Annex 1: Methodology
Scottish Sea Fisheries Statistics are obtained by data extractions from FIN (Fisheries Information Network) administrative data, and IFISH, the UK data warehouse. IFISH provides information on sea fishing activity, catches, landings and sales whilst FIN is used for vessel information in this publication.
Voyage and landings information is supplied by skippers. Vessels over 10 metres, are required by EU legislation to maintain logbooks or e-logbooks and provide landings declarations (see Glossary). For UK vessels over 12m in length, by law, this information must be recorded electronically in an e-logbook. Vessels between 10m and 12m, currently maintain the traditional paper logbook. The information from paper log books is input into FIN by hand by Marine Scotland Compliance Port Office staff, whilst the information from e-logs is processed and checked electronically before being imported into FIN. EU legislation does not require vessels of 10 metres and under to provide this information but in Scotland, these vessels provide equivalent information on the FISH1 forms.
Data on first sales of fish, which provides information on the value of landings, is provided by fish buyers and sellers under EU legislation on the Register of Buyers and Sellers (see Glossary). The information submitted forms the basis for reports to the Commission to meet the obligations of the EU legislation. Links to the relevant legislation are listed in Annex 3 under EU Legislation.
For four of the tables in the Statistical Bulletin, information from FIN/IFISH is supplemented by information obtained through a fishermen employment survey distributed to port offices in each of the 18 Scottish fishing districts. To improve the quality of this process since 2014 each port office were provided with a list of registered vessels for their district to aide in the collation of these numbers. Some offices indicated this was the procedure they already followed others found the list helpful for the task. The burden on respondents for this small survey in previous years was estimated to total no more than £1,000 per year, based on information obtained from each office on the time taken to complete the return and the grades of staff involved. It is not felt that the process followed since 2014 has led to any change in the burden. In two of the tables, this information is compared to information on the labour force obtained from the Labour Force Survey.
For table 1.11, figures for North Sea mackerel and West of Scotland mackerel have been extracted from FIN and figures for all other stocks have been extracted from IFISH. This is due to the allocation of North Sea mackerel and mackerel from the Shetland Box being more accurate on the FIN database. This does not affect the total quantity and value of mackerel landings as only a small amount of these landings by Scottish registered vessels were made into the rest of the UK ports (see table 1.1.b). Figures for all other stocks are for Scottish registered vessels landing into the UK and abroad.
Uses made of the statistics
Collection of information on sea fisheries is needed to produce reports for the EU Commission to meet the obligations of EU legislation. Internal users mainly require the underlying management information to monitor aspects of sea fishing, such as quota and effort uptake. The main use made of the published statistics is by external users, such as the Fish Producer Organisations.
The main macro-level use for the statistics is the assessment of the value of sea fishing to Scotland or specific sea areas. There is also a degree of political and media interest in the trends in the numbers of fishing vessels and numbers of fishermen employed. Scottish Parliament researchers use the information in briefings prepared on fisheries for MSPs and the Rural Affairs and Environment Committee. The published statistics are also used in the construction of the Scotland Performs Marine Environment Indicator -
The major micro-level use made by external users requesting specific data is to examine sea fishing activity in small areas of the sea around Scotland, often as input to environmental impact assessments for off-shore energy developments.
The information in the administrative data bases are subject to extensive checking before it is enters the database. These checks are supplemented by quality assurance work performed by the Data Team throughout the year. This ensures consistency between the two vessel file administrative data bases and checks for missing returns of landing declarations. Furthermore, stakeholders can make requests to get data corrected/investigated if they assess that it does not correctly reflect their landing of quota stocks or usage of days at sea.
The main issue for the quality of the published statistics is the completeness of the information in the administrative systems. Information on landings of fish species not subject to quota or fish landed abroad can often take months for the information to be entered into the relevant administrative data base. It is for this reason that provisional statistics are not published until about 3-4 months after the year to which they relate, and the final statistics are published a further 4-5 months later. We assess that 0.2% of landings (by value) of Scottish vessels are omitted from the final published statistics each year due to delays in receipt of information on landings out with the UK. However, this small incompleteness does not affect the trends shown by the statistics. Although the provisional figures are not published until coverage of quota stocks is reasonably complete, information on non-quota stocks are less complete. The table below summarises the change between the provisional and final statistics by species type for landings of Scottish vessels. (Shellfish species other than Nephrops are not subject to quota.)
Change in recorded landings by Scottish vessels since provisional statistics
|Species type ||2016 Provisional Statistics ||2016 Statistical Bulletin ||% change |
|Live weight (000 tonnes) ||Value (£m) ||Live weight (000 tonnes) ||Value (£m) ||Live weight (000 tonnes) ||Value (£m) |
|Demersal ||95.4 ||169 ||95.4 ||169 ||0.00% ||-0.08% |
|Pelagic ||294.4 ||226 ||294.4 ||222 ||0.00% ||-1.58% |
|Shellfish ||63.6 ||169 ||63.6 ||166 ||-0.01% ||-1.64% |
|Total ||453.3 || 563 ||453.3 ||557 ||0.00% ||-1.15% |
Value of landings information is derived from the Sales Notes which are submitted by UK vessels landing into EU countries, in line with the Buyers and Sellers legislation of 2005. This information is matched with the landing declaration for the values obtained for that landing. In instances where there is no Sales Note, for example when a UK vessel lands into a non-EU country, the value of the landing is estimated by using the average price obtained for the species in the previous quarter that the landing declaration was submitted.
One issue that concerns the quality of the statistics is that the statistics can only reflect the information supplied by the fishermen on their activity and catch. The automatic checking carried out on the data at the input stage, only checks for internal consistency of the information supplied. The introduction of the Buyers and Sellers legislation provides an external check on the declared landings of fish and undeclared (“black”) landings have been assessed by Marine Scotland Compliance as being at negligible. For vessels with a length of 12 metres and over, the Vessel Monitoring System (VMS) provides a check on the location of fishing activity recorded in fishermen’s log books. Further checks are performed regularly by Marine Scotland Compliance to ensure enforcement of legalisation. However, despite these checks, there could be inaccuracies in the information submitted.
Revisions to the published statistics
The statistics for previous years published in the Statistical Bulletin have all been revised to ensure users have access to the latest data available. Revisions typically affect fishing effort, landings and sales information where data comes from logbooks, landing declarations and sales notes which can be amended for small changes (usually in the order of 0.2%) due to late data entry or rectification of errors, as these do not affect the main trends presented they are not highlighted and not footnoted. The list of the main species displayed within the landings tables changes each years as the entry criteria is the total value landed into the UK or by UK vessels abroad meeting £2 million or more, so this can lead to changes also within the table and inevitably in the “other” category as species enter and exit this category.
On the rare occasions that such revisions are required due to the discovery of errors in the previously published figures which affect the main trends presented, the revised figures are marked "(r)" and suitably footnoted to explain the reason for the revision. The statistics are revised between the published provisional statistics and those published in the Statistical Bulletin – see above. However, provisional statistics are always explicitly identified as such.
In early years, figures on engine power have been underestimated to an unknown degree due to under declaration of engine power on vessels’ licences. Therefore, year on year power comparisons involving earlier years should be made with caution. A concessionary licensing arrangement and a timetable for compliance were introduced in 1999 and vessel owners had until the end of 2004 to declare the true engine power. Comparisons on vessel capacity (tonnage) are also complicated due to revisions in the measurement methodology. Various national and international standards collectively known as gross registered tonnage (GRT) were revised to a common EU standard known as gross tonnage (GT). A phased programme of re-measurement was introduced in the UK in 1996 and completed by early 2004.
Users should always refer to the latest figures published, previous editions of all publications are made available online should users require access.
Comparability with other UK countries
EU legislations cover information requirements for vessels over 10 metres and for all buyers and sellers, which results in the information derived from EU country data providers being comparable for all countries within the UK, as it is for all EU countries. The only difference between information collated in Scotland and that collated in the rest of the UK is that, through the FISH1 returns, Scotland obtains equivalent information on a full coverage basis for vessels of 10 metres and under. In the rest of the UK, this information is provided on a sample basis only. However, the vast majority of fish are caught by vessels over 10 metres, so the information is effectively comparable for all UK countries, in spite of the difference in information capture for the 10 metre and under vessels.
The method by which Scottish registered vessels are counted in Scotland is by totalling the number of active Scottish registered vessels there are on 31st December 2016. In comparison, the rest of the UK counts Scottish registered vessels based on the administration ports where vessels were licensed as at the end of 2016, regardless of whether vessels are active or inactive. This can lead to slight discrepancies between figures published at the Scottish level and those published at the UK level.