Spatial–temporal variation ofAchiruslarvae (Actinopterygii: Achiridae) in mangrove, beach and reef habitats in north-eastern Brazil

Abstract

<jats:p>The genus<jats:italic>Achirus</jats:italic>is made up of demersal fish that have a close relationship with the substrate and exhibit peculiar aspects during their larval stage. The aim of the present study was to determine whether the abundance of<jats:italic>Achirus</jats:italic>larvae differed among a set of habitats in the estuary of the Formoso River in the State of Pernambuco (north-eastern Brazil). Sampling was performed monthly between April 2009 and March 2010, and comprised horizontal hauls with plankton net during the day and night in mangrove, beach and reef habitats. Fish larvae were sorted, identified, measured and larval stage recorded. Density and body length values were used in a non-parametric analysis of variance for the determination of variations between seasons, habitats and diel periods. A total of 204 larvae were collected, with an average density of 2.1 larvae.100 m<jats:sup>−3</jats:sup>. Density was greater in the nocturnal samplings, with no differences found between habitats. The larvae occurred in the yolk-sac to post-flexion stage, with pre-flexion the most abundant stage (78%). Size segregation was observed. Larger larvae were captured at night and in the mangrove. The smallest larvae were caught on the reef, with length increasing toward the mangrove. The results indicate that<jats:italic>Achirus</jats:italic>larvae come from deeper regions near reefs, where spawning probably occurs, and perform ontogenetic migration towards the shallow waters of mangrove, where they settle.</jats:p>

Dynamics of early life‐history stages of fish along an estuarine gradient

“…Although there is little available information on the life cycle of Achiridae, fish from this family are known to exhibit more intensive spawning activity when water temperature is above 20°C (Futch, 1970). In fact, Achirus and Trinectes species also peaked in other estuaries when the water condition was similar (Arévalo-Frías & Mendoza-Carranza, 2015; Barletta & Barletta-Bergan, 2009;Silva-Falcão et al, 2013). Considering this, water temperature becomes a particularly important feature for their reproductive success, which makes these species vulnerable to climate-change impact.…”

“…However, specific behavior patterns, such as the ability of some species to remain/enter in estuaries related to vertical migration based upon a tidal rhythm ("selective tidal-stream transport,"Forward & Tankersley, 2001), can help the retention/immigration of fish larvae to estuarine nursery areas. This mechanism was observed for some species in different estuaries (e.g.,Ramos, Cowen, Paris et al, 2006;Silva-Falcão, Severi, & Araújo, 2013) but was not possible to verify in VB. First, because all samples were collected during ebb tides as a form of standardization and due to operational navigability issues.…”

Estrutura da assembleia ictioplanctônica em dois estuários tropicais de Pernambuco (Brasil), sujeitos a diferentes condições hidrológicas

“…Deste modo, uma maior densidade de larvas de peixes durante o período noturno é uma característica comum nas assembleias ictioplanctônicas em diferentes ambientes (Ré, 1999), tendo sido registrada em estudos pretéritos realizados na área de estudo (Pereira et al, 2010;Silva-Falcão, 2012;Silva-Falcão et al, 2013). Esta característica também foi observada nos ambientes estudados, indicando que o padrão é mantido mesmo em áreas sujeitas a diferentes impactos ambientais.…”

“…Destaca-se, nestes resultados, a contribuição de Achiridae na estrutura da comunidade de larvas em Rio Formoso. Esta família tem se mostrado bastante frequente e abundante nesta região (Castro, 2005;Silva-Falcão, 2012), onde a densidade de larvas pré-assentantes é significativamente maior nas áreas de manguezal (Silva-Falcão et al, 2013). Igualmente importante é a maior abundância de larvas de Hemiramphidae na área de Suape, que pode ter uma relação direta com a presença de maior quantidade de prados de fanerógamas (Silva, 2011), que servem de alimento e substrato de desova para algumas espécies da família que ocorrem na área.…”

“…Para o Estado de Pernambuco, podem ser destacados alguns trabalhos sobre ictioplâncton, como Ekau et al (1999) que estudaram o ictioplâncton na região costeira do estado; Ekau et al (2001) no Canal de Santa Cruz e El-Deir (2005) no estuário do Rio Jaguaribe, ambos no litoral norte do estado; enquanto no litoral sul podem ser citados Castro (2005), SilvaFalcão (2012) e Silva-Falcão et al (2013) no estuário do rio Formoso; e Bezerra-Júnior et al (2011) no estuário de Suape.…”