Influência do uso e cobertura do solo sobre a ictiofauna de riachos das cabeceiras do Alto Rio Paranapanema
Resumen
Human activities have generated unprecedented impacts on aquatic biodiversity. Thus,
knowing the impacts generated by these activities is extremely important, as fish from the
Neotropical regions represents approximately 1\5 of the world's fish species, or perhaps 10% of
all vertebrate species on the planet. Agricultural activities cause changes in the landscape and,
depending on land use, they can reduce permeabilization and percolation, increase runoff,
increase in sedimentation, fragmentation of forests, and the entry of pollutants into the
watercourse. These effects cause changes in the stream structure and, consequently, affect the
fish communities. However, different types of land use do not promote identical changes in
aquatic systems, so the effects on fish communities will be differentiated. Understanding the
direct and indirect effects that affect the structure of fish assemblages is of great relevance,
moreover, in studies that include several factors: land-use and land-cover (LULC), stream
structure, geographic and spatial (watercourse distance). These types of studies promote the
expansion of knowledge to support conservation measures. The present study aims to answer
whether there is a relationship between land use for agricultural activities and fish assemblages
and to test whether these relationships are dependent on the spatial scale. The study was
conducted in the southeastern of the Rain Forest in an extension of approximately 240 km from
the Upper Rio Paranapanema Basin. Sampling was carried out in 30 streams of headwaters that
include stretches of 2nd to 5th order. Satellite images were acquired to carry out the
classification of land-use and land-cover. Redundancy analyzes (RDA) were applied to test the
relationship between land use and composition and paths analyses to test direct and indirect
relationships between land use and the richness of stream fish species. The results showed that
there is a relationship between land use and the composition and richness of fish species, but it
is dependent on the spatial scale adopted. The analysis of partition of variance and redundancy
showed that in the catchment scale most of the variation in LULC was explained together with
by geographic and spatial factors indicating intercorrelation between these two sets of variables.
There was a relationship between local environmental variables and LULC on the catchment
scale. The RDA test showed that there is a relationship between composition and local
environmental variables and spatial factors. There is an indirect relationship between the
richness of fish species and land use, but it depends on the type of use practiced. The species
were associated with the type of land use. Generalist species are more common in streams
whose catchment has higher anthropic pressure. Our work indicates that the hierarchical
concept is valid to identify the environmental factors that affect the composition of the fish
assemblages. This study highlights the importance of catchment management in the
preservation of stream fish. The work also indicates that agriculture has a greater indirect
(negative) effect on the fish richness and that different types of land use indirectly affect the
fish richness of streams, as the land use on the watershed scale contributes to the alteration of
the stream structure, which consequently affects the assembly of stream fish.
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