PESO-COMPRIMENTO E FATOR DE CONDIÇÃO RELATIVO DE Bryconamericus iheringii EM RIACHOS DO PARANAPANEMA

Abstract

Foram analisados a relação peso-comprimento e o Fator de Condição Relativo (Kn) de peixes da espécie Bryconamericus iheringii capturados em três riachos da bacia do rio das Cinzas, Alto rio Paraná, para estimar, respectivamente, o tipo de crescimento e o bem-estar das populações. Análises de Variância (ANOVA Unifatorial) foram utilizadas para verificar diferenças significativas nos valores de peso, comprimento e Kn entre os riachos, e análises de correlação (Spearman) indicaram a relação entre esses parâmetros supracitados e os fatores físicos e químicos e densidade populacional nos riachos. Os indivíduos do riacho Ubá, considerado o mais preservado com relação à vegetação ripária entre os três estudados, apresentaram maiores valores de peso, comprimento e Kn. Os indivíduos dos riachos Água dos Anjos e Monjolinho exibiram crescimento alométrico negativo, com maior acréscimo em comprimento (mm), e os do riacho Ubá, alométrico positivo, com ganho maior em peso (g). O Kn se correlacionou (p < 0,05) negativamente com a densidade e a condutividade, e a condutividade baixa, por consequência, teve correlação com a alta extensão da mata ripária. Portanto, o presente trabalho mostra indícios de que os parâmetros de relação peso-comprimento e de Kn de peixes de riacho podem ser influenciados significativamente pelas características ambientais relacionadas principalmente à vegetação marginal, podendo ser boas métricas complementares para entender a resposta desses organismos às alterações antrópicas.

Length-Weight Relationship and Relative Condition Factor of 31 Small-Sized Fishes of the Paranapanema River Basin

“…The relative condition factor did not differ significantly between species and environments studied. So, it was not possible to carry out additional analysis to relate the fish condition with environmental circumstances, as in previous studies (Barrilli et al, 2015;Caetano and Jané, 2018). We can interpret the results not assuming that the environments are in good conditions, but from the fish populations in these sites.…”

“…In reservoirs, small-sized fish may become widespread and abundant in marginal zones (Orsi, 2010). Hence, the adjusted Kn values in the lentic environments (lagoons) demonstrates the supply of these populations, might be related to fish feeding habits (Silva Lourenço et al, 2008;Caetano and Jané, 2018) and the investment that adults individuals put on reproduction (Orsi et al, 2002(Orsi et al, , 2004. Additionally, it is a known that the aggregation of higher biodiversity in marginal lagoons is responsible for providing food resources (e.g., autochtones and alochtones items) to fishes, such as invertebrate, algae, and plant material (Ferrareze and Nogueira, 2011).…”

“…The application of this measure depends closely on the weight and length of the individuals (Froese, 2006). However, the relative condition factor (Kn) allows to evaluate the observed values in relation to the theoretically expected for each length, being more reliable to assess the fish healthiness (Anderson and Gutreuter, 1983) and distinguish environmental influential conditions (Barrilli et al, 2015;Caetano and Jané, 2018).…”

“…For the Paranapanema River basin, length-weight relationships have been largely described for 20 species of fishes in the Jurumirim Reservoir (Oliva-Paterna et al, 2009), and 37 in the Taquari River (Nobile et al, 2015), 15 in the Capivara Reservoir (Orsi and Britton, 2012), 18 in the Tibagi River (Orsi et al, 2002), and six in tributaries of the Taquaruçu Reservoir (Ribeiro et al, 2017). On the other hand, descriptions of the relative condition factor in the basin are less common, being reported to two species in the Tibagi River (Orsi and Shibatta, 1999;Orsi et al, 2004) and one species in the Cinzas River (Caetano and Jané, 2018), both tributaries of the Capivara Reservoir. Although rare so far for the basin, they can be an useful tool for the aquatic communities evaluation in response to the environmental impacts (Barrilli et al, 2015;Caetano and Jané, 2018) since this important tributary of the upper Paraná River were strongly impacted by dams (Orsi, 2010), deforestation (Rodrigues et al, 2019), discharge of human effluents (Cunico et al, 2006) and agriculture and pasture (Vidotto-Magnoni et al, 2015).…”

“…On the other hand, descriptions of the relative condition factor in the basin are less common, being reported to two species in the Tibagi River (Orsi and Shibatta, 1999;Orsi et al, 2004) and one species in the Cinzas River (Caetano and Jané, 2018), both tributaries of the Capivara Reservoir. Although rare so far for the basin, they can be an useful tool for the aquatic communities evaluation in response to the environmental impacts (Barrilli et al, 2015;Caetano and Jané, 2018) since this important tributary of the upper Paraná River were strongly impacted by dams (Orsi, 2010), deforestation (Rodrigues et al, 2019), discharge of human effluents (Cunico et al, 2006) and agriculture and pasture (Vidotto-Magnoni et al, 2015).…”