Freshwater parameters in the state of Rio Grande do Sul, southern Brazil, and their influence on fish distribution and aquaculture

Abstract

This study analyzed the relationship between several water quality parameters (pH, hardness, alkalinity, turbidity, iron and manganese) levels measured over a 16 year period with fish distribution and aquaculture in the state of Rio Grande do Sul, Southern Brazil. The mean pH values were within a neutral range (6.5-7.5), but the maximum and minimum values reached inappropriate levels for fish farming in some cities. Alkalinity levels were very low (except in the southwest region of the state), which may have contributed to pH variation. Hardness, turbidity, iron (except the region near Caçapava do Sul City) and manganese were within safe ranges for fish farming; however, turbidity levels occasionally increased to levels outside the safe range. In conclusion, the water quality in the Rio Grande do Sul, in general, can be considered adequate for aquaculture, but the fish farmers must be aware of the methods to reduce turbidity, such as the use of calcium sulfate.Este estudo analisou a relação entre vários parâmetros de qualidade da água (pH, dureza, alcalinidade, turbidez, ferro e manganês durante 16 anos) com a distribuição de peixes e piscicultura no estado do Rio Grande do Sul, Brasil. O pH ficou em média em uma faixa neutra (6,(5)(6)(7)5), mas valores máximos e mínimos atingiram níveis não apropriados para a piscicultura em algumas cidades. Os valores de alcalinidade foram baixos (exceto na região sudoeste do estado), o que poderia contribuir para oscilações no pH. Dureza, turbidez, ferro (exceto na região próxima à cidade de Caçapava do Sul) e manganês ficaram dentro de níveis aceitáveis para a piscicultura, mas a turbidez ocasionalmente elevou-se a níveis fora dessa faixa aceitável e os piscicultores devem ter algum mecanismo para reduzi-los. Em conclusão, de forma geral a qualidade da água do Rio Grande do Sul pode ser considerada adequada para a aquicultura, mas os piscicultores devem conhecer métodos para corrigir a turbidez, como a utilização de sulfato de cálcio.

Humic acid of commercial origin causes changes in gill morphology of silver catfish Rhamdia quelen exposed to acidic water

“…Freshwater environments are characterized by extremely variable chemical features (Dejours, ). Undesirable changes in water pH and ionic and gaseous composition, for example, are especially relevant for continental aquaculture, since they may impose a physiological challenge on the fish (Wood, ; Hwang & Lee, ; Baldisserotto, ; Souza, Pereira Junior, Garcia, Santos, & Baldisserotto, ).…”

“…Silver catfish is the native fish most studied in Brazil, and improvement of its production is continuously being sought. The species can be found throughout Brazilian waters, which may vary from the clear acidic‐neutral waters in South Brazil (Souza et al., ) to the acidic blackwater in North Brazil (Matos et al., ; Abrunhosa et al., ). Specimens that do not inhabit DOC‐enriched acidic waters are possibly not adapted to the naturally occurring beneficial effects promoted by DOC.…”

“…Silver catfish is the native fish most studied in Brazil, and improvement of its production is continuously being sought. The species can be found throughout Brazilian waters, which may vary from the clear acidic-neutral waters in South Brazil (Souza et al, 2016) to the acidic blackwater in North Brazil (Matos et al, 2005;Abrunhosa et al, 2016).…”

“…Specimens that do not inhabit DOC-enriched acidic waters are possibly not adapted to the naturally occurring beneficial effects promoted by DOC. However, non-constant water conditions are observed in fish farming, and oscillations in DOC content and pH level are likely to occur (Souza et al, 2016). Non-acidophilic fish species must show adaptations to enable maintenance of homeostasis when experiencing a low pH challenge, since water acidity may cause osmoregulatory, hematological, endocrine, metabolic, reproductive, and behavioral disturbances (Laurent & Perry, 1991;Vuorinen, Keinanen, Peuranen, & Tigerstedt, 2003;Carvalho & Fernandes, 2006).…”