Fish assemblage structure in an estuary of the Atlantic Forest biodiversity hotspot (southern Brazil)

Abstract

We described the fish assemblage in the estuary of the Guaraguaçu River (one of the largest tributaries of the Paranaguá Bay Estuary, located within Brazil's Atlantic Forest Biosphere Reserve) from June 2005 to May 2006, and assessed the seasonal and spatial effects of abiotic environmental attributes on the fish assemblage structure. Despite some oscillations in salinity, the upper and lower estuaries had year-round persistent oligohaline and polyhaline conditions, respectively. Despite high species richness (55 species), the Guaraguaçu River Estuary fish community contains a few dominant taxa; 11% of the richness accounts for [60% of its density and biomass. The most abundant species (in terms of both biomass and density) was Atherinella brasiliensis. Species whose densities were most strongly associated with the upper estuary were Centropomus parallelus, Ctenogobius schufeldti, Eucinostomus melanopterus, Platanichthys platana, Trinectes paulistanus, and Eugerres brasilianus. Those whose densities were most strongly associated with the lower estuary were A. brasiliensis, Sphoeroides greeleyi, Eucinostomus argenteus, Sphoeroides testudineus, Diapterus rhombeus, and Harengula clupeola. Throughout the year, canonical correspondence analysis identified: (1) the pattern of horizontal stratification of salinity along the river as being the most important variable for explaining most of the fish fauna structure; and (2) a strong relationship between the fish fauna and the salinity gradient along the estuary. Analysis of similarity further confirmed that each estuarine zone supports a year-round persistent and relatively homogeneous fish species assemblage. Total mean density and biomass remained constant over time in each estuarine habitat, but density shifted in the most abundant species, which appears related to recruitment patterns. Such species and abundance persistence likely occurs because seasonal rainfall-induced changes in river discharge are not sufficient to significantly shift runoff and salinity and thus fish assemblage structure (species composition, density and biomass) along the estuary. Such a lack of seasonal fish fauna movement as a response to changes in river flow contrasts with other estuarine systems around the world.

Ontogenetic development of the sagittal otolith of the anchovy, <em>Anchoa tricolor</em>, in a subtropical estuary

“…What, then, is the utility of the description presented in the current study? Although it is not possible to identify the other congeneric species, in the study area A. tricolor is the most abundant and important engraulid in the PEC (Contente et al 2011) and other coastal areas, including the inner continental shelf (<50m depth) (RossiWongtschowski et al 2014). This fact per se highlights the importance of an otolith description of this species, even disregarding other congenerics.…”

“…It has an isometric growth pattern RossiWongtschowski 2013, Franco et al 2013) and spawns between September and February (Araújo et al 2008). Very few studies on the relationship between the species and estuaries are extant: the exclusive presence of juveniles and young fish of the year have been reported in Sepetiba Bay and in the Paranaguá Estuarine Complex (PEC), Brazil, with the occurrence of adults in open beaches outside these ecosystems (Araújo et al 2008, Contente et al 2011). …”

Comparison of the temporal and taxonomic patterns of ichthyofauna captured with a fyke net in two sheltered environments in southern Brazil

“…However, the low abundance and richness of cryptic species showing limited displacement, such as Gobiidae (Ryan, 1992), indicates that a fixed net may be ineffective for the collection of these individuals. Gobiidae are apparently more abundant in the internal areas of estuaries (Spach et al, 2006;Vilar et al, 2011) and are generally among the families showing greater species richness in estuarine regions (Contente et al, 2011), although this is not the case for sheltered beaches (Pessanha et al, 2003;Félix-Hackradt et al, 2010). It is important to know the limitations of fyke nets, similar to other methods, as poor sampling in ecological studies may result in false representations of fish assemblages and lead to underestimations of possible impacts (such as the impact of building marinas) on the existing ichthyofauna (Griffiths, 2001).…”

Ichthyofauna as an environmental quality indicator of the Bertioga Channel, São Paulo (Brazil)

“…The ichthyofauna of Brazilian estuaries have been studied under various aspects, such as its composition and abundance (FELIX et al, 2006, DIAS et al, 2011, diversity (CASTRO, 2001;CARVALHO NETO;CASTRO, 2008;BARLETTA et al, 2003), assemblages (CONTENTE et al, 2010;ARAÚJO et al, 2013;HOSTIM-SILVA et al, 2013;PASSOS et al, 2013), resource exploitation (BARLETTA; COSTA, 2009), structure and seasonal dynamics of ichthyoplankton (BARLETTA-BERGAN et al, 2002;PORCARO et al, 2014), influence of environmental variables on fish distribution (BARLETTA et al, 2005;BARLETTA et al, 2008), recruitment (BOLZAN et al, 2014), biological and socioeconomic aspects of fisheries exploitation (CHAVES et al, 2003), and also as indicator of environmental quality (VIANA; LUCENA FRÉDOU, 2014). The main hydrographic characteristics of estuaries that influence the fish distribution are salinity, temperature, turbidity and dissolved oxygen BLABER, 1980;BARLETTA et al, 2008).…”