Drivers and spatial patterns of population synchrony of fish species in a floodplain

Spatial synchrony is the correlation between the temporal dynamics of local populations. This pattern may be driven by spatially correlated environmental variation (i.e., Moran effect), dispersal and trophic interactions. Investigating geographic patterns of synchrony can help disentangle the relative importance of these drivers. Using fish abundance data from long-term ecological research (17 years) in the Upper Parana River floodplain, we studied the relative roles of dispersal distance, density dependence differences, and environmental synchrony in determining spatial synchrony of the most common species in this floodplain. We also investigated the geography of spatial synchrony by estimating modularity and site-level contributions to synchrony and anti-synchrony networks. We found positive spatial synchrony for most species, but levels were relatively low. For most species, our explanatory matrices were poorly related to spatial synchrony. We detected modular structures in some species networks, which reflected complex spatial patterns in synchrony. We also detected sites with high importance to spatial synchrony patterns that could be managed to increase metapopulation stability. The variable levels of spatial synchrony for fish species in the Upper Parana River floodplain implies the need to monitor several sites to understand their dynamics in this region. Also, some migratory species of high importance to regional fisheries, such as Prochilodus lineatus, may deserve special monitoring attention due to the increased regional extinction risk associated with their high levels of spatial synchrony. Finally, we speculate that hydrological manipulation from upstream reservoirs should consider the timing of water releases to avoid spatially correlated population declines.

Automated summary

This study investigates the geographic patterns of spatial synchrony in fish populations and the drivers behind it using long-term ecological research data from the Upper Parana River floodplain. The study finds positive spatial synchrony for most species but at relatively low levels. It also highlights the complex spatial patterns in synchrony through modular structures in species networks. The study emphasizes the need for monitoring multiple sites and managing key sites to increase metapopulation stability.