Patterns in fish species composition and assemblage structure in the upper Salado River lakes, Pampa Plain, Argentina

Abstract

The Pampa Plain, in the central region of Argentina, is mostly drained by the Salado River. The fish fauna of this river is mostly known from field collections in lower reach lakes. Consequently, we aimed to explore the composition and structure of the fish assemblages in the upper Salado River lakes. Patterns in dominance and persistence of species and assemblage level attributes were correlated with environmental and human activity-derived (NO 3 :NH 4 ) variables. Overall, 19,913 individuals of 17 species included in 5 orders and 11 families were collected. Several species are first records for the upper Salado River lakes. There was a marked proliferation of species in the family Characidae. Conversely, the remainder 10 families were only represented by one or two species. The species composition along the study lakes changed slightly but their relative contribution to the total fish collected (dominance) varied greatly. Rather few species were present in all collections suggesting an important interannual variability in assemblage stability. The gradient in water conductivity was an important factor for the persistence of particular species in the lakes. The gradients in water conductivity and NO 3 :NH 4 ratio were associated with particular fish communities dominated by different groups of species. These results suggest that even when broad management and conservation strategies should encompass the system as a whole, lake-specific approaches must also be addressed. Overall, our results highlight that human impacts on surface waters may interact with environmental factors to influence the dynamics of fish species and the structure of their communities.A planície pampeana, na região central da Argentina, é em grande parte drenada pelo rio Salado. A ictiofauna desse rio é conhecida principalmente pelos estudos conduzidos nos lagos dos segmentos inferiores do rio. Em consequência, procuramos examinar a composição e a estrutura das assembleias de peixes dos lagos do alto rio Salado. Os padrões na dominância e persistência das espécies e os atributos das assembleias de peixes foram correlacionados com variáveis ambientais e variáveis indicadoras de perturbações antropogênicas (NO 3 :NH 4 ). Foram coletados 19913 indivíduos de 17 espécies pertencentes a 5 ordens e 11 famílias. Várias espécies foram registradas pela primeira vez para as lagoas do alto rio Salado. Houve uma marcada proliferação de espécies da família Characidae. Em contraste, as 10 famílias de peixes restantes foram representadas por uma ou duas espécies. A composição de espécies variou pouco ao longo dessas lagoas mas sua contribuição ao total de peixes coletados (dominância) foi muito variável. Poucas espécies estiveram presentes em todas as coletas, sugerindo uma importante variação interanual na estabilidade da assembleia de peixes. O gradiente na condutividade elétrica da água foi importante fator para a persistência de algumas espécies nessas lagoas. A condutividade elétrica da água e o gradiente na relação NO 3 :NH 4 estiveram associados com...

The influence of habitat on the spatial variation in fish assemblage composition in an unimpacted tropical River of Ganga basin, India

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Fish assemblage of a Pampean shallow lake, a story of instability

“…2, 3; Table 2). Rosso & Quirós (2010), based on a four consecutive summer sampling programme, demonstrated that water residence time, total phosphorus, NO 3 :NH 4 ratio and water conductivity determined fish abundance and distribution in several lakes of the upper Salado River basin. However, on a longer-term basis, our results indicate that flood and drought cycles coupled to extreme temperatures appear to be the main driving factors in structuring fish assemblages in Chascomús Lake.…”

“…These authors demonstrated that conductivity, water residence and land use were involved in temporal and spatial patterns of fish abundance and distribution in four Pampean lakes during four consecutive summers. Clearly, such an environmental-based approach emerged as relevant, considering that the fish assemblages of the Pampean lakes are composed of several species found in the southern distribution of the Brazilian subregion, inhabiting an extended and fluctuating ecotone which limits with the Austral subregion (Ringuelet, 1975;Baigún et al, 2002;López et al, 2002;Rosso & Quirós, 2010). Additionally, as a complementary source of changes for fish composition, Menni (2004) suggested that species movements among the waterbodies of the Pampean region occur during flood periods, when the connectivity increases and thus facilitates the ingression of several migratory species from the inner part of the Río de la Plata estuary.…”

The effect of a large-scale irrigation scheme on the fish community structure and integrity of a subtropical river system in South Africa

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