Identification of metiers based on economic and biological data: The Spanish bottom otter trawl fleet operating in non-Iberian European waters

Spanish bottom otter trawl (OTB) m tiers within the North-eastern Atlantic (ICES Subareas VI, VII, and Divisions VIIIabd) have been identified through the application of multivariate analyses of landing profiles in terms of value (economic data) and total catches (biological data) over the period 2004-2006. The economic data uses information taken from logbooks and auctions for the period 2004-2006; while biological data is based on information taken from on-board sampling carried out in the same period. In order to identify m tiers (homogeneous groups of fishing activity), a three-step process has been applied. Firstly, multivariate regression trees (MRT) are applied to obtain homogeneous groups which explain the inner structure of data by means of independent variables. Secondly, a list of specialized vessels is derived from each group obtained. Finally, an interview program is carried out with a representative number of skippers selected from the specialized vessels, who were asked about their fishing strategy, including target species. The results permitted identification of six metiers, taking into account the target species, which were, respectively: hake and deep-water species (OTB1), megrim (OTB2), hake (OTB3). Norway lobster (OTB4), a mixture of several species (OTB5), and anglerfish (OTB6). The combined use of both economic and biological data sources facilitates improved understanding of fleet activity: logbooks provide a comprehensive overview, while the scientific data from on-board sampling programs provide an ecological perspective to better contextualize the effects of fishing activity on the ecosystem. (C) 2012 Elsevier B.V. All rights reserved.