CM_1998_D_11.pdf (4.420Mb)

Resource Management Committee

REPORT OF THE

ICES CM 1998/D:ll Ref. G

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

IN 1994: QUARTER 2, 3 AND 4

by

The International Bottom Trawl Survey Working Group

This report is not to be quoted 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 Council.

International Council for the Exploration of the Sea Conseil International pour l'Exploration de la Mer

Palægade 2-4 DK-1261 Copenhagen K Denmark

TABLE OF CONTENTS

Section P age

l INTRODUCTION ... 2

2 SURVEY METHODS AND PARTICIPATION ... 2

3 STANDARD OUTPUT FROM THE ICES IBTS DATA BASE ... 2

4 RESULTS FOR 1994 ... 3

5 HYDROGRAPHIC DATA ... 4

5.1 HYDRO-CHEMISTRY SURVEY ... 4

6 REFERENCES ... 4

Tables 2.1-4.2 ... 5

Figures 3.1-5.6 ... 8

0:\Scicom\Rmc\lbtswg\Reports\1994_234\Report.Doc

l INTRODUCTION

This report presents the final results for the International Bottom Trawl Survey (IBTS) in the second, third and fourth quarter of 1994. The surve y was formerly called the International Y o ung Fish Surve y (IYFS). In 1990 it was decided to combine the effort of the International Y o ung Fish Survey with a number of national surveys such as the English and Scottish Groundfish Surveys into a quarterly coordinated bottom trawl survey, to be held for a period of 5 years. These quarterly surveys started in 1991. This report presents the results of the quarterly surveys in 1994. The results for the first quarter IBTS are also given in separate reports, but first quarter indices a..re given in this report as well to gi ve a hetter overview of the changes within a whole year.

The data in this report comprise the bottom trawl catches of the 8 standard species (herring Clupea harengus, sprat Sprattus sprattus, mackerel Scomber scombrus, cod Gadus morhua, haddock Melanogrammus aeglefinus, whiting Merlangius merlangus, saithe Pollachius virens 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 1994 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 referred to a description by Pedersen (1989). At request, copies of this paper are available at the ICES Secretariat.

In 1994 the Herring Assessment W orking Gro up 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 rectangles 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 shallower than l O m, or deeper than 200 m (250 m in Skagerrak), have been given less weight. The weighting factors are given in Figure 3.1.

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

Unsampled rectangles are allocated the mean catch rate estimated within "roundfish areas" and the index is expressed as the mean catch rate (number per hour) for the entire survey area. The indices 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 all2+-ringers in Skagerrak and Kattegat are local or Baltic spring spawners. The use 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 calculated directly from the indices.

The above mentioned rules for separation of autumn and spring spawners were intended for the first quarter IBTS data. In this report similar rules have been adopted as well for the second, third and fourth quarter data. The indices for 0-ringers in third and fourth quarter are calculated in a similar way as for the 1-ringers.

The IBTS 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 (see above) with the exception 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 lO and 150m depth are included. The standard area has remained the same: Division IVb only.

For the index of the remaining species (cod, haddock, 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 by taking the average of all rectangles within a species-specific standard area. Rectangles where no haul was made, are excluded from the calculation.

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The standard gear for IBTS is the GOV trawl, but in the third quarter of 1994 an Aberdeen 40ft trawl has been used by "Scotia". See Knijn et al. (1993) for specifications of the Aberdeen 40 ft trawl. In the calculation of indices it is assumed that all trawl types have the same size and fishing power.

4 RESULTS FOR 1994

In the analysis only day-light hauls are used for herring, whereas for the other species all valid hauls are used.

The number of hauls used for herring and for the other species is shown in Figures 4.1 and 4.2.

The number of otoliths sampled per target species, per roundfish area and quarter is given in Table 4.1.

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

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

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

Herring

Mean numbers of 0-, 1-, 2- and 3+ ringed herring are given per rectangle in Figures 4.3-4.6. Mean length per rectangle of 1-ringed herring are given in Figure 4.7. It should be noted 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 assumed to be autumn spawners, and this means that for instance age group l herring in February 1994 represent year dass 1992.

Sprat

The distributions of 0-, 1-, 2- and 3+ groups, and the mean length of 1-group fish are given in Figures 4.8-4.12.

Mackerel

The distributions of 0-, 1-, 2- and 3+ groups, and the mean length of 1-group fish are given in Figures 4.13-4.17.

C od

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

The distributions of 0-, 1-, 2-, and 3+ gro up, and the mean length of 1-group fish are given in Figures 4.23-4.27.

Whiting

The distributions of 0-, 1-, 2-, and 3+ group, and the mean length of 1-group fish are given in Figures 4.28-4.32.

0:\Scicom\Rmc\Ibtswg\Reports\ 1994_234\Report.Doc 3

Saithe

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

The distributions of 0-, 1-, 2-, and 3+ group, and the mean length of 1-group fish are given in Figures 4.36-4.40.

5 HYDROGRAPHIC DATA

5.1 Hydro-Chemistry Survey

Details concerning the data collected during the three surveys are as follows:

Quarter 2: 279 stations from 14 April to 11 June from four ships ("Walter Herwig", ''Tridens", "Scotia", and

"Argos")

Quarter 3: 273 stations from 6 August to 22 September from five ships ("Thalassa", "Tridens", "Cirolana", "Scotia", and "Argos")

Quarter 4: 349 stations from 16 October to 20 November from five ships ("Dana", G.O. Sars", "Isis", ''Tridens", and "Cirolana")

Charts showing 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 (gif) copies ofthese charts may be retrieved or viewed from ftp://ftp.ices.dk/dist/ocean/iyfs/1994. The ftp directory also includes charts showing the location of the stations.

6 REFERENCES

Knijn J.R, Boon, T.W, Heessen, H.J.L and Hislop, J.R.G. 1993. Atlas of North Sea Fishes. ICES Cooperative Research Report. No. 194, 268 pp.

ICES 1993. Report of the Herring Assessment Working Group for the Area South of 62°N. ICES Doc. CM 1993/ Assess: 15.

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

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

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

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Table 2.1 Participation and number of hauls in the IBTS for 1994.

Year Country Vessel Period Num ber of Hauls

1994

ABD

GOV

Quarter l Sweden Argos 31/1-17/2 48

Denmark Dana 2/2-20/2 48

Norway G.O. Sars 6/1-26/1 27

UK Scotland Scotia 12/2-4/3 56

France Thalassa 5/2-20/2 54

Netherlands Tri dens 3111-24/2 46

Germany Walter Herwig Ill 19/2-21/3 94

Quarter 2 Sweden Argos 18/4-4/5 51

Norway Michael Sars 18/5-2/6 67

UK Scotland Scotia 14/4-3/5 76

Netherlands Tri dens 2/5-26/5 52

Germany Walter Herwig Ill 12/5-9/6 71

Quarter 3 Sweden Argos 5/9-22/9 50

UK England Cirolana 6/8-28/8 79

UK Scotland Scotia 2/8-21/8 89

France Thalassa 4/9-19/9 55

Netherlands Tridens 15/8-26/8 42

Quarter 4 UK England Cirolana 21/10-22111 81

Denmark Dana 26/10-20111 70

Norway G.O. Sars 11110-8/11 78

Netherlands I sis 24110-3/11 22

Netherlands Tridens 24/10-3/11 33

Gear used:

ABD Aberdeen 48 ft trawl

GOV Grand Overture Verticale trawl

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Table 4.1

Number of otoliths sampled per species, roundfish area and quarter in 1994 Roundfish area

Species l 2 3 4 5 6 7 8 9 Total

Quarter l

Herring 576 620 536 433 120 565 515 740 579 4,684

Sprat 71 184 180 135 98 292 161 284 1,405

Mackerel 32 2 34

C od 451 634 157 259 30 246 98 244 267 2,386

Haddock 845 1,038 944 328 2 223 210 70 3,660

Whiting 621 818 701 362 410 559 126 163 175 3,935

Saithe 407 10 16 434

Norway pout 176 267 142 162 74 70 891

Quarter 2

Herring 437 788 679 499 316 298 289 655 611 4,572

Sprat 18 120 179 177 116 187 148 192 293 1,430

Mackerel 126 36 19 7 14 56 5 ^2f~

C od 497 410 96 184 13 173 303 233 243 2,1~-

Haddock 849 646 531 401 l 167 168 52 2,815

Whiting 638 505 453 462 165 311 169 142 181 3,026

Saithe 421 5 34 62 20 542

Norway pout 206 166 118 153 25 65 43 776

Quarter 3

Herring 604 649 651 296 150 303 242 533 640 4,068

Sprat 25 175 197 233 153 183 76 110 174 1,326

Mackerel 166 139 173 76 214 387 1,155

C od 802 872 136 451 109 451 265 270 236 3,592

Haddock 1,682 934 857 416 140 4,030

Whiting 985 705 581 483 329 483 172 3,738

Saithe 548 11 20 579

Norway pout 326 147 114 157 9 753

Quarter 4

Herring 741 499 42 353 260 335 284 2,514

Sprat 19 145 91 124 142 183 94 7"

Mackerel 173 91 40 72 50 182 46 6.)..,.

C od 650 509 120 305 48 503 374 186 146 2,841

Haddock 929 485 460 253 3 130 2,260

Whiting 230 258 253 198 85 464 118 127 133 1,866

Saithe 319 58 12 389

Norway pout 378 119 59 138 25 81 800

O:\Scicom\Rmc\Ibtswg\Reports\1994_234\Tab4l.Doc 6

Table 4.2

Age composition of standard species in 1994 for the relevant standard areas.

Age

Quarter o

l

2 3 4

⁵

6+

Herring l

.O

1,666.7 1,093.6 199.3 63.6 40.0

2

.O

2,890.3 595.8 141.6 74.6 28.8

3 1,552.0 1,653.1 889.0 197.0 180.5 133.0

4 2,989.1 825.8 196.0 43.8 24.0 19.7

Sprat l

.O

4,002.9 1,368.0 127.0 2.7 .6

2 .l 2,402.5 1,019.7 330.2 18.8

.O

3 5.2 4,298.1 500.8 131.1 12.3

.O

4 1,051.0 7,958.7 6,166.0 654.9 .2 .6

Mackerel l

.O

2.2 .l .l

.O .O .O

2

.O

2.5 3.7 1.7 .9 .2 .7

3

.O

82.6 64.6 14.8 5.0 4.3 7.2

4 .2 88.4 18.2 6.3 2.4 1.4 2.9

C od l

.O

14.8 4.4 3.0 .8 .5 .5

2

.O

30.8 4.1 2.2 .5 .2 .2

3 15.7 43.2 6.2 2.4 .2 .l .l

4 20.5 52.9 6.0 2.2 .3 .l .l

Haddock l

.O

228.7 503.9 98.3 23.3 1.6 .8

2

.O

249.1 338.6 40.9 11.1 .7 .3

3 1,771.9 194.3 264.8 32.4 8.4 .4 .l

4 3,404.7 345.5 354.6 53.4 11.8 .7 .l

Whiting l

.O

721.0 637.0 179.8 66.6 11.6 8.9

2 .4 736.7 330.7 94.9 24.8 9.3 5.7

3 609.9 674.5 222.5 76.3 19.8 4.8 3.2

4 925.5 926.2 564.0 180.7 55.4 19.9 9.6

Saithe

.O

.l .5 3.7 10.1 1.4 .6

2

.o .O

.l 1.3 6.0 1.2 .9

3

.o .o

.6 1.3 1.7 .9 .9

4

.O .O

.8 2.4 2.0 .5 .6

Norway pout l

.O

1,867.8 375.4 67.0 2.9 .2

.O

2

.O

2,813.7 436.6 59.7 2.3

.O .O

3 3,195.8 704.4 101.6 13.5 .3

.O .O

4 18,083.0 1,972.7 215.7 20.3 .3

.o .O

O:\Scicom\Rmc\Ibtswg\Reports\1994_234\Tab4-2.Doc 7

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Figure 3.1 Weighting factors used in the calculation of the indices for herring and saithe. Numbers denote the relative weight of a given rectangle. Only weighting factors less than l are shown, other rectangles are given a weight of l.

Number of daytime hauls. 1994 quarter 1 Number of daytime hauls. 1994 quarter 2

E6 E7 E8 Eg FO Fl F2 F3 F4 F5 F6 F7 F8 Fg GO Gl G2

-4 -3 -2 -1 o l 2 3 4 6 7 8 g 1 Q 1 1 1 2 1 3 -4 -3 -2 -1 o l 2 3 4 g 10 11 12 13

Number of daytime hauls. 1994 quarter 3 Number of daytime hauls. 1994 quarter 4

E6 E7 E8 Eg Fo Fl F2 F3 F4 F5 F6 F7 F8 Fg Go Gl G2

-4 -3 -2 -1 o 3 4 6 7 8 g 1 0 1 1 1 2 1 3 -4 -3 -2 -1 o l 2 3 4 5 6 g 1 0 1 1 1 2 1 3

Figure 4.1 Number of valid daytime hauls.

Number of hauls. 1994 quarter 1 Number of hauls. 1994 quarter 2

E6 E7 E8 Eg FO Fl F2 F3 F4 F5 F6 F7 F8 Fg Go Gl G2

-4 -3 -2 -1 o 1 2 3 4 5 6 7 8 g 10 11 12 13 -4 -3 -2 -1 o 1 2 3 4 5 6 g 1 0 1 1 1 2 1 3

Number of hauls. 1994 quarter 3 Number of hauls. 1994 quarter 4

E6 E7 E8 Eg FO Fl F2 F3 F4 F5 F6 F7 F8 F9 GO Gl G2 E6 E7 E8 Eg FO Fl F2 F3 F4 F5 F6 F7 F8 Fg Go Gl G2

-4 -3 -2 -1 o 1 2 3 4 5 6 7 8 g 10 11 12 13 -4 -3 -2 -1 o 1 2 g 1 0 1 1 1 2 1 3

Figure 4.2 Number of valid day- and nighttime hauls.

Herring, Age group O 1994 quarter 3

Max mean catch number per recangle: 87062

-4 -3 -2 -1 o 10 u 12 13

Figure 4.3 Herring: number per hour, 0-ringers.

Herring, Age group O 1994 quarter 4

Max rnean catch number per recangle: 96387

-4 -3 -2 -1 o g 10 11 12 13

Herring, Age group 1 1994 quarter 1

Max mean catch number per recangle: 31931

-4 -3 -2 -1 o g 10 u 12 13

Herring, Age group 1 1994 quarter 3

Max mean catch number per recangle: 114941

-4 -3 -2 -1 o 10 u 12 13

Figure 4.4 Herring: number per hour, 1-ringers.

Herring, Age group 1 1994 quarter 2

Max mean catch number per recangle: 63883

-4 -3 -2 -1 o 10 11 12 13

Herring, Age group 1 1994 quarter 4

Max mean catch number per recangle: 34584

-4 -3 -2 -1 o 10 11 12 13

Herring, Age group 2 1994 quarter 1

Max mean catch number per recangle: 68579

-4 -3 -2 -1 o g 10 11 12 13

Herring, Age group 2 1994 quarter 3

Max mean catch number per recangle: 38598

-4 -3 -2 -1 o g 10 11 12 13

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

Herring, Age group 2 1994 quarter 2

Max mean catch number per recangle: 20249

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Herring, Age group 2 1994 quarter 4

Max mean catch number per recangle: 10970

-4 -3 -2 -1 o 10 11 12 13

41 40

Herring, Age group 3 + 1994 quarter 1

Max mean catch number per recangle: 16184

-4 -3 -2 -1 o 10 11 12 13

Herring, Age group 3 + 1994 quarter 3

Max mean catch number per recangle: 27644

-4 -3 -2 -1 o 9 1 0 1 1 1 2 1 3

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

Herring, Age group 3+ 1994 quarter 2

Max mean catch number per recangle: 5974

-4 -3 -2 -1 o ^{10 11 12 13}

Herring, Age group 3 + 1994 quarter 4

Max mean catch number per recangle: 2886

-4 -3 -2 -1 o ^{10 11 12 13}

Herring, Age group 1 1994 quarter 1

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Herring, Age group 1 1994 quarter 2

~+r=~~~~~~~T=~=T~~~

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Herring, Age group 1 1994 quarter 4

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Sprat, Age group O 1994 quarter 3

Max rnean catch nurnber per recangle: 1750

-4 -3 -2 -1 o g 10 11 12 13

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

Sprat, Age group O 1994 quarter 4

Max rnean catch nurnber per recangle: 75215

-4 -3 -2 -1 o 1 2 g 10 11 12 13

Sprat, Age group 1 1994 quarter 1

Max mean catch number per recangle: 118926

- 4 -3 -2 -1 o 1 2 3 4 7 8 g 1 0 1 1 1 2 1 3

Sprat, Age group 1 1994 quarter 3

Max mean catch number per recangle: 70730

: :

-4 -3 -2 -1 o 1 2 3 4 7 8 g 1 0 1 1 1 2 1 3

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

Sprat, Age group 1 1994 quarter 2

Max mean catch number per recangle: 80766

-4 -3 -2 -1 o 1 2 3 4 5 8 7 8 g 10 11 12 13

Sprat, Age group 1 1994 quarter 4

Max mean catch number per recangle: 176891

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Sprat, Age group 2 1994 quarter 1

Max mean catch number per recangle: 10077

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-4 -3 -2 -1 o g 10 11 12 13

Sprat, Age group 2 1994 quarter 3

Max mean catch number per recangle: 8739

-4 -3 -2 -1 o g 10 11 12 13

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

Sprat, Age group 2 1994 quarter 2

Max mean catch number per recangle: 10094

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-4 -3 -2 -1 o g 10 11 12 13

Sprat, Age group 2 1994 quarter 4

Max mean catch number per recangle: 142277

Etl E7 E6 Eg FO Fl F2 F3 F4 F5 Ftl F7 F6 FO GO Gl G2

-4 -3 -2 -1 o 10 11 12 13

Sprat, Age group 3 + 1994 quarter 1

Max mean catch number per recangle: 16368

-4 -3 -2 -1 o g 10 11 12 13

Sprat, Age group 3 + 1994 quarter 3

Max mean catch number per recangle: 5396

-4 -3 - 2 -1 o g 10 11 12 13

Figure 4.11 Sprat: number per hour, age-group 3+.

Sprat, Age group 3 + 1994 quarter 2

Max mean catch number per recangle: 7814

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: : : : : : : : : l : : : : : : : : 52

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-4 -3 -2 -1 o g 10 11 12 13

Sprat, Age group 3 + 1994 quarter 4

Max mean catch number per recangle: 10985

-4 -3 -2 -1 o g 10 11 12 13

Sprat, Age group 1 1994 quarter 1

~

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-4 -3 -2 -1 o 1D u 12 13

Sprat, Age group 1 1994 quarter 3

t)9:

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-4 -3 -2 -1 o 1D u 12 13

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

Sprat, Age group 1 1994 quarter 2

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te l l l l l l l l l l

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l l l l l l l l l

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l l l l l l l l l

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.,

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-4 -3 -2 -1 o 1D u 12 13

Sprat, Age group 1 1994 quarter 4

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-4 -3 -2 -1 o ^{1D u 12 13}

co

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Mackerel, Age group O 1994 quarter 3

Max mean catch number per recangle: O

E6 E7 Ea E9 FO Fl F2 F3 F4 F5 Fa F7 Fa F9 Go Gl G2

l l l '

' l l ' l l l

fi---+--T,?.

r r••J···· ^!··••: r••r••••i···:··· ....

-4 -3 -2 -1 o g 10 11 12 13

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

Mackerel, Age group O 1994 quarter 4

Max mean catch number per recangle: 10

' ' '

. ' '

l ' l l l t l

----T---r·----r·----r·----r·----r·----T---: e :

l l l l l l l l l

: ---T---r-•·r·----r·----r·----r---T---r·----r--- -- --

-4 -3 -2 -1 o 1 2 g 1 0 1 1 1 2 1 3

Mackerel, Age group 1 1994 quarter 1

Max mean catch number per recangle: 187

-4 -3 - 2 - 1 o l 2 g 1 0 1 1 1 2 1 3

Mackerel, Age group 1 1994 quarter 3

Max mean catch number per recangle: 6436

-4 -3 -2 -1 o g 1 0 1 1 1 2 1 3

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

22

Mackerel, Age group 1 1994 quarter 2

Max mean catch number per recangle: 245

-4 -3 -2 -1 o g 1 0 1 1 1 2 1 3

Mackerel, Age group 1 1994 quarter 4

Max mean catch number per recangle: 8982

-4 -3 -2 -1 o ^{g 10 11 12 13}

Mackerel, Age group 2 1994 quarter 1

Max mean catch number per recangle: 9

-4 -3 -2 -1 o 9 10 11 12 13

Mackerel, Age group 2 1994 quarter 3

Max mean catch number per recangle: 3816

-4 -3 -2 -1 o 10 11 12 13

Figure 4.15 Mackerel: number per hour, age-group 2.

Mackerel, Age group 2 1994 quarter 2

Max mean catch number per recangle: 246

-4 -3 -2 -1 o 9 10 11 12 13

Mackerel, Age group 2 1994 quarter 4

Max mean catch number per recangle: 1374

-4 -3 -2 -1 o 10 11 12 13

Mackerel, Age group 3 + 1994 quarter 1

Max mean catch number per recangle: 3

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

Mackerel, Age group 3 + 1994 quarter 3

Max mean catch number per recangle: 727

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

Figure 4.16 Mackerel: number per hour, age-group 3+.

Mackerel, Age group 3 + 1994 quarter 2

Max mean catch number per recangle: 108

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

Mackerel, Age group 3 + 1994 quarter 4

Max mean catch number per recangle: 834

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

Mackerel, Age group

1 1994

quarter

1

-4 -3 -2 -1 o 10 11 12 13

Mackerel, Age group

1 1994

quarter

3

N

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-4 -3 -2 -1 o 10 11 12 13

Figure 4.17 Mackerel: mean length (cm below), age-group l.

25

Mackerel, Age group

1 1994

quarter

2

~ ;::::::;:::::r·--r---r---r---;---c:::;::::::~-

a:; 1---r---~-~-~---~---i---. :

r---r---

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-4 -3 -2 -1 o 10 11 12 13

Mackerel, Age group

1 1994

quarter

4

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-4 -3 -2 -1 o ¹⁰ 11 12 13

37

Cod, Age group O 1994 quarter 3

Max mean catch number per recangle: 944

-4 -3 -2 -1 o 1 2 3 4 5 tl 7 8 9 10 11 12 13

Figure 4.18 Cod: number per hour, age-group O.

26

Cod, Age group O 1994 quarter 4

Max mean catch number per recangle: V89

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H---~---~---c·---t--'7--7--i·---c··----.!oS~ ... ~:' ____ ----~·--7--~: ______ L____l i i 52

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-4 -3 -2 -1 O 1 2 3 4 5 tl 7 8 9 10 11 12 13

co "'

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Cod, Age group 1 1994 quarter 1

Max mean catch number per recangle: 497

-4 -3 -2 -1 o 10 11 12 13

Cod, Age group 1 1994 quarter 3

Max mean catch number per recangle: 967

-4 -3 -2 -1 o 10 11 12 13

Figure 4.19 Cod: number per hour, age-group l.

38

M

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Cod, Age group 1 1994 quarter 2

Max mean catch number per recangle: 1275

+--+--!---i'---f---L -

-i---1--- -+--+---+---+----+---i-

⁵²

: l : : : : : : 51

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⁵⁰

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-4 -3 -2 -1 o 10 11 12 13

Cod, Age group 1 1994 quarter 4

Max mean catch number per recangle: 1789

-4 -3 -2 -1 o 10 11 12 13

Cod, Age group 2 1994 quarter 1

Max mean catch number per recangle: 58

-4 -3 -2 -1 o 10 11 12 13

Cod, Age group 2 1994 quarter 3

Max mean catch number per recangle: 68

-4 -3 -2 -1 o 10 11 12 13

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

Cod, Age group 2 1994 quarter 2

Max mean catch number per recangle: 38

-4 -3 -2 -1 o ^{10 11 12 13}

Cod, Age group 2 1994 quarter 4

Max mean catch number per recangle: 49

-4 -3 -2 -1 o 10 11 12 13

C od, Age group

3

+

1994

quarter

1 Max mean catch number per recangle: 45

-4 -3 -2 -1 o 10 11 12 13

Cod, Age group

3+ 1994

quarter

3 Max mean catch number per recangle: 33

-4 -3 -2 -1 o 10 11 12 13

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

29

C od, Age group

3

+

1994

quarter

2 Max mean catch number per recangle: 26

-4 -3 -2 -1 o 10 11 12 13

Cod, Age group

3

+

1994

quarter

4 Max mean catch number per recangle: 44

-4 -3 -2 -1 o 10 11 12 13

Cod, Age group 1 1994 quarter 1

~

r--r---r---r---r---r---r---r----r----:-

r----r---r---r--- ---r---L

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-4 -3 -2 -1 o 10 u 12 13

Cod, Age group ^{1 1994} quarter ³

-4 -3 -2 -1 o 10 u 12 13

Figure 4.22 Cod: mean length (cm below), age-group l.

Cod, Age group 1 1994 quarter 2

~

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-4 -3 - 2 -1 o ^{10 u 12 13}

Cod, Age group 1 1994 quarter 4

~

r----r---r----;---r----r---r---r---r----:-

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o;

L_ __

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-4 -3 -2 -1 o

: 45

10 u 12 13

Haddock, Age group O 1994 quarter 3

Max mean catch number per recangle: 26979

-4 -3 -2 -1 o 9 1 0 1 1 1 2 1 3

Figure 4.23 Haddock: number per hour, age-group O.

Haddock, Age group O 1994 quarter 4

Max mean catch number per recangle: 31827

-4 -3 -2 -1 o g 10 11 12 13