as input data in analytical assessment models for coastal cod in subarea A. The corresponding estimates of length- and weight-at-age may be used as estimates of length- and weight-at-age in the stock.
For subareas B and C, the acoustic indices for biomass of age 2+ may be used in biomass models or to assess changes in stock abundance from year to year, using methods for data-limited stocks.
The trawl index series from 2003 to 2019, for age groups 2-10, may be used as input data in analytical assessment models for coastal cod in subarea A. The corresponding estimates of length- and weight-at-age may be used as estimates of length- and weight-at-age in the stock.
For subareas B and C, the trawl indices of biomass of age 2+ may be used in biomass models or to assess changes in stock abundance from year to year, using methods for data-poor stocks.
9 - References
Aglen, A., Berg, E., Mehl, S., and Sunnanå, K. 2005. Acoustic abundance of saithe, coastal cod and juvenile herring Finnmark – Møre Autumn 2005. Toktrapport/Havforskningsinstituttet, 2005/23.
Aglen, A., Nedreaas, K., Knutsen, J. A., and Huse, G. 2020. Kysttorsk nord for 62 grader nord. Vurdering av status og forslag til forvaltningstiltak og ny gjenoppbyggingsplan. Fisken og Havet, 2020/2: 1-64.
Berg, E., and Albert, O. T. 2003. Cod in fjords and coastal waters of North Norway: distribution and variation in length and maturity at age. ICES Journal of Marine Science, 60: 787-797.
Dahle, G., Quintela, M., Johansen, T., Westgaard, J. I., Besnier, F., Aglen, A., Jorstad, K. E., et al. 2018. Analysis of coastal cod (Gadus morhua L.) sampled on spawning sites reveals a genetic gradient throughout Norway's coastline. BMC Genet, 19: 42.
Dickson, W. 1993. Estimation of the capture efficiency of trawl gear. 1:Development of a theoretical model. Fisheries Research, 16: 239-253.
ICES 2020. Arctic Fisheries Working Group (AFWG). ICES Scientific Reports., 2:52. : 577
Johannesen, E., Johnsen, E., Johansen, G. O., and Korsbrekke, K. 2019. StoX applied to cod and haddock data from the Barents Sea NOR-RUS ecosystem cruise in autumn. Swept area abundance, length and weight at age 2004-2017. Fisken og Havet, 2019-6: 1-40.
Johnsen, E., Totland, A., Skålevik, Å., Holmin, A. J., Dingsør, G. E., Fuglebakk, E., Handegard, N. O., et al. 2019. StoX: An open source software for marine survey analyses. Methods in Ecology and Evolution, 10: 1523-1528.
Mehl, S., Aglen, A., Berg, E., Dingsor, G. E., and Korsbrekke, K. 2018a. Akustisk mengdemåling av sei, kysttorsk og hhyse Finnmark-Møre hausten 2017. Toktrapport/Havforskningsinstituttet, Nr. 2–2018.
Mehl, S., Aglen, A., Johnsen, E., and Skålevik, Å. 2018b. Estimation of acoustic indices with CVs for cod and haddock in the Barents Sea winter survey 1994 – 2017 applying the Sea2Data StoX software. Fisken og Havet, 5-2018.
Mjanger, H., Svendsen, B. V., Senneset, H., Fuglebakk, E., Skage, M. L., Diaz, J., Johansen, G. O., et al. 2020. Handbook for sampling fish, crustaceans and other invertebrates. pp. 1-157. Institute of Marine Research, Bergen.
Skants, K. D. 2019. Species composition, distribution and ecology of the demersal fish community along the Norwegian coast north of Stad under varying environmental conditions. In Department of Biological Sciences - Marine Biology. University of Bergen, Norway.
Staby, A., Mehl, S., Berg, E., Aglen, A., and Korsbrekke, K. 2020. Acoustic abundance of saithe and coastal cod Finnmark – Møre Autumn 2018. Toktrapport/Havforskningsinstituttet, Nr. 5–2020.
10 - Appendix A. Acoustic abundance indices
2.1 - Total area
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
Age 17
1995
0.031
26.961
11.015
7.254
7.207
7.023
4.618
1.561
0.678
0.340
0.042
0.134
1996
22.040
17.763
10.743
12.628
6.669
7.434
3.386
1.269
0.213
0.034
0.123
1997
0.018
17.724
17.907
20.326
9.288
5.243
2.652
0.919
0.393
0.059
0.014
0.019
1998
1.269
8.713
10.675
10.731
9.626
4.238
1.806
0.951
0.141
0.123
0.037
0.009
0.026
0.026
1999
2.562
3.990
4.112
3.283
2.794
0.941
0.214
0.030
0.067
0.015
0.005
2000
1.979
5.264
8.468
7.426
4.935
4.320
3.106
0.712
0.307
0.087
0.029
0.026
0.010
2001
0.207
2.725
4.847
4.734
4.343
2.516
1.637
1.018
0.219
0.031
0.036
0.029
0.009
0.018
2002
0.418
1.822
2.894
3.842
4.809
3.659
3.273
1.154
0.459
0.110
0.105
0.003
0.033
2003
4.819
3.324
2.401
3.516
3.757
2.245
1.743
0.749
0.423
0.207
0.024
0.004
0.026
0.016
2004
4.722
3.217
3.000
3.430
3.605
2.358
1.490
0.572
0.311
0.113
0.106
0.005
0.003
2005
0.037
1.264
1.723
3.226
2.716
2.107
1.321
0.473
0.263
0.155
0.028
0.064
2006
6.705
5.126
2.126
3.172
2.692
1.936
1.847
1.129
0.177
0.130
0.012
0.023
0.004
2007
26.051
2.543
3.567
3.118
4.005
2.557
1.703
1.258
0.456
0.123
0.026
0.014
0.005
2008
13.880
2.399
1.815
1.733
1.573
1.015
0.763
0.425
0.230
0.099
0.026
0.023
0.025
0.000
0.000
2009
2.032
3.973
1.945
2.898
3.289
1.738
0.812
0.471
0.558
0.199
0.033
0.065
0.002
0.001
0.002
2010
1.300
5.701
2.689
3.141
2.522
1.978
0.681
0.364
0.465
0.248
0.120
0.052
0.023
0.006
0.002
0.004
2011
0.518
3.795
3.527
2.746
3.011
2.018
1.544
0.421
0.355
0.149
0.094
0.019
0.060
0.013
2012
0.098
3.650
2.315
3.724
2.026
1.343
0.913
0.541
0.256
0.109
0.124
0.049
0.019
0.024
0.006
0.003
2013
0.583
5.142
3.306
1.857
1.960
1.510
0.952
0.695
0.451
0.216
0.088
0.089
0.062
0.004
0.006
0.002
0.006
2014
17.884
6.474
4.500
3.324
2.337
3.135
1.714
1.202
0.698
0.509
0.098
0.087
0.082
0.007
0.007
0.025
0.013
0.015
2015
0.262
4.888
5.054
3.311
2.849
1.434
1.489
0.560
0.411
0.370
0.161
0.038
0.052
0.003
0.012
0.001
2016
1.276
2.990
3.913
4.900
3.053
2.741
0.961
0.773
0.530
0.249
0.132
0.242
0.041
0.007
0.013
0.011
2017
6.506
1.063
3.440
3.298
2.524
1.884
1.209
0.497
0.282
0.185
0.054
0.095
0.020
0.014
2018
0.690
5.028
2.993
2.013
2.606
1.581
1.151
0.522
0.267
0.196
0.081
0.057
0.013
0.013
0.004
0.001
2019
0.925
3.464
3.443
4.787
3.112
3.160
1.942
1.222
0.317
0.384
0.158
0.059
0.094
0.013
0.003
0.007
0.005
2020
0.169
0.498
1.474
2.583
2.927
1.873
0.877
0.563
0.313
0.176
0.076
0.051
0.000
0.005
0.001
Table A.1.1. Abundance indices (millions)
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
Age 17
1995
1.007
0.165
0.103
0.063
0.112
0.125
0.200
0.163
0.308
0.477
0.408
0.221
1996
0.687
0.197
0.093
0.105
0.118
0.105
0.217
0.437
0.393
0.533
0.301
1997
0.970
0.228
0.214
0.134
0.134
0.127
0.229
0.218
0.412
0.903
0.815
1.060
1998
0.856
0.249
0.118
0.094
0.139
0.142
0.266
0.509
0.313
0.864
1.039
0.935
0.000
0.000
1999
0.237
0.092
0.093
0.169
0.154
0.184
0.157
0.459
0.132
0.923
0.917
2000
0.877
0.136
0.145
0.097
0.076
0.080
0.094
0.133
0.244
0.399
0.393
0.333
0.903
2001
1.052
0.178
0.294
0.163
0.139
0.161
0.163
0.201
0.286
0.701
0.689
0.475
0.745
0.864
2002
0.859
0.162
0.126
0.136
0.101
0.088
0.062
0.149
0.253
0.704
0.563
1.070
0.902
2003
0.310
0.262
0.238
0.122
0.120
0.113
0.142
0.160
0.188
0.245
0.344
1.032
1.687
1.009
2004
0.185
0.158
0.135
0.116
0.086
0.096
0.130
0.125
0.175
0.644
0.238
0.611
0.808
2005
0.915
0.131
0.159
0.124
0.067
0.096
0.130
0.117
0.265
0.329
0.326
0.843
2006
0.519
1.048
0.584
0.122
0.119
0.115
0.240
0.205
0.168
0.212
0.000
0.841
0.992
2007
0.634
0.203
0.176
0.174
0.142
0.156
0.150
0.201
0.297
0.433
0.841
1.296
1.253
2008
0.343
0.238
0.182
0.138
0.129
0.114
0.136
0.187
0.231
0.379
0.373
0.476
0.501
0.896
0.896
2009
1.030
0.213
0.152
0.106
0.095
0.134
0.106
0.154
0.135
0.234
0.308
0.205
0.863
1.097
0.601
2010
0.509
0.395
0.165
0.147
0.114
0.101
0.185
0.190
0.207
0.195
0.202
0.206
0.567
0.292
0.789
0.566
2011
0.827
0.125
0.126
0.110
0.119
0.108
0.125
0.252
0.163
0.192
0.277
0.517
0.338
0.866
2012
0.596
0.200
0.185
0.122
0.128
0.126
0.098
0.177
0.162
0.233
0.179
0.415
0.465
0.559
0.572
0.795
2013
0.543
0.129
0.149
0.120
0.133
0.119
0.118
0.165
0.195
0.312
0.345
0.357
0.485
0.919
0.569
0.905
0.666
2014
1.038
0.145
0.173
0.110
0.137
0.138
0.119
0.139
0.088
0.210
0.392
0.331
0.320
0.926
0.583
0.493
0.742
0.898
2015
0.706
0.151
0.097
0.089
0.068
0.086
0.096
0.142
0.140
0.130
0.271
0.360
0.427
0.804
0.554
1.010
2016
0.564
0.281
0.117
0.103
0.074
0.115
0.141
0.160
0.195
0.347
0.304
0.452
0.431
0.399
0.526
2.264
2017
0.635
0.326
0.151
0.119
0.151
0.133
0.166
0.206
0.257
0.421
0.246
0.410
0.522
0.746
2018
0.413
0.175
0.157
0.155
0.148
0.143
0.071
0.173
0.554
0.141
0.345
0.428
0.603
0.503
0.515
1.528
2019
0.232
0.137
0.172
0.117
0.093
0.083
0.101
0.100
0.194
0.232
0.235
0.207
0.631
0.518
1.053
1.170
1.069
2020
0.827
0.320
0.134
0.158
0.111
0.133
0.141
0.220
0.299
0.466
0.527
0.433
1.148
1.151
1.011
Table A.1.2. CV on abundance indices
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
Age 17
1995
0.000
1.595
3.414
5.298
10.124
14.865
12.579
7.364
4.352
2.460
0.144
2.387
1996
0.151
0.716
2.459
9.286
9.228
14.394
9.253
5.554
1.402
0.378
2.020
1997
0.000
0.742
4.335
13.470
12.866
10.135
7.839
2.911
1.564
0.570
0.151
0.098
1998
0.012
0.459
3.533
9.317
13.530
9.495
5.873
4.444
0.832
0.675
0.587
0.106
0.525
0.690
1999
0.163
1.110
3.412
5.253
5.734
2.634
0.974
0.225
0.768
0.033
0.083
2000
0.023
0.368
2.708
5.928
7.447
10.068
8.850
3.148
2.040
0.714
0.343
0.322
0.042
2001
0.001
0.202
1.940
4.520
7.163
5.798
5.105
3.435
1.292
0.213
0.453
0.516
0.078
0.275
2002
0.004
0.207
1.324
4.145
10.772
12.037
15.280
7.214
2.094
0.325
0.688
0.066
0.403
2003
0.044
0.232
0.878
2.892
5.256
4.996
5.326
2.982
2.183
1.278
0.216
0.008
0.288
0.404
2004
0.031
0.286
1.059
3.022
6.128
5.124
4.709
2.130
1.265
0.479
1.015
0.046
0.025
2005
0.001
0.132
0.724
3.068
5.706
5.325
3.886
1.927
0.906
0.745
0.378
1.061
2006
0.054
0.386
0.856
3.191
4.501
4.455
6.237
4.401
0.907
0.909
0.080
0.566
0.017
2007
0.169
0.263
1.806
3.331
7.546
6.659
5.502
5.810
2.963
1.387
0.447
0.038
0.098
2008
0.086
0.236
0.820
1.990
3.216
3.378
2.586
1.968
1.111
0.416
0.105
0.272
0.125
0.003
0.003
2009
0.018
0.295
0.779
3.265
6.285
4.643
2.904
2.071
2.668
1.144
0.153
0.254
0.005
0.002
0.015
2010
0.013
0.349
1.378
3.541
4.856
5.497
2.401
1.706
2.643
1.536
0.755
0.340
0.188
0.013
0.022
0.035
2011
0.004
0.263
1.323
3.126
6.611
6.104
6.308
2.243
2.143
0.960
0.491
0.070
0.498
0.060
2012
0.001
0.268
0.833
4.370
4.211
4.133
3.423
2.566
1.428
0.688
0.866
0.233
0.120
0.129
0.043
0.012
2013
0.007
0.423
1.246
1.662
3.477
4.405
3.267
2.707
2.361
1.239
0.363
0.805
0.768
0.014
0.049
0.032
0.090
2014
0.119
0.515
1.790
3.802
4.529
9.257
6.521
5.706
3.689
3.017
0.914
0.638
0.586
0.031
0.058
0.251
0.110
0.366
2015
0.001
0.372
2.001
3.673
5.571
4.061
5.054
2.655
2.078
2.252
0.970
0.335
0.257
0.031
0.118
0.015
2016
0.009
0.219
1.432
6.363
6.806
9.072
3.621
3.389
3.349
1.915
0.851
2.480
0.209
0.032
0.111
0.095
2017
0.024
0.084
1.782
3.530
5.057
5.635
4.825
2.249
1.998
1.168
0.337
0.902
0.102
0.213
2018
0.004
0.257
1.541
2.341
5.458
5.214
4.334
2.817
1.598
1.406
0.572
0.233
0.065
0.113
0.079
0.007
2019
0.008
0.230
1.264
5.626
6.381
9.351
7.683
5.747
1.634
2.419
1.091
0.477
1.047
0.127
0.027
0.082
0.038
2020
0.001
0.043
0.800
3.417
5.736
6.224
3.032
3.247
1.916
1.357
0.469
0.365
0.001
0.036
0.013
Table A.1.3. Biomass indices (kilotonnes)
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
Age 17
1995
10.32
18.93
32.17
42.33
51.98
59.07
64.26
77.92
84.99
87.89
66.98
121.24
1996
9.36
16.66
28.83
42.12
52.28
58.17
64.66
75.70
86.68
99.18
117.56
1997
9.01
16.70
29.27
40.89
51.93
58.40
66.89
68.71
71.67
102.00
104.42
83.00
1998
10.62
18.05
32.04
44.30
52.03
60.09
68.11
75.99
85.28
83.72
108.43
105.00
121.00
135.00
1999
19.52
31.19
44.18
54.57
59.18
65.77
75.68
89.32
101.33
59.00
118.00
2000
10.84
20.08
32.38
43.35
53.30
61.11
64.79
74.55
84.79
86.55
107.35
102.13
79.00
2001
8.09
19.99
33.90
45.84
55.13
60.77
65.76
67.88
81.74
87.23
107.06
114.32
99.84
112.68
2002
10.48
22.97
35.07
47.29
59.65
67.22
75.42
81.62
76.42
67.24
85.16
115.00
108.00
2003
9.71
19.33
33.45
43.70
52.16
60.48
67.16
72.87
77.01
80.32
92.80
61.00
106.31
143.00
2004
8.97
21.12
33.05
44.22
54.94
59.29
67.31
69.99
71.96
75.38
92.84
91.32
89.00
2005
11.44
21.97
34.80
45.10
57.91
62.71
64.88
71.87
71.14
75.26
106.58
108.92
2006
9.43
20.68
34.66
46.28
55.04
60.34
68.05
71.02
77.35
85.28
86.00
125.00
76.00
2007
9.20
21.46
36.33
47.10
56.90
62.92
67.66
74.15
84.14
100.71
113.68
63.01
123.00
2008
9.28
22.26
35.87
48.72
58.44
68.49
69.09
76.16
75.58
72.09
71.91
100.25
75.56
100.00
89.00
2009
9.74
19.82
33.65
47.88
57.25
64.28
70.03
75.13
75.49
81.68
75.17
69.32
69.00
73.00
94.94
2010
10.64
18.92
37.04
48.18
57.32
64.39
70.61
76.38
77.12
82.07
83.16
80.18
88.20
61.58
104.00
89.97
2011
9.48
20.10
33.60
48.36
60.20
66.93
72.32
78.96
80.93
81.32
77.59
74.36
93.14
75.21
2012
9.99
20.36
33.07
48.67
59.89
66.59
72.03
76.90
80.64
82.81
85.16
78.35
84.89
83.28
90.72
79.00
2013
11.56
20.96
34.05
45.15
56.49
66.80
70.65
72.89
78.61
82.37
74.51
90.29
100.75
69.54
88.38
113.00
125.00
2014
9.24
21.05
34.56
48.92
58.22
66.93
73.29
77.90
79.88
82.14
97.37
86.29
84.18
81.05
85.00
91.11
93.45
132.00
2015
9.65
20.22
34.23
48.23
58.38
66.30
69.47
77.15
78.70
82.51
84.53
88.98
77.69
95.00
98.15
101.00
2016
9.36
20.33
33.67
50.29
60.03
69.24
72.51
75.06
84.08
89.09
82.44
97.85
80.52
76.64
96.75
96.00
2017
8.24
20.34
37.27
47.73
59.03
66.82
73.90
78.31
86.45
84.19
84.37
96.94
83.08
111.43
2018
10.04
16.95
37.38
48.53
60.08
69.14
71.48
81.28
85.20
86.27
87.52
75.13
81.27
93.48
115.46
93.00
2019
10.11
19.89
33.35
49.27
59.27
67.46
73.53
77.35
79.47
82.90
85.52
91.33
96.75
99.46
96.00
109.00
96.00
2020
10.72
20.60
36.52
49.67
58.02
67.85
70.46
80.90
83.33
89.49
83.05
86.92
84.00
91.19
97.00
Table A.1.4. Length at age (cm)
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
Age 17
1995
9
59
310
730
1405
2118
2754
4733
6494
7359
3297
17869
1996
8
41
229
736
1385
1940
2702
4269
6627
10964
16213
1997
8
42
240
665
1384
1932
2947
3175
4264
9600
11387
5140
1998
10
53
332
869
1405
2229
3251
4432
5987
5884
16233
12260
19880
26100
1999
64
278
828
1602
2059
2811
4567
7363
11535
2190
18340
2000
12
70
320
798
1508
2329
2848
4424
6726
8851
12330
12873
4220
2001
5
74
390
953
1648
2300
3116
3386
5983
7187
11653
17035
8460
15001
2002
9
114
460
1077
2248
3295
4674
6289
4656
3785
7783
21980
12350
2003
9
68
366
821
1397
2225
3056
3965
5110
6049
8878
2030
12562
25600
2004
7
89
353
883
1702
2175
3158
3735
4004
4500
9936
9078
7130
2005
16
105
419
954
2103
2529
2952
4081
3466
4745
14164
15482
2006
8
84
424
1006
1673
2305
3380
3944
5151
6931
6530
25080
4220
2007
7
103
508
1069
1889
2612
3238
4638
6497
11158
15891
2981
21100
2008
6
100
453
1148
2046
3321
3392
4648
4869
4344
4077
10683
4730
9250
8520
2009
10
75
401
1127
1911
2668
3569
4374
4764
5720
4819
3817
3084
3122
9672
2010
10
64
507
1127
1927
2782
3545
4693
5714
6198
6336
6547
7962
2062
12154
7475
2011
8
69
374
1136
2195
3020
4096
5365
6040
6395
5275
3933
8509
4558
2012
8
74
359
1170
2084
3086
3748
4717
5530
6291
7000
5018
7205
6444
7052
4630
2013
12
83
377
893
1773
2915
3432
3911
5284
5662
4216
8854
12081
4092
7780
16220
16300
2014
7
80
399
1142
1935
2951
3804
4750
5282
5933
8898
7135
7062
4752
7920
9591
8282
24950
2015
8
76
395
1109
1956
2832
3397
4764
5073
6059
6231
8733
5427
10170
9930
11240
2016
7
74
367
1295
2230
3307
3777
4399
6283
7696
6307
10446
5020
4413
9411
8325
2017
4
83
519
1073
2006
2984
3990
4515
7030
6363
6225
9634
5089
14019
2018
5
52
512
1169
2099
3305
3771
5424
5961
7088
7024
4283
5345
9367
15761
7350
2019
9
67
367
1176
2049
2959
3958
4696
5085
6396
6804
8025
10306
9786
9585
12345
7040
2020
8
91
538
1313
1958
3318
3457
5706
6190
7737
6667
7430
5165
7911
9765
Table A.1.5. Weight at age (gram)
Index_2plus
SD_2plus
CV_2plus
1995
40.034
2.670
0.067
1996
42.500
2.417
0.057
1997
56.823
5.676
0.100
1998
38.388
2.848
0.074
1999
15.451
1.184
0.077
2000
29.426
2.112
0.072
2001
19.437
2.667
0.137
2002
20.341
1.462
0.072
2003
15.111
1.527
0.101
2004
14.994
1.001
0.067
2005
12.075
0.766
0.063
2006
13.247
1.345
0.101
2007
16.833
1.429
0.085
2008
7.728
0.770
0.100
2009
12.012
0.886
0.074
2010
12.295
0.910
0.074
2011
13.958
0.921
0.066
2012
11.452
0.939
0.082
2013
11.204
0.992
0.089
2014
17.758
1.520
0.086
2015
15.744
0.858
0.054
2016
17.567
0.860
0.049
2017
13.501
1.118
0.083
2018
11.498
1.015
0.088
2019
18.706
1.279
0.068
2020
10.920
0.780
0.071
Table A.1.6. Abundance index, standard deviation (SD) and Coefficient of variation (CV) for sum of age 2+ fish
2.2 - Subarea A: North of 67°N
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
Age 17
1995
0.031
26.495
8.774
4.974
6.382
6.440
4.373
1.309
0.532
0.319
0.041
0.090
1996
21.458
17.580
9.025
8.592
4.576
5.306
2.723
1.022
0.213
0.032
0.024
1997
0.018
16.567
15.358
16.930
7.710
4.484
2.316
0.716
0.328
0.059
0.014
0.019
1998
1.260
8.360
6.757
8.524
8.261
3.717
1.530
0.700
0.102
0.122
0.037
0.009
0.000
0.000
1999
2.494
3.486
3.387
2.788
2.498
0.751
0.172
0.030
0.022
0.015
0.005
2000
1.979
5.028
7.439
5.831
3.939
3.853
2.825
0.622
0.258
0.071
0.013
0.010
0.010
2001
0.207
2.711
4.551
4.246
3.776
2.184
1.499
0.974
0.149
0.029
0.036
0.029
0.009
0.018
2002
0.418
1.188
2.071
2.532
2.926
2.075
0.970
0.596
0.293
0.106
0.089
0.003
0.033
2003
4.798
3.276
2.168
3.026
3.303
1.838
1.519
0.651
0.364
0.190
0.024
0.003
0.026
0.016
2004
4.431
3.046
2.643
2.819
2.589
1.686
1.094
0.371
0.213
0.104
0.064
0.005
0.003
2005
0.019
0.904
1.201
2.228
1.816
1.490
0.843
0.234
0.233
0.127
0.015
0.064
2006
6.231
4.981
1.836
2.587
2.210
1.453
1.612
1.046
0.130
0.089
0.000
0.023
0.004
2007
26.051
2.458
3.037
2.778
3.794
2.437
1.632
1.215
0.441
0.120
0.023
0.014
0.005
2008
13.853
2.344
1.739
1.684
1.511
0.985
0.761
0.399
0.225
0.097
0.026
0.023
0.024
0.000
0.000
2009
1.804
3.907
1.502
2.084
2.596
1.373
0.605
0.386
0.378
0.140
0.031
0.029
0.002
0.001
0.002
2010
1.170
5.509
2.503
2.853
2.240
1.679
0.583
0.309
0.432
0.229
0.113
0.052
0.023
0.002
0.002
0.004
2011
0.363
2.104
2.542
1.869
2.372
1.469
1.215
0.394
0.278
0.137
0.074
0.018
0.046
0.013
2012
0.098
3.561
2.170
3.546
1.832
1.154
0.791
0.503
0.254
0.107
0.124
0.049
0.019
0.024
0.006
0.003
2013
0.421
4.694
3.084
1.597
1.770
1.287
0.838
0.657
0.430
0.216
0.083
0.089
0.062
0.004
0.006
0.002
0.006
2014
16.680
6.030
4.171
3.066
2.137
2.904
1.609
1.151
0.429
0.462
0.089
0.087
0.082
0.007
0.007
0.025
0.013
0.015
2015
0.262
3.421
3.122
2.465
1.802
1.017
1.128
0.477
0.363
0.303
0.158
0.038
0.052
0.003
0.012
0.001
2016
1.272
2.921
3.341
3.667
2.349
2.308
0.841
0.669
0.452
0.222
0.115
0.123
0.041
0.004
0.013
0.011
2017
6.506
1.018
3.289
3.202
2.335
1.764
1.122
0.450
0.256
0.181
0.054
0.095
0.020
0.014
2018
0.680
4.977
2.847
1.837
2.376
1.246
0.946
0.494
0.246
0.136
0.081
0.057
0.013
0.013
0.004
0.001
2019
0.305
2.607
2.992
3.724
2.221
2.149
1.272
0.656
0.212
0.262
0.106
0.040
0.092
0.013
0.003
0.007
0.005
2020
0.162
0.475
1.039
1.743
2.204
1.329
0.674
0.363
0.246
0.074
0.075
0.047
0.000
0.004
0.001
Table A.2.1. Abundance indices (millions)
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
Age 17
1995
1.007
0.168
0.130
0.090
0.124
0.136
0.211
0.194
0.395
0.505
0.412
0.328
1996
0.700
0.198
0.111
0.154
0.168
0.141
0.259
0.538
0.394
0.516
1.565
1997
0.970
0.239
0.246
0.160
0.156
0.142
0.250
0.259
0.470
0.903
0.815
1.060
1998
0.860
0.259
0.186
0.117
0.161
0.161
0.311
0.690
0.401
0.867
1.039
0.935
1999
0.243
0.105
0.114
0.198
0.173
0.229
0.193
0.472
0.402
0.923
0.917
2000
0.877
0.143
0.164
0.124
0.095
0.090
0.103
0.151
0.291
0.489
0.894
0.901
0.903
2001
1.052
0.179
0.313
0.182
0.159
0.186
0.176
0.209
0.406
0.719
0.689
0.475
0.745
0.864
2002
0.859
0.248
0.174
0.205
0.160
0.136
0.147
0.228
0.363
0.723
0.665
1.070
0.902
2003
0.311
0.266
0.263
0.140
0.137
0.137
0.161
0.182
0.218
0.262
0.346
0.694
1.687
1.009
2004
0.196
0.166
0.153
0.141
0.118
0.127
0.171
0.172
0.253
0.694
0.330
0.611
0.808
2005
0.774
0.181
0.228
0.177
0.099
0.136
0.204
0.228
0.298
0.400
0.606
0.843
2006
0.559
1.079
0.677
0.149
0.145
0.153
0.275
0.221
0.228
0.311
0.841
0.992
2007
0.634
0.209
0.201
0.194
0.149
0.163
0.156
0.207
0.307
0.446
0.969
1.296
1.253
2008
0.343
0.244
0.189
0.142
0.134
0.118
0.136
0.198
0.236
0.386
0.373
0.481
0.521
0.896
0.896
2009
1.160
0.217
0.197
0.146
0.118
0.168
0.139
0.183
0.192
0.314
0.246
0.442
0.863
1.097
0.601
2010
0.563
0.408
0.177
0.162
0.128
0.119
0.216
0.223
0.223
0.210
0.215
0.207
0.567
1.171
0.789
0.566
2011
1.075
0.218
0.170
0.159
0.146
0.147
0.155
0.268
0.205
0.195
0.347
0.510
0.443
0.866
2012
0.598
0.205
0.197
0.129
0.141
0.147
0.113
0.190
0.163
0.238
0.179
0.415
0.465
0.559
0.572
0.795
2013
0.681
0.140
0.160
0.140
0.147
0.139
0.134
0.174
0.204
0.312
0.365
0.357
0.485
0.919
0.569
0.905
0.666
2014
1.112
0.155
0.186
0.119
0.150
0.149
0.127
0.146
0.143
0.231
0.433
0.331
0.320
0.926
0.583
0.493
0.742
0.898
2015
0.706
0.211
0.157
0.114
0.100
0.118
0.121
0.160
0.157
0.163
0.267
0.360
0.424
0.804
0.554
1.010
2016
0.565
0.290
0.152
0.096
0.078
0.105
0.162
0.169
0.208
0.390
0.313
0.225
0.431
0.647
0.526
2.264
2017
0.635
0.341
0.158
0.123
0.163
0.142
0.179
0.227
0.282
0.432
0.246
0.410
0.522
0.746
2018
0.420
0.177
0.165
0.171
0.162
0.180
0.087
0.184
0.604
0.204
0.345
0.428
0.603
0.503
0.515
1.528
2019
0.679
0.180
0.198
0.147
0.127
0.120
0.151
0.176
0.283
0.333
0.348
0.275
0.636
0.518
1.053
1.170
1.069
2020
0.833
0.326
0.141
0.148
0.133
0.137
0.157
0.224
0.313
0.472
0.526
0.419
1.148
0.817
1.011
Table A.2.2. CV on abundance indices
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
Age 17
1995
0.000
1.541
2.472
3.574
8.904
13.457
11.950
6.114
3.126
2.269
0.143
1.576
1996
0.146
0.709
1.947
5.779
6.165
10.249
7.685
4.485
1.401
0.368
0.474
1997
0.000
0.677
3.790
11.041
10.756
8.589
6.793
2.140
1.152
0.570
0.151
0.098
1998
0.012
0.410
1.751
7.160
11.622
8.458
4.866
3.312
0.527
0.674
0.587
0.106
0.000
0.000
1999
0.155
0.947
2.695
4.204
4.894
2.062
0.733
0.217
0.144
0.033
0.083
2000
0.023
0.347
2.398
4.816
6.154
9.109
7.947
2.654
1.529
0.406
0.111
0.088
0.042
2001
0.001
0.199
1.778
3.973
6.276
5.075
4.503
3.240
0.679
0.205
0.453
0.516
0.078
0.275
2002
0.004
0.105
0.737
2.351
4.653
4.935
3.358
2.646
1.109
0.289
0.553
0.066
0.403
2003
0.044
0.228
0.783
2.488
4.716
4.167
4.746
2.687
2.016
1.232
0.216
0.006
0.288
0.404
2004
0.029
0.269
0.896
2.463
4.253
3.623
3.504
1.407
1.012
0.418
0.320
0.046
0.025
2005
0.000
0.089
0.526
1.947
3.135
3.291
2.133
0.860
0.813
0.706
0.129
1.061
2006
0.050
0.368
0.695
2.558
3.643
3.235
5.626
4.119
0.575
0.714
0.000
0.566
0.017
2007
0.169
0.239
1.469
2.959
7.057
6.266
5.159
5.471
2.811
1.347
0.400
0.038
0.098
2008
0.086
0.225
0.742
1.869
2.978
3.285
2.581
1.807
1.097
0.402
0.105
0.272
0.123
0.003
0.003
2009
0.014
0.288
0.537
2.152
4.877
3.708
2.308
1.786
1.960
0.763
0.150
0.164
0.005
0.002
0.015
2010
0.013
0.329
1.270
3.110
4.191
4.605
2.075
1.445
2.195
1.434
0.723
0.340
0.188
0.004
0.022
0.035
2011
0.003
0.125
1.024
2.183
5.403
4.579
4.488
2.024
1.561
0.855
0.388
0.067
0.360
0.060
2012
0.001
0.259
0.774
4.060
3.700
3.344
2.920
2.374
1.422
0.657
0.866
0.233
0.120
0.129
0.043
0.012
2013
0.005
0.399
1.184
1.469
3.215
3.913
2.883
2.593
2.101
1.239
0.350
0.805
0.768
0.014
0.049
0.032
0.090
2014
0.107
0.480
1.497
3.446
4.057
8.515
5.938
5.346
2.390
2.572
0.845
0.638
0.586
0.031
0.058
0.251
0.110
0.366
2015
0.001
0.252
1.275
2.748
3.860
3.036
4.249
2.297
1.916
1.795
0.962
0.335
0.254
0.031
0.118
0.015
2016
0.009
0.213
1.151
4.034
4.465
7.685
3.293
3.123
2.677
1.632
0.793
1.262
0.209
0.019
0.111
0.095
2017
0.024
0.080
1.655
3.379
4.591
5.205
4.488
2.104
1.811
1.131
0.337
0.902
0.102
0.213
2018
0.004
0.255
1.494
2.026
4.962
3.986
3.552
2.648
1.448
1.163
0.572
0.233
0.065
0.113
0.079
0.007
2019
0.002
0.163
1.112
4.212
4.414
6.413
4.854
3.382
1.272
1.623
0.840
0.392
1.042
0.127
0.027
0.082
0.038
2020
0.001
0.041
0.384
1.749
4.414
3.853
2.271
1.786
1.643
0.652
0.466
0.342
0.001
0.029
0.013
Table A.2.3. Biomass indices (kilotonnes)
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
Age 17
1995
10.32
18.86
31.39
42.05
51.83
58.77
64.27
77.55
82.36
87.08
67.02
123.50
1996
9.35
16.68
28.32
41.25
51.87
58.06
65.16
74.80
86.75
99.57
115.00
1997
9.01
16.61
29.56
40.75
51.99
58.11
66.89
66.80
68.62
102.00
104.42
83.00
1998
10.62
17.76
30.26
44.04
51.99
60.31
67.81
74.93
82.22
83.81
108.43
105.00
1999
19.41
31.17
44.06
54.06
58.69
65.44
74.00
88.95
88.21
59.00
118.00
2000
10.84
20.01
32.55
43.97
53.96
61.39
64.53
73.81
81.94
80.31
95.00
95.83
79.00
2001
8.09
19.97
33.70
45.70
55.37
61.09
65.17
67.64
76.07
87.23
107.08
114.32
99.84
112.68
2002
10.48
21.64
32.65
45.02
54.46
62.01
68.83
72.35
70.52
66.73
85.06
115.00
108.00
2003
9.71
19.30
33.32
43.76
52.60
60.94
67.73
73.67
78.79
81.86
92.81
61.00
106.31
143.00
2004
8.96
21.11
32.71
44.03
54.46
59.25
67.72
70.52
75.47
74.17
78.15
91.32
89.00
2005
10.83
21.55
35.73
44.69
55.45
60.55
62.61
71.42
71.73
80.28
93.20
108.92
2006
9.36
20.55
34.08
46.19
54.99
59.98
68.76
71.39
74.57
89.02
125.00
76.00
2007
9.20
21.18
35.90
47.15
56.79
62.73
67.32
73.73
83.42
100.54
116.00
63.01
123.00
2008
9.28
22.14
35.38
48.30
57.91
68.55
69.09
75.83
75.85
71.71
71.91
100.50
76.19
100.00
89.00
2009
9.31
19.77
32.91
46.75
57.08
64.72
71.36
76.56
76.92
81.20
75.56
77.44
69.00
73.00
94.94
2010
10.95
18.85
36.94
47.84
56.92
64.14
71.22
76.43
75.46
82.06
83.12
80.25
88.20
60.00
104.00
89.97
2011
9.48
19.13
34.62
48.69
61.02
67.55
71.22
78.14
80.80
80.53
78.30
74.68
91.37
75.21
2012
9.99
20.30
32.93
48.26
59.32
65.46
71.40
76.44
80.72
82.21
85.18
78.35
84.89
83.28
90.72
79.00
2013
11.52
21.22
34.28
45.56
56.92
67.73
70.94
73.28
77.28
82.37
75.33
90.29
100.75
69.54
88.38
113.00
125.00
2014
9.12
21.05
33.75
48.79
57.97
66.89
72.83
77.47
81.67
80.79
97.65
86.29
84.20
81.05
85.00
91.11
93.45
132.00
2015
9.65
19.89
34.64
48.32
60.32
67.78
72.64
77.88
79.92
82.17
84.77
88.98
77.76
95.00
98.15
101.00
2016
9.36
20.29
33.09
48.16
58.03
69.50
73.48
76.86
82.46
87.50
83.78
92.38
80.52
81.82
96.75
96.00
2017
8.24
20.30
36.98
47.56
58.69
66.70
73.97
79.48
85.96
83.97
84.37
96.94
83.08
111.43
2018
10.03
16.97
37.62
48.03
60.12
68.65
71.49
81.07
84.73
92.15
87.52
75.13
81.27
93.48
115.46
93.00
2019
9.51
19.64
33.67
49.05
59.01
68.22
73.51
80.38
84.43
84.10
91.63
97.77
97.12
99.46
96.00
109.00
96.00
2020
10.70
20.47
33.36
46.64
58.76
65.99
70.57
77.97
85.63
90.86
83.04
87.25
84.00
91.43
97.00
Table A.2.4. Length by age (cm)
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
Age 17
1995
9
58
282
719
1395
2091
2767
4693
5905
7211
3300
17490
1996
8
41
216
672
1349
1939
2779
4223
6638
11146
20000
1997
8
41
244
655
1393
1914
2921
2988
3768
9600
11387
5140
1998
10
49
259
840
1406
2261
3173
4320
5275
5896
16233
12260
1999
63
272
793
1508
1964
2759
4257
7262
6561
2190
18340
2000
12
69
322
826
1561
2363
2811
4260
5977
6061
8736
9458
4220
2001
5
74
377
933
1660
2320
2998
3338
4478
7193
11658
17035
8460
15001
2002
9
88
357
918
1595
2377
3468
4415
3868
3588
8921
21980
12350
2003
9
68
361
820
1427
2269
3127
4114
5493
6350
8881
2030
12562
25600
2004
6
88
338
877
1646
2153
3197
3810
4656
4184
5102
9078
7130
2005
14
99
436
878
1727
2205
2542
3666
3520
5562
8810
15482
2006
8
83
400
989
1649
2231
3502
3992
4445
8004
25080
4220
2007
7
97
486
1066
1865
2579
3168
4520
6363
11111
17480
2981
21100
2008
6
97
427
1109
1971
3327
3393
4543
4921
4270
4077
10741
4962
9250
8520
2009
8
74
357
1032
1878
2695
3803
4599
5146
5349
4886
5474
3084
3122
9672
2010
11
63
502
1088
1872
2745
3586
4684
5096
6263
6448
6562
7962
2635
12154
7475
2011
8
59
401
1165
2279
3109
3702
5163
5593
6174
5325
3982
8151
4558
2012
8
73
355
1141
2026
2907
3690
4688
5549
6118
7004
5018
7205
6444
7052
4630
2013
12
85
384
918
1817
3041
3438
3963
4926
5662
4340
8854
12081
4092
7780
16220
16300
2014
7
80
359
1122
1894
2929
3690
4646
5562
5550
9029
7135
7066
4752
7920
9591
8282
24950
2015
8
73
406
1115
2145
2987
3774
4839
5299
5869
6281
8733
5443
10170
9930
11240
2016
7
73
347
1101
1904
3327
3928
4689
5885
7273
6709
10371
5020
5773
9411
8325
2017
4
83
504
1058
1969
2943
3997
4676
6985
6306
6225
9634
5089
14019
2018
5
52
522
1109
2094
3206
3763
5391
5818
8438
7024
4283
5345
9367
15761
7350
2019
8
62
372
1131
1984
2983
3815
5141
5908
6420
7801
9778
10405
9786
9585
12345
7040
2020
8
91
368
1002
2001
2904
3374
4938
6718
8514
6665
7555
5165
7984
9765
Table A.2.5. Weight by age (gram)
Index_2plus
SD_2plus
CV_2plus
1995
33.395
2.667
0.080
1996
31.513
2.386
0.076
1997
47.938
5.599
0.117
1998
29.757
2.844
0.096
1999
13.154
1.183
0.090
2000
24.871
2.111
0.085
2001
17.500
2.666
0.152
2002
11.695
1.446
0.124
2003
13.128
1.526
0.116
2004
11.593
0.990
0.085
2005
8.253
0.766
0.093
2006
10.989
1.345
0.122
2007
15.494
1.420
0.092
2008
7.476
0.770
0.103
2009
9.128
0.883
0.097
2010
11.022
0.909
0.083
2011
10.425
0.917
0.088
2012
10.581
0.939
0.089
2013
10.131
0.993
0.098
2014
16.259
1.520
0.093
2015
10.942
0.857
0.078
2016
14.157
0.795
0.056
2017
12.782
1.118
0.087
2018
10.298
1.015
0.099
2019
13.753
1.271
0.092
2020
7.800
0.674
0.086
Table A.2.6. Abundance index, standard deviation (SD) and Coefficient of variation (CV) for sum of age 2+ fish
2.3 - Subarea B: Between 65° and 67°N
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
1995
0.000
0.319
1.494
1.205
0.390
0.219
0.204
0.155
0.117
0.020
0.000
0.044
1996
0.586
0.065
1.390
3.276
1.178
1.406
0.425
0.134
0.000
0.000
0.099
1997
0.000
0.934
1.928
2.312
1.023
0.383
0.094
0.036
0.005
0.000
0.000
0.000
1998
0.000
0.264
1.216
0.903
0.846
0.406
0.070
0.053
0.039
0.000
0.000
0.000
0.026
0.026
1999
0.036
0.360
0.466
0.260
0.202
0.127
0.023
0.001
0.045
0.000
0.000
2000
0.000
0.236
0.976
1.511
0.814
0.350
0.244
0.089
0.049
0.016
0.016
0.016
0.000
2001
0.000
0.110
0.315
0.358
0.382
0.399
0.162
0.064
0.065
0.005
0.000
0.000
0.004
0.000
2002
0.013
0.203
0.422
0.342
0.375
0.119
0.116
0.045
0.032
0.000
0.016
0.000
0.000
2003
0.021
0.085
0.293
0.764
0.518
0.436
0.237
0.116
0.085
0.023
0.000
0.004
0.000
0.000
2004
0.061
0.163
0.499
0.708
0.955
0.648
0.364
0.169
0.111
0.011
0.038
0.000
0.000
2005
0.018
0.126
0.464
0.730
0.445
0.432
0.240
0.188
0.035
0.027
0.015
0.000
2006
0.060
0.153
0.246
0.512
0.301
0.292
0.195
0.075
0.012
0.029
0.000
0.000
0.000
2007
0.049
0.086
0.540
0.325
0.162
0.123
0.166
0.052
0.011
0.000
0.000
0.001
0.000
2008
0.323
0.140
0.098
0.028
0.028
0.020
0.006
0.014
0.013
0.002
0.000
0.004
0.001
0.000
0.000
2009
0.228
0.118
0.538
0.484
0.617
0.280
0.195
0.065
0.162
0.062
0.001
0.013
0.000
0.000
0.000
2010
0.014
0.488
0.343
0.282
0.211
0.258
0.113
0.064
0.010
0.021
0.022
0.000
0.003
0.005
0.000
0.000
2011
0.155
1.784
1.046
0.828
0.553
0.425
0.178
0.028
0.069
0.004
0.014
0.001
0.012
0.000
2012
0.001
0.218
0.573
0.323
0.084
0.086
0.044
0.052
0.018
0.009
0.013
0.019
0.004
0.008
0.000
0.003
2013
0.165
0.620
0.618
0.509
0.340
0.303
0.164
0.075
0.044
0.020
0.015
0.009
0.015
0.000
0.000
0.000
0.000
2014
1.136
0.357
0.392
0.158
0.062
0.080
0.052
0.065
0.235
0.114
0.010
0.000
0.012
0.005
0.000
0.000
0.000
2015
0.000
1.371
0.849
0.714
0.792
0.335
0.230
0.067
0.035
0.059
0.061
0.004
0.015
0.000
0.005
0.000
2016
0.033
0.371
0.433
0.223
0.244
0.304
0.193
0.150
0.053
0.035
0.015
0.014
0.000
0.004
0.000
0.000
2017
0.000
0.055
0.209
0.120
0.053
0.123
0.054
0.059
0.022
0.013
0.013
0.009
0.005
0.002
2018
0.010
0.289
0.158
0.173
0.094
0.093
0.109
0.068
0.042
0.021
0.012
0.004
0.002
0.006
0.000
0.000
2019
0.631
0.874
0.616
1.017
0.850
0.681
0.191
0.237
0.066
0.087
0.054
0.027
0.004
0.000
0.000
0.000
0.000
2020
0.007
0.026
0.300
0.469
0.677
0.254
0.191
0.092
0.078
0.028
0.003
0.009
0.000
0.005
0.000
Table A.3.1. Abundance indices (millions)
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
1995
0.027
0.008
0.023
0.074
0.081
0.055
0.036
0.167
1.012
6.127
0.000
1996
0.355
0.635
0.011
0.010
0.054
0.055
0.115
0.174
0.000
1997
0.234
0.174
0.060
0.092
0.137
0.353
0.501
2.629
1998
0.145
0.075
0.100
0.080
0.104
0.464
0.240
0.443
8.401
0.000
0.000
1999
0.010
0.002
0.001
0.001
0.001
0.000
0.000
0.019
0.000
2000
0.038
0.013
0.012
0.027
0.075
0.101
0.080
0.038
0.103
0.000
0.000
2001
0.682
0.384
0.257
0.110
0.156
0.164
0.255
0.176
0.968
1.159
2002
2.110
0.263
0.394
0.096
0.048
0.298
0.564
0.981
0.662
0.000
2003
0.522
0.324
0.099
0.061
0.092
0.074
0.090
0.129
0.156
0.284
1.032
2004
0.347
0.052
0.075
0.079
0.061
0.102
0.113
0.143
0.109
1.036
0.303
2005
1.591
0.255
0.046
0.033
0.028
0.034
0.039
0.084
0.283
0.000
0.148
2006
0.000
0.041
0.031
0.021
0.049
0.036
0.036
0.089
0.202
0.000
2007
1.071
0.366
0.157
0.144
0.154
0.151
0.206
0.208
0.960
5.384
2008
0.723
0.555
0.336
0.708
0.471
0.101
0.856
0.584
0.695
0.201
0.685
0.040
2009
0.000
0.369
0.177
0.078
0.111
0.084
0.097
0.295
0.082
0.199
4.224
0.273
2010
0.221
0.367
0.172
0.146
0.080
0.076
0.076
0.062
0.444
0.708
0.248
5.180
0.805
0.000
2011
0.712
0.078
0.098
0.087
0.103
0.080
0.144
0.736
0.111
1.824
1.206
3.159
0.000
2012
1.698
0.213
0.507
0.524
0.318
0.305
0.457
0.434
0.408
0.442
0.369
0.656
0.769
0.807
0.795
2013
0.586
0.160
0.191
0.092
0.067
0.057
0.160
0.271
0.254
0.585
0.633
1.014
0.631
2014
0.118
0.145
0.158
0.176
0.108
0.231
0.273
0.412
0.039
0.335
0.711
0.745
1.254
2015
0.053
0.059
0.087
0.083
0.090
0.152
0.317
0.466
0.352
0.678
0.970
0.527
1.096
2016
1.416
0.828
0.216
0.335
0.242
0.232
0.291
0.377
0.464
0.407
0.753
0.590
0.639
2017
0.637
0.330
0.262
0.206
0.279
0.349
0.384
0.529
0.419
0.619
0.531
1.049
0.936
2018
0.638
0.533
0.167
0.147
0.170
0.367
0.506
0.648
0.594
0.625
0.626
0.852
0.684
1.026
2019
0.056
0.097
0.145
0.075
0.077
0.076
0.192
0.108
0.183
0.117
0.097
0.195
1.579
2020
3.801
0.853
0.400
0.222
0.162
0.337
0.310
0.350
0.471
0.519
1.056
1.242
1.369
Table A.3.2. CV on abundance indices
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
1995
0.000
0.029
0.528
0.814
0.573
0.469
0.517
0.822
1.037
0.188
0.001
0.811
1996
0.005
0.001
0.404
2.548
1.454
2.479
0.939
0.622
0.000
0.000
1.546
1997
0.000
0.053
0.377
1.398
1.149
0.663
0.257
0.113
0.008
0.000
0.000
0.000
1998
0.000
0.034
0.375
0.753
1.019
0.735
0.197
0.242
0.305
0.001
0.000
0.000
0.525
0.690
1999
0.004
0.088
0.302
0.306
0.384
0.325
0.107
0.008
0.624
0.000
0.000
2000
0.000
0.022
0.290
1.016
0.966
0.688
0.779
0.495
0.511
0.308
0.232
0.233
0.000
2001
0.000
0.010
0.097
0.234
0.421
0.519
0.577
0.190
0.499
0.037
0.000
0.000
0.050
0.000
2002
0.000
0.019
0.117
0.437
0.880
0.217
0.194
0.076
0.088
0.000
0.135
0.000
0.000
2003
0.000
0.006
0.104
0.466
0.540
0.775
0.590
0.321
0.283
0.054
0.000
0.008
0.000
0.000
2004
0.000
0.016
0.170
0.517
1.402
1.127
0.967
0.495
0.284
0.034
0.682
0.000
0.000
2005
0.000
0.009
0.157
0.475
0.687
0.987
0.663
0.566
0.101
0.040
0.278
0.000
2006
0.001
0.019
0.124
0.500
0.400
0.516
0.453
0.174
0.052
0.133
0.000
0.000
0.000
2007
0.000
0.011
0.254
0.258
0.229
0.255
0.409
0.157
0.071
0.000
0.000
0.001
0.000
2008
0.003
0.018
0.044
0.040
0.066
0.053
0.021
0.056
0.072
0.015
0.000
0.026
0.003
0.000
0.000
2009
0.004
0.009
0.192
0.577
1.041
0.696
0.529
0.167
0.593
0.386
0.003
0.026
0.000
0.000
0.000
2010
0.000
0.030
0.121
0.229
0.389
0.606
0.308
0.289
0.024
0.059
0.109
0.000
0.006
0.009
0.000
0.000
2011
0.001
0.146
0.298
0.783
0.895
1.020
0.541
0.093
0.560
0.010
0.046
0.003
0.119
0.000
2012
0.000
0.021
0.192
0.181
0.104
0.183
0.105
0.165
0.078
0.057
0.056
0.096
0.016
0.036
0.000
0.012
2013
0.002
0.037
0.147
0.321
0.393
0.675
0.400
0.231
0.199
0.085
0.038
0.031
0.061
0.000
0.000
0.000
0.000
2014
0.012
0.030
0.232
0.114
0.061
0.157
0.173
0.251
1.117
0.437
0.041
0.000
0.043
0.015
0.000
0.000
0.000
2015
0.000
0.106
0.233
0.759
1.233
0.793
0.522
0.207
0.127
0.460
0.228
0.019
0.066
0.000
0.036
0.000
2016
0.000
0.031
0.133
0.197
0.331
0.701
0.550
0.462
0.251
0.357
0.072
0.086
0.000
0.012
0.000
0.000
2017
0.000
0.005
0.073
0.104
0.101
0.309
0.173
0.190
0.084
0.077
0.058
0.040
0.020
0.024
2018
0.000
0.015
0.047
0.271
0.155
0.249
0.347
0.265
0.225
0.097
0.060
0.015
0.019
0.037
0.000
0.000
2019
0.006
0.069
0.184
1.140
1.734
1.720
0.582
0.841
0.199
0.370
0.251
0.143
0.015
0.000
0.000
0.000
0.000
2020
0.000
0.002
0.118
0.505
1.165
0.630
0.605
0.420
0.328
0.126
0.013
0.056
0.000
0.025
0.000
Table A.3.3. Biomass indices (kilotonnes)
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
1995
21.94
33.66
41.58
52.72
60.33
64.29
80.92
94.71
99.01
60.00
117.00
1996
9.77
13.00
31.63
42.75
51.16
57.11
61.34
80.03
118.00
1997
18.27
27.13
39.84
49.63
57.20
64.53
75.17
54.90
1998
24.38
31.97
43.56
49.98
57.23
65.97
77.02
93.29
57.00
121.00
135.00
1999
23.93
29.19
40.33
49.29
57.53
64.02
79.87
97.41
107.50
2000
21.57
31.06
40.66
49.45
58.17
67.45
79.64
98.84
109.64
114.00
105.00
2001
21.77
31.73
41.09
48.33
51.45
67.05
65.76
90.48
89.36
117.00
2002
10.00
21.90
30.75
48.87
60.98
55.74
53.59
54.19
64.97
97.00
2003
10.00
19.94
32.96
39.46
47.12
56.05
62.67
65.60
69.22
62.20
61.00
2004
8.77
21.73
32.25
42.14
51.94
55.44
63.72
65.75
64.19
72.07
119.47
2005
14.00
20.14
31.65
40.05
52.32
60.57
63.73
65.16
65.74
55.00
118.27
2006
11.67
23.74
36.59
45.65
51.04
55.71
61.58
62.43
77.27
75.96
2007
9.94
23.46
35.55
43.44
51.65
58.62
62.02
67.97
89.28
57.00
2008
10.73
25.27
36.20
53.57
62.11
63.98
69.17
71.80
79.42
88.53
88.78
69.99
2009
12.11
20.79
32.27
48.34
54.21
61.43
64.91
63.54
71.00
81.67
59.00
59.22
2010
12.04
19.15
32.56
42.28
55.82
60.52
64.49
74.88
61.81
66.77
81.14
58.00
60.00
62.00
2011
9.38
21.22
30.50
45.76
54.64
62.29
66.89
72.58
83.47
61.36
69.07
64.00
102.00
2012
10.16
22.09
32.88
39.24
51.02
59.62
63.48
67.44
74.07
83.81
74.30
78.35
73.00
75.00
79.00
2013
11.77
19.05
30.12
40.89
49.69
62.10
64.29
68.26
76.04
76.13
64.04
69.00
74.35
2014
10.74
21.22
38.24
42.25
47.29
58.78
70.43
73.78
76.04
74.19
81.04
72.99
75.00
2015
20.63
30.34
47.34
54.38
61.30
60.63
68.91
71.92
88.58
74.42
77.00
76.03
95.00
2016
9.90
21.41
32.22
42.52
51.41
60.40
65.69
66.74
77.77
96.51
75.68
83.88
73.00
2017
22.31
33.68
44.75
57.05
63.09
69.05
68.58
73.69
85.70
78.01
75.94
81.30
99.00
2018
10.43
17.57
32.07
50.93
54.46
63.45
66.72
72.57
77.50
77.15
78.02
74.66
98.00
80.03
2019
10.55
20.66
30.44
48.03
58.75
62.90
66.59
71.27
67.22
73.38
73.15
82.61
76.59
2020
11.37
22.57
34.54
46.72
54.72
62.14
66.55
75.63
75.15
77.74
79.23
82.83
83.00
Table A.3.4. Mean length (cm)
Age 0
Age 1
Age 2
Age 3
Age 4
Age 5
Age 6
Age 7
Age 8
Age 9
Age 10
Age 11
Age 12
Age 13
Age 14
Age 15
Age 16
1995
91
354
676
1470
2148
2538
5295
8844
9406
2400
18580
1996
8
17
291
778
1233
1763
2214
4688
15560
1997
57
198
604
1124
1733
2787
3282
1506
1998
128
309
835
1204
1809
2823
4634
7894
1655
19880
26100
1999
115
245
648
1175
1906
2556
4722
9728
13870
2000
92
297
672
1186
1962
3185
5549
10436
18769
14266
14380
2001
96
316
670
1106
1305
3618
2991
7694
7230
12000
2002
8
93
281
1286
2350
1887
1755
1800
2999
8358
2003
9
67
354
610
1045
1780
2491
2787
3325
2370
2030
2004
6
100
341
732
1468
1741
2663
2936
2558
3377
18589
2005
25
75
340
652
1545
2286
2761
3002
2942
1456
18343
2006
13
125
506
976
1329
1769
2318
2308
4444
4608
2007
7
134
474
796
1421
2083
2516
3047
6673
1648
2008
10
165
456
1543
2445
2691
3419
4277
5767
7574
6239
2733
2009
16
76
361
1194
1697
2487
2720
2575
3664
6374
2096
2034
2010
14
62
355
822
1852
2355
2731
4539
2398
2842
4951
2128
2285
1910
2011
8
82
286
947
1620
2404
3064
4232
8231
2328
3590
2440
10116
2012
9
96
338
581
1287
2206
2548
3215
4206
7036
4248
4862
3745
4325
4630
2013
13
60
241
631
1160
2225
2436
3071
4535
4334
2569
3425
4214
2014
11
85
601
725
982
2003
3272
4015
4751
3973
4625
3634
3340
2015
77
275
1061
1556
2373
2271
3186
3614
8353
3497
4310
4380
7785
2016
9
87
307
860
1360
2292
2796
3035
4734
10174
4596
5961
3425
2017
89
363
880
1901
2484
3206
3257
3827
6124
4306
4305
4379
10610
2018
5
48
296
1587
1643
2592
3083
3993
5141
4668
4787
3684
8695
5988
2019
10
79
299
1121
2042
2529
3058
3557
3014
4284
4647
5383
4261
2020
9
86
394
1073
1720
2512
3123
4707
4240
4690
3524
6025
5434
Table A.3.5. Mean weight (gram)
Index_2plus
SD_2plus
CV_2plus
1995
3.848
0.030
0.008
1996
7.908
0.072
0.009
1997
5.782
0.365
0.063
1998
3.587
0.104
0.029
1999
1.483
0.001
0.000
2000
4.082
0.033
0.008
2001
1.753
0.309
0.176
2002
1.467
0.289
0.197
2003
2.474
0.049
0.020
2004
3.503
0.067
0.019
2005
2.576
0.025
0.010
2006
1.662
0.022
0.013
2007
1.379
0.090
0.066
2008
0.214
0.060
0.279
2009
2.416
0.197
0.081
2010
1.331
0.108
0.081
2011
3.157
0.150
0.048
2012
1.238
0.565
0.457
2013
2.113
0.138
0.065
2014
1.184
0.068
0.057
2015
3.167
0.147
0.046
2016
1.668
0.344
0.206
2017
0.682
0.189
0.277
2018
0.783
0.233
0.298
2019
3.830
0.106
0.028
2020
2.107
0.289
0.137
Table A.3.6. Abundance index, standard deviation (SD) and Coefficient of variation (CV) for sum of age 2+ fish