Abstract:Fish assemblages were studied in a hypersaline tropical estuary in Northeastern Brazil. A total of 104 species were collected by beach seine during the dry and rainy seasons of 2012. Two families, Atherinopsidae and Gerreidae, were numerically dominant in all zones of the estuary; juveniles of Atherinella brasiliensis, Eucinostomus argenteus, Lile piquitinga, Ulaema lefroyi, Lutjanus analis and Sphoeroides greeleyi contributed 77% of the total catch. The factors that best explained the fish abundance pattern w… Show more
“…The low rainfall index combined with the high evaporation rate and the low fresh water inflow creates a salinity gradient that increases upstream (hypersaline conditions). Salinities varying between 30 and 50 are observed in this estuary (Sales et al ., 2018).…”
Section: Methodsmentioning
confidence: 99%
“…These estuaries are classified by salinity classes (lower zone: Mamanguape from 26 to 37 and Tubarão River from 30 to 39; upper zone: Mamanguape from 2 to 25 and Tubarão River from 40 to 50), as simplified from Figueiredo and Pessanha (2015) and Sales et al . (2018). Fish were collected with a beach seine net (10 m long, 1.5 m height, stretched mesh size 5 mm), which was hauled parallel to the shore for approximately 30 m and to a maximum depth of 1.5 m during low tide.…”
Section: Methodsmentioning
confidence: 99%
“…Such hypersaline estuaries are relatively scarce, and they are found mainly in arid and semiarid coastal regions, where the rate of evaporation is higher than the inflow of fresh water into the system. These characteristics substantially influence the distribution and abundance of fish species in these two types of coastal environments (Figueiredo & Pessanha, 2015; Sales et al ., 2016, 2018).…”
Salinity variation in estuarine environments influences the distribution of fish species as well as the availability of food resources to be used by them. This study examines the effect of the range of salinity on the trade‐off between growth and feeding intensity of Atherinella brasiliensis from two tropical estuaries (positive and hypersaline). To investigate the effects of salinity, we hypothesized that hypersalinity negatively affects foraging intensity, consumption and prey selection by the Brazilian silverside, leading to differences in body condition. Sampling was carried out using the beach seine method in two areas of the estuaries (upper and lower zone) during rainy and dry periods. A total of 2549 stomachs (1124 for the positive estuary and 1425 for the hypersaline estuary) were examined, and the results indicated a dissimilarity of 92.7% of the diet between environments. In the positive estuary, there was more predation on Calanoida, Gastropoda, Hymenoptera, Ceratopogonidae larvae and Decapoda larvae, while Alga and plant‐material characterized the diet in the hypersaline estuary. Significant correlations between the volume of food and salinity were observed in both estuaries. The vacuity index indicated that hypersaline environments presented higher contributions of semifull stomachs, indicating an intense consumption of algae. On the other hand,in the positive estuary, these values were less intense, but the stomachs were always with animal items. The variation found for both environments reinforces the effect of salinity on the physiological mechanism of the populations once the higher proportions of filled stomachs in the hypersaline environment indicate the need for constant and high ingestion of prey to guarantee the pronounced energy expenditure with osmoregulation.
“…The low rainfall index combined with the high evaporation rate and the low fresh water inflow creates a salinity gradient that increases upstream (hypersaline conditions). Salinities varying between 30 and 50 are observed in this estuary (Sales et al ., 2018).…”
Section: Methodsmentioning
confidence: 99%
“…These estuaries are classified by salinity classes (lower zone: Mamanguape from 26 to 37 and Tubarão River from 30 to 39; upper zone: Mamanguape from 2 to 25 and Tubarão River from 40 to 50), as simplified from Figueiredo and Pessanha (2015) and Sales et al . (2018). Fish were collected with a beach seine net (10 m long, 1.5 m height, stretched mesh size 5 mm), which was hauled parallel to the shore for approximately 30 m and to a maximum depth of 1.5 m during low tide.…”
Section: Methodsmentioning
confidence: 99%
“…Such hypersaline estuaries are relatively scarce, and they are found mainly in arid and semiarid coastal regions, where the rate of evaporation is higher than the inflow of fresh water into the system. These characteristics substantially influence the distribution and abundance of fish species in these two types of coastal environments (Figueiredo & Pessanha, 2015; Sales et al ., 2016, 2018).…”
Salinity variation in estuarine environments influences the distribution of fish species as well as the availability of food resources to be used by them. This study examines the effect of the range of salinity on the trade‐off between growth and feeding intensity of Atherinella brasiliensis from two tropical estuaries (positive and hypersaline). To investigate the effects of salinity, we hypothesized that hypersalinity negatively affects foraging intensity, consumption and prey selection by the Brazilian silverside, leading to differences in body condition. Sampling was carried out using the beach seine method in two areas of the estuaries (upper and lower zone) during rainy and dry periods. A total of 2549 stomachs (1124 for the positive estuary and 1425 for the hypersaline estuary) were examined, and the results indicated a dissimilarity of 92.7% of the diet between environments. In the positive estuary, there was more predation on Calanoida, Gastropoda, Hymenoptera, Ceratopogonidae larvae and Decapoda larvae, while Alga and plant‐material characterized the diet in the hypersaline estuary. Significant correlations between the volume of food and salinity were observed in both estuaries. The vacuity index indicated that hypersaline environments presented higher contributions of semifull stomachs, indicating an intense consumption of algae. On the other hand,in the positive estuary, these values were less intense, but the stomachs were always with animal items. The variation found for both environments reinforces the effect of salinity on the physiological mechanism of the populations once the higher proportions of filled stomachs in the hypersaline environment indicate the need for constant and high ingestion of prey to guarantee the pronounced energy expenditure with osmoregulation.
“…The estuary is not fed by a freshwater spring, and only receives fresh water from subjacent groundwater and the rains that occur mainly from March to May (Queiroz & Dias, 2014). The most upstream areas of the estuary showed hypersaline conditions due to the largest evaporation during all year (Sales et al ., 2018). Fig.…”
Section: Methodsmentioning
confidence: 99%
“…The juveniles of these species inhabit estuaries benefiting from optimal conditions for growth, including high food availability, water temperature and low predation risk (Aschenbrenner & Marques, 2016). The use of hypersaline habitats by early life stages snappers is related to the benefits associated with microhabitat quality, which may directly influence fish recruitment, growth and survival (Osório et al ., 2011; Sales et al ., 2018).…”
Resource partitioning is important for species coexistence. Species with similar ecomorphological characters have a high potential for competition, especially when close phylogenetically. The diet and resource partitioning of four snappers (Lutjanus alexandrei, L. analis, L. jocu and L. synagris) was studied in the Tubarão River, north-eastern Brazil, between March and November 2012. Specimens were caught using a beach seine, and a total of 731 stomachs were analysed. The highest abundance of snappers was found near to vegetated habitats in the middle estuary. Crustaceans were dominant in the diet of all four species, being found in over 90% of the stomachs, followed by fish and molluscs. The species did not appear to compete for common resources, probably because there was not always spatial overlap, and differences in the proportions of consumption of items were observed. Ontogenetic comparisons of dietary compositions suggested differences among species, with changes in the diet related to changes in the mouth area as the body size increased. The changes were more evident in L. analis and L. synagris where microcrustaceans (Calanoida, Cyclopoida and Amphipoda) were dominant in the diet of the smaller size classes, and benthic crustaceans (Brachyura) and fish in the diet of larger individuals. The intra- and inter-specific differences in the dietary compositions, differences in the mouth area and feeding strategy contribute to allow the co-existence of these snappers in the study area.
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