Definition of fleet components in the Spanish artisanal fishery of the Gulf of Cadiz (SW Spain ICES division IXa)

The Spanish artisanal fishery in the Gulf of Cadiz is of a notably multi-gear and multi-species nature, with target species occurring seasonally, where a fleet composed of about 1000 vessels captures more than 50 commercial species. From this complexity arises the need for defining fleet components (FCs) (i.e., groups of vessels developing the same fishing pattern through the year), which allow the design of simpler and more efficient sampling schemes on the basis of understanding the behaviour of such components. To define the artisanal FCs, the daily landings by species and vessel during 1996 were considered. In a preliminary analysis, a total of 53 fishing trip types were objectively characterised from the species composition of these landings using hierarchical Cluster Analysis (CA) techniques. A non-hierarchical K-means CA was applied later to re-classify the 1996 data and to classify 1997 landings data by trip type. The red seabream (Pagellus bogaraveo), red-banded seabream (Pagrus auriga), octopus (Octopus vulgaris) and striped venus (Chamaela gallina) types stood out according to their importance in landed weight. In a second stage, only those vessels with more than 50 daily landings regularly distributed through the year were selected. A matrix with as many rows (cases) as selected vessels and 53 trip types x 12 months = 636 columns (variables) was designed. A new CA was applied to group vessels which show similar fishing annual patterns. Eleven FCs were defined from these results. Two basic features of these components may be emphasised: they are highly related to the landing (home) ports and the fishing gears used, and they show definite seasonal fluctuations according to the main fishing trip types developed. (C) 2002 Elsevier Science B.V. All rights reserved.