Addendum 1 (1.926Mb)

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Resource Management Committee

REPORT OF THE

ICES CM 1999/D:2

Addendum l Ref. G

INTERNATIONAL BOTTOM TRA WL SURVEY IN THE NORTH SEA, SKAGERRAK AND KATTEGAT

IN 1996: QUARTER 2, 3 AND 4

The International Bottom Trawl Survey Working Group

This report is not to be quotcd without prior consultation with the General Secretary. The document is a report of an expert group under the auspices of the International Council for the Exploration of the Sea and does not necessarily represent the views of the Conncil.

International Council for the Exploration of the Sea Conseil International pour l'Exploration de la Mer Palægade 2-4 DK-1261 Copenhagen K Denmark

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TABLE OF CONTENTS

Section Pa e

llNTRODUCTION ...•... l

2 SURVEY METHODS AND PARTICIPATION ... 1

3 STANDARD OUTPUT FROM THE ICES IBTS DATA BASE ... 1

4 RESULTS FOR 1996 ...•... 2

5 HYDROGRAPHIC DATA ..•... 3

5.1 HYDRO·CHEMISTRY SURVEY ••••••••.•••••••••••••••••.•.•.•.•••••••••••••••••••••••••••...•.•.•.•.•.••••••••••••••.•.•...•••.••••••••••••.•.•.•.•.• 3

6 REFERENCES ... 3

Tables 2.1-4.10 ...•...•... 4

Fignres 4.1-5.6 ...•...•... 11

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- - - - ---~------

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l INTRODUCTION

This report presents the final results for the International Bottom Trawl Survey (IBTS) in 1996. The results for the first quarter IBTS are also given in separate reports, but first quarter indices are given in this report as well to gi ve a hetter overview of the changes within a whole year.

The data in this report comprisc the bottom trawl catches of the 8 standard spccies (herring Clupea harengus, sprat Sprattus sprattus, mackerel Scomber scombrus, cod Gadu.s morhua, haddock Melanogrammus aeRlefinus, whiting Merlangius merlangus, saithc Pollachius viren.!1· and Norway pout Trisopterus esmarki). Also summarised results of temperature and salinity sampling are presented.

2 SURVEY METHODS AND PARTICIPATION

For all matters on survey methodology, the reader is referred to the IBTS Manual (ICES 1996b). Details on the participation in the 1996 surveys are given in Table 2.1

3 STANDARD OUTPUT FROM THE ICES IBTS DATA BASE

For details on the standard analysis of the data the reader is referrcd to a description by Pedersen (1989). At request, eopies of this paper are available at the ICES Secretariat.

In 1994 the Herring Assessment Work:ing Group for the Area South of 62°N has adopted a new index for l- ringer abundance of North Sea autumn spawners. The new index is based on daytime catches in all statistical rcctangles sampled during the quarter l survey, both in the North Sea and in the Skagerrak/Kattegat. In the calculation of this index, catches made in rectangles with depth shallower than lO m, or deeper than 200m (250m in Skagerrak), have been given less weight (ICES 1993).

It is implicitly assumed that all l-ringer hcrring in the North Sea, Skagerrak, and Kattegat are autumn spawncrs.

Unsamplcd rectangles are allocated the mean catch rate estimatcd within "roundfish areas" and the indcx is expressed as the mcan catch rate (number per hour) for the entire survey area. The indiccs for 2+-ringers have been revised in the same way, with the exception that the catches in Skagerrak and Kattegat are assumed to be O.

This implicitly assumed that all 2+-ringcrs in Skagerrak and Kattegat are local or Baltic spring spawners. The usc of "zero" catches instead of "missing" catches of 2+-ringers in this area is convenient because it brings the indices of all age groups on a similar scale so that for instance mortalities can be calculatcd dircctly from the indices.

The above mentioned rules for scparation of autumn and spring spawners were intended for the first quartcr IBTS data. In this report similar rulcs have heen adopted as well for the second, third and fourth quarter data. The indices for 0-ringers in third and fourth quarter are calculatcd in a si mil ar way as for the 1-ringcrs.

The lBTS Working Group decided at the meeting in November 1995 (ICES 1996a) that saithe should be added to the list of standard species. The indices of saithe for each age group are calculated in a similar way as for l- ringer herring with the cxccption that also night-time hauls are used for saithe.

The Herring Assessment Working Group has also for sprat adopted a new index series (ICES 1993) in which only hauls between 10 and 150m depth are included. The standard area has remained the same: Division !Vb only.

For the index of the remaining speeies (cod, haddoek, whiting, Norway pout and mackerel), the catch at age per hour is averaged for all hauls within a rectangle, and the survey index is calculated hy taking the average of all rectanglcs withln a species-specific standard area. Rectangles where no haul was made, are excluded from the calculation.

The standard gear for IBTS is the GOV trawl, but in the third quarter of 1996 an Aberdeen 40ft trawl has been used hy "Scotia". See Knijn et al. (1993) for specifications of the Aberdeen 40ft trawl. In the calculation of indices it is assumed that all trawl types have the same size and tishing power.

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4 RESULTS FOR 1996

In the analysis only day-light hauls are used for herring, whereas for the other spccics all valid hauls are used, The number ofhauls used for hcrring and for the other species is shown in Figures 4.1 and 4.2.

The num ber of otoliths sampled per target species, per roundfish area and quartcr is given in Tab le 4.1.

Per spccies aset of figures gives the distributions of the 0-, 1-, 2-, and 3+ group and the mean length of 1-group fish per rectanglc. In the analysis a specific standard area for each species is used to calculatc the index of year class strength. This area is indicated in the figures. The distributions are given with dots of expanding sizc.

Within one page, showing 2 or 4 quarterly distrihutions, the same scaling has been used. The catch in number per hour of the higgcst dot is indicated. The surface area of each dot is relative to the averagc numbcr per hour caught.

The mean age composition of the eight standard species within the relevant standard areas is given in Table 4.2.

Historical abundance indices for the period 1991-1991 were recalculated November 1998, due to resubmission of data,

Herring

Indkes for 0-, 1- and 2-ringed herring are prcscnted in Table 4.3 and mean numbers per rectangle are given in Figures 4.3-4.6. Mean length per rectangle of 1-ringed herring are given in Figurc 4.7. It should be notcd that the term "age group" in herring refers to number of winter rings and not to years. All juvenile herring in the North Sea are assumcd to be autumn spawners, and this means that for instance age group l herring in February 1996 represent year el ass 1994.

Sprat

Sprat indices of 0-, 1- and 2-group are given in Table 4.4, The distribution of the same age groups and the 3+

group, as well a' the mean lcngth of 1-group per rectang1e, are shown in Figures 4,8-4.12,

Mackerel

Indices for mackerel are given in Table 4,5, The distributions of 0-, 1-, 2- and 3+ groups, and the mean length of l-group fish are given in Figurcs 4.13-4,17,

C od

Abundance indices are given in Tablc 4,6, The distributions of 0-, 1-, 2-, and 3+ group, and the mean length of 1-group fish are given in Figures 4, 18-4.22,

Haddock

Abundanee indices are given in Table 4,7, The distributions of 0-, 1-, 2-, and 3+ group, and the mean length of 1-group fish are given in Figures 4,23-4,27,

Whiting

Abundancc indiccs are given in Table 4,8, The distributions of 0-, 1-, 2-, and 3+ group, and the mcan length of 1-group fish are given in Figures 4,28-432.

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Saithe

Abundance indices are given in Tab le 4.9. The distributions of 2-, and 3+ group, and the mean length of 2-group fish are given in Figures 4.33-4.35.

Norway pout

Abundance indices are given in Table 4.10. The distributions of 0-, 1-, 2-, and 3+ group, and the mean length of 1-group llsh are given in Figures 4.36-4.40.

5 HYDROGRAPHIC DATA

5.1 Hydro-Chemistry Survey

Dctails concerning the data collccted during the three surveys are as follows:

Quarter 2: 201 stations from 12 April to 15 May from two ships (Michael Sars, Scotia))

Quarter 3: 308 stations from 13 July to 18 September from five ships (Walther Hcrwig, Tideman, Cirolana, Scotia, Argos)

Quarter 4: 140 stations from 9 October to 20 November from two ships (Dana, Cirolana)

Charts sbowing the distribution of bottom (<20m of bottom) temperature and salinity for each of the surveys are shown in Figures 5.1 to 5.6.

Digital (gil) copies of these cbarts may be retrieved or viewed from

http://www.ices.dk/oceanlproject/datasctsiiyfs.htm. The web si te also includes charts showing the location of the stations.

6 REFERENCES

Knijn LR, Boon, T.W, Heessen, H.J.L and Hislop, LR.G. 1993. Atlas of North Sea Fishcs. 1CES Cooperative Research Report. No. 194, 268 pp.

ICES 1993. Report of the Hcrring Assessment Working Group for the Area South of 62"N. ICES CM l 993/Assess: 15.

ICES 1996a. Report of the International Bottom Trawl Survey Working Group. ICES CM 1996/H: l.

ICES 1996b. Manual for the International Bottom Trawl Survcys. Rev. V. Addendum to ICES CM 1996/H: l.

Pedersen, L. 1989. International Young Fish Survey, computation of aggregatcd standard tables and charts. ICES Secretariat, scction computer management.

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Table 2.1 Participation and number of hauls in the IBTS for 1996.

Year Country Vessel Pc ri od Num ber of Hauls

1996 ABD GOV

Quarter l Sweden Argos 2911-15/2 49

Den mark Dana 2/2-18/2 46

Norway Michael Sars 1611-5/2 41

UK Scotland Scotia 8/2-25/2 45

Francc Tha1assa 14/2-27/2 41

Ncthcrlands Tri dens 2911-22/2 46

Germany Walter Herwig Ill 2011-6/2 62

Quarter 2 Norway Michael Sars 30/4-20/5 60

Quartcr 3 Sweden Argos 2/9-18/9 50

UK England Cirolana 10/8-8/9 86

Francc Thalassa (new) 3118-12/9 57

Netherlands Tridens 19/8-23/8 17

Germany Walter Herwig Ill 13n-4!8 33

Quarter 4 UK England Cirolana 23/ l 0-20/1 l 76

Denmark Dana 9/10-28/10 66

Norway G.O. Sars l 8/10-13/11 80

Gear used:

ABD Aherdeen 48ft trawl

GOV Grand Overture Verticale trawl

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Table4.1 Number of otoliths sampled per species, roundfish area and quarter in 1996.

Roundfish area

Specics l 2 3 4 5 6 ⁷ 8 9 Total

Quarter l

Herring 836 809 785 328 142 826 567 578 915 5,786

Sprat 131 278 115 208 159 328 203 109 247 1,778

Mackerel 167 8 ¹⁴ 189

C od 718 305 134 188 69 208 230 417 507 2,776

Haddock 693 818 940 399 15 239 219 144 3,467

Whiting 594 494 801 207 276 679 144 257 335 3,787

Saithe 155 4 5 43 207

Norway pout 240 270 279 124 59 87 52 ^1,111

Quarter 2

Herr ing 238 439 346 328 336 215 63 1,965

Sprat 34 137 122 142 124 43 602

Mackerel 120 46 58 5 229

C od 459 85 93 120 31 19 43 850

Haddock 700 416 377 151 l 3 48 1,696

Whiting 468 300 336 230 166 165 74 1,739

Saithc 181 7 38 226

Norway pout 156 58 93 44 27 379

Quarter 3

Herring 672 625 560 538 54 419 166 544 586 4,164

Sprat 45 78 Il l 145 223 229 24 207 1,062

Mackcrcl 267 227 120 81 130 509 1,334

C od 715 406 98 339 154 364 93 373 292 2,834

Haddock 1,727 885 750 564 24 76 276 99 4,401

Whiting 966 567 542 589 326 758 80 191 250 4,269

Saithe 726 9 4 l Il 751

Norway pout 543 163 141 37 19 113 73 1,089

Quarter 4

Herring 818 461 232 306 47 368 134 170 169 2,705

Sprat 20 156 157 106 39 225 56 7 96 862

Mackcrcl 92 50 7 25 4 134 312

C od 648 211 57 83 9 131 174 144 157 1,614

Haddock 1,110 513 527 274 lO 189 145 2,768

Whiting 592 329 316 189 139 198 134 1,897

Saithe 439 9 7 ^lO 146 611

Norway pout 301 107 72 47 22 549

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Table 4.2 Age composition of standard species in 1996 for the relevant standard areas.

Age

Quarter

o

l 2 3 4 5 6+

Herring l

.O

1,734.8 194.3 43.3 12.6 8.5

2 .O

1,313.5 900.7 220.6 25.8 16.4

3 ^2,677.0 ^1,286.0 ^189.7 ^113.0 ^47.2 ^42.1

4

^2,826.5 ^507.8 3,36.8 162.1 42.1 51.3

Sprat l

.O

232.6 557.5 176.9 22.4 I.l

2 .O 93.3 536.0 728.5 129.9

.O

3

^3.3 ^507.6 ^1,312.2 ^584.5 ^79.2 ^4.5

4

^4.2 ^349.5 ^338.5 ^73.7 ^3.5 ^.O

Mackerel l

.O

10.4 .7 1.2 .2 .2 .l

2

.o

^1.6 1.0 3.9 2.3 1.3 1.2

3

.o

48.4 49.4 23.0 4.9 3.5 7.7

4 19.9 5.7 2.3 3.1 1.4 .7 .5

C od l .O 3.5 8.0 6.0 .7 .6 .4

2 .O 1.2 5.7 3.1 .8 .3 .2

3 ^68.9 ^10.3 ^5.3 ^1.8 ^.4 ^.2

.O

4 ^23.3 ^20.4 ^3.4 ^1.2 .5 .2 .l

Haddock .O 267.4 813.3 65.9 46.7 7.7 3.1

2 .l 223.2 675.2 33.4 27.9 1.8 1.6

3 ^622.8 ^249.2 ^447.3 ^30.8 ^21.5 ^2.7 ^.9

4 879.4 218.6 518.2 32.9 28.7 3.5 1.7

Whiting .O 502.4 486.0 244.7 69.7 23.1 9.8

2 .O 378.3 381.8 165

o

50.7 9.1 4.2

3 ^314.9 ^545.0 283.2 125.6 32.7 7.5 4.0

4 270.4 365.8 334.7 88.5 37.0 11.3 6.9

Saithe

.O

.6 .6 1.8 17.9 1.5 .5

2

.O .o

^.l .4 6.3 1.4 1.4

3

.O

.4 .8 4.6 7.1 1.1 1.2

4 .2 .2 .6 6.0 18.8 .7 .5

Norway pout l .O 922.9 2,631.0 227.8 4.7 .l .O

2 .O 1,076.7 1,621.9 99.6

.O .O

.l

3 ^4,542.6 ^745.6 388.2 14.7 .8

.o .O

4 ^8,084.7 ^952.8 ^322.8 ^14.9 ^2.2 .l

.O

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Table 4.3 Herring IBTS indices as mean nnmber per hour within the species standard area.

O-ring l-ring 2-ring

Quarter Quarter Quarter

Year dass 3 4 l 2 3 4 l 2 3 4

1988 763 659 216 12

1989 1,180 1,867 2,570 454 380 767 453 300

1990 640 1,078 1,205 3,162 1,074 775 779 618 325 63

1991 2,902 3,317 2,954 2,121 1,137 294 1,094 596 889 196

1992 3,799 3,489 1,644 2,890 1,653 826 1,174 1,834 353 573

1993 1,552 2,989 1,215 2,560 503 2,798 194 901 190 337

1994 714 4,733 1,735 1,314 1,286 508

1995 2,677 2,827

Tab1e 4.4 Sprat IBTS indices as mean number per hour within the species standard area.

Age O Age l Age2

Year dass 3 4 l 2 3 4 l 2 3 4

1989 \14 644 !51 444

1990 1,118 !,liS 417 5,279 340 2,963 3,373 2,626

1991 16.8 l ,518 1,561 2,389 3,992 8,340 590 5,196 2,728 2,918

1992 56.5 2,916 1,689 7.815 2,575 9,476 1,368 1,020 501 6,166

1993 6.8 2,528 4,003 2,403 4,298 7,959 2,696 5,582 3,867 5.286

1994 5.2 1,051 l, !58 2,075 1,457 6,624 558 536 1,312 339

1995 0.3 526 233 93 508 350

1996 3.3 4

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Table 4.5 Mackerel IBTS indices as mean number per hour within the species standard area.

Age O Age 1 Age2

Year dass

3

4 l 2

3

4 l 2

3

4

1989 0.2 52.3 15.8 59.2

1990 6.9 11.3 26.0 60.0 0.4 2.7 46.7 6.2

1991 0.0 0.2 16.0 0.8 40.1 5.8 0.8 22.9 67.6 10.2

1992 O.l 1.4 l. O 3.8 91.3 8.5 O.l 3.7 64.6 18.2

1993 5.3 11.9 2.2 2.5 82.6 88.4 2.5 78.9 31.1 48.7

1994 0.0 0.2 0.4 1.9 15.1 9.7 0.7 l. O 49.4 2.3

1995 0.0 3.1 10.4 1.6 48.4 5.7

1996 0.0 19.9

Table4.6 Cod IBTS indiccs as mean number per hour within the species standard area.

Age O Age l Age2

Quartcr Quarter Quarter

Year dass 3 4 l 2 3 4 l 2 3 4

1989 4.7 5.4 2.5 1.9

1990 2.3 13.3 8.2 6.9 4.4 5.2 3.6 3.0

1991 29.4 28.4 13.0 51.2 43.8 36.4 19.5 13.6 8.0 5.6

1992 19.7 55.4 13.1 8.4 10.0 9.1 4.4 4.1 6.2 6.0

1993 17.0 25.4 14.8 30.8 43.2 52.9 22.1 20.5 17.4 13.6

1994 15.7 20.5 9.8 12.2 18.1 23.6 8.0 5.7 5.3 3.4

1995 15.1 21.9 3.5 1.2 10.3 20.4

1996 68.9 23.3

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Table 4.7 Haddock IBTS indices as mean number per hour within the species standard area.

Age O Age

l

Age2

Quarter Quarter Quarter

Year

dass 3

4

l

2

3

4

l

2

3

4 1989 133 74 23 35

1990 678 794 233 497 344 257 187 214

1991 720 1.134 l, 115 740 590 861 541 317 142 201

1992 2,717 2,474 1,254 1,121 604 906 504 339 265 355

1993 572 667 229 249 194 346 201 159 !06 213

1994 1,772 3,405 1,356 1,450 1,027 2,!08 813 675 447 518

1995 517 548 267 223 249 219

1996 623 879

Table 4.8 Whiting IBTS indices as mean number per hour within the species standard area.

Age O Age

l

Age2

Quarter Quarter Quarter

Year class

3

4

l

2

3

4

l

2

3

4 1989 6R6 335 159 251

1990 1,009 1,381 701 917 678 358

298

360 1991 529 759 904 881 595 682 524 244 177 324

1992 1,382 1,195 1,088 743 634 756 637 331 223 564

1993 916 1,014 721 737 675 926 449 637 291 498

1994 610 926 679 1,277 620 990 486 382 283 335

1995

⁷²⁹

1,666 502 378 545 366

1996 315 270

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Table 4.9 Saithe IBTS indices as mean number per hour within the species standard area.

Age2 Age3 Age4

Quarter Quarter Quarter

Year class 3

4 l

2 3 4

l

2 3 4

1987

^3.0 ^3.1 ^0.5 ^1.5

1988

^6.6 ^6.0 ^2.2 ^11.6 ^4.2 ^6.9 ^2.8 ^3.5

1989

0.7 0.6 0.8 0.8 1.4 1.5 1.5 1.6 2.8 1.9

1990

^0.4 ^0.3 ^0.6 ^1.2 ^8.7 ^7.3 ^10.8 ^6.8 ^1.6 ^2.0

1991

^1.9 ^1.6 ^4.0 ^1.4 ^1.3 ^2.3 ^I.l ^1.2 ^2.7 ^1.2

1992

^0.6 ^0.8 ^0.5 ^0.6 ^16.8 ^16.8 ^17.9 ^6.3 ^7.1 ^18.8

1993

0.7 0.6 1.8 0.4 4.6 6.0

1994

^2.8 ^0.6

Table 4.10 Norway pout IBTS indices as mean number per hour within the species standard area.

Age O Age

l

Age2

Quarter Quarter Quarter

Year class

3 4 l

2

3

4

l

2

3

4 1989

⁷¹³ ⁵⁸⁶ ²²² ⁴³

1990

^2,451 ^2,843 ^1,105 ⁸⁶³ ⁹³⁵ ^{l, 149} ⁶⁴⁰ ³¹³

1991

^7,383 7,451 8,095 7,134 4,366 4,658 2.644 1,253 609 580

1992

^2,588 5,984 2,681 2,075 1,832 1,767 374 437 102 216

1993

^4,104 ^4,775 ^1,870 2,814 704 1,973 785 710 597 260

1994

^3,196 ^18,083 ^5,940 10,387 4,440 5,610 2,631 1,622 388 323

1995

2,860 1,633 923 1,077 746 953

1996

^4,543 ^8,085

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Number of daytime hauls. 1996 quarter 1 Number of daytime hauls. 1996 quarter 2

~ ~ U EU YD Fl ~ ~ f4 F5 ru F7 ~ Fø GO Gi G2

l "

! 51

-4 -3 -2 -1 o 2 3 4 u ill 11 u JJ -4 -3 -2 -1 o

' "

~:llll121J

Number of daytime hauls. 1996 quarter 3 Number of daytime hauls. 1996 quarter 4

[O Ei E6 EO FO fl F~ F3 f4 F5 !'o F7 FH fQ r.o Gl G2 Eo E7 [1\ Eg FO Fl f2 fJ F4 f5 FO F7 f6 FQ GO Gl G2

.

'"

~

h

; ^____·~

:

'

i;:;~\,

-4 -3 -2 -1 o

' '

Q l J U l : l J J -~ -3 -2 -1 o l 2 J 4 ~ o 7 6 g Xl 11 12 13

Figure 4.1 Number of valid daytime hauls.

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Number of hauls. 1996 quarter

l

-4 - l -2 -1 o

' '

⁷ ¹¹ ^\l ^ID ¹¹ ¹² ¹³

Number of hauls. 1996 quarter 3

Eo E7 EB Eg Fo Fl F2 F3 f4 F5 F6 f7 f~ Fil CO Gl G2

>~

:r _-):::1(

"'· l i

-1 -3 -2 - l o

Figure 4.2

2 3 4 ~1()11~13

Number of valid da y- and nighttime hauls.

Number of hauls. 1996 quarter 2

-

^{l "}

"

..

J:: ^"

-4 -3 -2 -1 D

' '

Number of hauls. 1996 quarter 4

-4 -3 -2 - l o 1 2 3 4

, '

^!l ¹⁰ ¹¹ ¹² ¹¹

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Herring, Age group O

Abundance index: 2677

o <

:;~\\,

~ j

" '

-4. -3 -2 -1 o

1996 quarter 3

Figure 4.3 Hcrring: mcan catch number per hour, 0-ringers.

Herring, Age group O

-4 -3 -2 -1 o

1996 quarter ~

l

liJ 11 l2 13

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~rring, Age group

1

J

~~:Udancc

index: V35

1996 q~~ Herring, Age group

1

l

1996 · quarter 2

- :ff ... , ...

~

-- -- :

----~--~l~

····(

^-+--

---!

---! ---'--·---~--- --+

-4 -3 -2 -1 l) l 2 3 1 7 8 9 1 0 1 1 1 2 1 3

Herring, Age group

1

1996 quarter 3

~L.l

'

- r----....J

o ·

-4 -3 -2 -1 o

~-

• _•

•

40860 (max.) 13620

4540

234~578>11fl1112l1

33

Figurc 4.4 Herring: mean catch number per hour, 1-ringers.

,"

.

"

•

⁷⁴¹⁸

L_ _ _ _ _ ____ _ j

-131

-4 - 3 - 2 -1 o l 2 3 4 7 8 1 J D L 1 1 2 l 3

Herring, Age group 1 1996 quarter 4

:Ji

^u -····. um:

nf:',:"

o'!--- -i--~--

^j___ ^-__^••^••^•^••^•

-.•.-•.•_;,-~_--~,r_'_

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r:::::::::·::<::::r , __ ---:-

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~+---~-- ····'···f··*

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-~ : · • u • • • u u • • u u • • •

"!~<l::::" ~---,

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.

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-·1 -3 -~ - l o '

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8502 2844

7 il [l ID 11

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(19)

Herring, Age group 2 1996 quarter 1

Abundancc index: 194

~ E7 E6 ~ ~ ft ~ n ~ ~ ru f7 ~ ~ Go Gi G2

;~=

- 4 -3 - 2 - 1 lJ lO 1t 12 \3

Herring, Age group 2 1996 quarter 3

Abundanr:e index: 190

~ .,/-- V·---~).

'

"

l'

! l ~l

li ~o ,'

l i 49

-4 -3 -2 -1 o lO 11 12 1J

Figure 4.5 Herring: mean catch number per hour, 2-ringers.

15

Herring, Age group 2 1996 quarter 2

•

4822B (mB.'<.)

•

¹⁶⁰⁷⁶

-·1 -3 - 2 -1 o liJ 11 12 13

Herring, Age group 2 1996 quarter 4

Abundanr.r: indcx: 337

"

(20)

l Herring, Age group 3 + 1996 quarter 1 Herring, Age group 3 + 1996 quart~ ^"

1 EH D E~ ~ ru h n n ~ F5 rn F7 n ~ ~ Gl ~

-4 -3 -z -1 o 9 D U 12 L3 -·1 -~ -2 -1 o

Herring, Age group 3+ 1996 quarter 3

-!---~--

^-~---~.-'<)':

---~1-'-. -

'.:

•• .

^. .1~~,---'

•

""1---'---:-

···+---- t

l

-4 -3 -2 -1 o l l 9 } ) 1 1 1 2 1 3 -4 -3 -2 -1 o

Figure 4.6 Herring: mcan catch number per hour, 3+ringers.

----~~

"

: ::_·-_r=/~f

".~-~

s~!;;"t

·_- --- <:s1?

'~

--~·-pv:

\

·l·.::

^_·,50

"

)V 11 12 l3

In

! . .

l "

l

9 1 l J 1 1 1 2 1 3

(21)

l

Herring, Age group 1 1996 quarter 1 Herring, Age group 1 1996 quarter 2 :

_EQ _ru _fl _~_n _~_F5 _~_F7 _{~ ~ ~}_{Gl G2}

~-~F-+--'i='i'=

___ ,;=,-;=' ^{; = '}=t--···

.---~~~:=;c=:=::::o:~::::_c,,

~,---· ---~

++:}i -

ⁱ ^{i ' ---}

-Wr.

2

1

^{- i '}

·~

~ I :

ⁱ

^~

^---

i ^~ ^~ ::

~ -~··,;-~-:~:

^{i \ '} ^--

(~~

^'::

~ ):~:·=E::i;[::i::f;r;;;~~~~fi~. ::

: ~~\~l;,;l=~=t:r:::::::t~

1' ^'J~3_j ¹³²

ⁱ

^{142: 139} :-~~-: ~--:·~-:.~.:-~.: ... ';

Ea E7 E8

"

^----c

;o ···--·--- ---:

"

~ ~i~':)' ~c :;::-~

-~~~-' .-- -~-' - - -31

' ' - t- l - t

- 4 - 3 - 2 - l o l l 1 0 U l 2 1 J -1 -3 -2 -1 o

'

l ! J l l t . : ! l J

Herring, Age group 1 1996 quarter 3 Herring, Age group 1 1996 quarter 4

1 1"

"

-4 -3 -2 -1 o 1D 11 12 13 ll

Figure 4.7 Herring: mean length (mm). 1-ringers.

(22)

. · - · · ·

rat, Age group O

1ndance index: 3.3

-- . __ - -,!

/.S)\

-4. -3 -2 -1 o

1996 quarter 3

• _•

⁴⁶³^(max.)

154 51

'

ill n n

3~

;14 i 33

,,

'l li 32

11"

c

Sprat, Age group O

ALundance indox: 4.2

-·\ -3 - 2 - 1 o

Figure 4.8 Sprat: mean catch number per hour, age-group O.

1996 quarter 4

:0 11 12 D

(23)

Sprat, Age group 1 1996 quarter 1

f;:lt:

,.

^·---;o~·

····~

F:'"Jf

~"

TL((

o ;

"'i

1 ;

---·---..:---- ~ ... ,

: .... ···t.;

.)('kr_

A

:W;t-

~ i··'$· ' ....

i . i re- .> ...•.

f----1- -:-

i----_--·:·---i: ----\·----!---,

-~--···•· ·· ·--~ ··1--·--r

'

/ : --- ----. ' .. ' "" f-.., .J

/1). : - • : . : : . • ~-/. ^• ~ ^{' "}

: l, ... -c~.\.':···· ^L ^• ^•

:-; -~-- ~ --, --··: ---~---~----~---···· !) --.1 : 11f1~

l

! l '- ----·- ___ :-~.l.

:

^----y-- ^{• •}l, ~/Jf

y \

^~_/ ⁴⁰

:g

\+.- ---,---,--- • •• ~- ~. ~h~r)~,.-~

³⁹

~?' ~~---;- : • : • : -.-... ~ •• -.. ' : .) , ~--~ '

³⁸

~ ::::'~; \ ____ :_-~--1 • : • : . _ -- --:--:r:-j ~:f~:T~t

³⁷

.".

^~~

:. :.

^:-~(Sr~ ^i3tl

::_~---i •

^{i •}

-~ ~(---- 3~

"'-~ " i • : : ·l • 7923 (max.) 34

\.; ---~ ···/

.'='c ""/ ^'---'~

..c-~-~~_r]{-_:····

"'<-

^{·+ /}

---:·):::_~

^{: ::} ^{',-:,, ::}

l ~~--~-~~=:;:::=:;:=;:::::2:::;:=:;/~;::;::=:::;;;~;;==·---:_1

³¹

;;t i -•---j-"

- 1 -3 -2 -1 o O ID 11 ll 1J

Sprat, Age group 1 1996 quarter 3

EB E7 ~ ~ rn fl f2 f3 ~ ~ ~ ~ F6 ~ CO Gt l~

'

~"

!._j"

!i

50

I.l )(l 11 12 13

"'

'

; 4/\

Figure 4.9 Sprat: mean catch number per hour, age-group l.

Sprat, Age group

¹

1996 quarter 2

Abundance index: 93

-4 -~ -2 - 1 o ,. 10 u 12 13

Sprat, Age group 1 1996 quarter 4

-~ -3 -2 - t o

(24)

___

, _ " - - - · ,

~t. Age group 2 1996 quarter l

l Ab~r~dance

index: 558

-:--æ~ 11."

' ^::~"- l"

... ,. ...

~i---

;; ~ ... -..

:--

^--

:

,·~:::, .. : r ^{~, ,~~}

~ l--~---:

rk

--~

~ ^!

f--

'""·'/

;:; C-::J

---+----··!

--- -~- --, ----·l

'

-4 -3 -2 -1 o lV ll 12 13

Sprat, Age group 2 1996 quarter 3

EO E? E5 ~ ru Fl F2 ~ ~ FS ~ ~ fB ~ ~ Gt G2

•... ~-. ---. --- -+---+-

·+--

8.

+":•·:~·""

^{-'-- -+··}

11"

( 51

l ;o

! 49

- 4 -~ - 2 - l o 0 J D U 1 2 1 3

Sprat, Age group 2 1996 quarter 2

Abrmdance index: 536

Sprat, Age group 2 1996 quarter 4

o

·~·~;i

Figure 4.10 Sprat: mean catch number per hour, age-group 2.

20

(25)

Sprat, Age group 3 +

- 1 - 3 - 2 - 1 o

~-- ....,.-__:.

- l

' Sprat, Age group 3 +

-4. -3 -2 -1 o

1996 quarter l

" u ^U D

1996 quarter 3

9 1 0 l l l 2 L " 1

Sprat; Age group 3 +

~r ... .

~-i

-4 -3 -2 - t o

Sprat, Age group 3 +

Figure 4.11 Sprat: mcan catch number per hour, agc-group 3+.

1996 quarter 2

1:"

_{1 Sl}

--- t---t - - - ; -

6 \l 'Ill u 12 13

1996 quarter 4

• •

2011 (max.)

670 223

l l "

(26)

Sprat, Age group

1

1996 quarter 1

-4 -3 -2 - l o H U

Sprat, Age group 1 1996 quarter 3

"" ••

""~:"""+

g ···-+-- . 1-~

+---

~----.C~-- ^{: 121 :}

L

- 4 - 3 -2 -1 o ti u

Figure 4.12 Sprat: mean length (mm), agc-group l.

22

Sprat, Age group

1

F.O E7 EO Eg

~~-,---1-

+ ----)-

-~ -3 -2 - l o

1996 quarter 2

'

^H

l ::

"'

_ti

Sprat, Age group 1 1996 quarter 4

~::

1"

l

L.~-

-4 -3 -2 -1 o ID ti u

(27)

- - - c - - - -

Mackerel, Age group O 1996 quarter 3

Abundance index: 0.0

---.l,.;_-

---.. +---f- g -

····-r·---~

----, ... , ... , .... -,----,

o (max.)

o o

"

35

.

"

n

"

-4 -3 -2 -1 o 1 0 1 1 1 2 ! . 1

Mackerel, Age group O 1996 quarter 4

Abundance index: 20

~ >7

:-(

" \~

;__:;;:.,

_-_·_-_, _ _ _ , _ - _ ' _ ' _ _ _ _ _ _ _ _ _ ' _ _ ' _ \ ! JO - 11 12 L3

Figure 4.13 Mackerel: mean catch number per hour, age-group O.

23

(28)

Mackerel, Age group 1 1996 quarter 1

Abundance index: 10

Ea E7 U Eg ru h n n ~ ~ ~ F7 fB ~ CO Gl G2

'

^~

;; .:

~ .. ^.

^: ^<'^{~ ~}

^.hk

'\]

^. ^.^.

• ^·~~ _~t.

/}~

. _'

_.

""'t:

~

^... ^:

^- !:(<~

/

^.~^.,

. ^.^.

~{Y

^,

~

. . .

j ^.

(Vt. ~~ ·)

1:

^. ^. ^. ^. ^. ^.^:

' '

i 5

' ' ' ' ' •

• '

l '

~i ^: ^...

'. .

. ..

^~

.i

?~/]

,l; fr"; ^'

.. ~. :\.., > _' _'

^o

~

'~ ~!

^" ^)j

^E::l?

^{: 3}

~ _: V

'

.~

,;

'\_

~"·

'

~

,.L

^l ^•

'

'1 ' , no4 (max.)

'

•

³³⁵

"' /

i: ... '

.-~;;c·~ ^l

•,f •

¹¹²

_"

.

'

' ^--

'

^'

- 4 -:J -z ^-1 n 1 2 :l " 5 l:l 7 Il u ID n 12 JJ

Mackerel, Age group 1 1996 quarter 3

Abundance index: 48

'K:IBS (max.) 362

•

¹²¹

l ::

: 50

i -1!1 :,_Ul

"

'"

"

l "

~

^{l : :}

-4 -3 -2 -1 O l 2 3 4 ~ 5 7 6 !l ID 11 l2 13

Mackerel, Age group 1 1996 quarter 2

Abtmdance index: L6

~-:-

; i---:---

i :

>:'T"\ f .r''···!'j·!

) /

•

⁵⁸^(max.}

19 6

-4 -3 -2 -1 o 1 2 3 4 5 6 7 o il 10 11 12 13

Mackerel, Age group 1 1996 quarter 4

2f]'···' · ^' ^' .. · ^' ··· ...

. ~~-

^~

^.

;; i ... : .. · ' :;;,;~.J~

', . : -~-- ... ··· ' . .. ~p~

8,; : i · . ·~ ,.,,

--- .. ... -/1.,.._,.,..;.- fl '~,,::--~ /\

.

^.,

--- -- --'

---;.jO-~: /'L..J' -/'

~7 ·\

.. \ , ,-oc:

------~---__ : ______ :_ ----~---·-· .. ____ ; ___ _

v---•· .. . ,... ... ...

c__,·-~./

... .

"

;o

155 (max.} 34

•

52

"l_, - 17 32

s~e-e-'-"'='z ¹ ~··=··_-~:/"~--~;-~=~::;-.::::-;-;-;-~.~-=~"

-~ - 3 - 2 -1 O l 2 3 4 ~ 5 7 5 9 ID 11 l2 1.1

Figure 4.14 Mackerel: mcan catch number per hour, age-group l.

24

(29)

Mackerel. Age group 2 1996 quarter 1

Abtmdance index: O. 7

-4 -3 -2 -1 o Q l!} l1 12 13

Mackerel, Age group 2 1996 quarter 3

Abundance index: 49

697 (max.) ³⁴

299 ³³

~~~~~~~-·~

^{. - · '}⁰⁰^. ¹

^ri::

-t---+--+----t- '

---,---~

o l 2 3 { 1 ] [ ) 1 1 1 2 1 3

Maqkerel, Age group 2 1996 quarter 2

Abundance index: lO

---- ---c-- -

.

^~-^:. ^•----+--

l "

l' ::

g :--

~-~-i---

··f ·---~ ----,--

.'

... ;

---:

29 (max.) 10

3

- 4 - J -2 -1 o {l JO 11 12 1.3

Mackerel. Age group 2 1996 quarter 4

Abundance inJex: 2.3

E6 E7 E8 ~ FO n F2 F3 ~ ~ ~ n ~ ~ ~ Gt G2

'

?,J-"\~

l\

36jmax.)

12 4

1'. 1 0 1 1 1 2 1 3

"

Figure 4.15 Mackerel: rnean catch num ber per hour, age-group 2.

25

(30)

'0 \ , .

i

;''···'···c- ₁

1

'

•

-

-4 -3 - 2 - t o l l 3 4 5 tl 7 1l .. w 11 12 1.3

Mackerel, Age group 3 + 1996 quarter 3

•

• .. ti]lf

^{, ---c}--~-

l

-4 -3 -2 - l o ^l 2 3 4 5 Il

• ''"

i·

: 45

270 33

90 l

---~-J-131

'

6 \ l 1 D 1 1 1 2 1 3

Mackerel, Age group .3 + 1996 quarter 2

E5 D U rn ru Fl ~ h ~ F~ ~ F7 ~ ~ GO Gt ~

~f: ... -- '

1:

r1

·,: ____ __;

-4 - 3 - 2 - 1 o l 2 3 1

Mackerel, Age group 3 +

.,.

^-

^',,

l

"

7~\l11J1112l3

1996 quarter 4

E!l E7 EB Eg Fo Fl F~ f3 F4 F5 FO F7 F8 fg co Gt G2

~~

-4 -3 -2 -1 o l 2 3 4 ' 5 3 9 1 1 1 1 1 2 1 3

Figure 4.16 Mackcrel: mean catch number per hour, age-group 3+.

26

l·

(31)

Mackerel, Age group 1 1996 quarter

l

~-~·:·-···r··· ^... ^l:

: 23 :

: 21 ···r---~--

----{--- ---, ----' ---~

- 4 - 3 -2 - 1 o l l

11 ::

l'

1

·.'"

"

!. 4~

"

'

.,

l 0 1 1 1 2 1 J

Mackerel, Age group

l

1996 quarter 3

-~ -3 -2 -1 o ^Q u 11 1.2 1J

Figurc 4.17 Mackercl: rnean length (cm below), age-group l.

Mackerel, Age group

l

1996 quarter 2

- 4 - 3 - 2 - 1 o >l ID 11 12 13

Mackerel, Age group

^l

1996 quarter 4

l

J ^i:: ^" ^"

^H

c

l ! l i J l l U I J -~ - 3 -2 - l o

(32)

Cod, Age group O 1996 quarter 3

Abundance index: 69

~ ' • • '·---•---L --- -'----··-:·----:

:0 i---

---!--

----:---J, ----f ---+-- ---.---;---···;···i-···

---·--. ·t·--r_:-::r·

---,.

l ' ' • :

:" ^t:~ ' :

ⁱ

^~

^{: '}

., .

.

---

'' '\

~~j---7

~r"z

' • • _•

²⁴⁰¹⁶⁰⁰₂₆₇^(max.)

-4 -3 -2 -1 o

' •

^u

"

l,.

"

~ o

Figure 4.18 Cod: mean catch numher per hour, agc-group O.

28

Cod, Age group O 1996 quarter 4

Abundance index: 23

• ^•

_•

g:J _~:~

-1 -3 - 2 - l o

'

^ID ^{i l}

"

^o

l

"

n

"

_j

(33)

Cod, Age group 1 1996 quarter 1

• _•

²⁷⁰₉₀^(max.)

i_ 51

! 50

- 1 -3 - 2 - l o 1 2 3 4 ~ o 7 ~ 11 Il Il l2 IJ

Cod, Age group 1 1996 quarter 3

Abundance index: 10

Eo E7 EH EU ~ fl n ~ N F5 ~ F7 FB fG GO Gi ~

"

^~

Figure 4.19 Cod: mean catch numbcr per hour, age-group l.

29 Cod, Age group 1 1996 quarter 2

Abundance index: 12

"]' ^·~

:r ..

~'1.·.0'"

_:_/

"l!!\, .

^~

r.·[' : : ; \ ,

~t

~-

----; ---,-

.

^~~~

~/'7'

1!==;:::=;::::==-:_,~-

~~ ~~

.

• 30 (max.)

10

-4 -3 - 2 -1 o 3 4 5 B 7 6 9 . 0 t i 1 2 1 : l

Cod, Age group

¹

1996 quarter 4

Abtmdance index: 20

i_ Hl ' ~-4B '' 47

l

(34)

~---~---

Cod, Age group 2 1996 quarter 1

o o

l

~ i

...

···~

··l · • .L!.

• • • .. • ~ >;

l~ . . • • l. ^~;r

. . . . . ^.

^·~

,"

l .• 142

l"

-4 -3 -z -1 n 1 2 3 4 5 t1 7 ~'> 11 u u 12 J:t

Cod, Age group 2 1996 quarter 3

-4 -3 -2 -1 o 1 2 3 4

~ F5 ~ f7 n fQ CO Gt C2

' ' '

• •

136 (max.) 22

7

. t---+--c --+-

8 9 1 0 1 1

Figure 4.20 Cod: mean catch number per hour, age-group 2.

30

Cod, Age group 2 1996 quarter 2

J~"(,

-4 -3 -2 -1

'

o

~-

'

)~4

' '

58 (max.) 19

6

' '

⁷ ⁸ ^g ^ID ^Il

Cod, Age group 2 1996 quarter 4

Et! E7 E~ E9 FO 1'1 F'2 F3

:o - --'---·----

·+

g

l

,'

l.-

'

"

·.,

(35)

Cod, Age group 3 + 1996 quarter 1 Cod, Age group 3 + 1996 quarter 2

•

3e:J (max.) 127

-4 -3 -z -1 u O t J \ 1 1 2 1 3 -4 - 3 - 2 -1 o

'

^\0 ¹¹ ¹² ¹³

Cod, Age gro up 3 + 1996 quarter 3 Cod, Age group 3 + 1996 quarter 4

~ E7 Fa ~ ro Fl F2 F3 ~ ~ ~ ~ Fe ru ~ Gl ~ EC E7 E8 Eg ~ Fl ~ ~ ~ ~ ~ F7 n ru ^~Gl Gz

-'----'----1 '

' '

3 1 1 1 0 1 1 1 2 . 1 3

L

Figure 4.21 Cod: mcan catch number per hour, age-group 3+.

(36)

Cod, Age group 1 1996 quarter 1 Cod, Age group

1

1996 quarter 2

Ee E7 E6 Eu ru Ft f2 FJ ~ ~ F6 F7 ~ ~ ~ rn GZ

~"

51

;; i-

'19

l 'i:

-4 -3 - 2 -1 o ]() 11 12 13 -4 - 3 - 2 - l Il ID 11 12 13

Cod, Age group 1 1996 quarter 3 Cod, Age group 1 1996 quarter 4

E6 E? E8 Eg FO Fl f2 F3 F4 F" F6 F7 F6 Fil GO

... ··' .. ----~--

l,

g~i ----+--

-4 -3 -2 - l o

Figure 4.22 Cod: mean lcngth (cm below), agc·group l.