Identification of métiers of the Northern Spanish coastal bottom pair trawl fleet by using the partitioning method CLARA

Cluster analyses of catch profiles by fishing day and trip (1986–2007) are used to identify métiers in the Northern Spanish coastal bottom pair trawl fleet (PTB) operating in ICES Divisions VIIIc and IXa North. The method CLARA (Clustering Large Applications) was chosen to analyze these databases because it is a partitioning technique specifically designed to manage very large data sets. The results obtained allow us to identify two métiers, which are in concordance with knowledge of the fishery, one targeting blue whiting and hake (PTB1), and another targeting mackerel (PTB2). PTB2 shows a seasonal pattern related to the reproductive cycle of mackerel off the Cantabrian coast in the Bay of Biscay. The CLARA method is shown to be useful tool for analyzing this type of large data set, although the coverage level of its sampling algorithm must be taken into account.