Dynamics of the shallow‐water fish assemblage of the Patos Lagoon estuary (Brazil) during cold and warm ENSO episodes

Abstract

In southern Brazil, cold (La Niña) and warm (El Niño) episodes of the El Niño Southern Oscillation (ENSO) phenomenon cause drought and high rainfall, respectively. The low precipitation and freshwater outflow associated with La Niña during 1995-1996 were associated with an increase in the abundance of marine species in the Patos Lagoon estuary. During the 1997-1998 El Niño, high precipitation and river discharge were associated with low abundance of marine species in the estuary. ANOVA results showed a higher abundance during La Niña than El Niño for estuarine resident (RES) and estuarine dependent (DEP) fishes. During La Niña catch per unit of effort (CPUE) of RES increased from the marine to estuarine area, but during El Niño CPUE increased at the marine area and diminished during summer and autumn in some estuarine sites. DEP fishes had an opposite abundance pattern. During La Niña, these fishes were abundant at the coastal marine area and along some estuarine sites, but during El Niño, CPUE remained almost the same at the marine area but dropped along some estuarine sites. These different abundance patterns for dominant fish groups yielded a positive interaction between stations and climatic events. With higher river discharge and the consequent decline of dominant euryhaline fishes, such as Mugil platanus and Atherinella brasiliensis, freshwater species increased in abundance and richness in the shallow waters of the estuary. The ENSO phenomenon influences precipitation and estuarine salinity in southern Brazil and thereby seems to have a strong influence on recruitment, immigration, and emigration dynamics of fish species living within and adjacent to estuarine habitats. 2001 The Fisheries Society of the British Isles

Distribuição espacial e abundância das assembléias de peixes no Parque Nacional da Lagoa do Peixe, Rio Grande do Sul, Brasil

“…Esses dados são semelhantes aos encontrados para a zona estuarina do estuário da Lagoa dos Patos (GARCIA et al 2001), caracterizando os estuários como zonas de criação para diversas espéci-es de peixes (HAEDRICH 1983, VIEIRA et al 1996.…”

Alimentação de Hoplias aff malabaricus (Bloch, 1794) e Oligosarcus robustus Menezes, 1969 em uma lagoa sob influência estuarina, Pelotas, RS

“…Para as espécies de água doce que vivem em ambientes submetidos à influência estuarina a capacidade de utilizar os recursos alimentares provenientes do estuário pode ser crucial para o seu sucesso neste tipo de ambiente. De fato, Garcia et al (2001) mostraram que na Lagoa Pequena, ambiente submetido à influencia físico-química e biológica da zona estuarina da Lagoa dos Patos, sul do Brasil, a movimentação de peixes entre o ambiente estuarino e límnico pode ser uma importante via de subsídio lateral de energia conectando as tramas tróficas estuarinas e de água doce.…”

The influence of an extreme drought event in the fish community of a southern Europe temperate estuary

“…Also, predation pressure on these species could have increased due to the higher abundance of marine adventitious species (MA), particularly at the mouth of the estuary (for further discussion on this topic see . According to Garcia et al (2001), surveys in a warmetemperate south-western Atlantic intermittently closed lagoon (South Brazil) led to the conclusion that during La Niña episodes (cold and dry events) there was an increase in marine species inside the lagoon, as a consequence of low freshwater input and a higher intrusion of sea water into the upper reaches. The same pattern was observed by Ecoutin et al (2005) in a coastal lagoon in the Ivory Coast.…”

“…In estuaries, these effects have only been addressed in a few studies concerning invertebrates (Attrill et al, 1996;Attrill and Power, 2000) and fishes (e.g. Garcia et al, 2001;Ecoutin et al, 2005). Such environmental instability, combined with anthropogenic derived pressures such as dredging activities, waste water and general organic pollution, will have significant impacts on estuarine fish communities.…”