Interannual Variability of Fisheries Economic Returns and Energy Ratios Is Mostly Explained by Gear Type

• Published in: PLoS ONE
• Main Authors: Trenkel, Verena M., Daures, Fabienne, Rochet, Marie-Joëlle, Lorance, P.
• Other Authors: Unité Écologie et Modèles pour l'Halieutique (EMH), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Aménagement des Usages des Ressources et des Espaces marins et littoraux - Centre de droit et d'économie de la mer (AMURE), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: [SHS.ECO]Humanities and Social Sciences/Economics and Finance; [SDE]Environmental Sciences; Northeast Atlantic
• Online Access: https://hal.science/hal-00864022; https://doi.org/10.1371/journal.pone.0070165

on-line : http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0070165 International audience According to portfolio theory applied to fisheries management, economic returns are stabilised by harvesting in a portfolio stocks of species whose returns are negatively correlated and for which the portfolio economic return variance is smaller than the sum of stock specific return variances. Also, variability is expected to decrease with portfolio width. Using a range of indicators, these predictions were tested for the French fishing fleets in the Bay of Biscay (Northeast Atlantic) during the period 2001-2009. For this, vessels were grouped into eight fishing fleets based on the gears used and exploited species were grouped into five functional groups. The portfolio width of fleets ranged from 1-3 functional groups, or 4-19 species. Economic fleet returns (sale revenues minus fishing costs) varied strongly between years; the interannual variability was independent of portfolio width (species or functional groups). Energy ratio expressed by the ratio between fuel energy used for fishing and energy contained in landings varied from 0.3 for purse seines to 9.7 for trawlers using bottom trawls alone or in combination with pelagic trawls independent of portfolio width. Interannual variability in total sale revenues was larger than the sum of species specific sales revenue variability, except for fleets using hooks and pelagic trawlers; it increased with the number of species exploited. In conclusion, the interannual variability of economic returns or energy ratios of French fisheries in the Bay of Biscay did not decrease with the number of species or functional groups exploited, though it varied between fleets