A multi-model approach to analyse environmental effects on small (Sardina pilchardus) and medium (Scomber scombrus) pelagic fish species along the Portuguese coast

Intensive fisheries and overexploitation have been considered to be responsible for the decline of many fish stocks of target species in the world oceans. However, in recent decades fluctuations in Small Medium Pelagic (SMP) species abundance were found to be up to a great extend related to variations in environmental conditions. Hence, in future stock assessment the effects on fish population induced by human exploitation and the environment have to be considered as concurrent factors that determine species abundance. The aim of this study is to analyse the effects of several hydrographical and climatic variables, as well as fishing effort, as proxy for fishing pressure, on S pilchardus and S. scombrus LPUE time series (1989-2009) in three subdivisions, the Portuguese Northwest coast (IXaCN), Southwest coast (IXaCS) and the South coast (IXaS-Algarve) and for the whole Portuguese coast. For the purpose of this analysis a multi-model approach was used, applying different time series models for data fitting (Dynamic Factor Analysis, Generalized Least Squares) and forecasting (Autoregressive Integrated Moving Average, Surplus Production Models). The outcome of the study indicates the most important species-dependent environmental effects on the LPUE. S. pilchardus was found to be mainly affected by the sea surface temperature and the wind conditions, generating upwelling, whereas variations in S. scombrus LPUE could be almost solely related to the seasonal wind components and the wind related processes. In conclusion, it is necessary to consider environmental factors species-dependent, on a regional and seasonal scale. Thus an understanding of the major environmental impacts on the species will be crucial for a sustainable fisheries management, particularly in a future scenario of global climate change.

ISCED Categories

The highlighted icons, represent the fields of education (in compliance with ISCED Classification) engaged during this course/programme.