Abstract
ABSTRACT We investigated the intraspecific partitioning of food resources of the Brazilian silverside Atherinella brasiliensis in a tropical estuary. A total of 1,099 stomachs were analyzed, and the diet consisted mainly of Gastropoda, Ceratopogonidae larvae, Decapoda larvae, Calanoida, Cyclopoida, Hymenoptera and Brachyura. Ordination of the mean volumetric percentage contribution of preys indicated differences in the dietary compositions between sites and size classes. By SIMPER analysis, we detected high dissimilarity between size classes, suggesting ontogenetic niche shifts: the diet of the early juveniles was based in zooplankton, whereas adults consumed mainly benthic macroinvertebrates. These shifts were related to changes in feeding structures and foraging abilities that show a strong relationship with body size, and showed functional trade-offs in swimming capacity, and feeding strategies used to capture prey. Differences in the diet between size classes and habitat selection by Brazilian silverside are likely strategies to avoid intraspecific competition, clearly related to the abundance and accessibility of resources along the estuarine habitats.
Highlights
The niche concept proposes that interactions between resources and consumers depend, in part, on how resources affect fitness components of consumers (Leibold, 1995)
Brazilian silversides in the tropical estuary exhibited marked spatial abundance and ontogenetic diet shifts
Three characteristics of A. brasiliensis were identified as factors important to its success in estuarine areas: salinity tolerance (SouzaBastos, Freire, 2011), slow rates of growing with positive alometric coeficients and short-lived life cycle (Contente et al, 2011; Carvalho et al, 2017)
Summary
The niche concept proposes that interactions between resources and consumers depend, in part, on how resources affect fitness components of consumers (Leibold, 1995). Most direct effects of intraspecific food competition in fishes result in changes in population density, survival, and growth (Alanärä et al, 2001). Given such circumstances, understanding how mechanisms contribute to intraspecific partitioning has been a focus of ecological research. The estuarine fishes are excellent models because they can reduce the impact of competition by partitioning the resources along three main dimensions: habitat, trophic, and temporal segregation (Ross, 1986). Estuarine fishes exploit a wide range of prey types, which are locally abundant in the environment, and this has frequently been used to infer trophic plasticity (Hostim-Silva et al, 1995). Several studies of feeding habits in tropical estuarine fishes have reported shifts in prey consumption during the ontogeny (Pessanha, Araújo, 2001), which has e180108[1]
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