Input spreadsheet and initial data processing. Since 1999 (catch data 1998), the Working Group members have used a spreadsheet to provide all necessary landing and sampling data, which was developed originally for the Mackerel Working Group (WGMHSA) and further adapted to the special needs of the Herring Assessment Working Group. The current version used for reporting the 2002 catch data was v1.6.4. The majority of commercial catch data of multinational fleets was again provided on these spreadsheets and further processed with the SALLOCL-application (Patterson 1998). This program gives the needed standard outputs on sampling status and biological parameters. It also clearly documents any decisions made by the species coordinators for filling in missing data and raising the catch information of one nation/quarter/area with information from another data set. This allows recalculation of data in the future (as done by SG REDNOSE, see Section 1.4.1), choosing the same (subjective) decisions made today. Ideally, all data for the various areas should be provided on the standard spreadsheet and processed similarly, resulting in a single output file for all stocks covered by this Working Group.
The input format provided was used by all but one nation, and the quality of the input data has significantly improved over the last years. Unlike the uncomfortable handling of the exchange workbook, no major problems appeared during the transmission of data to the species coordinators. On the coordinators side, problems occurred only when nations filled in unsampled metiers themselves, as the SALLOCL application cannot handle these and filling-in decisions are not properly documented any more. The deadline for delivering the data was unfortunately not met by most nations, and the time-consuming data verification and procedures relevant to the splitting of North Sea autumn spawners and Western Baltic spring spawners in Division IIIa have not been done prior to the WG meeting. To avoid delaying the start of the assessments, it is necessary that the splitting data is made available on the first day of the WG.
Transparency of data handling by the Working Group. The current practice of data handling by the Working Group is that the data received by the coordinators is available in a folder called “archive”. These high-resolution data are not reproduced in the report. The archived data contains the disaggregated dataset (disfad), the allocations of samples to unsampled catches (alloc), the aggregated dataset (sam.out) and (in some cases) a document describing any problems with the data in that year. It is the intention of the Working Group that in the interim period until the standard database is developed (see below) the previous year’s archived data will be copied over to the current year directory and updated at the Working Group. Thus the archive for each year will contain the complete dataset available. Information on official, area misreported, unallocated, discarded and sampled catches are recorded on the WG-data exchange sheet (MS Excel). However, only sampled, official, WG and discards are available in the file Sam.out.
Current methods of compiling fisheries assessment data. As mentioned above each species coordinator is responsible for compiling the national data to produce the input data for the assessments. In addition to checking the input the major task involved is to allocate samples of catch numbers, mean length- and mean weight-at-age to unsampled catches. There are at present no defined criteria on how this should be done, but the following general process is implemented by the species coordinators. Searches are made for appropriate samples by gear (fleet) area quarter; if an exact match is not available the search will move to a neighbouring area if the fishery extends to this area in the same quarter. More than one sample may be allocated to an unsampled catch, in this case a straight mean or weighted mean of the observations may be used. If there are no samples available the search will move to the closest non-adjacent area by gear (fleet) and quarter, but not in all cases. In this context, national data submitters are again strongly encouraged to provide as much detail as possible of their sampling and filling-in procedures in the respective field of the exchange spreadsheet (sheet 2) instead of filling in unsampled metiers themselves.
The Working Group acknowledges the effort some members have made to provide “corrected” data, which in some cases differ significantly from the officially reported catches. Most of this valuable information is gathered on the basis of personal knowledge of the fishery and good relations between the scientist responsible and the fishermen. The WG is aware of the problem that this knowledge might be lost if the scientist leaves, and asks the national laboratories to ensure continuity in data provision. In addition the Working Group recognises and would like to highlight the inherent conflict of interest in obtaining details of unallocated catches by country and increasing the transparency of data handling by the Working Group. This issue will have to be carefully considered in light of any future development by ICES of a standard platform to store all fisheries disaggregated data, particularly with regard to confidentiality.
The WG considered the need of a long-term data storage for commercial catches and sampling, and the documentation of any primary data processing of these data. From 2000 on (catch data for 1999), the latest (consistency checked) versions of the input files together with standard outputs and a documentation of filling-in decisions made by the coordinators, ideally in the SALLOC-formats, are stored in a separate “archive” folder. This is updated yearly, and the complete collection (which is supposed to be kept confidential as it will contain data on misreporting and unallocated catches) will be available for WG members on request. As there was very little historical information available, WG members were asked to provide as much as possible national catch and historical data sets in any available format. National data provided in this year is stored in a “~historic” folder within “Archive”; they will be consistency checked and transferred into a database system as soon as this is available. Table 1.5.1 gives an overview of data available so far, and the source of the data. Members are encouraged to use the latest-version input spreadsheets if it is needed to re-enter catch data. Figure 1.5.1 shows the separation of areas as used for the long-term storage of data.
Future developments. Again a number of problems were encountered with the input data, some of them attributable to the notorious error-prone handling of spreadsheets. E.g., it was found that the direction of transfers and target area(s) of misreported or unallocated catches could not be clearly stated in the present format. A future input application should allow multiple entries for the same area, to cover each fraction of misreported catches (fractions that are transferred to a specific area) reported in a separate line.
The Working Group noted with satisfaction that after four years of expressing the urgent need for the development of an input file based on a stand-alone database application, ICES started to develop such a system. The WG repeats its opinion that the quality of the input data from commercial sampling proved to be crucial for the quality of the whole assessment procedure. The WG will support ICES in this effort wherever needed and recommends to seek the contribution of species coordinators of different groups as early as possible in the process. The application should be usable by all working groups, and any future format should provide an opportunity to clearly track changes of official landings made by WG members to compensate misreported or unallocated landings or discards. Further, a transparent and effective handling of sampling information obtained from market sampling in foreign ports should be possible.
Reference is made here again to a number of documents addressing this issue (e.g. Pastoors, 1999 WD to HAWG;
Zimmermann et al. 2000 WD to WGMHSA, EMAS Project report 2001).
However, if a database input is again not available for next year’s WG, the spreadsheet will be used again for the interim period. Obvious errors will be omitted intersessionally, but there will be no more general developments on this sheet. The reason for this is that it would represent a duplication of effort in light of the intention of ICES to develop a standard platform for the collection storage of disaggregated fisheries assessment data.
In this context, the Working Group recommends again that a directory be allocated on the ICES server to store relevant documentation and the most recent versions of exchange sheets and programmes used to aggregate the data, and that these items be available over the ICES web server.
1.5.2 Sampling
Quality of sampling for the whole area. The Working Group again produced a map indicating the level of catch sampling by area for all herring stocks covered by HAWG (Figure 1.5.2). The map indicates that the sampling level (in terms of fraction of catch sampled and number of age readings per 1000 t catch) is very different for the various areas.
Further details of the sampling quality can be found by stock in the respective sections (Sec. 2.2.4 for North Sea herring, 3.2.6 for Western Baltic Spring Spawners, 4.2.3 for Celtic Sea and VIIj herring, 5.2. for VIa(N) herring, 6.2.2 for VIa(S) and VIIb,c herring, 7.2.2 for Irish Sea herring).
The new EU sampling regime. HAWG has recommended for years that sampling of commercial catches should be improved for most of the stocks. In January 2002, a new directive for the collection of fisheries data was implemented for all EU member states (Commission Regulation 1639/2001). The provisions in the “data directive” define specific sampling levels. As most of the nations participating in the fisheries on herring assessed here have to obey this data directive, the definitions applicable for herring and the area covered by HAWG are given below:
Area sampling level per 1000 t catch
Baltic area (IIIa (S) and IIIb-c) 1 sample of which 100 fish measured and 50 aged
Skagerrak (IIIa (N)) 1 sample 100 fish measured 100 aged
North Sea (IV and VId): 1 sample 50 fish measured 25 aged
NE Atlantic and Western Channel ICES areas II, V,
VI, VII (excluding d) VIII, IX, X, XII, XIV 1 sample 50 fish measured 25 aged Exemptions to the sampling rules mentioned above are:
Concerning lengths:
(1) the national programme of a Member State can exclude the estimation of the length distribution of the landings for stocks for which TACs and quotas have been defined under the following conditions:
(i) the relevant quotas must correspond to less than 5 % of the Community share of the TAC or to less than 100 tonnes on average during the previous three years;
(ii) the sum of all quotas of Member States whose allocation is less than 5 %, must account for less than 15 % of the Community share of the TAC.
If the condition set out in point (i) is fulfilled, but not the condition set out in point (ii), the relevant Member States may set up a coordinated programme to achieve for their overall landings the implementation of the sampling scheme described above, or another sampling scheme, leading to the same precision.
Concerning ages:
(1) the national programme of a Member State can exclude the estimation of the age distribution of the landings for stocks for which TACs and quotas have been defined under the following conditions:
(i) the relevant quotas correspond to less than 10 % of the Community share of the TAC or to less than 200 tonnes on average during the previous three years;
(ii) the sum of all quotas of Member States whose allocation is less than 10 %, accounts for less than 25 % of the Community share of the TAC.
If the condition set out in point (i) is fulfilled, but not the condition set out in point (ii), the relevant Member States may set up a coordinated programme as mentioned for length sampling.
If appropriate, the national programme may be adjusted until 31 January of every year to take into account the exchange of quotas between Member States;
The HAWG reviewed the implementation of the new sampling regime for the EU countries. It is expected that the overall sampling level might be improved, and this was demonstrated e.g. for North Sea herring this year (see Section 2.2.3). However, there is concern that the new regime may lead to a deterioration of sampling quality, because it does not assure an appropriate sampling of different métiers (each combination of fleet/nation/area and quarter). Given the diversity of the fleets harvesting most stocks assessed by HAWG, an appropriate spread of sampling effort over the different métiers is more important to the quality of catch-at-age data than a sufficient overall sampling level. The EU data directive appears to not assure this. The WG therefore recommends that all metiers with substantial catch should be sampled (including by-catches in the industrial fisheries), that catches landed abroad should be sampled and information on these samples should be made available to the national laboratories.
Most of the issues raised here have also been addressed by the Planning Group on Commercial Catch, Discard and Biological Sampling (see Section 1.4.4.).
1.5.3 Terminology
The WG noted that the use of “age”, “winter rings” and “rings” still causes confusion outside the group (and sometimes even among WG members). The WG tries to avoid this by consequently using “rings” or “ringers” instead of “age”
throughout the report. It should be observed that, for autumn-spawning stocks, there is a difference of one year between
“age” and “rings”. HAWG in 1992 (ICES 1992/Assess:11) stated that
“The convention of defining herring age rings instead of years was introduced in various ICES working groups around 1970. The main argument to do so was the uncertainty about the racial identity of the herring in some areas. A herring with one winter ring is classified as 2-years-old if it is an autumn spawner, and one-year-old if it is a spring spawner.
Recording the age of the herring in rings instead of in years allowed scientists to postpone the decision on year of birth until a later date when they might have obtained more information on the racial identity of the herring.
The use of winter rings in ICES working groups has introduced a certain amount of confusion and errors. In specifying the age of the herring, people always have to state explicitly whether they are talking about rings or years, and whether the herring are autumn- or spring spawners. These details tend to get lost in working group reports, which can make these reports confusing for outsiders, and even for herring experts themselves. As the age of all other fish species (and of herring in other parts of the world) is expressed in years, one could question the justification of treating West-European herring in a special way. Especially with the present trend towards multispecies assessment and integration of ICES working groups, there might be a case for a uniform system of age definition throughout all ICES working groups.
However, the change from rings to years would create a number of practical problems. Data files in national laboratories and at ICES would have to be adapted, which would involve extra costs and manpower. People that had not been aware of the change might be confused when comparing new data with data from old working group reports.
Finally, in some areas (notably Division IIIa), the distinction between spring- and autumn spawners is still hard to make, and scientists preferred to continue using rings instead of years.
The Working Group discussed at length the various consequences of a change from rings to years. The majority of the Group felt that the advantages of such a change did not outweigh the disadvantages, and it was decided to stick to the present system for the time being.”
The text table below gives an overview over the correlation between age, rings and year class for the different spawning types in late 2002:
Year class (autumn spawners) 2001/2002 2000/2001 1999/2000 1998/1999
Rings 0 1 2 3
Age (autumn spawners) 1 2 3 4
Year class (spring spawners) 2002 2001 2000 1999
Rings 0 1 2 3
Age (spring spawners) 0 1 2 3
1.6 Methods used by this Working Group