Multi-scale spatial variability in fish assemblages associated with Posidonia oceanica meadows in the Western Mediterranean Sea

摘要: Fish assemblages associated with Posidonia oceanica from three locations of the western Mediterranean (Mallorca, Formentera and Alacant, Spain) were sampled in order to assess their spatial variability at different scales ranging 100 km. Sampling was carried out using a beam trawl. Simultaneous sampling these appropriate number replicates implies huge effort which is rarely possible achieve. Consequently, we propose an arrangement data coming programs, after testing making sure specificities each program cannot be confounded variability. The two preliminary experimental designs adopted combine datasets were: (1) differences between consecutive years tested by same meadow (Formentera) June 2001 2002; (2) attributable structure evaluated meadows (Mallorca 2000 2001). absence any significant correlation pattern for univariate community descriptors multivariate species-specific densities (i.e. individuals per hour) related both between-year within-location structural meadows, allow us (Formentera 2001, Mallorca Alacant 2000) single analysis aimed determining how much explained considered. between-location scale (>100 km) most variable (multivariate approach). Spatial smallest (<1 also considerable, but corresponding intermediate (<10 found non-significant. This expected result fishes given that individual transects not large compared high mobility many species observed placed km apart are due changes relative density rather than composition. Between-location univarite significant. However, (intermediate scale) biomass. small one site. These results consistent hypothesis P. might display similar carrying capacity although large-scale hydrodynamic conditions level lead differently shaped fish communities (for example, larger complexity favour smaller sizes, since and/or known find more shelter food there), while remain irrelevant.