Margin of Tolerance

There was a general concern within UK fishing industry groups regarding the ability of  their members to apply the EU-prescribed limit of 8% tolerance between catch  estimates recorded and declared on board and those from landings declarations of verified on landing by inspections for certain fish stocks. The basis of this report was therefore to investigate whether the percentage margin is in fact attainable under ‘at sea’ conditions.

The project utilised independent Defra-authorised observers who joined selected UK vessels on five fishing trips. The trips were standard fishing trips but vessels were chosen to reflect the main fishery, gear type and vessel sizes operating around the UK. The principal remit of the observers was to make independent estimates of the weight of the catch on board the vessel by species, sufficient to complete the standard European Communities Logbook (i.e. catch by species kept on board in kilograms live weight on a per day basis).  At present there are two figures available for the weight of the catch: the skipper’s estimate on board, which is recorded in the vessel logbook, and the landed catch weight. Margin of tolerance rules require that the first of these must be within 8% (by species) of the second for selected species. The observed trips provided a third independent figure for the catch weight on board and the principle purpose of the analysis was to determine whether these estimates are within expected margin of the landed catch weight.

In order to provide the necessary data, the observers recorded catches independently from the captain and crew but essentially using the same estimation methods.  Where possible, 100% of all fishing operations were observed. MRAG was responsible for recruiting, training and deploying all the observers as well as developing the sampling design and protocols, collecting and analysing the data and reports and producing the final report to be disseminated amongst the industry.