COOPERATIVE RESEARCH REPORT NO. 168 PART 1 Reports... · COOPERATIVE RESEARCH REPORT NO. 168 PART 1 REPORTS OF THE ICES ADVISORY COMMITTEE ON FISHERY MANAGEMENT, 1989 Copenhagen,

REPORTS OF THE ICES ADVISORY COMMITTEE ON FISHERY MANAGEMENT, 1989
Copenhagen, 23 - 31 May 1989 Copenhagen, 31 October - 8 November 1989
International Council for the Exploration of the Sea Palregade 2-4, DK-1261 copenhagen K, Denmark
February 1990
MEMBERS OF THE ADVISORY COMMITTEE ON FISHERY MANAGEMENT 1988/1989 ................ 2
MEMBERS OF THE ADVISORY COMMITTEE ON FISHERY MANAGEMENT .1989/1990 3
REPORTS OF THE ADVISORY COMMITTEE ON FISHERY MANAGEMENT MAY AND NOVEMBER 1989 ............................................................. 4
CHART OF ICES FISHING AREAS ....................................................... 6
REPORT TO THE NORTH-EAST ATLANTIC FISHERIES COMMISSION ..... .... ................... 7
1 . INTRODUCTORY ITEMS ............................................................ 7
1.1 Review of Nominal Catches in NEAFC area .................................. 7 1.2 Review of ACFM Advice for 1989 ........................................... 8
2. STOCKS IN NEAFC REGION 1 .........................•............................ 8
2.1 North-East Arctic Cod .................................................... 8 2.2 North-East Arctic Haddock ................................................ 11 2.3 North-East Arctic Saithe ................................................. 13 2.4 Redfish in Sub-areas I and II ............................................ 15
2.4. 1 Sebastes mentella in Sub-areas I and II ........................... 15 2.4.2 Sebastes marinus in Sub-areas I and II ............................ 16
2.5 Greenland Halibut: in Sub-areas I and II .................................. 17 2.6 Stocks off East Greenland ................................................ 18
2.6.1 East Greenland cod (Sub-area XIV) ................................. 18 2.6.2 Pandalus in East Greenland waters (Denmark Strait,
Divisions XIVb-Va) ................................................ 22
2.7 Redfish in Sub-areas V and XIV ........................................... 23
2.7.1 Advice from the May 1989 ACFM meeting ............................. 23 2.7.2 Advice from the November 1989 ACFM meeting....... ..... ............ 23
2.7.2.1 Sebastes marinus in Sub-areas V and XlV....... ........ ... 23 2.7.2.2 sebastes mentella "traditional" fishery in Sub-areas
V and XIV ................................................ 23 2.7.2.3 Sebastes mentella "oceanic type" in Sub-arElas XII and XIV 23
2.8 Greenland Halibut in Sub-areas V and XlV................................. 23 2.9 Icelandic saithe (Division Va) ........................................... 24 2.10 Demersal Stocks at the Faroe Islands ............................ ;. ....... 24
2.10.1 Faroe saithe (Division Vb) ........................................ 24 2.10.2 Faroe Plateau cod (Sub-division Vb1) .............................. 24 2.10.3 Faroe Bank cod (Sub-division Vb2) ................................. 24 2.10.4 Faroe haddock (Division Vb) ....................................... 25
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2.11.1 Iceland summer-spawning herring (Division Va) .......... ........... 26 2.11.2 Norwegian spring-spawning herring.................... ............. 27
2.12 Cape lin .................................................................. 29
2.12.1 Barentss~a capel in (Sub-areas I and II, excluding Division IIa west of 5 W) ...................................................... 29
2.12.2 Cape lin in th~ Ic~land-East Greenl~nd-Jan Mayen area (Sub-areas V and XIV and D1V1S10n IIa west of 5 W) ................... .......... 30
3 . STOCKS IN NEAFC REGION 2 ...................................................... 33
3.1 o Herring Stocks South of 62 N ............................................ .
3.1.1 3.1.2 3.1.3 3.1. 4 3.1.5 3.1.6 3.1.7 3.1.8 3.1. 9
General considerations ........................................... . Herring in Divisions IVa, b ....................................... . Herring in Divisions IVc, VIId (Downs herring) ................... . Herring in Sub-divisions 22-24 and Division IlIa ................. . Celtic Sea and Division Vllj herring ............................. . Herring in Division VIa (North) .................................. . Clyde herring (Division VIa) ..................................... . Herring in Divisions VIa (South) and Vllb,c ...................... . Irish Sea herring (Division VIla) ................................ .
33
33 34 37 38 40 42 43 45 47
3.2 Industrial Fisheries in the North Sea and Adjacent Waters ........... ..... 48
3.3
3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.2.7 3.2.8 3.2.9 3.2.10 3.2. 11 3.2.12 3.2.13 3.2.14 3.2.15
Data available ................................................... . Trends in the industrial fishery in the North Sea ................ . Trends in the industrial fisheries in Division IlIa .............. . Norway pout in Division IlIa ..................................... . Norway pout in Sub-area IV ....................................... . Norway pout in Division VIa ...................................... . Sandeel in Divis,ion IIIa ......................................... . Sandeel in the Southern North Sea ................................ . Sandee.l in the Northern North Sea ................................ . Sandeel in the Shetland area ..................................... . Sandeel in Division VIa .......................................... . Sprat in Division IIIa ........................................... . Sprat in Sub-area IV ............................................. . Sprat in Division VIa ............................................ . Sprat in Divisions Vlld,e ........................................ .
Demersal Stocks in Division IlIa
3.3.1 3.3.2 3.3.3 3.3.4 3.3.5 3.3.6 3.3.7
Cod in the Kattegat .............................................. . Cod in the Skagerrak ............................................. . Haddock in Division IIIa ......................................... . Whiting in Division lIra ......................................... . Plaice in the Kattegat ................... , ....................... . Plaice in the Skagerrak .......................................... . Sole in Division IlIa ............................................ .
48 48 48 48 49 49 50 50 51 53 54 55 56 57 57
58
59 60 61 62 63 64 65
3.4 Pandalus borealis in Division IlIa and the North Sea .......... ..... ... ... 66
3.4.1 3.4.2 3.4.3
Introduction ..................................................... . Pandalus borealis in Division IlIa ............................... . Pandalus borealis In Division IVa - the Norwegian Deeps .......... .
66 67 68
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Panda Ius borealis in Division IVa - the Fladen Ground ............ . Panda Ius borealis in Division IVb - the Farn Deeps ............... .
69 69
3.5 Cod, Haddock, Whiting, and Saithe in the North Sea (Sub-area IV) ......... 70
3.5.1 Roundfish in Sub-area IV: overview................................ 70
3.5.1.1 3.5.1.2
Advice from the May 1989 ACFM meeting ................... . Advice from the November 1989 ACFM meeting .............. .
70 70
3 . 5 . 2 Cod in Sub-area IV (North Sea) .................................... 73
3.5.3
3.5.2.1 3.5.2.2
Fishing for cod with 120 mm mesh ....................... . Effects of the cod box in the German Bight .............. .
Haddock in Sub-area IV (North Sea)
3.5.4 Whiting in Sub-area IV (North Sea)
75 75
76
78
3.5.5 Saithe in Sub-area IV and Division IlIa (North Sea) .. ............. 80
3.6 Cod, Haddock, Whiting, and Saithe in Sub-areas VI and VII................ 81
3.6.1 3.6.2 3.6.3 3.6.4 3.6.5 3.6.6 3.6.7 3.6.8 3.6.9
Roundfish in Sub-areas VI and VII: overview ...................... . Cod in Division VIa (West of Scotland) ........................... . Cod in Division Vlb (Rockall) ....................................• Haddock in Division VIa (West of Scotland) ....................... . Haddock in Division Vlb (Rockall) ................................ . Whiting in Division VIa (West of Scotland) ....................... . Whiting in Division Vlb (Rockall) ................................ . Saithe in Sub-area VI (West of Scotland and Rockall) ............. . Cod in Divisions Vlld,e (English Channel) '" ..................... .
3.6.9.1 3.6.9.2
Cod in Division Vlld (Eastern English Channel) Cod in Division VIle (Western English Channel)
81 82 82 83 84 85 85 86 87
87 88
3.6.10 Whiting in Divisions Vlld,e (English Channel) ..................... 89
3.6.10.1 Whiting in Division Vlld (Eastern English Channel) 3.6.10.2 Whiting in Division VIle (Western English Channel)
89 89
3.7 Irish Sea/Bristol Channel and Celtic Sea Stocks .......................... 91
3.7.1 3.7.2 3.7.3 3.7.4 3.7.5 3.7.6 3.7.7 3.7.8
Ir ish Sea cod .................................................... . Irish Sea whiting ................................................ . Irish Sea plaice ................................................. . Irish Sea sole ................................................... . Celtic Sea cod (Divisions Vllf and g) ............................ . Celtic Sea whiting (Divisions Vllf and g) ........................ . Celtic Sea plaice (Divisions Vllf and g) ......................... . Celtic Sea sole (Divisions VIIf and g) .............. : ............ .
92 94 96 98 99
100 101 102
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3.8 Sole and Plai~e in the North Sea, English Channel, and Bay of Biscay ..... 103
3.8.1 3.8.2 3.8.3 3.8.4 3.8.5 3.8.6
North Sea sole ................................................... . North Sea plaice ................................................. . Sole in Division VIId ............................................ . Sole in Division VIle ............................................ . Plaice in Divisions Vlld,e ....................................... . Sole in Divisions VllIa,b (Bay of Biscay) ........................ .
103 105 106 107 108 109
4. STOCKS IN NEAFC REGIONS 2 AND 3 ............................................... 110
4.1 Hake in Sub-areas IV and VI-IX........................................... 110
4. 1 . 1 Hake - Northern stock (Oi vision IVa, Sub-areas VI and VII, and Divisions VIIla,b) ................................................ 110
4.1.2 Hake - Southern stock (Divisions Vlllc and IXa) ................... 111
4.2 Fisheries Units in Sub-areas VII and VIII ................................ 112
4.2.1 4.2.2 4.2.3 4.2.4 4.2.5
Introduction ..................................................... . Current state of the stocks and fisheries ........................ . Assessment of mesh changes ..................... . ................ . Appraisal of minimum landing size regulations .................... . Recommendations .................................................. .
112 112 113 114 116
4.3 Horse Mackerel in Sub-areas IV and VI-IX ................................. 117
4.3.1 4.3.2 4.3.3
General comments ................................................. . North Sea horse ma.ckerel (Divisions IlIa, IVb-c, VIld) ........... . Western horse mackerel (Divisions IIa, IVa, Vla,Vlla-c,e-k, VIlla,b,d,e) ..................................................... . Southern horse mackerel (Divisions Vlllc and IXa) ................ .
117 118
119 122
5. STOCKS IN NEAFC REGION 3 ...................................................... 123
5.1 Sardine in Divisions Vlllc and IXa ....................................... 123 5.2 Anchovy in Divisions Vlllb,c (Bay of Biscay) ...... ..... ................. 124
6. STOCKS IN NEAFC REGIONS 1, 2, AND 3 ........................................... 126
6. 1 Mackerel................................................................. 126
6. 1 . 1 6.1.2 6.1.3 6.1.4
Introduction ..................................................... . North Sea mackerel ............................................... . Western mackerel ................................................. . Mackerel in Divisions VIllc and IXa .............................. .
126 127 128 131
6.2 Nephrops in Sub-areas III, IV, V, VI, VII, VIII, and IX .................. 132
6.2.1 6.2.2 6.2.3 6.2.4
6.2.6 6.2.7 6.2.8
General comments ................................................. 132 Nephrops in Division IlIa (Skagerrak and Kattegat) ............... 133 Nephrops in Sub-area IV (North Sea) .............................. 134 Nephrops in Division Vb (Faroes) and Sub-area VI (West of Scotland) ........................................................ 135 Nephrops in Sub-area VII (Irish Sea, Celtic Sea, and West of Ireland) ......................................................... 136 Nephrops in Divisions VIIIa,b (Bay of Biscay) .................... 138 Nephrops in Division VIIlc (Spanish coast) ....................... 139 Nephrops in Sub-areas IX and X (Spanish and Portuguese coasts) ... 140
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6 . 3 Bl ue Whiting ............................................................. 141
6.3.1 Blue whiting in the northern area (Sub-areas I-VI and XIV, and Divisions VIIb,c) ................................................. 141
6.3.2 Blue whiting in the southern area (Divisions Vlld,e,g-k and Sub-areas VIII and IX) ............................................ 142
6.3.3 Distribution in time and space of different life history stages of blue whiting ............................................ 143
6.4 Elasmobranch Stocks ...................................................... 144
6.4.2.1 6.4.2.2 6.4.2.3
144 144 144
PREFACE
This volume of the Cooperative Research Report contains the reports of the Advisory Com mittee on Fishery Management in 1989.
After the May meeting, ICES issued the complete report to the International Baltic Sea Fishery Commission (IBSFC), Part I of the report to the North-East Atlantic Fisheries Com mission (NEAFC), and the report to the NOrth Atlantic Salmon Conservation Organization (NASCO). The second part of the report to the NEAFC was issued after the November meeting. In order to distribute the advice to managers as fast as possible, the reports were issued in sections and distributed immediately after they had been completed.
The two reports to NEAFC have been edited into one report, placing the stocks in logical se quence and including all advice on each stock in one place.
The report to NEAFC is followed in Part 2 by the reports to IBSFC, NASCO, and the Govern ment of Norway.
Copenhagen, February 1990 Richard Grainger
Secretary to ACFM
198811989
Dr V.C. Anthony Mr E. Bakken Dr E.A. Ojaveer
Dr R. De Clerck (Alternate: Mr M . 1 (Alterna te : J.J. agu~re
Mr N.A. Nielsen1 (Alternate: Mr M. Hilden (Alternate: Dr J. Guequen (Alternate: Dr O. Rechlin Mr H.P. ~~~~~~al (Alternate: Dr S.A. (Alternate: Mr D. de G. Griffith Dr R. Boddeke 1 (Alternate: Prof. J. Hamre (Alternate:
~~o:: ~~t~:idanpal ,3 (Alternate: (Alternate:
Mr J.A. Pereiro (Alternate: Mr B. Sjostrand (Alternate: Dr R.S. Bailey (Alternate: Dr F.M. Serchuk Dr Y. Efimov (Alternate:
Dr ~:s~e~:~~!tt2~ Mr Mr E. Kirkegaard ) Mr R. Parmanne) Mr B. Mesnil )
Dr G. Rauck) Mr O.K. Palsson)
Prof. N. Daan)2 Mr T. Jakobsen ) Dr J. Kleniewski) Dr C. Sousa Reir) Mr A. Astudillo ) Mr J. Modin) Dr J.G. Shepherd)
Dr V.N. Shleinik)
Belgium Canada Denmark Finland France German Democratic Republic Federal Republic of Germany Iceland Ireland Netherlands Norway Poland Portugal Spain Sweden UK USA USSR
Mr M.J. HOldrn1 (Alternate: Mr W. BrUgg~2), Observer, Commission of the European Communities Mr K. Hoydal (Alternate: Mr H. Lassen ), Observer, Faroe Islands and Greenland
Dr R. Grainger, ICES Statistician, Secretary to ACFM
lDid not attend May 1989 meeting. ~Attended May 1989 meeting in place of the regular member. Represented by Dr M. Lima Dias at May 1989 meeting.
MEMBERS OF THE ADVISORY COMMITTEE ON FISHERY MANAGEMENT
1989/1990
Mr. B. Vaske Chairman
Prof. N. Daan Chairman, Demersal Fish Committee Mr E. Bakken Chairman, Pelagic Fish Committee Dr W. Weber Chairman, Baltic Fish Committee
Dr R. De Clerck (Alternate: Dr F. Redant) Belgium Mr J. J. Maguiret (Alternate: Mr J.S. Beckett)2 Canada Mr N.A. Nielfen (Alternate: Mr E. Kirkegaafd ) Denmark Mr M. Hilden (Alternate: Mr R. Parmanne ) Finland Mr B. Mesnil (Alternate: Mr A. Forest) France Dr O. Rechlin German Democratic Republic Mr H.P. Cornus (Alternate: Dr G. Rauck) Federal Republic of Germany Dr S.A. Schopka t (Alternate: Mr O.K. pals:!;on) Iceland Mr D. de G. Griffith (Alternate: Mr J. Molloy) Ireland Dr R. Boddeke Netherlands Mr T. Jakobsen (Alternate: Mr I. RllIttingen) Norway
~~o~: ~~t~:~danpat ,3 (Alternate: Dr J. Kleniewski) Poland (Alternate: Dr C. Sousa Reir) Portugal
Mr J.A. Pereiro (Alternate: Mr A. Astudillo ) Spain Mr B. Sj6strand1 (Alternate: Mr J. Modin ) Sweden Dr R.S. ~:!~~~kt (Alternate: Dr J.G. Sh~pherd) UK Dr F.M. (Alternate: Mr R. Mayo ) USA Dr Y. Efimov (Alternate: Dr V.N. Shleinik4) USSR
Mr M.J. Holdent (Alternate: Mr W. Brugge2), Observer, Commission of the European Communities Mr H. i Jakupsstovu (Alternate: Mr F. Riget), Observer, Faroe Islands and Greenland
Dr R. Grainger, ICES Statistician, Secretary to ACFM
t Did not attend November 1989 meeting. ~Attended November 1989 meeting in place of regular member.
Represented by Ms M.de F. Cardador at November 1989 meeting. 4Attended November 1989 meeting for several days in place of regular member.
3
4
Introduction
MAY ANO NOVEMBER 1989
In 1982, it was decided to change the time table for the ACFM meetings. Instead of having one main meeting in July dealing with most of the stocks, with an additional minor one in November taking care of a few stocks, the work has now been more equally divided between the two meetings, one in mid-May and one in late October/early November.
The time table of the assessment working groups had to be changed accordingly, and the ad vice on different stocks has been distributed between the two meetings, taking into account various factors such as the deadlines set by the management authorities for receiving ad vice, timing of surveys, and collection of other scientific data, etc.
Basis of the Biological Advice Provided
There has been no change in the last eight years in the basic criteria on which ACFM bases its advice. ACFM still considers that the biological advice provided should not be seen in isolation from economic considerations and welcomes continuing dialogue with the other parties in the management process in order to tailor the biological advice to best suit the needs of the subsequent stages in the process of achieving viable management.
As described in earlier reports, the stocks are grouped for the purpose of providing manage ment advice into the following categories:
1. Stocks which are rapidly depleted and suffering from recruitment failure. In these cases, ACFM shall not calculate options but shall recommend a single figure.
2. Stocks which are fished at levels largely in excess of the levels indicated by biolo gical reference points. In these cases, ACFM shall give options inside safe biological limits and shall recommend one of these options according to the general principles of aiming at more stable levels of stock and catch.
3. Stocks which are fished at levels not very different from the biological reference points. In these cases, ACFM shall give options inside safe biological limits, but shall not recommend any particular one of these. It shall only indicate a preference which is in line with the general principles mentioned above.
4. Stocks where at present it is not possible to carry out any analytical assessment with an acceptable reliability. In these cases, ACFM shall indicate precautionay TACs to re duce the danger of excessive efforts being exerted on these stocks.
5. In cases where fisheries on a stock are not subject to TAC regulation, there may be a danger of catches taken from stocks of the same species in adjacent areas being mis reported as having been taken in areas of unregulated fisheries. To reduce the risk of this happening, ACFM, on occasion of the request of management bodies, has advised on implementation of TACs and their levels on this basis. Since, in the majority of cases, the data on these stocks are inadequate for analytical assessment, they too will gener ally be recommended as precautionary TACs based on historic catch levels.
In order to allow more flexibility to the management authorities, the type of recommendation given for a category 2 stock is that fishing mortality should be reduced to one of the bio logical reference points as quickly as possible, or (in some cases) towards these points.
Biological Reference Points
F is the level of flshing mortality at which the maximum long·· term average annual catch c~gXbe taken under the present exploitation pattern. It is based on the relationship between the yield per recruit and fishing mortality.
Fa 1 is the level of fishing mortality at which the slope of the yield-per-recruit curve is one tenth of its slope at the origin, Fa is always less than F ; the catch is only slightly less than at F ,but the implied reduction in fishing mort~i1ty is much greater and so the catch per mH~it effort is higher with consequent economic benefits. Fa 1 is, therefore, essentially an economic concept. .
ACFM noted the proposal by the Methods Working Group in 1984 for the biological reference points F d and Fh' h' which are intended to provide guidelines for levels of fishing mortalitymeat which i~ is probable (in the case of F d) and doubtful (in the case of FI' h) that recruitment ",ill, in the long-term, be sufficieWf to sustain a stable stock. 11g
The values of F d and Fh' h may be calculated very simply from stock and recruitment scatter diagrams aWa plots of b10mass per recruit which are generally provided by ICES working groups. The procedure is simply to draw lines through the origin of the scatter plot which leave about 10% (in the case of Fh' h) and 50% (in the case of F d) of the points above the line, The slopes of these line§gcorrespond to values of recruitm~nt per unit bio mass, and the reciprocals of these values are estimates of the spawning biomass per recruit (an estimate of survival) which must be maintained for the stock to be sustainable, The fishing mortalities (conditional on the assumed exploitation pattern) to which these bio mass-per-recruit values correspond may be determined from the plot of the relationship bet",een these quantities and yield the estimates of Fh' band F d' Estimates based on percentiles are used rather than means because they are lesl;g5ensitilll~ to the actual size of extreme year classes.
FI' h thus corresponds to a level of F at which survival is so 10'" that recruitment (per uJi~ biomass) is insufficient to maintain the stock in about nine years in ten. Whilst it cannot necessarily be taken as an estimate of the F at which collapse will occur, it is a level for which the available data provide very little evidence that it could be maintained indefinitely. It is, therefore, not a target or option level of F, but, on the contrary, a level which is probably dangerous to approach or maintain.
F ,on the other hand, is a level for ",hich there is sufficient evidence that it should be s~~~,ainable (assuming, of course, that the underlying envi.ronmental or ecological conditions to ",hich the data relate are maintained), Below or in the vicinity of F d' there should, therefore, be no undue cause for concern about sustainability, and F dm~OUld, therefore, in some circumstances, serve as a target for management, though many otN~r factors (yield, exploitable biomass, etc.) are, of course, also relevant.
Fl corresponds to a level for which there is sug~ainable, subject to the same qualifications as for
plenty of evidence that the stock is
Fmed'
ACFM has found F d in particular to be a useful quantity in providing guidance in preparinq management oPtioW~, and reference to it will be found in this report where appropriate. ACFM also stresses that biological reference points are intended to provide gQidance concerning management options, and that no single reference point can possibly serve as a universal target for management,
ACFM advice is, however, based on the evaluation of as many relevant factors as possible, including levels of F in relation to biological reference points, spawning stock size in re lation to historic levels, trends and recent levels of recruitment, and the precision of the assessments. Different factors dominate in different situations,
5
6
XIVb
XII
X
"":~~. ,'<:;!:::io;:
1. INTRODUCTORY ITEMS
1.1 Review of Nominal Catches in NEAFC Area
The assessments presented in this report are carried out using the best catch data available to the working groups and to ACFM. These data are not necessarily identical with the offi cial statistics but, where appropriate, include estimates of unreported landings as well as corrections for misallocation of catches by area and species. Despite considerable effort exerted to this problem, there is no guarantee that all instances of misreporting were dis covered.
In the assessments, the working groups try to estimate the total catch taken, including slipped catches, discards, landings which are not officially reported, and the composition of the industrial by-catches. These amounts of different species, which have to be included in the estimates of what has been taken from a given stock in order for the assessments to be correct, thus appear in the tables and figures produced by the working groups. These levels of discards, slipped fish, unreported landings, and industrial by-catches vary considerably between different stocks and fisheries, being negligible in some cases and constituting important parts of the total removal from other stocks.
The catch data used in the assessments are given in the table section. In cases where there might be doubt, it has been indicated if discards, by-catches, and estimates of unreported landings are included in the assessments. Estimates of catches landed as by-catches, espe cially from the industrial fisheries, are included in the assessments wherever data allow it and are included in the catch options.
It should be noted that, in general, catches of protected species above the minimum landing size, which are sorted out and landed for human consumption, are included in the estimates of human consumption landings, both in the catch input data and in the projected catch options. Estimates of industrial by-catches cover, in most cases, that part of the by-catch which is used for reduction purposes.
Questions related to fisheries statistics were considered by ACFM on the basis of requests from the Norwegian Ministry of Fisheries and from the Commission of the European Community. Both requests point to the problems associated with discrepancies between the official landing figures reported to ICES by member countries and corresponding catch data used by assessment working groups. A comparison between catches reported in Bulletin Statistique and those used by assessment working groups can be found in the Progress Report for 1988/1989 by the ICES Statistician (C.M.1989/D:21).
ACFM recognizes the need for a clear identification of the categories of the catch data used for assessments. It was decided to incorporate in the instructions to working groups a request for specification of the catch data used to estimate fishing mortalities. It is necessary that the working groups clearly identify factors contributing to the total fishing mortality in the various stocks, e.g.:
recorded landings, discards at sea, slipping of unwanted catches, losses due to burst nets etc., unreported landings, catch reported as other species, catch reported as taken in other areas, catch taken as by-catch in other fisheries.
7
8
It is recognized by ACFM that working groups should not be required to reveal the sources of the data. The groups, should, however, indicate whether the data originate from sampling programmes, field observations, interviews, etc., in order to allow ACFM and other interested parties to evaluate the quality of the data, and hence the basis for the assessment.
The overall responsibility of obtaining reliable and adequate fisheries statistics for publication in Bulletin Statistique does not rest with ACFM. The problem has been discussed on various occasions and was also brought to the attention of the Delegates at the 1989 Statutory Meeting. It is the opinion of ACFM that national offices for fisheries statistics are responsible for providing the catch data needed for assessments and that catch statistics should be collected on a gear basis. Such offices should undertake to determine the species composition of landings in the case where landings are made unsorted by species.
1.2 Review of ACFM Advice for 1989
In response to a request to review its procedure for revising catch possibilities, ACFM wishes to stress that its definitive advice on each stock is based on all the data available to ICES, and that the timing of the advice on each stock is determined by the need for that advice to be as accurate as possible.
While new information can be used to redefine the advice, ACFM considers that mid-year re visions are in general unnecessary. The precision of stock size estimates is such that there would need to be quite major changes before any reV1Slon in advice was justified. Minor changes would simply serve to create instability in advice.
ACFM nevertheless recognizes that it has a responsibility to draw the attention of managers, as early as possible, to any necessary alteration in scientific advice and to the need for a change in management action.
2. STOCKS IN NEAFC REGION
2.1 North-East Arctic Cod
Source of information: Working paper.
At the request of the Commission of the European Communities, ACFM reviewed the state of the stock of North-East Arctic cod.
The new information available was preliminary landings for 1988, weiqht-at-age data for the catches in 1988, and results of Norwegian and autumn 1988 and winter 1989. In additional, some survey indices have been
catch-at-age USSR surveys
and in
ACFM concludes that the new information does not give sufficient basis for a revision of the advice for 1989. Advice for 1990 will be given in November 1989 on the basis of the new assessment which will be made by the Arctic Fisheries Working Group in September.
2.1.2 North-East Arctic cod: Advice from the November 1989 ACFM meeting
Source of information: Arctic Fisheries Working Group report, September 1989 (C.M.1990/ Assess:4).
Year
1982
<434 300 364
Sp. stock biomass 373 Recruitment (age 3) 158 Mean F (5-10,u) 0.74
lpredicted or assumed. advice May 1988: 325,000 recruitment in millions.
1983
197 156
0.75
20ver period 1969-1988. JNorweqian coastal cod not included. 4 New - 363,000 t. Agreed TAC reduced to 451,000 t. Weights in '000 t,
catches: After reaching the lowest level in 39 years in 1984, landings increased rapidly in response to improved recruitment, but a new sharp decline started in 1988 (Tables 2.1.1 and 2.1.2). In 1989, landings are expected to decrease by about 100,000 t, and the spawning fishery in Lofoten was still at a historic low level. The available information indicates that discard rates were high in 1986 and 1987.
Data and assessment: Analytical assessment based on catch-at-age data, including estimates for 1989. VPA tuned using 6 time series of trawl and acoustic surveys and commercial CPUE data. Recruitment estimated by combination of data from 16 index series.
Fishing mortality: Reached the highest level on record (0.95) in 1987, but decreased to 0.84 in 1988 (Figure 2.1). A further decrease to 0.68 is expected in 1989, which is 1.5 x Fmed (0.46).
Recruitment: After a series of poor year classes, recruitment was considerably improved with 1983 as an outstanding year class. However, the estimates of the year classes 1982 and later have been gradually reduced as more indices become available. All the year classes after 1983 are now estimated to be well below the long-term average.
State of stock: Stock biomass has decreased from about 1.5 million t in 1986 to 689,000 t in 1990. Spawning stock biomass estimates are considered to be uncertain, but 181,000 t is indicated in 1990 and the recent level may have been the lowest in the stock history.
Eotg~gst fQr 1990: Assuming F(89) = 0.68 Catch(89) = 330,000 t.
Predicted Option Basis F(90) Consequences/implications
SSB(90) Catch(90) SSB(91)
A F 0.15 181 88 285 SSB increasing B FO. 1 0.24 134 259 SSB increasing C Fmax 0.32 172 238 SSB increasing D Flow 0.46 233 205 SSB moderately increasing E F~M) 0.68 312 163 SSB d·ecreasing
Weights in '000 t.
Continued fishing at current fishing mortalities will lead to a decline in spawning stock biomass. Catches will be decreasing in 1991.
9
10
Recommendation: At current fishing mortalities the spawning stock biomass will in 1991 fall close to the lowest previously recorded level, and there is no evidence of good year classes recruiting to the stock in the near future. The stock may, therefore, be in danger of recruitment overfishing. ACFM recommends that the fishing mortality in 1990 is reduced to FI ,corresponding to a TAC of 172,000 t. As in previous years, this TAC includes all cod ca8~ht except the Norwegian coastal cod.
Special comments:
1. In the Working Group assessment, the VPA was tuned with 4 series of survey indices and one series of catch-per-unit effort which was a combination of data from the Norwegian and the USSR commercial trawl fleets. ACFM felt that it. was more appropriate to keep the data from the two fleets separate in the VPA tuning. The assessment was, therefore, revised, giving a reduction in fishing mortalities in 1989 and accordingly higher stock numbers and predicted catches in 1990.
2. An examination of the biological reference points for the North-East Arctic cod shows that the estimates of F and, to a lesser extent, FO 1 are not very reliable and that F d is much more robust.m"Bwever, the estimate of F d used last year was too high and hl\'~ been revised. ACFM reiterates that F d is a mor&eappropriate reference point for the North-East Arctic cod which may be ~~ed as a target level of fishing mortality for a healthy stock. In the current stock situation, however, a lower fishing mortality is needed to ensure a recovery of the stock, and Flow is recommended as a suitable level.
3. In the period 1986-1989, there have been major changes in the assessments of the North East Arctic cod stock and consequently in the management advice from ACFM. The reasons are as follows:
Based mated data
on recruitment surveys, the 1983, 1984, and 1985 year classes were in 1986 esti to be very abundant, especially the 1983 year class. From historic weight-at-age and previously assumed natural mortality, the prospects for the stock to increase
were good.
Surveys during year classes to ment in 1986.
the years 1987, 1988, and 1989, however, showed the 1983, 1984, and 1985 be less and less abundant compared to the levels estimated in the assess-
The reduction in number of the three year classes compared to the previous assessments might be explained by the following:
a) The cannibalism observed in the cod stock during these years was higher than in other years and has caused a larger decrease in numbers of young cod than expected in the predictions.
b) The growth rates of these year classes have in later years been only approximately 50% compared to what was forecast in 1986. The lower weights-at-age thus observed have induced a higher fishing mortality, because it was necessary to catch a larger number of fish to achieve the TAC.
c) Discarding is known to have taken place, but it is not possible to assess the extent of this reliably. However, discarding in 1986-1987 was probably increased by the poor condition of the young fish.
A regulation to ban discarding was introduced in 1988, and more frequent closing of areas with much undersized fish might have reduced discarding substantially in 1988 and 1989.
11
Source of information: Working paper.
At the request of Norway, ACFM reviewed the state of the stock of North-East Arctic haddock.
The new information available was preliminary landings for 1988, catch-at-age and weight-at age data for the catches in 1988, and results of Norwegian and USSR surveys in autumn 1988 and winter 1989. In addition, some survey indices have been corrected.
ACFM concluded that the new information does not give sufficient basis for a revision of the advice for 1989. Advice for 1990 will be given in November 1989 on the basis of the new assessment which will be made by the Arctic Fisheries Working Group in September.
2.2.2 North-East Arctic haddock: Advice from the November 1989 ACFM meeting
Source of information: Arctic Fisheries Working Group report, September 1989 (C.M. 1990/ Assess: 4) .
Year
Sp. stock biomass Recruitment (age 3) Mean F (4-7,u)
1982
110
47
0.54
1 Predicted or assumed. 20ver period 1969-1988. Weights in '000 t, recruitment in millions.
Catches: in 1987, pected to
Landings increased from 17,000 but are now rapidly declining decrease to 57,000 t, which is
t, the lowest level on record, in 1984 to 151,000 t (Tables 2.2.1 and 2.2.2). In 1989 landings are ex-
26,000 t below the agreed TAC.
Data and assessment: Analytical assessment based on catch-at-age data, including estimates for 1989. VPA tuned using 4 time series of trawl and acoustic surveys. Recruitment estimated by combination of data from 11 index series.
Fishing mortality: Increasing from further decrease to 0.40 is expected (0.13).
1984 to 1987, but decreasing in 1989. This is 1.15 x Fmed
in 1988 (0.35)
(Figure 2.2). A and 3.1 x FO.l
Recruitment: After a series 1984, recruitment was good in 1992, appear to be very poor.
of poor year classes which recruited to the fishery in 1980- 1985-1987. The 1985-1989 year classes, recruiting in 1988-
State of stock: The spawning stock biomass reached a recent peak level of about 110,000 t in 1988 and is now declining. Because of the poor recruitment, this decline will continue un less the fishery is stopped.
12
Predicted option Basis F(90) Consequences/implications
S5B(90) Catch(90) SSB(91)
A ro.1 0.13 84 14 80 SSB slightly decreasing B Fmed 0.35 35 61 SSB decreasing C F(89) 0.40 39 58 SSB decreasing
Weights in '000 t.
Continued fishing at current fishing mortalities will lead to reduction in spawning stock biomass which in a few years may be the lowest on record.
Recommendation: The low abundance of the year classes 1985-1989 will keep the stock at a low level in the next few years. Fishing mortalities are moderate but in excess of F d. The spawning stock biomass is declining and will fall to extremely low levels if fisWrng mor tality is not substantially reduced. To halt the decline, catches in 1990 must be reduced to less than 10,000 t, but unavoidable by-catches of haddock in the cod fisheries are likely to exceed this level. ACFM, therefore, recommends that no directed fishery for haddock be al lowed in 1990.
Special comments: The most recent information indicates that the growth has returned to a normal level. As for cod, a reduction in survey indices for the year classes 1983-1985 is observed, giving higher fishing mortality in 1989 than estimated for the actual level of landings.
The fact that haddock is to some extent an unavoidable by-catch in the cod fishery, makes it difficult in practice to restrict catches to biological safe levels when the stock is at a low level. The level of these by-catches is difficult to predict, but if fishing mortality on haddock is reduced by the same ratio as the recommended TAC implies for cod, catches of about 20,000 t may be expected, and this is likely to represent an upper level of by catches.
13
Source of information: Arctic Fisheries Working Group report, September 1989 (C.M.19901 Assess:4) .
Year 1982 1983 1984 1985 1986 1987 1988 1989 Max 2 Min2 Mean 2
Recomm. TAf 130 1303 1033 853 743 <90 <83 120 Agreed TAC 120 Actual landings 168 157 159 107 70 92 114 262 70 175
Sp. stock biomass 158 161 186 162 1461 154 193 2051 574 146 289 Recruitment (age 1) 160 195 320 225 99 161 2001 2001 466 99 253 Mean F(3-8,u) 0.45 0.42 0.48 0.38 0.27 0.26 0.54 0.18 0.40
1 Predicted or assumed. 20ver period 1969-1988. 3Catch at F . Reduction to this level as quickly as possible was recommended. Target set by NOrwegi~RXauthorities. Weights in '000 t, recruitment in millions.
Catches: Landings declined sharply from 1984-1986 to the lowest level on record (Table 2.3), but are currently moderately increasing.
Data and assessment: Analytical assessment based on catch-at-age data VPA tuned using CPUE from Norwegian trawlers and purse seiners. Reliable recruitment indices are not available.
Fishing mortality: Decreased from 1984 to 1986, but increased in 1988 and may increase further in 1989 (Figure 2.3). The level in 1988 was close to Fmed (0.37). The level in 1989
will probably be higher, but it is uncertain due to little information on abundance of the recruiting year classes.
Recruitment: The 1983 year class is the strongest since 1978 and appears to be above average strength. Also, the 1984 year class is relatively abundant, whereas the 1985 year class appears to be poor. Little is known about more recent year classes, but reports from coastal areas indicate a relatively high abundance.
State of stock: The stock biomass has been declining but is level of about 500,000 t until 1991. Spawning stock biomass is 1983 year class, but is expected to decrease in 1990 and 1991.
expected to be stable at the increasing because of the
Forecast for 1990: Assuming F(89) - 0.46, Catch(89) = 120,000 t.
A F 0.17 182 B FO. 1 0.25 C Flow 0.28 D Fmax 0.36 E F~M) 0.46
48 190 SSB slightly increasing 69 177 SSB slightly decreasing 76 172 SSB slightly decreasing 93 161 SSB decreasing
105 148 SSB decreasing
Weights in '000 t.
continued fishing at current levels of fishing mortality will lead to a reduction of the spawning stock biomass.
14
Recommendation: Current fishing mortality is above F d' The spawning stock biomass will in the short term decline for all options of fishing mO~fality higher than Fa 1 because of the poor 1985 year class. ACFM recommends that fishing mortality is reduced at least to the F d level, corresponding to a TAC of no more than 93,000 t in 1990. me
Special comments: Sampling of landings of spawning saithe, especially in the gillnet fisheries, has been poor for many years, In last year's assessment, this caused severe pro blems, but these have been sorted out this year. The reduction in the TAC is caused chiefly by an overestimate of the 1985 year class in last year's assessment. Uncertainty about the size of recruiting year classes remains a large problem in the catch predictions.
15
2.4 Redfish in Sub-areas I and II
Total redfish landings in Sub-area I and II have been declining continuously from 132,000 t in 1982 to 36,000 t in 1987, but increased to 38,039 t in 1988 (Tables 2.4.1 - 2.4.4).
The proportion of Sebastes mente II a in the landings has declined from 85\ in 1983 to 30\ in 1987, but increased to 38% in 1988 (Table 2.4.5).
2.4.1 Sebastes mentella in Sub-areas I and II
Source of information: Arctic Fisheries Working Group report, September 1989 (C.M.1990/ Assess: 4) .
Year 1982 1983 1984 1985 1986 1987 1988 1989 Max 2 Min2 Mean 2
Recomm. TAC 70 70 70 85 85 703 11 12 Agreed TAC 70 100 90 85 85 85 Actual landings 115 105 73 63 23 11 14 269 7 81
Sp. stock biomass 183 148 94 65 54 49 54 581 319 49 183 Recruitment (age 6) 82 88 75 1 751 1211 155 1 255 1 2741 590 75 319 Mean F (10-15,u) 0.44 0.68 0.81 0.68 0.31 0.13 0.16 0.81 0.01 0.33
1 Predicted Weights in
or assumed. 20ver period 1969-1988. 3precautionary TAC based on recent catches. '000 t, recruitment in millions.
Catches: Landings have been declining from 1982 to 1987 (Table 2.4.5), but increased to 14,000 t in 1988 and a further increase to 18,000 t is expected in 1989.
Data and assessment: Analytical assessment based on catch-at-age data. VPA limited time series of USSR CPUE data and a plot of F vs Effort. Both methods low level of fishing mortality in 1988. Recruitment from USSR estimates based fecundity.
tuning with a indicated a
on population
Fishing mortality: Peaked in 1983-1985, but subsequently appears to have been rapidly reduced (Figure 2.4.).
Recruitment: The year classes recruiting to the fishery (at age 6) were about 500 million individuals in 1970-1977. In 1982-1985 the level was reduced to less than 100 millions, but since then there appears to have been a gradual improvement with the 1982 year class as the most abundant.
State of stock: Total biomass less than 20\ of the peak levels stopped the decline and there is
and spawning stock biomass have been declining and are in 1975, but the reduction in fishing mortalities currently a slightly increasing trend.
Forecast for 1990: Assuming F(89) = 0.18, Catch(89) = 18,000 t.
Weights in '000 t.
both has
Continued fishing at current fishing mortalities will lead to a slight increase in the spawning stock biomass.
16
Recommendation: Because of large problems with the age readings, the assessment is not con sidered very reliable, especially with regard to the current level of exploitation. The indications are that fishing mortality is low and spawning stock biomass is increasing. However, the stock size is small compared to historical levels and continued low fishing mortalities are needed to allow the stock to recover. ACFM recommends that fishing mortality is kept at the current low level, corresponding to a TAC of 18.000 t in 1990.
Special comments: There are large discrepancies between age-length relationships from dif ferent countries related to different age-reading techniques. This problem needs to be re solved before the age-based assessment can be considered reliable. However, it is unlikely that this will happen in the next few years, and alternative methods for the assessment should, therefore, be explored.
2.4.2 Sebastes marinus in Sub-areas I and II
Source of information: Arctic Fisheries Working Group report, September 1989 (C.M.19901 Assess:4).
Year 1982 1983 1984 1985 1986 1987 1988 1989 Max2 m~ Mean 2
Recomm. TAC 14 1~ 1~ 1~ 1~ 4 15 24 Agreed TAC 14 17 17 15 15 Actual landings 16 19 28 29 30 24 24 49 13 26
lpredicted or assumed. 20ver period 1969-1988. cautionary TAC is set based on recent catches.
3precautionary TAC. 4Recommended that a pre Weights in '000 t.
Catches: Landings decreased from 49,000 t in 1976 to 16,000 t in 1982, followed by an in crease to about 30,000 t in 1984-1986, and a new decrease to 24,000 t in 1987-1988 (Table 2.4.5).
Data and assessment: Catch-at-age data are available, but are considered unreliable. In the absence of a reliable analysis, a SHOT forecast was made.
Fishing mortality: Unknown.
Recruitment: Unknown.
State of stock: Survey data indicate that the stock, especially of younger fish, has been declining, but there are indications of an increase in the most recent surveys.
Forecast for 1990: Assuming Catch(89) = 24,000 t. For continued fishing at the current level of exploitation, a catch of 23,000 t for 1990 is predicted.
Recommendation: ACFM advises that the current level of exploitation should be maintained and, therefore, prefers a status guo catch in 1990 corresponding to a TAC of 23,000 t.
17
Source of information: Arctic Fisheries Working Group Report, September 1989 (C.M.1990/ Assess: 4).
Year
Sp. stock biomass Recruitment (age 3) Mean F(7-11 ,u)
1982 1983 1984 1985 1986 1987 1988 1989
12 12 17
0.37
1 Predicted or assumed. zOver period 1970-1988. JRecommended that a precautionary TAC is set based on recent catches. Weights in '000 t, recruitment in millions.
Catches: Landings have been fairly stable at about 20,000 t in recent years, but are still considerably below the level in the 1970s (Tables 2.5.1 - 2.5.4).
Data and assessment: Analytical assessment based on catch-at-age data. VPA tuned using 2 time series of commercial CPUE data. Reliable recruitment indices are not available.
Fishing mortality: Relatively stable since 1983 at about 1.5 x Fmax ' but expected to be reduced in 1989 (Figure 2.5).
Recruitment: Has generally varied little between years, but longer periods of high or low recruitment are indicated.
State of stock: Spawning stock biomass has been stable since 1978, but is less than 30% of the 1970 level.
Forecast for 1990: Assuming F(89) = 0.27, Catch(89) - 14,000 t.
A F 0.13 54 8 68 SSB increasing B FO. 1 0.25 14 62 SSB slightly increasing C F~~~) 0.27 15 61 SSB slightly increasing D F(88) 0.39 21 55 SSB unchanged
Weights in '000 t.
Continued fishing at current levels of fishing mortality will lead to a slight increase in the spawning stock biomass.
Recommendation: The stock appears to be small compared to historic levels and a strategy for rebuilding the stock should be adopted. Provided that recruitment remains stable, an increase in the stock is expected with continued fishing at the current exploitation level. ACFM recommends that fishing mortality should not be increased from the estimated 1989 level which corresponds to a TAC of 15.000 t in 1990.
18
2.6.1 East Greenland cod (Sub-area XIV)
2.6.1.1 Adyice from the May 1989 ACFM meeting
Source of information: Report of the Working Group on Cod off East Greenland, February 1989 (C.M.1989/Assess:8).
Year 1982 1983 1984 1985 1986 1987 1988 1989 Max 2 Min 2 Mean 2
Recomm. TAC 12 6 6 4 4 5 5 5 12 4 6 Agreed TAC 11 . 5 11 .5 11 .5 11 .5 11 .5 11.5 11.5 11.5 11.5 11 .5 11 .5 Actual landings 273 13 8 2 5 7 9 27 2 10
Sp. stock biomass 49 27 25 16 42 21 20 221 49 16 29 Mean F(5-10,u) 1.40 0.53 0.40 0.13 0.14 0.38 0.32 1.40 0.13 0.47
lpredicted or assumed. 20ver period 1982-1988. 3rncluding discards. Weights in 'ODD t.
Cg:!;cb~s: After a peak in 1982, catches decreased sharply to 1985 (Table 2.6.1). Since 1986, catches have increased moderately.
Data and assessment: Stock estimates are derived from the bottom trawl survey of the Federal Republic of Germany, catch-in-numbers data, and certain assumptions about immigration and emigration.
Fishing mortality: From low levels in 1985-1986, fishing mortality increased in 1987. In 1988, a slight decrease occurred.
Recruitment: The very abundant 1984 year class, which recruited in 1988, is dominating the stock, followed by the reasonable 1985 year class which will recruit in 1989. A very low recruitment from the 1986 and 1987 year classes is expected.
State of stock: From a low level in 1985, the spawning stock increased in 1986 due to immi gration from West Greenland, but declined in 1987 due to fishing and emigration. The spawn ing stock in 1988 is at the same level as in 1987.
Forecast for 1989: (Figure 2.6.1)
Predicted Option Basis F(89)
SSB(89) Catch(89)
A TAC = 5 0.12 22 5 35 B TAC = 11.5 0.30 11 .5 29 C F(88) 0.32 12 29
l Does not include immigrants from West Greenland in 1990. Weights in 'ODD t.
Continued fishing at current levels of fishing mortality which is close to the agreed TAC will lead to a moderate increase in SSB.
Recommendation: The increased catches in 1988 were counterbalanced by immigration from West Greenland. This results in a spawning stock biomass on the same level as in 1987. There are strong indications from the West Greenland survey results that no immigration will occur in 1989 supporting the spawning stock biomass at East Greenland. ACFM, therefore, reiterates its advice from the November meeting that catches should not exceed 5,000 t.
19
Special Comments: ACFM is concerned about the difficulties of advising on this stock.
a) The survey upon which the assessment is based, has to be conducted in September/October for biological reasons. ACFM, therefore, is not able to provide advice based on an analy tical assessment before May.
b. A fixed annual TAC has been set for the period of an agreement on fisheries between Greenland and the EC. For that reason any advice from ACFM on TAC levels is meaningless. Until the end of the agreement in 1990, ACFM will, therefore, restrict itself to advise on the state of the stock.
20
2.6.1.2 East Greenland cod (Sub-area XIV): Advice from the November 1989 ACFM meeting
Source of information: Working Paper on results of Federal Republic of Germany groundfish autumn surveys.
1981 1982 1983 1984 1985 1986 1987 1988 1989 Max ,
Min' Mean ,
Recomm. TAC 12 6 6 4 4 5 5 5 12 4 6 Agreed TAC 11 .5 11.5 11. 5 11 .5 11.5 11. 5 11 .5 11.5 11.5 11.5 11 .5 Actual landings 16 272 13 8 2 5 7 9 27 2 10.9
, Period 1981-1989. 2 Including discards. Weights in '000 t.
Results of Groundfish Survey: From the Federal Republic of Germany bottom trawl survey off East Greenland in the autumn of 1989 which ended mid-October, provisional estimates of stock abundance and trawlable biomass are available. These are given in the text table below together with the corresponding figures from the 1980-1988 surveys:
Biomass Abundance Year Season Ship
.3 %3 Tonnes • ( '000) Remarks
1980 Oct/Nov FMS IIKarlsJ:mrgli 62,944 33 15,425 34 1981 Nov/Dec FFS "Walther Herwig" 88,336 43 19,448 35 1982 Sep/Oct 19,782 35 6,106 52 1983 Sep/Oct 26,980 38 6,730 33 1984 Oct FFS "Anton Dohrn" 21,151 42 6,488 51 1985 Oct FFS "Walther Herwig" 21,842 26 7,815 27 1986 Oct 44,288 34 17,554 32 1987 Sep/Oct 33,929 36 25,296 37 1988 Sep/Oct 41,816 47 18,859 40 1989 Sep/Oct 125,604 57 49,277 43 2
~OnlY 36 valid hauls. Preliminary.
3confidence intervals are given at ± 95% significance level.
Survey results are evaluated using stratification by geographical areas and depth zones.
Fisheries: In Sub-area XIV, the agreed TAC for 1989 is 11,500 t. Almost 90% of the total internation~l quota was taken by June. The largest part of the catches was taken in the area south of 63 N. The catches mostly consist of the 1984 and 1985 year classes.
Data and Assessment: Age composition of the surveyed stock is not yet available. Not all of the catch samples have been worked up and, therefore, no age-based or length-based analysis could be carried out at present.
Recruitment: Survey results in 1989 show no indications of a good 1989 year class.
Migration: Results of the ongoing survey at West Greenland have first to be evaluated in or der to quantify the emigration rate from the West Greenland stock. Adverse environmental conditions at West-Greenland (low water temperatures in 1989) may be the reason for a more southerly and easterly distribution of the West Greenland stock which appears as emigration.
21
State of the stock: Compared to the results of the 1988 survey, there is a sUbstantial in crease in trawlable biomass (by a factor of 3.0), and the stock abundance is now 2.6 times higher than in 1988. This increase can only be explained by immigration of fish from West Greenland (because of the lack of recruitment at East Greenland) and an increase of biomass caused by growth. The spawning stock biomass and abundance are also expected to increase as immigrating fish from West Greenland are mostly mature (year class 1984). The stock is dominated by the 1984 and 1985 year classes.
Special comments: The final advice for 1990 will be given in May 1990 when the report of the Working Group on Cod Stocks off East Greenland has been evaluated by ACFM.
22
2.6.2 Pandalus in East Greenland waters (Denmark strait. Divisions XIVb - Va)
Source of information: NAFO Scientific Council, Provisional Report, June 1989 (SCS, Doc. 89/17).
Year 1982 1983 1984 1985 1986 19871 19881 1989
Advised TAC 3 4.2 4.2 4.2 5.0 10.02
Implemented TAC 4.5 5.7 5.2 6.1 7.24 7.24 8.7' 9.0' Actual landings 4.9 4.2 6.7 8.1 11.0' 12.24 12.54 12.5 1.3 7.4
1 Provisional data. 2Advised for a f(w years as a precautionary measure. 30n western side of the G5eenland-Iceland midli~e only. Implemented TACs do not include Greenland fishery north of 66 30'N but catches do. Over period 1979-1988.
Catches: The fishery began in 1978 with total catches of 400 t. Catches increased rapidly to 8,400 t in 1980, decreased to less than 5,000 ~ in 1981-1983 and have increased since 1984 to reach 12,500 t in 1988 (catches north of 66 30'N inclusive).
Data and assessment: Total available fishing ground varies depending upon ice conditions. There has been an increase in gear size for at least some of the fleets and the CPUE from different fleets show different trends. In 1988, however, catch rates declined substantially for all fleets when compared with 1987. Discards are estimated to be small (2.2% on average) and it is the smaller (about 22 mm CL) shrimp that are discarded. By-catches of small juvenile redfish increased substantially in 1987 and 1988 compared with previous years. Research surveys have been conducted since 1983, but their usefulness as indicators of stock size is considered to be limited at present because of inconsistent sampling of the shrimp distribution due to variable ice coverage and ensuing difficulties in completing the random stratified sampling design.
Fishing mortality: No estimates.
Recruitment: No estimates.
State of stock: Indications from the commercial fisheries suggest a decrease in CPUE between 1987 and 1988.
Forecast for 1990: No basis to forecast catches to 1990.
Recommendation: Last year, ACFM concurred with the NAFO Scientific Council that catches in the present fishing area in Denmark Strait be held at approximately 10,000 t for a few years as a precautionary measure to allow time for any impact of the recent increase in catches on recruitment to be detected. ACFM shares NAFO Scientific Council's view that there is no basis for a change in the advice provided in 1988, but is concerned that the decline in CPUE may indicate a decline in stock size. Therefore, ACFM recommends that catches should be limited to 10,000 t.
Special comments: Discards of juvenile redfish have apparently been high in 1987 and 1988. The Scientific council of NAFO is asked to present yearly/quarterly estimates of the numbers and length distribution of redfish discards. The information will be used by the ICES North-Western Working Group to assess the impact of these discards on redfish stocks in Sub areas XIV and V. Despite the problems encountered with the research surveys, ACFM recommends that they should be improved and continued.
23
2.7.1 Advice from the May 1989 ACFM meeting
Total landings of redfish from Sub-areas V and XIV amounted to 204,000 t, 203,000 t, and 203,000 t for 1986, 1987, and 1988, respectively. For the last year landings from the "traditional" fishery increased by 6,000 t in Division Va, decreased by 3,000 t in Division Vb and increased by 2,000 t in Sub-area XIV, whereas landings of the "oceanic" type fishery seem to have remained at the same level (catches from one country not yet available). No further information was available.
2.7.2 Redfish in Sub-areas V and XIV: Advice from the November 1989 ACFM meeting
The total landings from the Irminger Sea redfish stock complex reached a peak of 228,000 t in 1986. The catches amounted 205,000 t in 1987 and 209,000 t in 1988. The total landings of redfish in Division Va increased from 87,000 t in 1986 to 95,000 t in 1988 (Table 2.7.1). In 1989 landings are expected to decline to 85,000 t. In Division Vb landings have been decreasing from the peak of 22,000 t in 1986 to 15,000 t in 1988 (Table 2.7.2), whereas the landings in 1989 are expected to increase to 16,000 t. In Sub-area XIV the landings in the "traditional" fishery decreased from 15,000 t in 1986 to 8,000 t in 1987 but increased slightly to 10,000 t in 1988 (Table 2.7.3). Preliminary catch figures for the first nine months in 1989 indicate a sharp decline in landings to only 5,000 t.
2.7.2.1 Sebastes marinus in Sub-areas V and XIV
Landings of ~. marinus increased from 77,000 t in 1987 to 87,000 t in 1988. No information is available on the splitting between the ~. marinus and ~. mentella for Sub-area XIV and Division Vb in 1989 but in Division Va the ratio between ~. marinus and ~. mentella is the same in the 1989 catches as in 1988. Based on this, the expected catches of ~. marinus in 1989 will be similar to the level preferred by ACFM of 77,000 t.
2.7.2.2 Sebastes mentella "traditional fishery" in Sub-areas V and XIV
Catches of ~. mentella from the traditional fisheries in Sub-areas V and XIV declined from 46,000 t in 1986 to 33,000 t in 1988. No split between the ~. marinus and ~. mentella catch for 1989 was available but the expected catches will be less than the precautionary TAC of 40,000 t recommended by ACFM for 1989 and 1990.
2.7.2.3 Sebastes mentella "oceanic type" in Sub-areas XII and XIV
The fishery on the "oceanic" type ~. mentella stock outside the 200 nautical mile national fisheries zone in Sub-areas XII and XIV decreased from 105,000 t in 1986 to 91,000 t in both 1987 and 1988. No information on the expected catches in 1989 is available. The 1988 catches were at about the preferred level of ACFM, i.e., around 90,000 to 100,000 t in 1989 and 1990, respectively.
2.8 Greenland Halibut in Subareas V and XIV
2.8.1 Advice from the May 1989 ACFM meeting
Total landings of Greenland halibut were 33,000 t, 47,000 t, and 53,000 t in 1986, 1987, and 1988, respectively. The increase of 6,000 t in 1988 almost all came from Division Va. The landings of 53,000 t are nearly twice the recommended TAC. No further information was avail able.
24
2.8.2 Greenland Halibut in Sub-areas V and XIV; Advice from the November 1989 ACFM meeting
Total landings increased from 33,000 t in 1986 to 47,000 t in 1987 and 52,000 t in 1988 (Table 2.8.1). The increase of 4,000 t in 1988 almost all came from Division Va (Tables 2.8.2 2.8.4). In the analyses of this stock, the recent development in the fisheries caused problems in defining the exploitation pattern and, therefore, ACFM was only able to recommend a preliminary TAC for 1989 of 33,000 t. It was expected that ACFM could revise this advice at its May 1989 meeting but no further information was available. Landings from this stock in 1989 are expected to be about 60,000 t, almost twice the preliminary TAC recommendation. A recent Icelandic assessment [Greenland Halibut p. 24-27 in "State of marine stocks and environmental conditions in Icelandic waters 1989. Fishing prospects 1990". Marine Research Institute, Fjolrit 19, Reykjavik, August 1989 (Mimeographed in Ice landic with an English summary)] of this stock, points out that the stock cannot sustain a continuation of the present high fishing and it will decline rapidly in the years to come. The North-Western Working Group will meet in spring 1990 to assess this stock and ACFM will then be in the position to advise on a TAC for 1990 at its next May meeting.
2.9 Icelandic Saithe
The total ively. The available.
landings were 66,000 t, 81,000 t, and 78,000 t in 1986, 1987, and 1988, respect landings in 1988 are 22% above the recommended TAC. No further information was
2.9.2 Icelandic Saithe (Division Va); Advice from the November 1989 ACFM meeting
Total landings were 66,000 t, 81,000 t and 77,000 t in 1986, 1987 and 1988, respectively (Table 2.9). The landings in 1988 were 2,000 t above the assumed catch used in the pro jections for the 1989 and 1990 advice. In 1989, it is expected that landings will be about the recommended TAC of 80,000 t. A new assessment of this stock will be available to the ACFM meeting in May 1990 where final advice for 1990 will be given.
2.10 Demersal Stocks at the Faroe Islands
2.10.1 Faroe saithe (Division Vb)
Total landings were 42,000 t, 41,000 t, and 45,000 t in 1986, 1987, and 1988, respectively (Table 2.10.1). The landings in 1988 were 2,000 t above the assumed catch used in the pro jections for the 1989 and 1990 advice. In 1989, it is expected that the landings will be close to the 1988 figure.
2.10.2 Faroe Plateau cod (Sub-diyision Vb1)
Total landings in 1986, 1987, and 1988 were 35,000 t, 24,000 t, and 25,000 t, respectively (Table 2.10.2). The landings in 1988 were 3,000 t larger than assumed in the projections for the 1989 and 1990 advice, and the catch in 1989 will probably show an increase compared to 1988. Preliminary estimates made at the Faroese Laboratory in 1989 indicate this to be an effect of higher fishing mortality.
2.10.3 Faroe Bank cod (Sub-division Vb2)
The landings of cod from the Faroe Bank were 1,900 t, 2,000 t, and 1,400 t in the years 1986, 1987, and 1988, respectively (Table 2.10.3). There is no assessment of this stock.
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2.10.4 Faroe haddock (Division Vb)
Total landings of haddock from the Faroe area (Tables 2.10.4 and 2.10.5) were 14,000 t in 1986, 15,000 t in 1987, and 12,000 t in 1988. The 1988 figure is 3,000 t less than assumed in the projection for 1989 and 1990. For 1989, the same landings as in 1988 are expected.
The fishery at the Faroes for cod, haddock, and saithe is to a large extent a mixed fishery, in so far as the same fleets exploit all three stocks. Variation in availability to the fishery by each stock, therefore, affects the effort directed to one stock relative to another one.
At January 1989, the minimum legal mesh size in the trawl fisheries was increased from 135 mm to 155 mm. In the forecasts for 1989 and 1990, ACFM took account of this on theoretical grounds. The real effects, however, have yet to be assessed.
New assessments on the stocks of cod at the Faroe Plateau, Faroe haddock and saithe will be available to the ACFM meeting in May 1990. Pending this, ACFM reiterates its advice of November 1988 that the effort in the demersal fisheries at Faroes is too high, and should be reduced.
26
Source of information: Atlanto-Scandian Herring and Capelin Working Group report, October 1989 (C.M.1990/Assess:5).
Year
Sp. stock biomass 3
1982 1983 1984 1985 1986 1987 1988 1989
50 50 50 52.5 57 59
215 257
318 525
20ver period 1970-1988. 3At in '000 t, recruitment in million.
July. 4 From acoustic estimate.
Catches: Stable up to 1985, increasing from 1986, now higher than any year since 1969 (Table 2.11 .1)
Data and assessment: Based on catch-in-number data and winter acoustic surveys. The database is satisfactory, giving reliable estimates of stock size.
Fishing mortality: Has fluctuated around F = 0.22, now slightly higher (Figure 2.11.1).
Recruitment: Variable with a number of above-average year classes in the last few years.
State of stock: A continuing recovery from the low level in the early 1970s; now at highest level since 1947. The spawning stock biomass in 1988 is now estimated as 20% lower than in last year's report.
A 0.22 430 80 460 SSB increasing B Status 9l!Q 0.26 90 445 SSB increasing slightly C 0.30 100 430 SSB stable
Weights in '000 t.
Recommendation: TAC for the 1989 season has been set at 90,000 t. Continued fishing at present level will result in a catch of 90,000 t in 1990 and a slight increase in spawning stock biomass. As the herring stock has probably been underestimated in the 1988 November/December acoustic survey, advice on the TAC for the 1990 season is deferred until after the 1989 November-December acoustic survey.
27
Source of information: Atlanto-Scandian Herring and Capelin Working Group Report, October 1989 (C.M.1990/Assess:5).
Year 1982 1983 1984 1985 1986 1987 1988 1989 Max 2 Min 2 Mean 2
Recomm. TAf 0 0 38 50 150 150 120-150 100 150 0 72.6 Agreed TAC 12 21 38 60 126 115 120 1004 126 12 70.3 Actual landings 16.7 23.1 53.5 169.8 225.3 127.3 164.5 225.3 16.7 111 .5
Sp. stock biomass 532 590 621 552 492 513 1336 15141 1336 492 662.3 Recruitment (age 3) 730 125 89 134 10200 237 499 601 10200 89 1716.3 Mean F(4-9,u) .02 .03 .09 .36 .52 .21 .20 .52 .02
1 Predicted or assumed. 20ver period 1982-1988. 3National quotas. 4Includes estimated 10,000 t slipping. Weights in '000 t, recruitment in millions.
Catches: Kept at a low level until 1984, but have increased in later years (Tables 2.11.2.1- 2.11.2.2).
Data and assessment: Analytical assessment, catch-at-age (VPA) and abundance estimates based on acoustic survey.
Fishing mortality: Kept at a low level except for the years 1985 and 1986, when unrecorded fishing mortality appears to have formed a considerable part of the total mortality (Figure 2.12.2.2).
Recruitment: Extremely low except for the 1983 year class.
State of stock: Depleted. Spawning stock biomass is currently decreasing and about 1/6 of the level before the stock decline started (Figure 2.11.2.1).
A No fishing 0.00 1539 0 1476 Spawning stock decreasing B 0.8 F(89) 0.04 67 1409 Spawning stock decreasing C 0.05 80 1393 Spawning stock decreasing D F(89) 0.06 100 1377 Spawning stock decreasing
Weights in '000 t.
Continued fishing at current levels of fishing mortality will lead to a decline in the spawning stock.
Recommendation: The current spawning stock biomass is about 60% of the lowest level (2.5 million t) known to have given good recruitment in the past. A further decline is inevitable in the short-term. From a biological point of view, no fishing should take place on this stock until a sUbstantial increase in biomass is evident. However, since stopping the fishery may be unrealistic, ACFM recommends a reduction in fishing mortality to a maximum level of F - 0.05 which corresponds to a TAC of no more than 80.000 t in 1990.
28.
Special comments: ACFM noted that unrecorded fishing mortality due to discards and breaking of gear has formed a considerable proportion of the total mortality on this stock in recent years. It is stressed that this should be taken into account when setting the TAC.
Apart from the obvious gain in long-term yield, a reason for rebuilding the stock to its former high level may be its role in the ecosystem. Thus, there is an increaslng concern that the depletion of the stock has disturbed the ecological balance in a large part of the Norwegian Sea and the Barents Sea.
2.11.3 Distribution in time and space of the Norwegian spring-spawning herring
A description of available knowledge on the migration and distribution of Norwegian spring spawning herring is published in the 1985 ACFM report. The account below gives additional information provided by the Atlanto-Scandian Herring and Capel in Working group in 1989 (C.M.1990/Assess:5):
1. The herring presently spawn along the Norwegian coast from Sklinna in the north to Stadt in the south in February to March. In 1989, some spawning was also observed at Karm¢y.
2. The larvae drift northwards with the coastal current and into the fjords. In 1988 and 1989, large parts of the larval population also drifted into the Barents Sea.
3. At present, the adult herring have their feeding areas west of the LofQten-Vesteralen area, mainly within 200 nautical miles off the coast. They are present in this area in early June. In July 1988, some herring were observed west of 00 by a Soviet research vessel but this has not been observed in 1989. By the middle of August, herring have congregated close to the coast in the Vesteralen-Lofoten area and gradually move into the fjords. They stay in this area until the middle of January, when they start migrating south to the spawning areas.
The distribution pattern in the period 1986-1989 is summarized in Figure 2.11.3.
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2.12 Cape lin
2.12.1 Barents Sea capelin (Sub-areas I and II. excluding Division IIa west of 50W)
Source of infQrmation: Atlanto-Scandian Herring and Capelin Working Group report, October 1989 (C.M.1990/Assess:5).
Year 1982 1983 1984 1985 1986 1987 1988 1989 Max 2 Min2 Mean 2
Recomm. TAC 1600 2300 1100 1000 0 0 0 0 Agreed TAC 1700 2300 1400 1100 120 0 0 0 Actual landings 1759 2375 1481 868 123 0 0 0 2940 0 1371
Sp. stock biomass (1 Jan) 582 122 219 83 36 16 1671 1501 1767 16 454 Recruitment (age 2) 307 425 372 246 11 4 291 1871 735 4 386
1predicted or assumed. 20ver period 1973-1989. Weights in '000 t, recruitment in billions.
Catches: Drastic decline in catches after a peak in 1983. Since May 1986, there has been no fishing (Table 2.12.1).
Data and assessment: Assessment based on acoustic survey.
Fishing mortality: Not estimated.
Recruitment: Recruitment to the spawning stock is expected to improve from 1991-1992 when the 1988 and 1989 year classes start maturing.
State of stock: Depleted, although the O-group and 1-group abundance is approaching levels in 1981-1985. Target spawning stock biomass of 400,000-500,000 t will not be reached in 1990.
Recommendation: No catch in 1990.
Special comments: Data from the acoustic surveys indicate that natural mortality for the 1986 and 1987 year classes is lower than for the 1982-1985 year classes. This may be due to reduced predation by cod.
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2.12.2 Ca!!elin in the Iceland-East ~reenland-~an Mayen area (Sub-areas V and XIV and Division IIa west of 50W)
2.12.2.1 Advice from the May 1989 ACFM meeting
Source of information: Report of the Atlanta-Scandian Herring and Capelin Working Group, October 1988 (ICES C.M.1989:Assess 7) and Working paper.
Year 1982 1983 1984 1985 1986 1987 1988 1989 Max 2 Min2 Mean 2
Recomm. TAC3 366 0 375 300 700 1100 5004 915 Agreed TAC3 0 640 920 1280 1290 1050 1065 Actual landings 3 626 0 573 897 1307 1332 1112 1023 1332 0 816
Sp. stock biomass 140 260 440 460 450 420 400 4461 460 140 341 Recruitment (age 1 ) 48 145 134 220 102 1071 220 48 104
1predicted or assumed. 20ver period 1981-1988. 3The figures in the TAC table reter to a fishing season ending in the year indicated, starting in July and ending in March. TAC for the period July-November. Weights in '000 t. Recruitment in billions.
Catches: Catches have varied according to agreed TAC recommendations and state of stock, but are currently at a high level.
Data and assessment: Analytical assesment based on acoustic survey and catch-at-age data.
State of stock: Generally variable due to the short life span, but stable in recent years.
Forecast for December 1989/March 1990 season: Deferred until November 1989.
Recommendation: ACFM recommends that the TAC for the period July-November 1989 should not exceed 900,000 t. TAC recommendations for the period December 1989 - March 1990 is deferred until November 1989.
S!!ecial comments: On the basis of the results of an acoustic survey of stock abundance, car ried out in October 1988, ACFM calculated that a TAC of 915,000 t could be set for the 1988/1989 season leaving 400,000 t to spawn in 1989 (Coop.Res.Rep., No.161). However, in its October 1988 report (C.M.1989/Assess:7), the Atlanto-Scandian Herring and Capelin Working Group noted that at the time of the survey at least half of the fishable stock had not re turned from its feeding migrations to the East Greenland-Jan Mayen area. The Working Group pointed out that under such circumstances, experience had shown that acoustic measurements of stock abundance tended to produce underestimates.
Another survey of the fishable stock was, therefore, carried out in January 1989. The survey of this stock component was successful, the fishable stock at the time being relatively restricted area off East Iceland. On the basis of the January 1989 it was calculated that the TAC for the 1988/1989 season could be increased by to 1,065,000 t leaving the target 1989 spawning stock of 400,000 t.
located in a survey results some 150,000 t
The exploitable stock in the 1989/1990 season will consist of the 1987 year class and that part of the 1986 year class which did not mature and spawn in 1989. In November 1988, ACFM stated that calculations based on the target spawning stock size (400,000 t) and an acoustic estimate of 1-group capelin in August 1988 would result in a TAC of 1,025,000 t for the
31
1989/1990 season. It was also pointed out that considerable further information on both year classes involved was expected upon the completion of the January 1989 survey. For that reason, and due to uncertainties involved in a prediction based on the short 1-group data series, ACFM recommended that advice on a TAC for the 1989 summer and autumn season be de ferred until May 1989.
In the January 1989 survey, by far the largest and densest schools of immature capelin oc curred in the immediate vicinity of the ice border. Evidently the abundance was underesti mated to an unknown degree. Since the autumn of 1988, no significant new information on the age groups comprising the fishable stock in the 1989/1990 season has, therefore, become available.
The calculations indicating a TAC of 1,025,000 t for the 1989/1990 season have in the two previous seasons considerably underestimated the stock abundance. Thus, for the 1988/1989 season, the actual catch was 253,000 t higher than indicated by the preliminary calcu lations, and another 42,000 t might have been taken inside the agreed TAC. A corresponding underestimate for the 1989/1990 season would mean that the TAC could be 1,300,000 t.
ACFM feels that a TAC of 900,000 t for July-November 1989 represents a level which will en sure that the target stock of 400,000 t is conserved to spawn in 1990, also taking into con sideration the progressive cooling of the area which is likely to reduce growth, as already observed in 1988. Advice for the period December 1989 - March 1990 is deferred until November 1989 when the results of the autumn survey will be available.
32
2.12.2.2 Capelin in the Ice~and-East Greenland-Jan Mayen area (Sub-areas V and XIV and Divi sion IIa west of 5 WI: Advice from the November 1989 ACFM meeting
Source of information: Atlanto-Scandian Herring and Capelin Working Group report, October 1989 (C.M.1990/Assess:5).
Year
1982 1983 1984 1985 1986 1987 1988 1989
366
626
346 127
lpredicted or assumed. 20ver period 1981-1988. J The figures in the TAC table refer to a fishing season ending in the year indicate~, starting in July and ending in March. Prelim inary TAC for the period July-November. Age 1 at the beginning of the season. Weights in '000 t, recruitment in billions.
Catches: Catches have varied according to agreed TAC recommendation and state of stock (Table 2.12.2).
Data and assessment: Assessment based on acoustic survey and catch-at-age data.
State of stock: Highly variable due to the short life span.
Recommendation:
1. ACFM at their May 1989 meeting recommended that TAC for the period July-November 1989 should not exceed 900,000 t. TAC for the remainder of the seaSon (December 1989-March 1990) should be deferred until the autumn survey of 1989 (in November) is completed.
2. TAC recommendation for the 1990 summer/autumn season will be given by ACFM May 1990 meeting.
Special comments: A TAC for the 1989 July-November season has been set at 900,000 t. This is based on a 1988 acoustic estimate of 1-group capelin. A recommendation for the period December 1989 - March 1990 was deferred until completion of an autumn 1989 survey. The sur vey will not take place until November 1989 and, therefore, a TAC for the remainder of the season will be set when the survey results have been evaluated.
Information about the 1990 summer/autumn season is currently based solely on the August 1989 1-group survey. The acoustic estimate would result in a TAC of 965,000 t, spread evenly over the period.
As these computations are based on a short time series and considerable additions could be made to the database during a planned survey in January/February 1990, ACFM will give advice on TAC for the 1990 summer and autumn season at its May meeting 1990.
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3.1 Herring Stocks South of 620 N
3.1.1 General considerations
In giving advice on stocks of herring, ACFM has considered whether there is a single management target that is appropriate for all stocks. As in stocks of other species, the overriding consideration is to maintain the spawning stock biomass above a level at which recruitment may be adversely affected. For stocks above that level, a further consideration is to maintain the stability of catching opportunities within the constraints imposed by natural fluctuations in recruitment.
For stocks that are exploited at relatively high levels of fishing mortality (e.g., North Sea herring), the priority is to reduce fishing mortality to a level that will allow recruitment to build up a buffer against short-term decreases in recruitment. As a first step, the F d value may be looked upon as a useful guide to the upper limit of fishing mortality ~5 achieve some stability. However, there is no doubt that greater stability can be achieved without loss of yield by fishing at lower levels of fishing mortality. With stocks that are fished around the FO 1 level (e.g., herring in Division VIa north), there is no advantage in recommending fishing· at a higher level. The value of F recommended thus depends on the state of the stock in question and takes into account the difficulty of reducing fishing mortality and associated catch levels to reach this objective in one step.
For a number of herring stocks (Celtic Sea, Divisions IVc, VIId, Irish Sea) there are diffi culties in the assessment or lack of data which rule out the possibility of giving precise catch options. Because catch rates of herring can be maintained even at low stock sizes, ACFM reiterates the need for estimates of stock size for these stocks based on fishery independent surveys.
3.1.1.2 General considerations; Advice from the November 1989 ACFM meeting
In its May 1989 report, ACFM recognized that it has a responsibility to draw any necessary alterations in its advice to the attention of managers as early as possible. Advice on TAC levels for herring in 1990 was based on assessments carried out by the Herring Assessment Working Group in the first few months of 1989. For two stocks, new information has been ob tained and ACFM considered if its advice is still applicable.
34
Source of information: Report of the Herring Assessment Working Group for the Area South of 62"N, April 1989 (C.M.1989/Assess:15).
Year
Sp. stock biomass 2+ stock biomass Recruitment (l-ring) Mean F(2-6,u)
1982
0
167
Divisions IVa.b
469 496 581 646 646 10 276
Sea (Sub-area IV and Division VIId)
757 801 821 822 961 1 822 58 305 880 888 1,000 1.001 1,159 1 1,000 64 415
13.0 19.4 22.0 29.9 18.4 29.9 0.9 9.6 0.61 0.53 0.55 0.58 1 .41 0.05 0.59
1predicted assuming catch in 1989 do[s not exceed TAC; if F 89 = F 8 ,corresponding predictions are 865 (SSB) and 1046 (2+). Over period 1972-1988. ~e~~ht iA ~OOO t, recruit ment in billions.
Catches: Considerably in excess of 1988 TAC. Unallocated catches were 2,000 t. O-group catches amounted to 14,800 t and l-group catches to 109,000 t. Total North Sea catches are given in Table 3.1.2
Data and assessment: Catch at age adequate. Assessment of total North Sea (Sub-area IV and Division Vlld) tuned against time series of relative SSB estimates. Recruitment estimated from IYFS. 23,000 t of the catch in the North Sea were Division IlIa/Baltic herring and this was transferred to the assessment of that stock.
Fishing mortality: High and stable since 1985 (Figure 3.1.2).
Recruitment: 1986 and 1987 year classes recruiting to adult fisheries in 1989 and 1990 reasonable; 1988 year class may be below average.
State of stock: Only small increase since 1984 in spite of good recruitment.
Forecast for 1990 for total North Sea (Sub-area IV and Division Ylld)
A. Assuming F(89) = 0.42, Catch (89) = 514,000 t, TAC for entire North Sea and eastern Chan neL
SSB 2+ stock Catch SSB 2+ stock (90) (90) (90) (91) ( 91 )
A FO. l 0.14 1 , 311 1,544 197 1,562 1,711 Increased SSB B 0.30 1,178 1,391 403 1,212 1,338 Slow increase in SSB C 0.8F(88) 0.45 1,069 1,265 566 964 1,072 No further recovery of SSB
35
SSB 2+ stock Catch SSB 2+ stock (90) (90) (90) ( 91) (91)
A F (0.1) 0.14 1, 161 1,381 177 1,415 1,562 Increased SSB B 0.30 1,044 1,245 362 1, 101 1,225 Stabilization of SSB C 0.8F(88) 0.45 948 1,133 508 878 985 No further recovery of SSB
Weights in '000 t.
Continued fishing at current levels of fishing mortality will lead to a decrease in SSB to below the minimum safe level of 800,000 t by 1991.
Recommendation: ACFM recommends that F should be reduced to a level that will allow some increase in SSB (F = 0.30). The corresponding catch in 1990 depends on what is taken in 1989. If the TAC of 514,000 t is strictly enforced, then ACFM recommends a TAC of 403,000 t in 1990. If F in 1989 is allowed to reach its 1988 level, then the appropriate TAC at an F of 0.30 in 1990 would be 362,000 t. The TAC agreed for Divisions IVc and Vlld should be sub tracted from this amount to give a TAC for Divisions IVa and b.
Existing regulations designed to protect juvenile em minimum landing size, 32 mm minimum mesh size, tained. The spawning area closures in Division IVb
Special comments:
North Sea herring (sprat box closures, 20 by-catch regulations) should be main should be maintained.
1. The estimated spawning stock biomass in 1988 of 822,000 t is considerably less than that predicted by ACFM in May 1988 (1,171,000 t). This is explained by a combination of a) the considerable overshooting of the TAC in 1988, b) overestimation of the 1985 year class which recruited to the adult fisheries in 1988, c) a small overestimate of the adult stock in 1988 and d) a further decrease in the growth rate of herring. There is also some uncertainty about the spawning stock size in this year's assessment.
2. The future development of the North Sea herring stock depends on the efficacy of manage ment. As shown in the forecast tables above, overshooting of the TAC in 1989 by allowing F to remain at its 1988 level makes a considerable difference to the chances and speed of recovery. If the 1988 level of F continues into 1990 and 1991, then there is expected to be a decrease in spawning stock if the 1988 year class is confirmed to b

Documents

COOPERATIVE RESEARCH REPORT NO. 168 PART 1 Reports... · COOPERATIVE RESEARCH REPORT NO. 168 PART 1 REPORTS OF THE ICES ADVISORY COMMITTEE ON FISHERY MANAGEMENT, 1989 Copenhagen,