Resumen del producto

Understanding how fish assemblages are affected by environmental fluctuation is critical to ecosystem and fisheries management. A factor that makes achúrate characterization of assemblage dynamics difficult is that fishes often move large distances though time, and static, regional sampling regimes typically encompass only a fraction of the biogeographic range of most taxa. To provide a more synoptic view of fish assemblage dynamics in the California Current system (CCS), we analyzed ichthyoplankton samples collected between 1997 and 2011 from northern (Oregon), central (California), and southern (Baja California) regions of the CCS. Redundancy analysis (RDA) showed that assemblages differed significantly by season and region, and pairwise comparisons indicated that the magnitude of difference was greater between Oregon and California or Mexico than between California and Baja California. Variance partitioning of RDA models revealed that local environmental conditions (temperature and salinity) explained more of the variation in assemblage structure than regional (upwelling) or basin-scale (MEI) indices for each combination of region by season. However, upwelling and MEI were important in Oregon and Baja California in spring. In addition, temperature and salinity were much more effective in explaining assemblage structure in deep (> 2000 m) than shallow waters in California, but the opposite was trae in Mexico. Comparison of the interannual dynamics in presence/absence for taxa found in multiple regions showed that several oceanic (e.g., Mexican lampfish, Panama lightfish) and coastal-oceanic (e.g., Pacific sardine, northern anchovy) taxa fluctuated in synchrony in Baja California and California. By contrast, there were no Sorong correlations in the interannual dynamics of taxa found in both California and Oregon. Logistic regression analyses modeling the presence of individual taxa against temperature and salinity identified notable regional differences in the sign and degree of correlation for taxa with different habitat affinities (oceanic, coastal-oceanic, coastal). These results demonstrate that the response of fishes to environmental change can differ greatly at different latitudes and highlight the need for broad-scale sampling to characterize ecosystem variability in the ocean.

Palabras clave: California Current; ichthyoplankton

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