Abstract
ABSTRACT This study aimed to determine whether fish species occupy different mesohabitats, as defined by specific criteria of substrate types in Atlantic Forest blackwater streams. We sampled fourteen coastal blackwater rivers along the coast of São Paulo State, Brazil, during the low-flow season (June-September/2016). For each stream, we selected three mesohabitat types (sand, leaf-litter and trunks) in a 100 m river stretch. We sampled 41 mesohabitats, 31 of which contained fish, resulting in 15 species. When multivariate analysis of variance (MANOVA) was applied to the mesohabitat abiotic variables, no significant differences were indicated between them. ANOSIM for species density and biomass and Redundancy Analyses (RDAs) for species density, biomass and fish community indexes showed similar patterns of community structure among mesohabitats. Nevertheless, fish biomass, diversity and richness were associated with such unique environmental features as low shading and shallow habitats. The observed dispersion among mesohabitats suggests that these communities are subject to some level of disturbance, which may affect the value of patches as refugia. Thus, the sharing of these mesohabitat patches among species may represent an opportunistic strategy to maximize the use of available resources for these low density populations living in these unique environments.
Highlights
Different spatial scales are important in structuring fish communities, ranging from the influence of local processes, such as water quality, substrate, and channel morphology, to those at basin level, such as geology, soil type and use, topography, and climate (Wang et al, 2003)
We examined the relationship between community indexes and environmental variables with a Redundancy Analysis (RDA) after performing a Detrended Correspondence Analysis (DCA) to distinguish between linear or unimodal species response
The RDA based on the community indexes for the three mesohabitats showed eigenvalues of 0.086 and 0.060 for the two first axes, respectively (Fig.5)
Summary
Different spatial scales are important in structuring fish communities, ranging from the influence of local processes, such as water quality, substrate, and channel morphology, to those at basin level, such as geology, soil type and use, topography, and climate (Wang et al, 2003). The Atlantic Forest biome is one of the 25 global biodiversity hotspots (Myers et al, 2000) with levels of endemism of 90% for some organisms, which is surpassed only by Amazonia (Costa et al, 2000). Most studies on species distributions in Atlantic Forest streams were conducted in Brazilian clear-waters (Rezende et al, 2010; Terra et al, 2013a, 2013b; Terra et al, 2016; Wolff, Hahn, 2017), which are typically high-gradient streams that form an intricate network of torrents and waterfalls (Por, 1992)
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