This paper not to be cited without prior reference to the author.
INTERNATIONAL COUNCIL FOR
TUE EXPLORATION OF TUE SEA
C.M. 19811G : 72
Dcmersal Fish Commillcc
Ref: Pelagic Fish Cllee
PROGRESS REPORT ON THE NORTH SEA
STOMACH SAMPLING PROJECf 1981
by
N.Daan
Nethcrlands Institute for Fishery Investigations
Haringkade I,
1976 CP IJmuiden. The Netherlands.
C.I.E.M.
ERRATA:
C.M. 1981/H:72
Page 4, 1igne 18, au 1ieu de 0.008299 lire 0,998299
Page 5, 1igne 7, au 1i eu de 283 lire 282
Page 16. Tab.5 (1979) au
l~eu
de ?n 372 et 79806 lire respectivement
f
876 etJ9 809
This paper not be cited without prior reference to the author.
International Council for
the Exploraiton of the Sea
C.M. 1981/G:72.
Demersal Fish Committee.
Ref: Pelagic Fish Cttee.
PROGRESS REPORT ON THE NORTH SEA
STOMACH SAMPLING PROJECT 1981
by
Niels Daan
Netherlands Institute for Fishery Investigations,
Haringkade 1,
1976 CP IJMUIDEN,
The Netherlands.
Introduction
The Ad hoc Working Group on Multispecies Assessment Model Testing, which
met in Copenhagen in March 1980, recommended (ICES C.M. 1980/G:2) that
an intensive stomach sampling programme for cod, whiting, saithe, mackerel
and haddock should be implemented in the North Sea in 1981, in order that
species interaction can be taken into account in stock assessment in 1982.
During its statutory meeting in Copenhagen in October 1980 ICES endorsed
this recommendation by the following resolution (C. Res. 1980/2:22):
i) an intensive stomach sampling scheme for cod, whiting, saithe,
mackerel and haddock should be implemented in the North Sea in 1981,
and member counties are urged to make available the research effort
to meet the requirements as defined in the report of the former'
ad hoc Working Group on Multispecies Assessment Model Testing, both
in terms of research vessel time and analytical labour;
ii) Dr. N. Daan should be Coordinator of the sampling, and he should,
if necessary, meet with the coordinators for individual fish species
for three days in IJmuiden in early 1981;
iii) the coordinator should report to the Demersal Fish and the Pelagic
Fish Committee at the next Statutory Meeting.
Since it appeared to be absolutely essential for the internal consistency
of the work of the different species coordinators that the different
aspects of standarization in data collection, recording and processing
were discussed in detail, a meeting was held in IJmuiden from 13 - 15
January 1981, which was attended by:
Mrs. J. Beaudouin (haddock)
Dr. N. Daan (cod)
Mr. H. Gislason (saithe)
Dr. J.R.G. Hislop (whiting)
Mr. T. Westgard (mackerel)
-France
-The Netherlands
-Denmark
-UK (Scotland)
-Norway
"
- 2 -
In addition ~rr. J.G. Pope (UK; England) and Mr. P. Spasse (Denmark)
were invited to the meeting in order to ensure that the results of the
programme would in the end meet the requirements for their use within
the context of multispecies assessment trials.
During the meeting a detailed Draft Manual for the Stomach Sampling
Project wes prepared, which was meant to serve as the basis for the
work to be done during the proces of sampling at sea and during the
analysis of the stomaehs and the processing of data in the laboratory.
This manual has been distributed among the scientists directly and
indirectly involved in the project, but a limited number of copies is
still available from the Netherlands Institute for Fishery Investigations.
The present report, which meets the request expressed in the third
paragraph of the Council Resolution 1980/2:22, does not deal with the
methods employed but presents information on the sampling intensity
reaehed during tbe first two quarters of 1981 and the state of affairs
in analysing and proeessing the sampies.
Sampling at sea.
Since sampling at sea 1S earried out by a variety of countries during
a variety of cruises and sinee the sampies are subsequently transported
to the different laboratories dealing with individual speeies, it causes
considerable logistical problems of keeping an overvieuw of bow many
sampies and how many stomaehs are collected and where they are at any
particular point of time. Therefore, at the time this report had to be
prepared some information may be laeking and tbe sehemes presented can
only be approximate.
Table Ia und b present tbe number of sampies and the total number of
stomaebs eolleeted by individual eountries during tbe first and second '
quarter of 1981 respeetively witb an estimate of the total number of
stomacbs involved.
In tbe report of the ad hoc Working Group (ICES C.M. 1980/G:2) it bas been
tentavily suggested tbat approximately 1500 stomaehs per quarter of the
year should be collected in order to give food composition data at a
reasanable level af precision. During the first quarter of 1981 wben
five'countries partieipated in the sampling at sea during the International
Yaung Fish Survey tbis number was greatly exceeded for cod, baddaek and
whiting, whereas for saithe and maekerel it bas not been possible to
reaeb tbe target.
During the secandquarter sampling intensity for tbe four roundfish species
bas been redueed by half but except for saitbe the target has still been
exceeded. Althaugh 500 mackerel stomaehs could be collected in this quarte~
this number is still far belaw the estimated number required.
Fig. 1 a and b present information on the global distribution of sampling
effort over tbe Nartb Sea during tbe first twa quarters of 1981. As cauld
be expected from the nature of tbe IYFS tbe Nortb Sea has been extremely
weIl covered by the sampling effort during the first quarter. Since
several squares have been sampled more tban ance it would seem apprapriate
to cut down the number of stomaehs ta be analysed far haddock and whiting
by making a selection out of the available sampIes if the work load for these
species interferes with the technical labour available ror analysis~
During the second quarter the coverage has been less good which is partly
due to the ract that the stomach sampling cruise of DANA was cancelled
- 3 -
because of gear problems. Both the Scottish waters and the Southern
North Sea have been adequately sampled but in the Central North Sea
there is a big gap.
Processing
Due to the logistical problems in the exchange of samples some delay
was caused in the processing of sampIes in the laboratory. However, the
majority of the sampIes taken so far seem to have arrived at their place
of destination and the analysis is in progress. In order to indicate the
present state of affairs tabel 11 provides information on the number of
stomachs analysed by the end of July 1981. Punching of data for computer
processing is lagging behind even more, but computer programmes have been
developed at the institutes in Aberdeen, Bergen and IJmuiden to take
ac count of the further analysis.
Results
Obviously it is too early to present any definite results here.However,
some general observations can be made. Firstly, it appears that for cod,
haddock and whiting the level of sampling intensity reached so far should
result in reliable information on the food composition of the North Sea
stocks of these species, although the coverage in the second quarter has
been less good. This is particularly unfortunate since 1981 has turned out
to be an extremely interesting year because of the extremely high
abundance of O-group cod throughout large areas of the North Sea
(lCES C.M. 1981/G:46). This O-group cod has been noted to turn up ln both
cod and whiting stomachs from the second quarter.
For saithe and mackerel the present sampling scheme does not seem
adequate for the ultimate purpose. It can only be hoped for that some
very general information on the food composition of these two species will
be produced on the basis of the limited number of sampIes available. The
few mackerel stomachs collected during the first quarter were all almost
empty except for a few containing enphausids. The mackerel stomachs from
the second quarter indicate relatively more fish, mostly sandeeIs, to
be consumed in the Southern North Sea than along the Norwegian deeps.
General comment
In view of the unavoidable delay in the exchange of samples after collectinn
and of the time required in analysis and computer processing it has
turned out to be irrealistic to expect the data tobe worked ur to a
stage that they can be used in multispecies assessment trials before the
next round of assessment Working Group meetings. In fact, before that
stage will be reached it would seem necessary to convene a meeting of
the species coordinators in order to put the results of the programme
together in a form that is suitable for further handling in multispecies
assessment trials. It is recommended that such a meeting is planned as
late as possible in 1982 but in time to report to the Council Meeting
in that year.
- 4-
Table I - Level of stomach sampling intensity by species and countries
(n = number of samples; N = number of stomachs).
Country
Saithe
n/N
Mackerel
n/N
Haddock
n/N
Whiting
n/N
A. 1st Quarter of 1981
IYFS
ENGL
122/465
G.A.Reay
?/2:2 50
?/543
?/1280
GERM
IYFS
Solea
?/1398
?/796
7/49
NEI'H
IYFS
278/1600
Corrnnercial
vessels
15/261
212/1378
347/2304
12/22
8/8
NORW
IYFS
92/343
188/1228
17/7
3/3
SCOT
IYFS
88/254
96/606
15'7/2:80 5
114/568
2:6 300
+100
Source
Cod
n/N
92/324
16/97
Total Nr of stomaehs
3344
2:5000
1/1
11
B. 2nd Quarter of 1981
NEl'H
GOV-Survey 195/1190
Waddensea
progr.
57/458
SCOT
Bottom Trawl
Survey.
79/185
NORW
Herring
Survey
Commercial
vessels
Total Nr of stomaehs
76/408
217/1659
2/7
192/1540 155/1061
2/2
?/364
?/77
?/180
?/36
32/205
?/35
?/290
1910
2312
45
2900
530
Tabel II - Nr of stomaehs analysed by the end of july 1981.
1st Quarter 1981
2nd Quarter 1981
Cod
Haddock
Whiting
Saithe
3090
1648
?
3627
966
?
?
Mackerel
11
169
E~
61
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Fig. 1a.
Distribution of sacples effort during ~
the first Quarter of 1981
NS
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