Octopus vulgaris abundance and sea surface temperature off the Portuguese coast: Preliminary analysis

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The aim of the present study is to estimate an abundance index for the common octopus (Octopus vulgaris) on the Portuguese continental shelf and to understand how this index correlates with environmental variables. Because of the high commercial value of the common octopus, all captured individuals are landed, most on commercial ports, so this information is considered a good abundance index. The rough data is organised in a central database at the Directorate General for Fisheries (DGPA), where, for each vessel and day of landing, port, weight and commercial value of sale are reported. All vessels that landed cephalopods at least once a year were selected. Second day landings only were extracted to ensure effort units of 24 hours. The obtained series is compared with sea surface temperature data. SST’s time series are obtained from satellite data and organized by month. The analysis is carried out for four distinct areas of the Portuguese continental shelf. As a preliminary study, data starting in January 2002 were used for a total exceeding 3000 vessels.