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Spatiotemporal Variation in Fish Assemblage in a Coastal Lagoon without Direct Contact with the Sea (Southeastern Brazil)

Jorge Iván Sánchez-Botero, Erica Pellegrini Caramaschi and Danielle Sequeira Garcez
Journal of Coastal Research
Vol. 24, No. 4C, Supplement (Jul., 2008), pp. 225-238
Stable URL: http://www.jstor.org/stable/40065089
Page Count: 14
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Spatiotemporal Variation in Fish Assemblage in a Coastal Lagoon without Direct Contact with the Sea (Southeastern Brazil)
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Abstract

The Cabiúnas Lagoon is a narrow water body that is perpendicular to the sea and isolated from it by a sandbank. Before 1991, the sandbank was sometimes opened for a few days by local residents, but at present seawater only enters by limited groundwater seepage or by overtopping the sea barrier in storms. In 1998 the Restinga de Jurubatiba National Park was established, including the Cabiúnas Lagoon. Studies on the structure and spatial distribution of the fish assemblage were performed between 1991 and 1994; we carried out one year (2001-2002) of monthly monitoring of the lagoon to identify spatiotemporal variations in the lagoon fish assemblage. The closed sandbank altered salinity content, and favoured oligohaline conditions and the increase of the aquatic macrophyte abundance, promoting freshwater species dominance and reduction of the marine dependent and some coastal lagoon resident species of fish adapted to paralic ecosystems. Two freshwater, two coastal lagoon resident, and five marine dependent fish species, which had been registered in the first studies (1991 and 1994), were not captured in the subsequent samplings. The mean number of individuals (N m⁻² )decreased significantly (Kruskal-Wallis [KW] = 9.977; p = 0.0068); the decrease in biomass was found to be 80%. Species richness and diversity were also significantly reduced. Differences in the current conditions regarding specific composition along the longitudinal axis of the lagoon were observed. Temperature, salinity, and macrophyte coverage were important variables that influenced fish spatial distribution, abundance, and biomass. /// A lagoa Cabiúnas, localizada no Parque Nacional da Restinga de Jurubatiba, RJ/Brasil, apresenta um perfil alongado perpendicular ao litoral com uma barra arenosa que a separa do mar adjacente, sujeita, atualmente, à influência marinha por ressacas de curta duração. Entre 1991 e 1994 foram realizados estudos com o objetivo de caracterizar a estrutura e distribuição espacial da ictiofauna neste ambiente. Posteriormente, um monitoramento mensal na lagoa durante um ano (2001-2002), teve por objetivo identificar as mudançãs na ictiofauna quando comparada com os estudos anteriores. A barra permanentemente fechada neste ambiente favoreceu condições oligohalinas e incremento da abundância de macrófitas aquáticas, promovendo aumento na abundância e dominância das espécies dulcícolas e diminuição na constância das especiés de peixes marinho dependentes e algumas residentes de lagoas costeiras adaptadas a ecossistemas salobros. Duas espécies de peixe de origem dulcícola, duas residentes de lagoas costeiras e cinco marinho dependentes, registradas nos primeiros estudos (1991 e 1994), não foram capturadas nas coletas posteriores. As médias do número de individuos (N.m⁻²) diminuíram significativamente (Kruskal-Wallis KW = 9,977; p = 0,0068) e a biomassa diminuiu em 80%. Da mesma forma, valores de riqueza de espécies e diversidade foram significativamente diferentes. Também foram observadas diferenças quanto à composiçāo específica ao longo do eixo longitudinal da lagoa. Variáveis que influenciaram a distribuição espacial, abundância e biomassa de peixes, foram temperatura, salinidade e cobertura de macrófitas.

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