Characterisation and standardisation of a red shrimp Aristeus antennatus, (Risso, 1816) fishery off the Alicante gulf (SE Spain)

Abstract

The red shrimp (Aristeus antennatus) is a target species of a deep trawl fishery in the Gulf of Alicante. This paper describes the fishery by following the activity of this trawl fleet between 1992 and 1999. Principal Components Analysis (PCA) of specific catch compositions identified five main components that explained 92% of the variability, and the catches were grouped into three main species: red shrimp, hake and blue whiting. Hierarchical Clustering Grouping of the percentage species catch composition allowed the fleet to be considered as two main groups, according to monthly landings and by differentiating the origin of the catches (slope or shelf). The species composition of the catch and the red shrimp catch rates (CPUE) differed between the two fleet groups. The application of Generalised Linear Modelling (GLM) to the CPUE series gave consistent indices of abundance. The fleet group, year and season had significant effects on shrimp catch rates, with the fleet group being the most important, and these models explained up to 62% of the total deviance. The abundance indices showed little variation from 1992, although 1994 had the highest value and 1997-1998 the lowest. Comparison with survey indices showed similar trends, while mean uncorrected CPUE differed. Monthly variations of shrimp indices showed a lower abundance in summer, which was attributed to the reproductive patterns of the species. As a result, the use of some fleet grouping techniques is recommended before standardising CPUEs to obtain trends or to calibrate assessment in a fishery.