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Indicators of the Balance Between Fleet Capacity and Fishing Opportunities

其他書名	Discrepancies Between the Dutch National Fleet Report and STECF
出版	Wageningen Marine Research, 2020
URL	http://books.google.com.hk/books?id=NoKrzQEACAAJ&hl=&source=gbs_api

註釋The 2019 report of the Balance Expert Working Group, STECF-19-13, paid particular attention to the discrepancy in indicators values between the national fleet reports and their own calculations for the year 2017. They observed that the Netherlands used a different fleet segmentation, thereby making comparisons difficult. Furthermore, they found large differences in the two biological indicators and some small differences in the economic indicators, which in some cases even indicated a different state of balance compared to what the Dutch national fleet report concluded. This report therefore investigated the discrepancy in balance indicator values from 2017, with the aim to explain the observed differences and to re-calculate the indicators for the national fleet report for the 2017 data with the same fleet segmentation and methods as STECF-19-13. For the biological indicators, differences in indicator values were caused by a wrong interpretation in the Dutch national fleet report of the equations in the 2014 Commission guidelines. Furthermore, not all stocks that were fished upon by fleet segments were included in the analysis of the fleet report, thereby excluding stocks that were still overexploited. Different procedures on how to divide the landings data by species over the stocks may also have led to the discrepancy in biological indicators. Differences in the economic indicators were small compared to the biological indicators, and both the fleet report and STECF-19-13 came to the same conclusions regarding the balance of the fleet from an economic point of view. The small discrepancies were caused using different interest rates and real values. No difference in technical indicators was observed for the pelagic fleet segment. Redoing the calculations for the national fleet report with the 2017 data and the same fleet segmentation as STECF led to the same or very similar values for most indicators. Future work is needed in close cooperation with the Balance EWG to make sure that the methods are aligned with both the Commission guidelines and STECF. This is particularly applies to the biological indicators, for which some small differences with the STECF values were still observed after improving the methods. Based on the findings in this report, it is recommended to become more actively involved in the Balance EWG, preferably by having somebody with biological expertise attending future EWG meetings who can solve the remaining issues in the national fleet report calculations and avoid any discrepancies in the future. Furthermore, the biological section of the national fleet report should include time series of the biological indicators, as management measures may take time before the desired state and balance are reached. Future fleet reports should also use a landings data splitting procedure tailored to the year of interest and to the Dutch landings. Regarding the economic and technical indicators, it is recommended to use both the STECF fleet segmentation (to allow for comparison with the EWG) and the clustered segmentation to ensure that local knowledge and context of the fleet is provided, as the data of particularly the small-scale fleet segment, and therefore also its indicators, need to be interpreted with caution.