SARDYN
Sardine dynamics and stock structure in the north-east Atlantic

This project will provide a comprehensive study of the life history and structural dynamics of the sardine (Sardina pilchardus) in the European Atlantic waters with an emphasis on the aspects required for improving the assessment and management of this species. The study will lead to the modification / extension of existing assessment models or to the development of a new model based on biologically defensible definitions of the stock boundaries. It will also lead to a better understanding of the sardine dynamics within the stock area of distribution. A multi-disciplinary team will study the stock structure of sardine in the North East Atlantic (NEA), describe the sardine dynamics in relation to the environment and integrate the results into models that can be used to enhance the quality of management advice.

Objectives
The principal objective of this project is to improve the basis for management advice provided for sardine (Sardina pilchardus) in European Atlantic waters. This will be achieved by undertaking a comprehensive analysis of the factors influencing the spatial structure of sardine recruitment, growth, movement, reproduction and mortality. Survey design, assessment models and management strategies will be reviewed and extended to incorporate biologically defensible definitions of the stock boundaries and internal dynamics. A multi-disciplinary team will study sardine stock structure in the NEA, describe the spatial dynamics of sardine in relation to environmental variability, and integrate the results in models that can be used to enhance the quality of management advice.

Progress to Date
The morphometric analysis of 14 sardine samples, collected in 2000 from the Bay of Biscay to northern Morocco and from the Azores to the western Mediterranean has been concluded and is undergoing publication (Silva, in press). Principal components analysis on size-corrected truss variables, and cluster analysis of mean fish shape using landmark data, indicated that the shape of sardine off southern Iberia and Morocco is distinct from that in the rest of the area. The two groups of sardine were significantly separated by discriminant analysis. There was also some (counterintuitive) evidence that fish from the western Mediterranean and the Azores form a separate morphometric group. These results question both the homogeneity within the Atlanto-Iberian sardine stock and the validity of its current boundaries. On the other hand, preliminary results from allozymes do not indicate population sub-divisions within the Bay of Biscay.

Exploratory analysis of otolith chemistry in small sardine (fish < 12 cm total length, mean otolith weight 0.7 mg) indicated that the concentration of nine elements (Sr, Cal, Mg, Va, Na, Co, Mn, Li and K) could be estimated consistently and with a satisfactory co-efficient of variation (generally < 10%) in samples pooling material from 10, 6, 4, 2 and 1 otolith. Another ten elements were found in concentrations below the limit of the method´s detection and will be excluded from further analysis, which will be performed separately for each sampled fish.

Finally, preliminary analysis of the acoustic survey abundance estimates off Iberia suggests that the signal in the Spanish series (March) is different from that in the Portuguese series (November and March), thus indicating that sardine tend to move into Spanish waters at an older age. This is in agreement with the spatial trend in mean female weight observed during the DEPM surveys. Also, cohort abundance over time provides coherent trends in the autumn and spring Portuguese acoustic surveys, both appointing to an annual mortality rate of 0.7-0.8.

Classified in FISHERIES AND AQUACULTURE, QUANTITATIVE APPROACHES AND MODELLING

Scientist responsible for the project