CM_2004_R_32.pdf (808.2Kb)

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International Council for The Exploration of the Sea

CM: 2004 R:32

ICES COORDINATED ACOUSTIC SURVEY OF ICES DIVISIONS IIIa, IVa, IVb AND Via (NORTH)

2003 Results

E J Simmonds¹, C. Zimmermann⁴ E, Gőtze⁶ S Jansen⁴ E Torstensen², Bo Lundgren³, D G Reid¹ S Ybema⁵ and A S Couperus⁵

1FRS Marine Laboratory, PO Box 101, Victoria Road, Torry, Aberdeen, AB11 9DB, Scotland, UK

2Institute of Marine Research, Bergen, Norway

3Danish Institute for Fisheries Research, The North Sea Centre, Hirtshals, Denmark

4Inst Seefischerei, Hamburg

5RIVO, Ijmuiden, The Netherlands

6Inst Fischereitechnik, Hamburg

ABSTRACT

Six surveys were carried out during late June and July covering most of the continental shelf north of 52^oN in the North Sea and to the west of Scotland to a northern limit of 62^oN. The eastern edge of the survey area was bounded by the Norwegian and Danish, Swedish and German coasts, and to the west by the shelf edge between 200 and 400 m depth. The surveys are reported individually in the report of the planning group for herring surveys, and a

combined report has been prepared from the data from all surveys. The combined survey results provide spatial distributions of herring abundance by number and biomass at age by statistical rectangle; and distributions of mean weight and fraction mature at age. The estimates of North Sea autumn spawning herring are consistent with previous years at 3.1 million tonnes and 18,400 million herring. The survey also shows two exceptional year classes of herring (the 1998 and 2000 year classes) in the North Sea, which is consistent with the observation of exceptionally large year classes observed in the MIK and IBTS surveys.

The estimates of Western Baltic spring spawning herring SSB are 106,000 tonnes and 823,000 herring and show a substantial decrease compared with the previous year. The Western Baltic survey produces a rather noisy signal but the indications are of a stock that is slightly higher than during the period 1996 to 2000. The West of Scotland survey estimates of 739,000 tonnes and 4,000 million herring and shows the high 1995 year class again this year. The 1998 year class now (4 ring) is now confirmed also a large one. Indications are that the 2000 yearclass is also good. Total adult mortality shows low mortality again ( 0.1 ) but the mean mortality over the last 4 years has been around 0.3: this is consistent with the 2003 assessment that the stock is lightly exploited.

INTRODUCTION

Six surveys were carried out during late June and July covering most of the continental shelf north of 52^oN in the North Sea and to the west of Scotland to a northern limit of 62^oN. The eastern edge of the survey area was bounded by the Norwegian and Danish, Swedish and German coasts, and to the west by the shelf edge between 200 and 400 m depth. The surveys are reported individually in appendices IIa-f of the report of the planning group for herring

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surveys (ICES, 2003). The vessels, areas and dates of cruises are given below and in Figure 1:

Vessel Period Area

FV Enterprise 01 July – 21 July 56°- 60°N, 3° - 7° W

R.V Sarsen 1 – 22 July 56°30’- 61° N, 2° - 6° E

Scotia 27 June – 20 July 58°- 62° N, 4° W - 2° E

Tridens 23 June – 18 July 54°30 – 58° N, west of 3° E

Walther Herwig III 26 June – 13 July 52° - 57° N, east England / 3° E

Dana 27 June – 8 July North of 57°NS & 56° N, Kattegat

east of 6° E

The data have been combined to provide an overall estimate. Estimates of numbers at age, maturity stage and mean weights at age are calculated as weighted means of individual survey estimates by ICES statistical rectangle. The weighting applied is proportional to the length of survey track for each vessel that has covered each statistical rectangle. The data have been combined and estimates of North Sea autumn spawning herring, Western Baltic spring spawning herring, and West of Scotland (VIanorth) herring are shown in Tables 1-3.

METHODS

The acoustic surveys were carried out using Simrad EK60, EK500 and EY500 38 kHz sounder echo-integrator with transducers mounted on the hull, drop keel and towed bodies.

Further data analysis was carried out using either BI500, Echoview or Echoann software.

The survey track was selected to cover the area giving a basic sampling intensity over the whole area based on the limits of herring densities found in previous years. A transect spacing of 15 nautical miles was used in most parts of the area with the exception of some relatively high density sections, east and west of Shetland, and in the Skagerrak where short additional transects were carried out at 7.5 nmi spacing.

The following target strength to fish length relationships have been used to analyse the data:

herring TS = 20 log L - 71.2 dB

sprat TS = 20 log L -71.2 dB

gadoids TS = 20 log L - 67.5 dB

mackerel TS = 21.7 log L - 84.9 dB Combined Acoustic Survey Results for 2003

The estimates of North Sea autumn spawning herring SSB are 3.1 million tonnes and 17,300 millions herring (Table 1). The North Sea survey is consistent with previous years, giving a total adult mortality of about 0.45 over the last 3 years, which is similar to the estimates from the assessment. The SSB rose from 2.4 million tonnes in 2001 (Table 4) to 2.9 million tonnes in 2002 and again to 3.1 million tonnes in 2003. The survey shows again two exceptional year classes of herring (the 1998 and 2000 year classes) in the North Sea, which is consistent with the observation of exceptionally large year classes observed in the MIK and IBTS surveys (ICES 2001a). The 2003 estimate of the 2000 yearclass suggests it is higher than the 1998 yearclass at 1.5 times at age 2wr. Growth of the 2000 yearclass seems to be slower than previously at 1.5 cm smaller, and 20g lighter than the 1998 yearclass at the same age. In addition only 43% are mature compared to 77% and 86% for 1998 and 1999 yearclasses.

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A B

D

-12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14

51 52 53 54 55 56 57 58 59 60 61 62

63 20 Jul 2003^{27 Jun -}^Scotia

Sarsen 01 Jul - 22 Jul 2003

27 June -Dana 08 July 2003

Walther Herwig III 26 Jun -13 Jul 2003 Tridens

23 Jun - 18 Jul 2003

Charter 01 Jul - 20 Jul 2003

Dense transect spacing (15nm) Wide transect spacing (30nm)

Overlap areas:

A - Scotia/Sarsen B - Scotia/Tridens C - Scotia/Charter D - Sarsen/Tridens

C

Figure 1 Survey area layouts and dates for all participating vessels in the 2003 acoustic survey of the North Sea and adjacent areas. Heavily shaded areas indicate areas of overlap.

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Table 1 Total numbers (millions of fish) and biomass (thousands of tonnes) of North Sea autumn spawning herring in the area surveyed in the acoustic surveys July 2003, with mean weights, mean lengths and fraction mature by age ring.

Age ( ring) Numbers Biomass Maturity weight(g) Length (cm)

0 2589.9 15.7 0.00 6 9.3

1 9829.4 453.1 0.00 46 18.0 2 18949.4 1967.5 0.43 104 22.5 3 3081.0 568.7 0.93 185 26.3 4 4188.9 876.3 1.00 209 27.5 5 675.1 144.2 1.00 214 28.0 6 494.8 120.2 1.00 243 28.9 7 568.3 159.7 1.00 281 30.0 8 145.5 42.2 1.00 290 30.3 9+ 177.7 54.6 1.00 307 31.0 Immature 23420.9 1403.3

Mature 17279.2 2998.9 Total 40700.1 4402.1

Table 2 Total numbers (millions of fish) and biomass (thousands of tonnes) of Western Baltic spring spawning herring in the area surveyed in the acoustic surveys July 2003, with mean weights, mean length and fraction mature by age ring.

Age ( ring) Numbers Biomass Maturity weight(g) length (cm) 0 0.0 0.0 0.00

1 1833.1 79.0 0.00 43 17.7

2 1110.0 91.5 0.19 82 21.6

3 394.6 41.4 0.36 104.9 21.7

4 323.4 41.7 1.00 128.8 25.3

5 103.4 13.9 1.00 134.2 25.7

6 25.2 4.2 1.00 165.4 27.0

7 12.0 2.0 1.00 167.2 27.7

8 5.2 0.9 1.00 170.2 27.5

9+ 0.2 0.0 1.00 173.5 28.5

Immature 2975.1 168.2

Mature 832.0 106.4

Total 3807.1 274.6

Table 3 Total numbers (millions of fish) and biomass (thousands of tonnes) of autumn spawning of West of Scotland herring in the area surveyed in the acoustic surveys July 2003, with mean weights, mean lengths and fraction mature by age ring.

Age ( ring) Numbers Biomass Maturity weight(g) Length (cm) 0 0.0 0.0 0.00

1 438.8 28.3 0.00 64 19.1

2 1039.4 143.3 0.76 138 24.5

3 932.5 164.2 1.00 176 26.5

4 1471.8 280.3 1.00 190 27.2

5 181.3 37.0 1.00 204 27.8

6 129.2 27.5 1.00 213 28.2

7 346.7 75.3 1.00 217 28.4

8.00 114.3 25.5 1.00 223 28.6

9+ 75.2 17.2 1.00 228 28.8

Immature 693.9 59.3

Mature 4035.2 739.2

Total 4729.1 798.6

The estimates of Western Baltic spring spawning herring SSB are 106,000 tonnes and 830,000 herring (Table 2) and show a large reduction compared with previous years. This survey produces a rather noisy signal but the indications are still that of a stock that is slightly higher now than between 1996 to 2000. Last years estimate was high, as some year classes were seen to increase from 2001 to 2002, Results this year are more comparable with 2001.

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Table 4 Estimates of North Sea autumn spawners (millions) at age from acoustic surveys, 1984-2003. For 1984-1986 the estimates are the sum of those from the Division IVa summer survey, the Division IVb autumn survey, and the Divisions IVc, VIId winter survey. The 1987 to 2003 estimates are from the summer survey in Divisions IVa,b and IIIa excluding estimates of Division IIIa/Baltic spring spawners. For 1999 and 2000 the Kattegat was excluded from the results because it was not surveyed. Smoothed Z are those estimated over 2 years providing an estimate of mortality that is less noisy.

Year/age 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

1 551 726 1,639 13,736 6,431 6,333 6,249 3,182 6,351 10,399 3,646 4,202 6,198 9,416 4,449 5,087 24,735 6,837 23,055 9,829 2 3,194 2,789 3,206 4,303 4,202 3,726 2,971 2,834 4,179 3,710 3,280

3,799 4,557 6,363 5,747 3,078 2,922 12,290 4,875 18,949 3 1,005 1,433 1,637 955 1,732 3,751 3,530 1,501 1,633 1,855 957 2,056 2,824 3,287 2,520 4,725 2,156 3,083 8,220 3,081 4 394 323 833 657 528 1,612 3,370 2,102 1,397 909 429 656 1,087 1,696 1,625 1,116 3,139 1,462 1,390 4,189 5 158 113 135 368 349 488 1,349 1,984 1,510 795 363 272 311 692.1 982.4 506.4 1,006 1,676 794.6 675.1 6 44 41 36 77 174 281 395 748 1,311 788 321 175 98.7 259.2 445.2 313.6 482.5 449.6 1,031 494.8 7 52 17 24 38 43 120 211 262 474 546 238 135 82.8 78.6 170.3 138.6 266.4 169.6 244.4 568.3 8 39 23 6 11 23 44 134 112 155 178 220 110 132.9 78.3 45.2 54.3 120.4 97.7 121 145.5 9+ 41 19 8 20 14 22 43 56 163 116 132 84 206 158.3 121.4 87.2 97.2 58.9 149.5 177.7 Total 5,478 5,484 7,542 20,165 13,496 16,377 18,262 12,781 17,173 19,326 13,003 11,220 18,786 22,028 16,104 15,107 34,928 26,124 39,881 38,110

Z2+/3+ . 0.92 0.57 1.02 0.81 0.11 0.11 0.57 0.37 0.74 1.21 0.53 0.43 0.40 0.76 0.52 0.32 0.38 0.47 0.59

Smooth Z2+/3+

. . 0.73 0.76 0.91 0.30 0.11 0.25 0.46 0.52 0.94 0.80 0.48 0.41 0.55 0.63 0.41 0.35 0.425 0.53 SSB

(‘000 t) 807 697 942 817 897 1,637 2,174 1,874 1,545 1,216 1,035 1,082 1446.2 1,780 1,792 1,534 1,833 2,622 2,948 2,999

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-10 -8 -6 -4 -2 0 2 4 6 8 10 12 52

53 54 55 56 57 58 59 60 61 62

315.6 98.6 0.2

89.1 84.6 35.9 69.2

0.7 15.4 81.9 89.0 157.6 15.9 0.0 0.3 0.3

0.0 47.3 68.5 54.6 97.1 71.6 15.8 0.0 3.9 21.2

0.0 70.6 30.8 76.2 76.8 97.7 67.3 3.2 84.3 0.8 21.1 3.4

11.5 59.1 50.2 21.5 17.0 126.6 51.5 69.1 65.3 147.1 3.4 17.2 2.2

0.0 74.8 33.4 47.0 0.0 0.0 14.1 82.6 130.3 30.7 48.2 42.0 10.5 6.7 0.8 2.1 3.0

0.0 61.2 16.2 0.0 1.0 1.3 25.6 36.4 66.0 9.3 0.0 5.0 2.3 3.5 1.6 0.3 1.4 2.8 6.2

0.0 138.6 1.5 0.0 0.0 0.0 0.0 1.9 15.7 1.8 5.3 18.6 56.7 1.7 1.7 4.5 4.5 6.2 9.3

0.5 60.5 0.0 0.0 0.0 20.6 2.3 20.9 9.1 4.2 7.0 4.3 1.7 1.7 4.5 1.1 9.3 18.7

0.0 65.2 41.0 3.8 0.0 0.0 33.9 98.1 110.3 38.0 1.4 0.1 0.3 5.9 2.1 0.3 9.3 18.7 4.7

0.6 7.3 2.4 0.0 0.0 0.0 13.0 151.7 101.0 73.4 0.0 0.0 0.6 11.5 32.0 18.7 9.3

0.0 88.9 15.8 0.0 13.5 0.0 0.1 1.5 2.1 0.3

0.0 23.1 33.8 0.0 0.0 0.1 0.1 1.6 6.0 0.3

16.1 293.0 0.0 0.0 0.0 0.0 0.4 23.9 0.0

5.1 1.7 0.1 0.0 0.0 0.0 0.3 0.1 0.2 0.0

0.1 0.0 0.0 0.0 0.2 0.0 0.0 0.0

0.2 0.3 0.0

0.4 0.2

0.2 0.1 0.0

1271 397 1

372 367 162 281

3 62 419 472 788 72 0 2 2

0 283 324 304 540 358 64 0 29 155

0 366 160 415 477 766 435 18 434 4 122 25

60 306 293 159 143 1182 455 454 420 743 20 102 21

0 388 374 353 0 0 138 667 914 197 233 265 83 60 11 38 54

0 321 105 1 14 13 214 294 484 60 0 44 21 31 18 4 25 51 129

0 726 17 0 0 0 0 23 191 27 54 168 1034 29 29 82 82 129 265

2 317 0 0 0 250 28 254 116 73 128 78 29 29 82 21 265 530

0 384 246 81 0 0 413 1193 1342 407 25 2 5 158 55 7 265 530 132

3 40 15 0 0 0 158 1845 1228 893 0 0 17 309 862 530 265

0 1082 193 0 165 1 1 39 57 9

0 208 358 0 0 1 4 42 159 8

171 3105 0 0 0 0 11 635 0

98 44 3 0 0 1 9 3 5 0

3 0 0 0 6 0 0 0

6 7 0

12 4

6 2 1

Figure 2 Abundance of Autumn spawning herring from combined acoustic survey July 2003. Numbers (millions) (upper figure) and biomass (thousands of tonnes) (lower figure).

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-10 -8 -6 -4 -2 0 2 4 6 8 10 12 52

53 54 55 56 57 58 59 60 61 62

1227 383 1 347 330 140 269

3 60 276 300 617 62 0 1 1

0 139 235 159 283 280 62 0 18 95

0 313 136 237 199 135 175 10 318 3 86 15

51 262 177 30 16 24 28 173 172 493 16 77 3

0 331 37 65 0 0 0 59 254 81 167 182 21 13 0 1 1

0 309 61 0 1 0 15 26 104 24 0 18 9 14 2 0 1 1 2

0 699 1 0 0 0 0 1 8 0 16 77 0 1 1 2 2 2 0

2 305 0 0 0 11 1 11 4 0 0 0 1 1 2 0 0 0

0 264 160 0 0 0 17 50 56 8 0 0 0 0 0 0 0 0 0

3 34 10 0 0 0 7 78 52 38 0 0 0 0 0 0 0

0 46 8 0 7 0 0 0 0 0

0 147 20 0 0 0 0 0 0 0

9 170 0 0 0 0 0 0 0

12 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0

0 0

0 0 0

0 0 0 0

0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 2 10

0 0 0 0 0 18 0 0 0 0 0 1

0 0 2 3 5 41 16 0 0 0 0 0 4

0 0 281 16 0 0 6 0 0 0 0 0 3 1 11 31 44

0 0 29 0 12 1 2 0 0 0 0 0 4 4 5 3 21 41 116

0 0 14 0 0 0 0 4 37 12 18 22 747 21 21 65 65 116 264

0 0 0 0 0 48 5 49 29 52 52 56 21 21 65 16 264 529

0 0 0 81 0 0 79 228 257 0 10 0 1 155 54 7 264 529 132

0 0 0 0 0 0 30 353 235 171 0 0 16 295 838 529 264

0 207 37 0 32 1 1 37 57 8

0 49 98 0 0 1 3 40 149 7

47 853 0 0 0 0 10 592 0

54 38 3 0 0 1 9 3 5 0

2 0 0 0 6 0 0 0

6 7 0

12 4

6 2 1

44 14 0

25 37 22 12

0 2 143 172 171 10 0 1 1

0 144 89 144 257 77 2 0 9 51

0 53 23 177 278 613 260 8 115 1 35 9

9 44 114 126 121 1117 411 281 248 250 3 25 14

0 56 56 271 0 0 132 607 660 117 66 83 59 46 0 6 9

0 12 15 0 1 13 197 267 380 35 0 25 7 13 11 1 4 8 12

0 28 3 0 0 0 0 18 147 16 20 68 287 7 7 15 15 12 1

0 12 0 0 0 192 21 194 82 21 76 22 7 7 15 4 1 1

0 120 85 0 0 0 316 914 1028 398 15 2 4 3 1 0 1 1 0

0 6 5 0 0 0 121 1414 941 684 0 0 1 14 25 1 1

0 829 148 0 126 0 0 2 0 1

0 12 240 0 0 0 0 3 9 0

115 2082 0 0 0 0 1 43 0

33 5 0 0 0 0 0 0 0 0

1 0 0 0 0 0 0 0

0 0 0

0 0

0 1 0

Figure 3 Numbers (millions) of Autumn spawning herring from combined acoustic survey June - July 2003. 1 ring (upper figure), 2 ring (centre figure), 3+ (lower figure).

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-10 -8 -6 -4 -2 0 2 4 6 8 10 12 52

53 54 55 56 57 58 59 60 61 62

96 96 96

95 94 94 95

96 96 91 92 94 94 + 62 62

+ 89 91 91 91 94 96 + 62 62

+ 89 89 91 75 56 73 78 84 89 85 77

89 89 72 66 30 29 50 72 74 75 94 76 45

+ 89 58 66 + + 22 52 62 74 75 81 74 39 + 6 6

+ 73 75 54 54 22 45 52 58 74 + 64 22 33 28 6 6 6 6

+ 73 55 + + + + 24 24 11 17 33 8 6 6 6 6 6 6

73 73 + + + 24 24 24 23 6 0 8 6 6 6 6 6 6

+ 89 89 + + + 24 24 24 43 0 0 4 42 41 39 6 6 6

73 87 89 + + + 24 24 24 24 + 75 78 50 61 6 6

+ 24 24 + 24 75 75 76 + 0

+ 0 44 + + 75 75 77 77 77

44 44 + + 75 87 80 50 79

91 79 80 100 74 + + 79 + +

84 + + 62 + + 87 +

+ 64 74

+ 66

68 100 68 100 100 100

100 100 100 100

100 100 98 98 99 100 + 92 92

+ 80 98 97 97 99 100 + 92 92

+ 99 99 97 90 84 90 92 95 95 94 90

99 99 100 100 97 84 84 87 84 92 84 88 +

+ 99 97 100 + + + 84 84 84 93 100 89 67 + 9 9

+ 100 99 98 98 + 84 84 84 84 + 100 54 75 68 9 9 9 9

+ 100 93 + + + + 88 88 + 54 75 + 9 9 9 9 9 +

100 100 + + + 88 88 88 88 + + + 9 9 9 9 + +

+ 100 100 + + + 88 88 88 100 + + + + + + + + +

100 100 100 + + + 88 88 88 88 + 100 + + + + +

+ 88 88 + 88 100 100 + + +

+ + 100 + + 100 100 + + +

100 100 + + 100 + + + +

100 100 100 100 100 + + + + +

100 + 100 100 + + + +

+ 100 +

+ 100

100 + 100

+ + +

+ + + +

+ + + + + + + 76 76

+ + + + + + + + 76 76

+ + + + + 57 + + + + + 88

+ + 84 84 61 61 57 + + + + + 88

+ + 68 70 + + 61 + + + + + 79 80 72 52 50

+ + 70 61 61 61 61 + + + + + 63 68 74 56 52 52 45

+ + 70 + + + + 53 53 55 59 68 51 54 54 52 52 45 35

+ + + + + 53 53 53 53 53 50 51 54 54 52 52 35 35

+ 57 57 48 + + 53 53 53 + 50 + 50 37 37 37 35 35 35

+ 57 57 48 + + 53 53 53 53 + 37 37 37 37 35 35

+ 53 53 + 53 37 37 37 37 37

+ 37 57 + + 37 37 37 37 37

57 57 + + 37 37 37 37 37

37 37 37 + 37 37 37 37 37 +

37 + + 37 37 + 37 37

37 37 37

37 37

37 37 37

159 159 159 157 156 155 158

159 159 150 150 155 155 + 104 104

+ 120 150 149 149 155 159 + 104 104

+ 154 154 149 139 120 132 143 147 154 147 114 154 154 133 127 109 108 113 133 140 140 151 136 105

+ 154 131 127 + + 104 120 130 140 141 121 119 104 + 66 68

+ 162 144 121 121 104 117 120 126 140 + 95 98 94 89 69 66 66 65

+ 162 130 + + + + 86 86 76 89 94 65 66 66 66 66 65 51

162 162 + + + 86 86 86 85 69 59 65 66 66 66 66 51 51

+ 142 142 + + + 86 86 86 92 59 59 62 47 47 46 51 51 51

162 145 142 + + + 86 86 86 86 + 50 50 48 49 51 51

+ 86 86 + 86 50 50 50 + 42

+ 64 103 + + 50 50 50 50 50

103 103 + + 50 51 51 48 51

52 50 51 53 50 + + 51 + +

51 + + 49 + + 51 +

+ 49 50

+ 49

49 53 49

1wr weight , 2wr weight 2wr mature, 3wr mature

Figure 4 Mean weight & maturity of Autumn spawning herring from combined acoustic survey June - July 2003. Four values per ICES rectangle, percentage mature

(lower),2 ring (left), 3 ring (right), mean weights gram (upper),1 ring (left) ,2 ring (right) ,0 indicates measured percentage mature, + indicates surveyed with zero abundance blank indicates an unsurveyed rectangle

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-10 -8 -6 -4 -2 0 2 4 6 8 10 12 52

54 56 58 60 62

Figure 5 Numbers of mature autumn spawning herring from combined acoustic survey June -July 2003.

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-10 -8 -6 -4 -2 0 2 4 6 8 10 12 52

53 54 55 56 57 58 59 60 61

Figure 6 Biomass of immature autumn spawning herring from combined acoustic survey June -July 2002.

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Table 5 Numbers (millions) of Western Baltic Spring Spawning herring at age ( rings) from acoustic surveys 1989 to 2003. The 1999 survey was incomplete due to the lack of participation by RV DANA.

Year 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 0 31 3,853 372 964

1 135 277 103 5 2,199 1,091 128 138 1367 1509 66 3346 1833 2 1,105 1,497 1,864 2,092 2,768 413 1,887 1,005 715 1,682 1143 1891 641 1576 1110 3 714 549 1,927 1,799 1,274 935 1,022 247 787 901 523 674 452 1392 394.6 4 317 319 866 1,593 598 501 1,270 141 166 282 135 364 153 524 323.4 5 81 110 350 556 434 239 255 119 67 111 28 186 96 88 103.4 6 51 24 88 197 154 186 174 37 69 51 3 56 38 40 25.2 7 16 10 72 122 63 62 39 20 80 31 2 7 23 18 12.0 8+ 4 5 10 20 13 34 21 13 77 53 1 10 12 19 5.4 Total 2,288 2,680 5,177 10,509 5,779 3,339 6,867 2,673 2,088 3,248 3,201 4,696 1,481 7,002 3,807

3+

group 1,183 1,017 3,313 4,287 2,536 1,957 2,781 577 1,245 1,428 691 1,295 774 2,081 864

Table 6 Numbers at age (millions) and SSB of West of Scotland Autumn Spawning herring at age ( rings) from acoustic surveys 1987, 1991 to 2003. #In 1997 the survey was carried out one month early in June as opposed to July when all the other surveys were carried out

Age 1987 1991 1992 1993 1994 1995 1996 1997^# 1998 1 249.1 338.3 74.3 2.8 494.2 441.2 41.2 792.3 1,221.7 2 578.4 294.5 503.4 750.3 542.1 1,103.4 576.5 641.9 794.6 3 551.1 327.9 211.0 681.2 607.7 473.2 802.5 286.2 666.8 4 353.1 367.8 258.1 653.1 285.6 450.3 329.1 167.0 471.1 5 752.6 488.3 414.8 544.0 306.8 153.0 95.4 66.1 179.1 6 111.6 176.3 240.1 865.2 268.1 187.1 60.6 49.5 79.3 7 48.1 98.7 105.7 284.1 406.8 169.1 77.4 16.3 28.1 8 15.9 89.8 56.7 151.7 173.7 236.5 78.2 29.0 13.9 9+ 6.5 58.0 63.4 156.2 131.9 201.5 114.8 24.4 36.8

SSB: 273.0 452.0 351.5 866.2 533.7 452.1 370.3 140.9 375.9

Age 1999 2000 2001 2002 2003 1 534.2 447.6 313.1 424.7 438.8

2 322.4 316.2 1,062.0 436.0 1039.4 3 1,388.8 337.1 217.7 1,436.9 932.5 4 432.0 899.5 172.8 199.8 1471.8 5 308.0 393.4 437.5 161.7 181.3 6 138.7 247.6 132.6 424.3 129.2 7 86.5 199.5 102.8 152.3 346.7 8 27.6 95.0 52.4 67.5 114.3 9+ 35.4 65.0 34.7 59.5 75.2

SSB: 460.2 500.5 359.2 548.8 739.2