Date: | 2014-03-06 |
Speaker: | Tiago Malta |
Local: | IPMA Algés Lisboa |
Email contact: | info@ipma.pt |
Phone contact: | 214770000 |
The study of historical population dynamics of marine resources has gained interest in the recent years. In the case of resources exploited for centuries, such as Iberian sardine (Sardina pilchardus), analysis of the response of the stock to environmental and fishing variations over time allows a better understanding of the current resource productivity and the definition of management measures. In this study we describe long-term variations in the recruitment of sardine off the Portuguese coast in relation to environmental conditions and exploitation history. A historical recruitment index (HRI) was developed based on a time series of length distribution samples collected from purse-seine fleet landings from 1947 to 2012. HRI was calculated as the proportion of recruits in annual length frequency distributions of sardine. A prior selection of data was made to identify the length classes, time periods and areas to be used in HRI. An analysis of the HRI and national landings taking into account the fisheries socio-economic history was made to evaluate the impact of fisheries policies on this time series. The effects of environmental factors and climatic variation on recruitment were explored using Generalized Additive Models (GAM). The results indicate that the Atlantic Multidecadal Oscillation (AMO), the East Atlantic Pattern (EA), the sea surface temperatures (SST) and upwelling have a significant influence on sardine recruitment.