TY - JOUR T1 - Interannual Changes in Biomass Affect the Spatial Aggregations of Anchovy and Sardine as Evidenced by Geostatistical and Spatial Indicators A1 - Barra,Marco A1 - Petitgas,Pierre A1 - Bonanno,Angelo A1 - Somarakis,Stylianos A1 - Woillez,Mathieu A1 - Machias,Athanasios A1 - Mazzola,Salvatore A1 - Basilone,Gualtiero A1 - Giannoulaki,Marianna AD - Inst Coastal & Marine Environm, Detached Units Capo Granitola, Mazara Del Vallo, Italy. AD - Inst Coastal & Marine Environm, Detached Units Capo Granitola, Naples, Italy. AD - IFREMER, Lab Ecol Halieut, Nantes, France. AD - Hellen Ctr Marine Res, Inst Marine Biol Resources & Inland Waters, Iraklion, Greece. UR - https://archimer.ifremer.fr/doc/00276/38758/ DO - 10.1371/journal.pone.0135808 N2 - Geostatistical techniques were applied and a series of spatial indicators were calculated (occupation, aggregation, location, dispersion, spatial autocorrelation and overlap) to characterize the spatial distributions of European anchovy and sardine during summer. Two ecosystems were compared for this purpose, both located in the Mediterranean Sea: the Strait of Sicily (upwelling area) and the North Aegean Sea (continental shelf area, influenced by freshwater). Although the biomass of anchovy and sardine presented high interannual variability in both areas, the location of the centres of gravity and the main spatial patches of their populations were very similar between years. The size of the patches representing the dominant part of the abundance (80%) was mostly ecosystem- and species-specific. Occupation (area of presence) appears to be shaped by the extent of suitable habitats in each ecosystem whereas aggregation patterns (how the populations are distributed within the area of presence) were species-specific and related to levels of population biomass. In the upwelling area, both species showed consistently higher occupation values compared to the continental shelf area. Certain characteristics of the spatial distribution of sardine (e.g. spreading area, overlapping with anchovy) differed substantially between the two ecosystems. Principal component analysis of geostatistical and spatial indicators revealed that biomass was significantly related to a suite of, rather than single, spatial indicators. At the spatial scale of our study, strong correlations emerged between biomass and the first principal component axis with highly positive loadings for occupation, aggregation and patchiness, independently of species and ecosystem. Overlapping between anchovy and sardine increased with the increase of sardine biomass but decreased with the increase of anchovy. This contrasting pattern was attributed to the location of the respective major patches combined with the specific occupation patterns of the two species. The potential use of spatial indices as auxiliary stock monitoring indicators is discussed. Y1 - 2015/08 PB - Public Library Science JF - Plos One SN - 1932-6203 VL - 10 IS - 8 ID - 38758 ER -