Daily variation feeding of Astyanax lacustris (Lütken 1875) in a subtropical river

This study aimed to know the daily variation of Astyanax lacustris (Lütken 1875) feeding in a lotic environment. Fish were caught with a net for three days every three hours in the summer to capture ten individuals per hour in a stretch of the Ijuí River, Middle Uruguay River, Brazil. The captured specimens had their stomachs removed and the content analyzed and separated into seven food categories with the aid of stereomicroscope. For the analysis of food items were used the frequency of occurrence methods, volumetric method and applied the Alimentary Index (IAi). Two hundred stomachs were analyzed, of which 95% had food content. The most abundant items were algae and autochthonous insects. Astyanax lacustris feeds throughout the day especially early in the morning (9 hours) and reduces its feeding at night (24 hours and 3 hours). It was also verified variation of AI of different food items throughout the day. It is concluded that A. lacustris feeds throughout the day, especially in the daytime and that throughout the 24 hours it varies its diet due to photoperiod and food availability.

Evaluation of the reproductive parameters of female neotropical migratory fish from a lotic and lentic environment of a dammed river

The fragmentation of watercourses caused by dams is considered to be one of the main threats to aquatic biodiversity worldwide, especially for ichthyofauna. Several studies have shown that the environmental modifications caused by dammed water bodies can change the various reproductive parameters of freshwater fish. Therefore, the present study aims to comparatively analyze the reproductive potential of female Megaleporinus reinhardti, a migratory species, sampled in the lentic environment of the Três Marias Reservoir and the lotic environment of the São Francisco River. Biometric data were obtained from 79 females and the biological indices were subsequently calculated. Additionally, the microscopic analysis of the gonads was performed, and the follicular atresia index was compared. The results of the study show that fish from the lotic environment presented higher gonadal volume, fecundity, and oocyte diameter, and a lower follicular atresia index when compared to fish from the lentic environment. In summary, the data suggest that environmental changes, i.e. from a lotic to lentic environment, caused by river damming, may negatively affect the reproductive process of migratory fish, such as M. reinhardti, and impair the maintenance of the population of this species in lentic environments

Nutrient Concentrations in Macrophytes from Lotic and Lentic Environments of the Middle Parana River, Argentina

Objectives: The purpose of this work was to compare nutrient concentrations in water, sediment, and in plant tissues of Eichhornia crassipes and Panicum elephantipes from lotic and lentic environments of the Middle Parana River floodplain (Argentina). Materials and Methods: The study was carried out over an 18-month period. Plants, water, and sediment were collected in a lake (lentic environment) and in a river (lotic environment) from the Middle Parana River floodplain. Water and sediment were sampled in sites where P. elephantipes or E. crassipes were predominant and in sites without vegetation. Results and Discussion: The lentic and lotic environments dominated by E. crassipes showed the highest ammonium concentrations. The sediment from the lotic environment showed total phosphorus (TP) and total Kjeldahl nitrogen (TKN) concentrations significantly lower than those found in the sediment from the lentic environment. In the lentic environment, the sediment from the lake with the dominance of E. crassipes showed the highest TKN concentration, while the sediment from the lake dominated by P. elephantipes showed the highest TP concentration. For both plant species and for both environments, TKN and TP tissue concentrations were significantly higher in leaves in comparison with roots. Conclusions: Our results could be used to optimize the efficiency of treatment wetlands. Additionally, the use of locally available macrophytes as contaminant bioaccumulators in the Middle Parana River floodplain is completely feasible.

Dinâmica Fluvial e Caracterização Limnológica do Córrego do Cedro, Presidente Prudente -São Paulo/ Brasil

A necessidade de estudos sobre as questões ambientais, tais como os recursos hídricos, são cada vez mais essenciais como forma de mitigar os impactos adversos promovidos pelas ações antrópicas. Neste sentido o presente artigo visa analisar a dinâmica fluvial e sua relação com as características limnológicas do córrego do Cedro localizado no município de Presidente Prudente- SP. Para tanto, este estudo avaliou três seções transversais situadas no alto, médio e baixo curso deste ambiente lótico, sendo realizadas coletas em campo de amostras dos principais parâmetros associados a geometria hidráulica do canal como: vazão (Q), largura (w), profundidade (d), e velocidade (v). Para a caracterização limnológica do córrego em questão coletou-se informações sobre o Potencial Hidrogeniônico (pH), com o auxílio de um pHmetro, e a Turbidez (para a qual se utilizou um turbidímetro) e ainda a coleta de sedimentos em suspensão e de leito. A avaliação da carga detrítica em suspensão e de fundo ocorreram no Laboratório de Geologia, Geomorfologia e Recursos Hídricos da Universidade Estadual Paulista (UNESP) campus de Presidente Prudente- SP. Os resultados obtidos demonstram que tanto a dinâmica fluvial quanto as variáveis limnológicas analisadas vêm sofrendo com as formas de uso da terra na bacia repercutindo na entrada de material alóctone de origem tecnogênica, promovendo mudanças no ajuste do sistema fluvial e alterações na característica física e química da água. Dessa forma o estudo tem se mostrado eficaz na correlação entre os dados de geometria hidráulica e limnologia na avaliação ambiental da área em questão. Fluvial Dynamics and Limnological Characterization of Cedro Stream, President Prudente-SP A B S T R A C TThe need for studies on environmental issues, such as water resources, is increasingly essential as a way of mitigating the adverse impacts caused by human actions. In this sense this article aims to analyze the river dynamics and its relationship with the limnological characteristics of the Cedro stream located in the city of Presidente Prudente-SP. For this, this study evaluated three cross sections located in the high, medium and low course of this lotic environment. Samples were collected in the field of the main parameters associated with the channel hydraulic geometry, such as flow (Q), width (w), depth. (d), and velocity (v). For the limnological characterization of the stream in question we collected information about the Hydrogenionic Potential (pH), with the aid of a pH meter, and the Turbidity (for which a turbidimeter was used), as well as the collection of suspended sediment and bed. The evaluation of the suspended and bottom detrimental load occurred at the Laboratory of Geology, Geomorphology and Water Resources of the Universidade Estadual Paulista (UNESP), Presidente Prudente-SP campus. The results show that both the river dynamics and the limnological variables analyzed have been suffering from land use in the basin, resulting in the entry of allochthonous material of technogenic origin, promoting changes in the fluvial system adjustment and changes in the physical and chemical characteristics of the water. Thus, the study has been shown to be effective in correlating the data of hydraulic geometry and limnology in the environmental assessment of the area in question.Keywords: Hydraulic geometry. Limnology. Environmental diagnosis

Comparative analysis of the reproductive activity of Leporinus piau (Characiformes: Anostomidae) in lentic and lotic environments

In this study, we determined the main reproductive parameters of piau gordura, Leporinus piau, in two sections of the São Francisco River basin. Between May 2015 and April 2016, a total of 573 specimens were captured from a lentic environment (section 1), the Três Marias Reservoir (TMR), and a lotic environment (section 2), downstream of the TMR at the confluence of the São Francisco River (SFR) with the Abaeté River. Analysis of reproductive activity showed that L. piau from both sections reproduced, but females and males from section 1 exhibited higher total length, body weight, Fulton condition factor, and gonadosomatic index values, as compared to section 2. Sexual dimorphism was evident in the species, with females being larger than males. Moreover, males reached first gonadal maturation at a smaller size than females. The peak maturation/mature stage was observed in November/April for females and males in section 1 and in November/December in section 2, coinciding with high temperatures and precipitation in the region. In both sections of the river, L. piau exhibited the typical characteristics of partial spawning, with a prolonged spawning period, and preferential reproduction in lentic environments.

New records of the sponge Radiospongilla inesi (Porifera: Spongilidae) and the slug Omalonyx matheroni (Gastropoda: Succineidae) in the Vale do Paraíba, southeast Brazil

This report provides the new record of the sponge Radiospongilla inesi and the slug Omalonyx matheroni for the Vale do Paraiba, State of São Paulo, southeastern Brazil, besides the symbiosis among R. inesi and individuals of some benthic macroinvertebrates. Monthly collections were carried out in the Ribeirão dos Mottas, with a 0.5 cm sieve in the edge vegetation, as well as collections by hand. Three specimens of R. inesi were found, from a lotic environment under pebbles. In addition, individuals of four insect families, Sisyridae, Hydropsychidae, Chironomidae e Simuliidae, were found on the sponge aquiferous system. Six individuals of the semi-aquatic slug O. matheroni were also caught under rocks and cans. Despite the sponges are commonly found in the most of the environments, the freshwater species represents one of the most unknown animal groups of the world. R. inesi was report at first time in Brazil in Pernambuco State, northeastern Brazil region, and this report represents just the second record of this species in Brazil, and the first time to the southeastern region. The presence of individuals of four insect families pointing out the importance of R. inesi on the life history of these animals. Despite some records of Omalonix sp. to the São Paulo State, this report seems to be the first record of the O. matheroni to the Vale do Paraíba, northern of the São Paulo State.

Evaluation of Total Mercury in Sediments of the Descoberto River Environmental Protection Area—Brazil

To evaluate the total mercury accumulation (THg) in the Descoberto river basin environmental protection area (DREPA), nine sediment and water samples were collected from the Descoberto reservoir (lentic environment), and 23 in its tributaries (lotic environment), which are located in a densely urbanized area within the Descoberto river watershed, Brazil. The following physicochemical parameters of water were determined: dissolved oxygen (DO); hydrogen potential (pH); total dissolved solids (TDS); nitrate (NO3−); chloride (Cl−); temperature (T); sulfate (SO42−), and in sediment, the concentration of total mercury (THg) and volatile material (VM) was determined. THg concentrations in sediments showed a significant difference (p = 0.002) between tributaries (0.03 µg g−1 ± 0.02) and reservoir (0.08 µg g−1 ± 0.04), indicating accumulation in the lentic environment. Most of the results evaluated for ecotoxicological risks presented values below the concentration, at which adverse effects would rarely be observed, ERL (effects range low). However, in relation to the enrichment factor (EF), applied to identify the anthropogenic contribution, the results indicate that most of the samples are moderately polluted through atmospheric deposition due to vehicular traffic and agriculture. These results show that the likelihood of methylation in the lentic environment is higher than in the lotic environment.

Diet of European Catfish in a Newly Invaded Region

Biological invasions are considered to be one of the leading causes of biodiversity loss worldwide. Freshwater ecosystems are amongst the most biodiverse, containing about 50% of the world’s known fish species but, ironically, are the most invaded ecosystems. In Portuguese freshwaters, there are currently 20 identified non-native fishes, arriving at an unprecedented rate of a new species every two years. A recent non-native is the European catfish Silurus glanis, a top predator native to Central and Eastern Europe, that arrived at the Lower Tagus (Portugal) circa 2006. This study compares the dietary habits of this top predator in two different habitats of the Lower Tagus in order to evaluate its potential impact. The stomach contents of 96 individuals were analyzed, 61 from the lotic environment and 35 from the lentic systems. A total of 66 stomachs contained prey items, 38 from the lotic and 28 from the lentic. Diet varied considerably between habitats, with shrimp and crayfish being the most abundant prey items in the lentic systems and shrimp and fish the most abundant prey items in the lotic section. Tendency to piscivory was observed in large-sized individuals. Overall, the findings in this study provide the first evidence of the potential impacts of European catfish through predation on the fish communities.

Colonization of benthic invertebrates on artificial and natural substrate in a Neotropical lotic environment in Southern Brazil

The objective of this research was to validate the colonization process on natural and artificial substrates by benthic invertebrates in a tropical stream in South Brazil. The samples were performed in July and August-2012, and 32 samplers were used, being 16 natural and 16 artificial substrates. In each sample, two replicas were taken for each substrate at the 2th, 4th, 7th, 14th, 21th 28th, 35th and 42th days of colonization. The organisms were identified to the lowest possible taxonomic level. In both substrates 3,070 benthic invertebrates were detected, of which 1,753 individuals were collected on the natural substrate, and 1,317 on the artificial substrate. From the identified taxa 8.5% were not dominant (Anacroneuria, Orthocladiinae, Tupiara, Smicridea, Baetodes, Tupiperla, Macrogynoplax, Gripopteryx, Cylloepus, Macrelmis, Microcylloepus, Hetaerina, Argia, Coryphaeschna, Atopsyche, Pomacea, Corydalus, Leptohyphes and Eccoptura), and 31.5% were dominant (Tanypodinae, Chironominae, and Paragripopteryx). The genus Simulium was very common, dominant and abundant, representing 65% of the collected individuals. No significant difference was found in the abundance and species composition between artificial and natural substrates. On the natural substrate, the higher colonization index was at the 35th day with 459 individuals, and the lowest was at the 14th day, with 87. On the artificial substrate the highest index was at the 42th day with 337 individuals, and the lowest was at the 4th day, with 85. Both natural and artificial substrates are efficient in characterizing the benthic community. In the evaluation of the ecological succession, it was not possible to observe a pattern that described the process, since the composition was nearly constant throughout the study period.