Distribution, abundance and biomass of Chaetognaths off São Sebastião region, Brazil in February 1994

Abstract

(Praça do Oceanográfico, SP, Brasil) lavega@usp.br• Abstract: The distribution, abundance, biomass, population structure and feeding habits of chaetognaths collected off São Sebastião region, Brazil, in February 1994 are described. Bongo nets were hauled obliquely to collect zooplankton samples. Forty-three samples obtained with the 333 urn mesh were analysed. In this study, 7 chaetognath species belonging to two genera were identified. Sagitta friderici, S. tenuis and S. bipunctata were grouped into the neritic category, and Sagitta enflata, S. hispida, S. minima and Krohnita pacifica into the semi-neritic group. The analysis of the community structure distinguished 3 zones: 1) a nearshore zone evidenced by low richness; 2) an offshore zone evidenced by higher number of species and 3) another offshore zone, located south and south-westward of São Sebastião Island, characterised by higher richness but with dominance of one species. The nearshore zone was dominated by the neritic species S. friderici and S. tenuis, whereas the offshore zone was dominated by S. enflata. Abundance and biomass increase from nearshore toward offshore zones by about two orders of magnitude. Gut content analysis revealed over 90% of empty guts. The chaetognath population was composed mainly of juveniles. The diets among the different chaetognath species was very similar, composed mostly of small copepods and appendicularians.• Resumo: No presente trabalho foram estudados a distribuição, abundância, biomassa, estrutura da população e hábito alimentar dos quetógnatos coletados na região de São Sebastião, Brasil, em fevereiro de 1994. As 43 amostras de zooplâncton utilizadas na elaboração deste trabalho foram obtidas através de arrastos oblíquos usando uma rede Bongô (333 um), providas de fluxômetro. Foram identificadas sete espécies de Chaetognatha pertencentes a dois gêneros. Sagitta friderici, S. tenuis e S. bipunctata foram agrupadas como espécies neríticas, enquanto que Sagitta enflata, S. hispida, S. minima e Krohnita pacifica semi-neriticas. A análise da estrutura da comunidade, mostrou a existência de 3 zonas: 1) zona costeira caracterizada por poucas espécies; 2) zona oceânica com muitas espécies e 3) zona oceânica, ao sul e sudoeste da Ilha de São Sebastião, com muitas espécies, mas predominância de uma espécie. A zona nerítica foi dominada pelas espécies S. friderici e S. tenuis, e a zona oceânica por S.enflata. Abundância e biomassa do grupo aumentou da região costeira para a oceânica. A população foi composta principalmente de jovens. A análise do conteúdo intestinal revelou mais de 90% de indivíduos com o trato digestivo vazio. A dieta das diferentes espécies foi bastante similar, sendo composta principalmente de pequenos copépodos e apendiculários.

Relationship between spatial distribution of chaetognaths and hydrographic conditions around seamounts and islands of the tropical southwestern Atlantic

“…According to Marazzo and Nogueira (1996), it is typical of surface waters and specially abundant at the continental shelf where salinity ranges from 35 to 36. Liang and Vega-Pérez (2001) found low densities of F. enflata in the coastal region off Vitória, and observed that this species seemed to be limited to the areas of high salinity values (>36 PSU) found in the tropical waters of the region, since this is a semi-neritic species (Liang and Vega-Pérez 2002).…”

“…Thirty-nine species have been reported in the South Atlantic so far, between 0 and 60°S (Boltovskoy 2005). Studies on chaetognaths in southeastern Brazil have concentrated on coastal and oceanic waters where these organisms are abundant (Almeida Prado 1968, Vega-Pérez and Liang 1992, Marazzo and Nogueira 1996, Liang and Vega-Pérez 2001, 2002, Vega-Pérez and Schinke 2011. However, chaetognaths can also be found in Brazilian estuaries, as reported by Lansac Tôha and Lima (1993) in the estuary of the Una do Prelado river, by Lira and Magalhães (1996) in the Mandaú/ Manguaba system in Alagoas, by Lopes (1996) in the estuaries of the Juréia-Itatins ecological station, by Montú (1980) in the Patos Lagoon estuary in Rio Grande and by Paranaguá and NascimentoVieira (1984) in the Botafogo river estuary.…”

Reproduction and structure of the population of the Chaetognath Parasagitta friderici in Guanabara Bay (Brazil) based on short term sampling

“…In Brazil, chaetognath studies have dealt mainly with distribution (Almeida Prado 1961a, Fernandes et al 2005 or population structure and feeding (Nair and Sankarankutty 1988, Vega-Pérez and Liang 1992, Liang and Vega-Pérez 1994, 1995, 2002. In Guanabara Bay, three species of chaetognaths are abundant; Parasagitta friderici Ritter-Zàhony is the dominant species, followed by Flaccisagitta enflata Grassi and Ferosagitta hispida Conant (Marazzo and Nogueira 1996).…”

Checklist do filo Chaetognatha do Estado de São Paulo, Brasil

“…Dentre esses destacam-se: "Nave Liguria" (Baldasseroni, 1915), "Meteor" (Thiel 1938) e "Terra Nova" (Burfield 1930). Posteriormente, outros trabalhos foram realizados por Vanucci & Hosoe (1952), Hosoe (1956), Alvariño (1980), Gusmão (1986), Nair & Sankarankutti (1988), Liang (1998) Almeida-Prado (1960, 1961a,b, 1963, Costa (1970Costa ( , 1971, Coelho (1993), Liang (1993), Liang & Vega-Pérez (2002), Resgalla & Montú (1995), Marazzo-Nogueira et al (1996), Vega-Pérez & Liang (1999), Liang et al (2003) e Vega-Pérez & Schinke (2008), estudaram a ocorrência e distribuição das que ocorrem nas regiões sudeste e sul. Aspectos relacionados aos hábitos alimentares dos quetógnatos foram abordados por Almeida-Prado (1968), Vega-Pérez & Liang (1992, Liang & Vega-Pérez (1995) e Marazzo et al (1997).…”