Size-dependent response of tropical wetland fish communities to changes in vegetation cover and habitat connectivity

Abstract

Context The replacement of native vegetation by exotic grasses for livestock production is driving landscape homogenization, habitat fragmentation and reducing connectivity between habitat patches in floodplains ecosystems. Objective In this context we examined how changes in native and exotic vegetation cover, connectivity and water depth affect the attributes of the small [standard length (SL)\80 mm as adults] and large-sized fish assemblages (SL C 80 mm as adults). Method We assessed the effects of water depth, exotic and native vegetation cover and habitat connectivityonthe abundance, species richness, body size andbiomassoffishassemblagesina25 km 2 areaofthe seasonal habitats of the Pantanal wetland over 5 years. Results We showed that fish assemblage response to meso-scale variation in water depth, vegetation cover and habitat connectivity in seasonal habitats is sizedependent. The gradient from exotic to natural vegetation cover did not affect the assemblages of small-sized fish,whichweremostlyregulatedbywaterdepth,habitat connectivity and the gradient from grassland to forest. However, besides being affected by water depth and habitat connectivity, large-sized fish were also affected by the gradient from exotic to natural vegetation cover. Conclusion Our results indicate that transformations in the landscape and changes in the dynamics of inundation may have negative consequences for the long-term persistence of fish assemblages in the Pantanal wetlands.