Spanish otter trawl fisheries in the Cantabrian Sea

A non-hierarchical classification technique (clustering large applications, CLARA) was used to identify four fishing tactics of Spanish otter trawlers in the Cantabrian Sea (ICES Division VIIIc) from 1983 to 2004: mixed fishing, blue whiting fishing, horse mackerel fishing, and mackerel fishing. There were no significant differences in the fishing tactics employed by two trawl fleets identified using a nonhierarchical classification technique (partition around medoids). There was, however, a decline in the use of the blue whiting fishing tactic from 2000 on, perhaps as a result of competition with pairtrawls, a gear whose main target species is blue whiting. There was an increase in the number of trips using the mackerel fishing tactic from 1996, a change possibly caused by improved market conditions. Between 2000 and 2004, the fleets had two distinct behaviour patterns, identified depending on the area in which they operated. The study area could therefore be subdivided into two areas based on the prevalence of the fishing tactic followed. The horse mackerel fishing tactic was more commonly used in the west, and the mixed fishing tactic in the east.