The comprehensive ICCAT Atlantic-Wide Research Programme on Bluefin Tuna (ICCAT GBYP) is required to improve basic data collection for assessment models. An important element of this Programme is to use the existing data sets which are not currently incorporated in the ICCAT database on bluefin tuna, to support the improvement of the analytical work assessment.
Three new datasets with catch data of eastern BFT were made available to the GBYP programme recently. These datasets brought together information from market sales, corporate records, and official statistics not currently used to calculate the catches for the stock assessment. As the data in the 3 datasets come from sources not currently used to provide estimates of total catches of EBFT they have the potential to provide an independent perspective of exploitation of the eastern BFT stock.
This project analysed the datasets to develop estimates of catch removals of EBFT based on the information from the 3 datasets. The first part of this work focused on cleaning the data and developing the database structure to facilitate the analysis and ensure that records are reliable and provided the information needed. The datasets were also critically reviewed to understand weaknesses and sources of uncertainty and get an insight into their potential in supporting analysis to calculate total catches of BFT. The final version of the datasets (once unreliable records were excluded) were then used to calculate catches per year under different assumptions for key components of the analysis such as fattening ratios and catch weight.
The results highlighted differences between the official catch statistics (Task I) used for stock assessment and catch estimates derived from the 3 new datasets and key sources of uncertainty.