Interannual Changes in Biomass Affect the Spatial Aggregations of Anchovy and Sardine as Evidenced by Geostatistical and Spatial Indicators

摘要: Geostatistical techniques were applied and a series of spatial indicators calculated (occupation, aggregation, location, dispersion, autocorrelation overlap) to characterize the distributions European anchovy sardine during summer. Two ecosystems compared for this purpose, both located in Mediterranean Sea: Strait Sicily (upwelling area) North Aegean Sea (continental shelf area, influenced by freshwater). Although biomass presented high interannual variability areas, location centres gravity main patches their populations very similar between years. The size representing dominant part abundance (80%) was mostly ecosystem- species-specific. Occupation (area presence) appears be shaped extent suitable habitats each ecosystem whereas aggregation patterns (how are distributed within area species-specific related levels population biomass. In upwelling species showed consistently higher occupation values continental area. Certain characteristics distribution (e.g. spreading overlapping with anchovy) differed substantially two ecosystems. Principal component analysis geostatistical revealed that significantly suite of, rather than single, indicators. At scale our study, strong correlations emerged first principal axis highly positive loadings occupation, patchiness, independently ecosystem. Overlapping increased increase but decreased anchovy. This contrasting pattern attributed respective major combined specific species. potential use indices as auxiliary stock monitoring is discussed.