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THIS PAPER NOT TO BE CITED WITHOUT PRIOR REFERENCE TO THE AUTHORS International Council for the

Exploration of the Sea

ICES CM 1976/F:12

Demersal Fish (Northern) Committee THE RESULTS OF THE INTERNATIONAL O-GROUP GADOID SURVEY IN THE NORTH SEA, 1976

by

N Daan, Netherlands, Institute for Fishery Investigations, Ijmuiden J R G Hislop, Marine Laboratory, Aberdeen

M J Holden, Fisheries Laboratory, Lowestoft W G Parnell, Fisheries Laboratory, Lowestoft

H Knudsen, Danish Institute of Fisheries and Marine Investigations, Charlottenlund J Lahn-Johanesson, Institute of Marine Research, Bergen.

INTRODUCTION

The 1976 survey was carried out in the period~~3-30 June by 5 vessels.

CORELLA (England), DANA (Denmark), EXPLORER (Scotland), JOHAN HJORT (Norway) and TRIDENS (Netherlands). All vessels fished· the Dutch version of the international young gadoid pelagic trawl (IYGPT) except the EXPLORER, which fished the Scottish version. The survey was designed so that each of the statistical squares within the heavy broken line shown in Figure 1 was sampled twice, insofar as possible by different vessels, at as great a time interval as possible and in general more than 7 days. Each sample haul was of 1 hour's duration made in the manner described by Daan et a!., (1975), except that in water deeper than 150 m this depth was taken as the bottom and the mid-water haul made at 75 m or at the thermocline if one existed. In some parts of the northern North Sea two thermoclines were found, one close to the surface and one at a lower depth, in which case the latter was fished.

RESULTS Area fished

The statistical squares fished by each vessel are shown in Figures 1 and 2.

The survey was carried out as planned except that statistical rectangles 48 E7, 47 E7 and 46 F2 were sampled only once and that most of the samples from

statistical rectangles 41 F4-7 and 42 F4-7 were taken within 4 days. The hauls shown in Figure 1 are referred to as the first survey and those in Figure 2 as the second survey. Mean numbers of O-group cod, haddock and whiting per Ih haul for the three areas described by Daan ~ al., (1975) are shown in Table 1 and

average numbers per haul, mean length, standard deviation and range for all species by groups of 4 statistical rectangles in Tables 2 and 3.

1

Distribution

The mean numbers of each species of O-group gadoid caught in each survey by statistical rectangle are shown in Figures 3-8.

Cod were very widely distributed and, for the first year since the present coverage was achieved, were much more abundant off the Danish coast than elsewhere.

They were also more abundant off the east coast of Britain than in previous years, particularly during the second survey.

Haddock were, as usual, most abundant to the east of Shetland, on 'both , surveys. Few were caught off the Danish coast. They were widely distributed,

although not very abundant, along the east coast of Britain. In this area catches of haddock were noticeably greater during the second survey than in the first.

The distribution of whiting was different in the two surveys. In the first survey the largest catches were taken round the Orkneys and to the east of

Shetland, with small numbers occurring off the Danish coast; few whiting were found along the east coast of Britain. However, during the second survey the main area of abundance was along the British east coast. The numbers caught off the Danish coast and to the east of Shetland were also higher than in the first survey.

In both surveys saithe were scarce off the coasts of Britain and Denmark (ie south of latitude 57o

N). To the north of this latitude their distribution was widespread, with no real centre of abundance.

The distribution of Norway pout followed its usual pattern, large numbers being caught mid-way between Norway and Shetland and relatively few elsewhere.

In the second survey the main area·of concentration was farther to the north than in the first.

Small catches of blue whiting were made in four rectangles only, all in the northern part of the survey area.

For all species, except saithe and Norway pout, there was an increase in average nmnbers per haul between the first and second surveys (Figures 2-8 and Table 1).

Length distributions

In both surveys both the mean length and the size of the largest cod caught were smaller off the British east coast than elsewhere and the same was true for haddock. (Tables 2 and 3). The mean length of whiting in the second survey was lower off the British east coast than to the north and east of Scotland (Table 3).

2

Growth

Mean lengths of the different species varied widely over the North Sea.

Because of the effects to be expected from the exact timing of the hauls in each particular group of rectangles the strictly regional differences cannot be easily extracted from the data and a detailed analysis had to be postponed.

However, to present a gener'al idea of the situation in 1976 weighted length data in 4 major' areas are given in Tables 2 and 3. In interpreting the results it should be noted that the Danish coast was sampled for the second time only three days after the first. Any difference for' this region should therefor'e be explained in terms of random variability of trawl catches rather than of apparent growth.

Figure 9 gives the mean lengths of the total popUlation caught during each of the surveys plotted at the midpoints of the survey periods, together with the data for 1975 and 1974. Nearly all species were slightly larger than in 1975, at a comparable time period, but considerably smaller than in 1974. The apparent negative growth of the cod in 19'76 can be attributed to smaller sized fish being caught in the nOr'theastern ar'ea in the second survey. The Norway pout shoals are known to consist of different sized fish even within a statistical square

(stratification experiment 1975, Daan et al., 1975) and, because of the very large catches involved in particular hauls, the overall mean lengths for' this species are likely to show large random variability. The blue whiting data are based on very limited numbers only. The other species do indicate some growth over the time interval between the two surveys, but their higher vulnerability during the second survey, as indicated by the incr'eased catch rates, may to some extent bias the observed growth rates.

Prediction of year-class strengths

The geometric mean of the numbers of cod, haddock and whiting were calculated for the ar>eas in which the average abundance of each species was highest for

the period 1969-75; these areas, which are shown in Figures 2, 3 and 4 for cod haddock and whiting respectively, were based on Figures 9-11 in Daan et al., (1975).

The results are shown in Table 4; for the period 1969-71 the surveys were carried out by Scotland only and the group consider'ed that the data for those years gave a reliable estimate of O-group abundance only for haddock. Also

shown in Table 4 are the results from the International Young Herring Survey (IYHS) and the VPA estimates of year-class size from the North Sea Roundfish Working

Group (Anon., 1976a).

One of the problems that the group had in correlating any two estimates of year-class size for both cod and whiting were the limited number of data sets,

3

3 years for VPA data and 4 years for IYHS data, which are effectively reduced to 3 sets for cod because the 1975 data are for the whole of sub-area IV and are not comparable with previous years when data for division IVa was given separately from those for IVb, c. For cod and whiting it is too early to state whether the O-group surveys provide an early indication of year-class size and in view of the relatively late and prolonged spawning period of whiting it is

doubtful whether estimates of the year-class size of this species can be calculated from surveys made at the appropriate time for cod and haddock. For haddock the correlation between the results from the O-group surveys and the VPA estimates is better than that between the former and the results fr'om the IYHS (r = 0.35 for 4df compared with 0.17 for 5 df), although both are non-significant. This

was because the 1973 year-class of haddock was estimated as being large by the IYHS.

However, the correlation between the results of the IYHS and the results from the VPA for this limited data series is also non-significant (r = 0.15), although the North Sea Roundfish Working Group found a highly significant relationship when 10 years data were considered (Anon, 1976a). (This group used the data for IVb, c even though it is given as for sub-area IV in its Table 35). More data points are therefore required before it can be stated whether the surveys can be used to predict year-class size for haddock.

PLANNING OF THE 1977 SURVEYS

The group discussed the planning of the 1977 survey in the light of the results obtained in 1976. The higher catches of cod, haddock and whiting during the second survey showed that a proportion of the popUlation of eac~ of these species was not available to the trawl during the first survey but, because both spawning times and growth rates are likely to vary from year to year, it was felt that there would be little point in changing the sut'vey dates for 1977.

It was agreed that the system adopted in 1976, when almost the \~hole survey was covered twice and most rectangles were sampled by different vessels should be used ,in 1977. However, if ships' time allowed, a partial third survey should be carried out. All the present participants agreed to continue the work during 1977 but additional participants would be welcome and should contact the

co-ordinator (Holden).

REFERENCES

ANON, 1976a. Report of the North Sea Roundfish Working Group, ICES C.M. 1976/F:19 pp 52 (mimeo).

ANON, 1976b. Report of the meeting on abundance estimates of juvenile cod, haddock and whiting from the 'International Young Herring Surveyst in the North Sea. ICES CM 1976/F:5.

4

Table 1. Mean numbers, based on geometric means, and 95% conf'idence limits, of' O-group cod, haddock and whiting caught in 1h hauls: areas are shown in Figure 2. 1915 excludes Danish results. Yea.:c-class size are millions of' 1 year old f'ish f'rom virtual population analyses*, taken f'rom Table 35, Anon. (1916) 1912 1913 1914 1915 1916 (f'irst 1916 (second survey) survey) COD

-

Northern North Sea n 11.2 2.7 14.4 5.7 23.5 60.3 95% 6.5-18.8 1.6-4.1 40.6-135.9 3.1-9.8 13.1-40.0 32.2-112.9 British east coast

-

9.6 0.7 7.1 47.8 n 4.1 1.3 95% 5.1-11.4 1.8-10.6 0.5-2.5 0.1-1.7 3.6-14.0 11.8-128.8

-

Danish coast n 20.1 12.9 229.9 4.7 168.5 519.4 95% 7.6-53.1 5.0-33.5 31.8-1662.5 1.1-13.2 51.5-55Q.7 74.7-3610.6 Yea.:c-class size 182 138 (196) HADDOCK

-

Northern North Sea n 34.0 56.5 1625.2 147.5 168.8 381.5 95% 20.7-55.5 28.7-110.6 683.6-3861.8 60.5-357.6 81.3-350.1 171.2-850.3

-

British east coast n 1.7 1.0 0.3 0.3 1.8 7.4 95% 0.1-3.1 0.4-1.8 0.1-0.5 0.1-0.5 1.2-2.8 3.5-15.1

-

Danish coast n 0.4 3.6 34.1 32.5 0.1 3.4 95% 0.2-0·5 1.6-8.2 1.1-155.6 1.1-149.5 0.5-1.1 1.5-7.8 Yea.:c-class size 219 939 (2718) w:r.rnfG

-

Northern North Sea n 124.6 10.1 302.8 43.8 6.4 8.3 95% 71.8-215.9 6.2-18.0 138.2-662.5 21.0-90.1 4.0-10.3 5.1-13.8

-

British east coast n 16.6 11.3 0.1 1.2 0.6 24.1 9~;6 6.9-31.9 6.2-44.8 0.0-0.3 0.4-2.5 0.4-0.9 9.9-58.6

-

Danish coast n 69.1 190.5 4.1 76.4 2.5 19.6 95% 13.1-347.7 40.3-899.4 1.5-11.2 32.4-180.6 1.0-6.1 5.1-61.6 Year class size 2316 2550 (3015) *Assuming a value f'or M of' 0.2.

Tabl.e 2. Oatch rates, mean length (cm), staDdard deviatioIlB and rm:J89S of lengths bT species and blocks of 4 statistical rectangles: 1st survey :Block 52-51 FO-1 52-51 F2-3 50-49 FO-1 50-49 F2-3 48-47 FO-1- 48-47 F2-3 46-4510-1 46-45 F2-3 44-4310-1 44-43 F2-3 llelm 50-49 E8-9 ~7 1:4-5 48-47 E6-7 48-47 E8-9 46-45 E4-5 46-45 E6-7 46-45 E8-9 44-43 E6-7 44-43 E8-9 5eIID. 42-41 E6-7 42-41 EB-9 42-41 FO-1 40-39 E8-9 40-3910-1 38-37

E8-9 38-37 FO-1_ 5eIID.

Dates Ship (JUlle) 17, 21 JBjE 17 JH 16, 21 JBjE 17 JH 16, 20 JBjE 16 JH 14. 19 JII/Eft 15 JH 13, 17 JHi.r 13. 14 JH 21 E 16 E 16, 18 E 18, 19 E 17 E 17. 200jE 18, 19 Eft 20 0 18, 19 oft 17, 19 0 18, 19 C 17, 18 oft 16, 17 0 16, 17 0 15 0 15 0 42-41 F4-5 15, 16 T 42-41li'6-7 15. 16 T Helm MeaD . (all BUrVIIY)

Cod li L Sd

:aanee

< 1 5.25 -5.0-5.4 101 5.01 0.61 2.0-1.4 16 3.38 0.49 2.5-3.9 60 4.66 0.96 2.5-7.9 35 4.10 0.53 3.0-5.4 11 3.62 0.51 2.5-5.4 192 4.43 0.97 3.0-6.4 1 2.15 0.50 2.0-3.4 < 1 3.50 0.35 3.0-3.9 418 4.52 0.93 2.0-7.9 23 3.38 0.80 2.5-5.4 < 1 4.00 0.35 3.5-4.4 3 4.93 1.19 3.0-6.9 6 3.83 1.24 2.5-6.4 7 3.02 0.51 2.0-3.9 2 3.13 0.52 2.0-3.9 17 3.90 0.48 2.5-4.9 1 3.65 0.55 2.5-4.4

Haddock li L Sd Ba:nge 23 2.32 0.80 1.0-5.4 142 4.16 1.14 467 3.46 0.85 283 5.48 1.39 273 4.28 0.66 4 2.85 0.60 216 4.42 0.92 < 1 2.25 - 1 3.50 0.35

1.0-9.4 1.5-6.9

2.5-10.9 2.5-

7.9 1.5-4.4 2.5-7.4 2.0-2.9 3.0-4.4 1410 4.22 1.25 1.0-10.9 67 3.29 1.03 1.5-8.4 5 3.50 1.42 1.5-6.9 31 3.84 0.52 2.5-5.9 5 3.44 0.48 2.5-4.9 28 3.77 0.74 2.0-5.9 6 4.63 0.98 3.0-6.4 2 2.81 0.31 1.5-4.4

Whiting N L Sd Ba:nge 7 1.56 0.33 1.0-2.9 31 2.47 0.81 1.0-6.4 38 2.30 0.82 1.0-6.0 152 7 25 7 17 349 27 ^{6 8}

2.43 0.49 1.75 - 3.12 0.81 2.51 0.53 2.60 0.83 2.63 0.51 1.96 0.30 3.25 0.44 2.07 0.33

1.0-4.4 1.5-2.4 1·0-5.4 1·0-3.9 1.0-4.9 1.0-5.4 1.0-3.4 2.0-4.4 1.5-3.4

Saithe N L Sd Ba:nge 2 4.25 0.50 3.5-5.4

36 18 16 ² 124 78 ² 45

5.31 1.44 2.92 0.24 4.68 1.91 4.25 - 4.54 1.10 4.79 1.14 2.61 0.56 3.20 0.56

3.0-9.4 2.5-3.9 1.5-9.4 4.0-4.9 2.0-7.4 2.5-6.9 1·5-3.9 1.5-5.4

323 4.40 1.30 1.5-9.4 6 6.00 1.13 4.0-7.9 4 4.19 1.32 2.5-7.9 1 5.62 0.95 4.0-6.9 5 4.47 1.51 2.5-7.9 1 5.25 -5.0-5.9 4 5.72 0.93 4.5-7.9 60 3.61 0.84 2.0-6.9 144 3.56 0.93 1.5-8.4 598 2.56 0.56 1.0-5.4 21 5.18 1.33 2.5-7.9 7 2.82 0.55 2.0-3.9 2 2.75 0.60 1.5-3.4 2 2.42 0.58 1.5-2.9 3 2.90 0.34 2.0-3.4 29 2.79 0.33 2.0-3.4 26 1.98 0.37 1.0-2.9 1 3.00 0.25 2.5-3.4 70 2.49 0.54 1.0-3.9 -471 3.13 0.63 1.5-6.9 36 3.30 0.65 1.5-5.4 507 3.14 0.631.5-6.9

1 1.75 - 1 3.25 0.50 1 2.25 - 7 2.84 0.24 2 2.08 0.29

1.5-2.4 2.5-4.4 2.0-2.9 1.5-4.9 1.5-2.9

15 5.56 0.54 4.5-7.4 22 5.01 0.68 3.5-8.4 2 5.25 1.34 4.0-8.4 12 2.61 0.49 1.5-4.9 15 5.56 0.54 4.5-7.4 24 5.03 0.71 3.5-8.4 1 2.75 -2.5-3.4 1 3.25 0.65 2.5-4.9 2 3.00 0.35 2.5-4.9

4 3.34 0.51 2.0-4.4 1 2.75 - 2 3.54 1.15 1.5-5.4 < 1 4.25 - 2·5-3.4 4·0-4.9

6 3.41 0.66 1.5-5.4 2 3.50 1.06 2.5-4.9

No~Pout li L Sd Ba:nge 6 3.02 0.36 2.0-4.9 12891 3.67 0.70 2.0-6.9 2528 3.51 0.54 1.5-5.4 8635 4.00 0.46 2.5-6.4 3739 3.58 0.39 2.5-4.9 7621 4.61 0.30 2.5-6.4 37095 4.19 0.56 2.5-5.9 6 4.06 0.96 2.0-5.9 25 3.32 0.98 1.5-5.9 72546 4.06 0.63 1.5-6.9 608 2.21 0.31 1.5-3.9 8 1.81 0.32 1.0-2.4 1 2.08 0.29 1.5-2.9 1 3.00 0.29' 2.5-3.9 < 1 2.25 -2.0-2.9 7 3.40 0.80 1.0-5.4 2 3.31 1.10 2.0-5.9 628 2.22 0.35 1.0-5.9

:Blue Whiting li L Sd Ba:nge 1 8.75 --8.5-9.4 8 3~5O 0.53 2.5-4.9 1055 3.67 1.05 1.0-7.9 1568 4.15 1.24 1.0-10.9 657 2.62 0.14 1.0-1.4 310 4.48 1.29 1.5-9.4 73114 4.04 0.65 1.0-6.9 9 4.08 1.82 2.5-9.4

Table 3. Catoh rates, mean length (cm), standard deviations and :ranges of lengths by speoies and blocks of 4 statistical reotSll8'les: 2nd survey I1lock 52-51 FO-1 52-51 F2-3 50-49 FO-1 50-49 F2-3 48-47 FO-1 48-47 F2-3 46-45 FQ.:.1 46-45 F2-3 44-43 FO-1 44-43 F2-3 Mean 50-49 E8-9 48-47 E4-5 48-47 E6-7 48-47 E8-9 46-45 E4-5 46-45 E6-7 46-45 E8-9 44-43 E6-7 44-43 E8-9 l!ean

Dates (June) 22,23 22 21-23 19,21,22 21,24,25 20,21,25 22,24,26 25,26,28 20,22,26 20,26,28 23,25 22 ²² 23,24 21 21,30 21,23 29.30 21,27

42-41 E6-7 29 42-41 E8-927,28 42-41 FO-1 28 42-41 F2-3 .28 40-39 EB-9 23-25 40-39 FO-1 24 38-37 E8-9 25,26 . 38-37 FO-1 26 Mean. .-

Ships m m Dim :n/.rn: :ti/.JIifr D/.rn:

~ ~

^{JHft T T JHft T Eft oft E ojE E E E T o o o o}

42-41 F4-5 28 T ~-41 F6-7 18,19,26 D Mean Bean (all survey)

Ood N

o o _{96 52 55}

112 1

12 112 30

L Sd 4.80 0.62 3.73 0.49 4.58 0.83 4.39 0.72 2.25 - 2.63 0.72 2.20 0.57 1.93 0.31

Bange 3.0-6.9 2.0-6.4 3.0-6.9 3.0-7.9 2.0-2.4 1.5-3.9 1.0-5.5 1.0-3.0

Haddook N L Sd o o

661 291 293 412

1 41 1 3

5.49 1.29 4.97 1.22 5.74 1.13 5.28 1.34 3.58 1.53 3.79 0.93 2.25 - 1.70 0.44

Bange 2.0-9.4 1.5-7.9 2.5-9.9 1.5-9.9 2.0-5.4 1.0-7.4 2.0-2.4 1 .• 0-2.9

Whiting N L

o o

Sd Range 109 o o ^{2 1 1} o o

3.47 1.31 2.0-7.4 3.25 0 3.25 - 3.75 -

3.0-3.4 3.0-3.4 3.5-3.9

Saithe N L

o o

Sd Range 3 5.10 1.56 3.5-7.9 < 1 9 5.24 0.94 4.5-8.9 7 3.56 0.68 2.0-5.4 1 4.75 0.71 4.0-5.9 < 1

Norwa;y Pout N L o o 3805 13930 23551 44655

4 69 7 1

3.37 4.12 4.28 3.53 4.42 3.29 4.04 3.00

Sd 0.76 4.8 0.71 0.49 0.87 0.80 1.16 1.78

Bange 1.5-5.4 1.0-5.4 2.5-5.9 1.0-5.9 1.5-5.9 1.0-5.9 2.0-5.9 1.0-4-.9

I1lue Whiting N L Sd

o o

Range 5 3.62 0.28 3.0-4.4

o o o o o o o

470 3.69 1.27 1.0-7.9 1703 5.34 1.31 1.0-9.9 113 3.46 1.29 2.0-7.4 20 4.61 1.19 2.0-8.9 86022 3.82 0.67 1.0-5.9 15 4.83 1.19 2.0-6.9

o o ₁₂

4.07 0.85 2.5-7.4 o 9 3.63 0.37 3.0-4.4 2 3.69 0.39 3.0-4.4 11 3.50 0.75 2.0-7.9 4 3.57 0.30 2.5-4.4

62 3.70 0.72 1.5-7.4

o o ₄₃ ⁴ _{30 22 11} ⁶

4.38 5.25 3.34 4.53 4.95 3·59

1.18 0.57 0.82 0.73 1.83 0.75

2.0-9.4 4.5-5.9 2.0-6.9 2.5-6.4 2.5-8.9 2.5-6.4

38 o 2 3 4 292 3 46 2

,.os

0.53 1.5-4.4 2.15 0.82 2.85 0.46 4.75 0 3.60 0.71 2.71 0.42 3.59 1.02 3.17 0.49

1.0-3.4 2.0-3.4 4.5-4.9 1.0-6.9 1.5-3.4 2.0-6.4 2.5-3.9

4 5.10 1.69 3.5-8.9

o o 2 5.14 2.03 3.0-8.4 o 5 7.25 0 7.0-7.5 62 6.37 0.88 3.0-8.4 o 20 5.55 0.60 4.0-7.4 53 4.04 0.98 2.0-7.4 174 3.99 1.07 2.0-9.4 386 3.52 0.76 1.0-6.9 93 6.16 0.99 3.0-8.9 156 36 o _{36 45} 1 3 1

2.98 0.57 1.5-4.9 2.73 1.10 1.5-4.9 5.49 1.11 3.08 0.46 2.75 - 2.70 0.28 2.75 -

1.5-6.9 2.0-4.4 2.5-2.9 2.0-3.4 2.5-2.9

278 3.28 1.12 1.5-6.9 348 2.87 0.53 1.5-6.9 44 2.77 0.45.1.5-5.9 392 2.86 0.52 1.5-6.9

28 3.21 13 3.17 2 2.50 2 3.00 10 3.59

o o o 0.73 1.12 0.35 0.36 0.88 2.0-5.4 1.0-5.9 2.0-2.9 2.5-3.4 2.0-5.9

105 10 o 4 16 1 5 3

2.31 0.47 1.0-4.4 1.93 0.54 1.0-3.4 3.50 0.28 2.35 0.45 2.75 - 2.66 0.27 2.65 0.42

3.0-3.9 1.0-3.9 2.5-2.9 2.0-3.4 2.0-3.4

2 5.63 0.48 5.0-6.4

o o o o o o o

55 3.24 0.85 1.0-5.9 144 2.34 0.51 1.0-4.4 2 5.63 0.48 5.0-6.4 o 10 4.67 1.50 2.5-9.4 15 3.81 1.27 1.5-6.9 0 5 3.30 0.79 1.5-4.9 8 2.69 0.91 1.0-5.4 0 15 4.21 1.44 1.5-9.4 23 3.42 1.26 1.0-6.9 0

16 2.49 0.28 1.5-3.4

o o ₄₅

4.78 0.59 3.0-5.9

o o ₃₄

3.87 0.59 2·5-5.4 o 1 5.00 0.27 4.5-5.4

3 3.97 0.56 2.5-4.9

o o o o o o o o

96 4.08 0.99 1.5-5.9 0 1 2.25 -2.0-2.4 0 2 2.25 0.66 1.0-3.4 0 o 0 o 0 o 0 o 0 o 0 o 0 3 2.25 0.47 1.0-3.4 0

o o o

o o o 1193 3.34 "1.10 1.0-7.9 1947 5.15 1.38· 1.0-9.9 666 3.25 0.98 1.0-6.9 115 5.88 1.17 2.0-8.9 86121 3.82 0.67 1.0-5.9 8 3.75 0.41 2.5-4.9

Table 4. Estimates of year-class size from O-group surveys and as 1 year olds from the International Young Herring Surveys (IYHS) (Anon. 1976b) and from VPA estimates (Anon. 1976a). For 1975 only value for cod available is that for sub-area IV Cod Haddock Whiting j,...rea IV IVa IVb9c IV IVa IV IV IV IV IV Year Class O-gp IYHS IYHS YEA O-gp IYHS YEA O-gp IYRS VEil,. 1969 3.2 61 377 248 45 111 86 686 1970 75.0 142 501 34 2114 901 296 688 1971 1.1 3 89 4068 3044 1363 110 1656 1912 26 1.9 46 182 93 461 279 138 4272 2316 1973 8 11.0 10 138 301 3685 939 40 703 2550 1974 157 0.2 121 (196) 2173 1663 (2718) 276 1292 (3015) 1975 17 131 622 312 70 1306 1976( 1+2) 188 579 16 Average 79.2 247.2 1014.6 1617.7 1052.8 108.0 688.6 1818.5

DAAN, N., HISLOP, J. R. G., HOLDEN, M. J. and LAHN-JOHANESSON, J., 1975. Report of the pelagic O-group gadoid survey in the North Sea in 1975. ICES C.Ma 1975/F:33 pp 7 (mimeo).

HISLOP, ,'J. R. G., HOr~DEN, M. J. and DAAN, N.) 1974. A com:qined report on the pelagic O-group gadoid surveys undertaken by ,Scotland, England and the Netherlands in the North Sea in 1974. ICES CM 1974/F:15.

5

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27

su rvey with date each square fished: C:=CORELLA; D=DANA;

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E=EXPLORER; JH=JOHAN HJORT; T=TRIDENS: see text for

explanation of heavy line.

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Figure 2 Statistical squares fished by each vessel during second survey with date each square fished: C=CORELLAi D=DANAj E=EXPLORERi JH=JOHAN HJOHT; T=TRIDENS.

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26

first survey; lower figure, second survey. -

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Figure 9 Mean lengths of each species 1974-6; data for 1974 are taken from Table 11 (Hislop, 1974); two data points for 1976 are first and second surveys.