This memorandum provides an estimation of the costs for four variant closures for the protection of the benthic ecosystem on the Frisian Front and the Central Oyster Grounds for the Dutch fishing sector in addition to the cost-benefit analysis carried out in Van Oostenbrugge et al. (2015). The two preferential variants lead to similar costs for the fisheries sector, whereas the costs of the two alternative combinations are either 20% higher or lower. The user may reproduce, distribute and share this work and make derivative works from it. Material by third parties which is used in the work and which are subject to intellectual property rights may not be used without prior permission from the relevant third party. The user must attribute the work by stating the name indicated by the author or licensor but may not do this in such a way as to create the impression that the author/licensor endorses the use of the work or the work of the user. The user may not use the work for commercial purposes.LEI accepts no liability for any damage resulting from the use of the results of this study or the application of the advice contained in it. Depending on the assumptions taken, the total costs for the Dutch fishing sector, measured as the negative effect on net present value of the gross value added, range from 0 to 8.9m euro. From the compiled overview of costs (Table S.1) the variants can be characterised as follows. COA_FFAPreferential variant A comprises three larger areas, one in the Central Oyster Grounds and two in the etc.) and the behavioural changes of fishermen and their economic consequences. Displacement scenario C assumes that the fishermen will be able to reallocate their fishing activities without having any costs. S.2 Complementary findingsWhen compared to the original variants as defined in Van Oostenbrugge et al. (2015), The costs for the Dutch fishing sector were estimated using the methodology developed by Van Oostenbrugge et al. (2015). The main steps taken are: An inventory of the fishing activities in the variants is based on an analysis of detailed vessel position data (VMS), official logbook data and economic data from the LEI panel. Estimation of the economic value of the areas were made using four Policy, Economy and Innovation scenarios (PEI scenarios) which combined expected developments on fish stocks, fish prices, fuel prices, technical developments, management measures and other area closures. Costs of closing the areas were assessed using three displacement scenarios. These were based on scientific publications (scenario A), expert knowledge from the fishing sector (scenario B) and the assumption that the sector would be able to reallocate their activities without any costs (scenario C). The resulting costs were combined into one indicator for the economic costs: the Net Present Value of the gross value added over a 30-year period.  De daaruit volgende kosten werden samengevoegd tot één indicator voor de economische kosten:de netto contante waarde van de bruto toegevoegde waarde ...

Kraak, S. B. M., Buisman, F. C., Dickey-Collas, M., Poos, J. J., Pastoors, M. A., Smit, J. G. P., van Oostenbrugge, J. A. E., and Daan, N. 2008. The effect of management choices on the sustainability and economic performance of a mixed fishery: a simulation study. – ICES Journal of Marine Science, 65: 697–712. Alternative management scenarios were evaluated in a simulation framework that mimicked the recent exploitation of sole and plaice in the North Sea. A large proportion of plaice is taken as bycatch of the beam trawl fleet targeting sole, yet current management of the two stocks assumes no interaction in their exploitation. The evaluation criteria included biological and economic sustainability, and stability in the management measures. The fishery was assumed to respond to management restrictions by dropping the least profitable trips. We investigated two contrasting management strategies, single-species total allowable catches, and effort regulation. Under the assumptions made, the latter strategy performed better. The results suggest that, given assessment error and bias, a strategy that accounts for the mixed nature of a fishery and that occasionally results in perceived underexploitation may work best. Stability in fishing mortality reinforces itself, through lower assessment bias, and management corrections become less frequent. The common assumption in many stock assessments in EC waters that fishing mortality in the most recent year should resemble the value obtained in previous years (“shrinkage”) had a negative effect on the stability of control measures.

Exploiting several fish species simultaneously reduces variability in daily catches. The reduction depends on the number of species, the catch-frequency distributions of individual species, and the level of co-occurrence of species in the catch. We explore theoretically the reduction of variability (coefficient of variation; CV) in the total catch by combining the distributions of daily catches of individual fish species, including zero catches, into a total catch frequency distribution. Theoretical findings are tested with an example from a stationary lift-net fishery for schooling small pelagic species around Ambon Island in the Central Moluccas, Indonesia. This fishery catches over 30 species, all with high daily variability (CV = 2.2-13.4). The reduction of variability in the total catch (CV = 1.7) is a result of the dominance and independent occurrence of the three main species. We conclude that in this fishery the information value of the total catch as an indicator of the catches of the individual species is low.Résumé : L'exploitation simultanée de plusieurs espèces de poissons peut réduire la variabilité des captures journalières. L'importance de cette réduction dépend du nombre d'espèces, de la distribution de fréquence des espèces dans la récolte et du niveau de la co-occurrence des espèces dans la récolte. Nous examinons en théorie la réduction de la variabilité (coefficient de variation; CV) dans les captures totales en combinant les distributions des captures journalières d'espèces particulières, incluant les captures nulles, dans la distribution de fréquence des captures totales. Un exemple tiré d'une pêche commerciale à carrelet de petits poissons pélagiques vivant en bancs près de l'Îsle Amboine (Moluques, Indonésie) permet de tester les résultats théoriques. Les récoltes incluent plus de 30 espèces de poissons, chacune avec une variabilité journalière élevée (CV = 2,2-13,4). La réduction de la variabilité dans la capture totale (CV = 1,7) est le résultat de la dominance et de l'occurrence indépendante des trois espèces principales. Dans cette pêche commerciale, la valeur prédictive de la capture totale comme indicateur de la capture des espèces particulières est basse.[Traduit par la Rédaction] van Oostenbrugge et al. 1043

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