Feeding ecology of three juvenile mojarras (Gerreidae) in a tropical estuary of northeastern Brazil

Abstract

Distributions and feeding ecology of mojarra species from shallow water of a tropical estuary in Northeastern Brazil were observed aiming to investigate differences in distribution and resource partitioning among juveniles of three species of mojarras. Fishes were collected with a beach seine across four sites along a salinity gradient from January to December of 2011. Highest abundances were recorded during the rainy season in the upper and middle estuary. Microcrustaceans, mainly copepods, were the preferential prey items of all mojarras, irrespective of size or hydrological season, suggesting these areas may be important nursery habitats. Juveniles of mojarra used two important mechanisms for exploitation of resources: (1) spatial segregation along the salinity and temperature gradient, such as abundance of Eucinostomus melanopterus increased from downstream to upstream estuary, while Eugerres brasilianus displayed an opposite pattern; (2) differences related to the volumetric proportion of the main prey items, with indications that E. melanopterus and Diapterus rhombeus fed predominantly on Calanoida and Cyclopoida, while the diet of E. brasilianus was dominated by items of infauna. Such strategies were important for resource partitioning, favouring the coexistence of these three species in the estuary.A distribuição e a ecologia alimentar de gerreídeos capturados em águas rasas de um estuário tropical no nordeste do Brasil foram abordados com o objetivo de investigar diferenças na distribuição e partição de recursos entre três espécies de gerreídeos juvenis. Arrastos de praia foram realizados ao longo de quatro locais ao longo do gradiente de salinidade entre janeiro e dezembro de 2011. Maiores abundâncias foram registradas durante a estação chuvosa na zona superior e média do estuário. Microcrustáceos, principalmente copépodos, foram as principais presas para as três espécies, independente do tamanho ou do período hidrológico, sugerindo que essas áreas são importantes para o recrutamento. Gerreídeos juvenis usaram dois importantes mecanismos para exploração dos recursos: (1) segregação espacial no uso dos habitats ao longo do gradiente de salinidade e temperatura, com a abundância de Eucinostomus melanopterus aumentando em direção a parte inferior para porção superior do estuário, enquanto Eugerres brasilianus apresentou um padrão oposto; e (2) diferenças relacionadas com a proporção volumétrica das principais presas ingeridas, com indicações que E. melanopterus e Diapterus rhombeus alimentaram-se principalmente de Calanoida e Cyclpoida, enquanto a dieta de E. brasilianus foi dominada por itens da infauna. Tais estratégias foram importantes para partição dos recursos, favorecendo a coexistência dessas três espécies no estuário.

Does environmental heterogeneity explain β diversity of estuarine fish assemblages? Example from a tropical estuary under the influence of a semiarid climate, Brazil

“…These results were consistent with other studies in Mamanguape estuary to investigate spatial patterns of fish assemblages [ 60 , 73 ]. Similarly, Araújo et al [ 74 ] reported that the mojarra fish species (Gerreidae) used spatial segregation in the use of habitats along the estuarine gradient, while Araújo et al [ 75 ] indicated the environmental variations influencing the distribution of two puffer fish species ( S . testudineus and Colomesus psittacus ).…”

Resource partitioning among juvenile snappers in a semi-arid estuary in north-eastern Brazil

“…Competition between species for shared resources generally increases differential resource utilization and decreases niche overlap between species (Amorim et al ., 2016). Sympatric species that interact are theoretically expected to evolve niche separation and resource partitioning to reduce competition (Araújo et al ., 2016). Thus, ecological resource partitioning mechanisms, such as prey and habitat selection and time segregation, minimize competition and allow these species to coexist (Carvalho & Tejerina-Garro, 2014).…”