Environmental perception of artisanal fishermen in the region of Ilha Grande National Park, PR/MS, after the formation of the Itaipu reservoir: traditional knowledge and human-nature interaction

O alagamento das Sete Quedas para a formação da usina hidrelétrica de Itaipu, no rio Paraná, gerou impactos sobre a pesca. O objetivo deste estudo foi analisar a percepção ambiental dos pescadores da região do Parque Nacional de Ilha Grande sobre as mudanças ambientais ocorridas após a formação do reservatório de Itaipu e sua relação com a pesca da região. A coleta de dados foi realizada por meio de entrevistas, com roteiro semiestruturado, devidamente aprovado pelo conselho de ética da Universidade Estadual do Oeste do Paraná. Esse roteiro contém 26 perguntas direcionadas ao levantamento das características socioeconômicas da atividade e das alterações ocorridas desde 1980 até 2020. As variáveis qualitativas foram analisadas. Os resultados mostraram que os pescadores possuem conhecimento e percepção sobre as mudanças ambientais ocorridas nos últimos 40 anos e sobre as consequências destas nos espaços de pesca e moradia onde estão inseridos. Demonstraram discernimento sobre as alterações no leito, no curso e nas margens do rio Paraná, sobre assoreamento, bem como ciência da diminuição e/ou extinção de espécies de peixes, alinhados com o encontrado na literatura científica. Assim, para os pescadores artesanais, o alagamento acarretou perdas sociais, culturais e econômicas. Torna-se necessária a atuação dos poderes públicos, amparados por informações científicas, orientando ações de educação ambiental e medidas mitigadoras dos impactos ambientais gerados e de apoio aos pescadores.The flooding of the Sete Quedas fall for the formation of the Itaipu hydroelectric power plant, on the Paraná River, had impacts on fishing. The objective of this study was to analyze the environmental perception of fishermen in the region of Ilha Grande National Park, the environmental changes that occurred after the formation of the Itaipu reservoir and their relationship with fishing in the region. Data collection was carried out through interviews, with a semi-structured script approved by the Ethics Committee of Western Paraná State University. This script consisted of 26 questions aimed at identifying the socioeconomic characteristics of the activity and the changes that occurred from 1980 to 2020. Qualitative variables were analyzed. The results showed that fishermen have knowledge and perception of the environmental changes that have occurred in the last 40 years, and of the consequences of these changes in the fishing and housing spaces where they are inserted. Moreover, they demonstrated knowledge about changes in the river bed, in the course and on the banks of the Paraná River, about silting up and the decrease and/or extinction of fish species, in line with what has been found in the scientific literature. Thus, for these artisanal fishermen, the flooding caused social, cultural and economic losses. It is necessary for public authorities to act, supported by scientific information, guiding environmental education actions and measures to mitigate the environmental impacts generated and to support the fishermen

Environmental conditions in river segments intercepted by culverts

The conservation and maintenance of the quality of the rheophilic environment are directly related to knowledge of the physical and chemical characteristics and structural patterns of these systems, especially in streams. Long stretches of small water bodies are highly altered by the construction of highways and roads, which tend to modify their natural characteristics, affecting the environmental quality. This study describes vegetation and morphogeometric parameters of streams with culverts along their courses, reporting spatial differences in environmental characteristics (vegetation, morphogeometric, physical, and chemical) between sampling points upstream and downstream of the culvert. Specifically, we evaluated the width, depth, riparian vegetation, substrate background, and physical and chemical properties of the water, to identify possible differences between the sections above and below (upstream and downstream) of the culvert. The rapid assessment protocol (RAP) was applied to stretches of 200 meters upstream and downstream of culverts in two Neotropical streams, between the months of November 2009 and October 2010. The vegetation and morphogeometric attributes differed between the portions upstream and downstream of the culverts, the latter because of the impoundment effect of these structures. The upstream section becomes flooded, is often shallow, and directly influences the movement of sediment. The physical and chemical variables of the water showed no spatial variation.(Condições ambientais de segmentos fluviais interceptados por bueiros). A conservação e a manutenção da qualidade ambiental do ambiente reofílico está diretamente relacionada ao conhecimento de características físicas e químicas e dos padrões estruturais destes sistemas, especialmente em riachos. Longos trechos de pequenos corpos aquáticos são altamente alterados pela construção de rodovias e estradas e tende a modificar as suas características naturais, interferindo na qualidade ambiental. Neste sentido, o objetivo deste estudo foi descrever parâmetros fito-morfogeométricos de riachos com bueiros em seu curso longitudinal, reportando diferenças espaciais nas características ambientais (fito-morfogeométricos e físico-químicas) entre os pontos amostrados (montante e jusante do bueiro). Especificamente, avaliamos a largura, a profundidade, vegetação ripária, substrato de fundo e atributos físicos e químicos da água, verificando as possíveis divergências entre os trechos de acima e abaixo (montante e jusante) do bueiro. Para isso, o protocolo de avaliação rápida (PAR) foi aplicado em trechos de 200 metros a montante, bem como a jusante de bueiros em dois riachos neotropicais entre os meses de novembro de 2009 e outubro de 2010. Verificou-se que os atributos fito-morfogeométricos diferem entre os trechos de montante e jusante, pois o bueiro tem efeito de represamento. Esse fato transforma o trecho a montante em ambiente alagado, muitas vezes rasos e influenciando diretamente o movimento de sedimentos. As variáveis físicas e químicas da água não apresentaram variação espacial

Population structure, condition and diet of Oligosarcus paranensis (Menezes & Gery, 1983) (Osteichthyes: Characidae) at two reservoirs in South Brazil

This study investigated the population parameters, condition and diet of Oligosarcus paranensis at Fiú and Mourão Reservoirs, located in Paraná State, Brazil. The fishes were collected quarterly between 1996/1997 and 1998/1999 using gillnets. Food items were quantified by volumetric method. The specimens at Fiú showed comparatively smaller length and worse condition. Sex ratio was statistically equal to 1:1 at Mourão, whereas there was a significant predominance of males at Fiú. Sex ratio also varied among size classes. Allometric growth prevailed among the studied groups. The diet consisted mainly of fishes and was complemented with invertebrates and plant matter in both reservoirs. There was a change in the feeding pattern as the standard length increased. Fishes changed from invertivores to piscivores, except for males in Mourão, for which a reverse trend occurred

Diet and trophic structure of the fish fauna in a subtropical ecosystem: impoundment effects

This study examined the diet and trophic structure of the fish fauna, over temporal and spatial scales, as affected by the impoundment of the Iguaçu River in the region of Salto Caxias, Paraná State, Brazil. Sampling was conducted before (March 1997 - February 1998) and after the impoundment (March 1999 - February 2000), at four sampling sites. The stomach contents were analyzed by the volumetric method. The species could be organized in 10 trophic guilds: algivores, carcinophages, detritivores, herbivores, aquatic insectivores, terrestrial insectivores, invertivores, omnivores, piscivores, and planktivores; the first and last guilds were represented only in the post-impoundment period. Similarity patterns and feeding changes were summarized by a non-metric Multi-dimensional Scaling (nMDS) analysis and statistically tested by a Permutational multivariate analysis of variance (PERMANOVA). Most species showed feeding changes, except for the piscivores and detritivores. These changes were related to the temporal factor (impoundment phases), such as reduced intake of benthic organisms and allochthonous food, which were usually replaced by resources from the reservoir itself (algae, microcrustaceans, and fish), simplifying the food spectrum of the fish fauna. A different indicator of food resources (IndVal) corroborated these changes in the feeding of the species. The proportions of the trophic guilds evaluated based on the catch per unit of effort (CPUE) and tested by ANOSIM were significantly different before and after the impoundment. Herbivores and piscivores were the guilds that contributed (SIMPER) to these differences, especially the high increase in biomass of the piscivore guild after the impoundment. Variations in the abundance of trophic guilds were more directly related to changes in the feeding habits of the fish fauna than to increases in the number and biomass of the species that constitute these guilds

Diet and trophic structure of the fish fauna in a subtropical ecosystem: impoundment effects

This study examined the diet and trophic structure of the fish fauna, over temporal and spatial scales, as affected by the impoundment of the Iguaçu River in the region of Salto Caxias, Paraná State, Brazil. Sampling was conducted before (March 1997 - February 1998) and after the impoundment (March 1999 - February 2000), at four sampling sites. The stomach contents were analyzed by the volumetric method. The species could be organized in 10 trophic guilds: algivores, carcinophages, detritivores, herbivores, aquatic insectivores, terrestrial insectivores, invertivores, omnivores, piscivores, and planktivores; the first and last guilds were represented only in the post-impoundment period. Similarity patterns and feeding changes were summarized by a non-metric Multi-dimensional Scaling (nMDS) analysis and statistically tested by a Permutational multivariate analysis of variance (PERMANOVA). Most species showed feeding changes, except for the piscivores and detritivores. These changes were related to the temporal factor (impoundment phases), such as reduced intake of benthic organisms and allochthonous food, which were usually replaced by resources from the reservoir itself (algae, microcrustaceans, and fish), simplifying the food spectrum of the fish fauna. A different indicator of food resources (IndVal) corroborated these changes in the feeding of the species. The proportions of the trophic guilds evaluated based on the catch per unit of effort (CPUE) and tested by ANOSIM were significantly different before and after the impoundment. Herbivores and piscivores were the guilds that contributed (SIMPER) to these differences, especially the high increase in biomass of the piscivore guild after the impoundment. Variations in the abundance of trophic guilds were more directly related to changes in the feeding habits of the fish fauna than to increases in the number and biomass of the species that constitute these guilds

Effects of impoundment on the body condition of fish in the Manso reservoir, Mato Grosso State, Brazil

AIM: This study evaluated the body condition de Acestrorhynchus pantaneiro, Auchenipterus osteomystax, Pimelodus maculatus, Psectrogaster curviventris and Schizodon borellii in the Manso reservoir, Mato Grosso State, Brazil, during the first years after its formation (years I, II, III and IV). We hypothesized that sudden environmental changes alter differently the body condition, according to the time (sampling years) and sex of individuals. Also, we checked the influence of the amount of food ingested and the reproductive status on nutritional status of the species. METHODS: The body condition (Kn), the feeding activity (SRI) and reproductive (GSI) were calculated only for adults. The difference between the sampling years and sexes (used as factors) was assessed using the nonparametric Kruskal-Wallis test. Temporal influence was tested by Spearman correlation and the interaction between both factors by PERMANOVA. RESULTS: The values of the Kn showed two groups: group 1: species whose body condition decreased in the year II, with a posterior increase (A. pantaneiro, P. curviventris and S. borelli), considered sensitive to the reservoir filling; group 2: species whose body condition increased in the year II (A. osteomystax and P. maculatus), indicating a more rapid adaptation to new environmental conditions. Still, all parameters investigated were somehow affected by the dam, mainly the body condition and gonadosomatic index for several species. On the other hand, the least affected factor was the feeding activity. CONCLUSIONS: The results did not evidence a same pattern of either increase or decrease of body condition for all species examined, since everything indicates that responses are species-specific. Even with a lack of consistency in some results, we can draw some suggestions for future investigations. Responses to these questions will certainly contribute to aggregate data to help better explain the body condition of fish species in dammed environments

Astyanax paranae Eigenmann, 1914 (Characiformes: Characidae) in the Alagados Reservoir, Paraná, Brazil: diet composition and variation

Aspects of the feeding ecology of a small characin, Astyanax paranae, were studied during 1996/1997 and 1998/1999 in the Alagados Reservoir, Paraná, Brazil (25º01'50.0'' S; 050º03'41.9'' W). Fishes were quarterly captured from the reservoir's riverine and lacustrine zones and stomachs contents of 711 adult individuals were analyzed by volumetric method. Species' feeding spectrum and spatial, temporal and sexual variations on diet were evaluated. Data matrix was summarized by detrented correspondence analysis (DCA) and the axes scores from DCA were used as variables in one-way ANOVA of null models to test diet variations. Astyanax paranae fed on detritus/sediment, plant matter, algae and aquatic and terrestrial invertebrates. The time-space prevalence of detritus/sediment and plant matter on diet characterized the feeding habit as detritivorous tending to herbivory. Significant differences on food items proportions occurred between the sampling months and sampling sites and were related to resources availability, characterizing the species trophic opportunism

Environmental conditions in river segments intercepted by culverts

The conservation and maintenance of the quality of the rheophilic environment are directly related to knowledge of the physical and chemical characteristics and structural patterns of these systems, especially in streams. Long stretches of small water bodies are highly altered by the construction of highways and roads, which tend to modify their natural characteristics, affecting the environmental quality. This study describes vegetation and morphogeometric parameters of streams with culverts along their courses, reporting spatial differences in environmental characteristics (vegetation, morphogeometric, physical, and chemical) between sampling points upstream and downstream of the culvert. Specifically, we evaluated the width, depth, riparian vegetation, substrate background, and physical and chemical properties of the water, to identify possible differences between the sections above and below (upstream and downstream) of the culvert. The rapid assessment protocol (RAP) was applied to stretches of 200 meters upstream and downstream of culverts in two Neotropical streams, between the months of November 2009 and October 2010. The vegetation and morphogeometric attributes differed between the portions upstream and downstream of the culverts, the latter because of the impoundment effect of these structures. The upstream section becomes flooded, is often shallow, and directly influences the movement of sediment. The physical and chemical variables of the water showed no spatial variation.(Condições ambientais de segmentos fluviais interceptados por bueiros). A conservação e a manutenção da qualidade ambiental do ambiente reofílico está diretamente relacionada ao conhecimento de características físicas e químicas e dos padrões estruturais destes sistemas, especialmente em riachos. Longos trechos de pequenos corpos aquáticos são altamente alterados pela construção de rodovias e estradas e tende a modificar as suas características naturais, interferindo na qualidade ambiental. Neste sentido, o objetivo deste estudo foi descrever parâmetros fito-morfogeométricos de riachos com bueiros em seu curso longitudinal, reportando diferenças espaciais nas características ambientais (fito-morfogeométricos e físico-químicas) entre os pontos amostrados (montante e jusante do bueiro). Especificamente, avaliamos a largura, a profundidade, vegetação ripária, substrato de fundo e atributos físicos e químicos da água, verificando as possíveis divergências entre os trechos de acima e abaixo (montante e jusante) do bueiro. Para isso, o protocolo de avaliação rápida (PAR) foi aplicado em trechos de 200 metros a montante, bem como a jusante de bueiros em dois riachos neotropicais entre os meses de novembro de 2009 e outubro de 2010. Verificou-se que os atributos fito-morfogeométricos diferem entre os trechos de montante e jusante, pois o bueiro tem efeito de represamento. Esse fato transforma o trecho a montante em ambiente alagado, muitas vezes rasos e influenciando diretamente o movimento de sedimentos. As variáveis físicas e químicas da água não apresentaram variação espacial