Alberto Carvalho Peret

Herbivory by the Dusky Damselfish Stegastes fuscus (Cuvier, 1830) in a tropical rocky shore: effects on the benthic community

Experiments were carried out on rocky shores at Arraial do Cabo (Southeast Brazil) to evaluate how the dusky damselfish, Stegastes fuscus (Cuvier, 1830) affects the benthic community structure. Cage exclusion showed that S. fuscus strongly influences the algal community in its territories, keeping it in an early succession stage and preventing dominance by Jania spp. Diversity and biomass of the epilithic algal community (EAC) were higher inside territories than outside. These dense mats hold a diverse and abundant cryptofauna (≅72 ind/100 cm2) that was significantly higher inside territories. Algae comprise 70% of the S. fuscus diet, with the remaining 30% composed of animal material. The fish feeds selectively mainly on red filamentous algae, such as Polysiphonia spp., Ceramium spp. and Centroceras clavulatum, albeit it also ingests a great amount of calcareous algae (25% of total algae). Total assimilation and nitrogen assimilation were low in S. fuscus. Gut contents turnover varied from 3.7 in summer to 4.1 in winter. The net primary productivity (NPP) values of EAC within territories were intermediate ranging from 0.86 to 2.34 gC day−1 territory−1 in winter and in summer, respectively. Grazing rates did not vary greatly between seasons. In summer damselfish do not appear to affect production on territories, but in winter consumption could remove 100% of primary production, indicating a high turnover rate by EAC. S. fuscus plays an important trophodynamic role in this system, since its abundance is high and overall energy flux is enhanced inside its territories.

Invasion of the dinoflagellate Ceratium furcoides (Levander) Langhans 1925 at tropical reservoir and its relation to environmental variables

Dinoflagellates of the genus Ceratium are chiefly marine but there are rare occurrences in freshwater. In this study we analyze the invasion and progressive establishment of Ceratium furcoides, an exotic species, in the Furnas Reservoir. Samples were taken at 36 points in the reservoir, during the months of March, June, September and December, 2007. Measurements of some physical and chemical variables were simultaneously performed at each site. The occurrence of C. furcoides was registered at 20 sites, with densities varying between 0.57 and 28,564,913.0 ind.m-3. Blooms of this species were recorded in points which were classified as mesotrophic, coinciding with the places receiving high amounts of untreated domestic sewage. C. furcoides density was correlated with temperature, nutrients (nitrate and nitrite) and water electric conductivity. The highest density was recorded in June when temperature was low. The presence of Ceratium furcoides in the reservoir apparently has not yet affected the reservoir water quality or other plankton communities. However, if it becomes fully established it could perhaps become a problem in the reservoir or even to spread out to other reservoirs in Rio Grande basin.

Field and laboratory studies to assess the effects of Vertimec(®) 18EC on Daphnia similis.

The present study aimed to evaluate the interactions of the pesticide Vertimec(®) 18EC in aquatic ecosystems. In this respect, soil plots were contaminated with Vertimec(®) 18EC at the concentration indicated for strawberry crops (0.125L of solution m(-2)). After the contamination, torrential rainfall was simulated and the surface runoff was collected and transferred to mesocosm tanks in five treatments, run in triplicate: (1) control-C; (2) runoff from an uncontaminated plot-UR; (3) runoff from the plot contaminated with Vertimec(®) 18EC-CR; (4) direct application of Vertimec(®) 18EC in the water-V and (5) water samples gathered randomly to verify whether there was contamination between the mesocosms-RS. Water samples from these tanks were also submitted to ecotoxicological tests with Daphnia similis and analyses to evaluate the limnological characteristics, in five collection periods over 10 days (240h). Physical and chemical differences were observed in the water samples, mainly related to increased turbidity, suspended solids and nutrients (nitrogen and phosphate forms). Acute toxicity was observed for the direct application treatment for the entire experimental period, and in some periods for the CR treatment (from 48h to 168h). The results obtained suggest that the pesticide did not fully degrade during the study period (10 days) in the direct application treatment, demonstrating that the presence of other substances in the commercial formulation contribute to the maintenance of toxicity. This represents a potential risk for aquatic ecosystems in areas adjacent to where the chemical is applied.

Dynamics of fipronil in Óleo Lagoon in Jataí Ecological Station, São Paulo-Brazil

Fipronil is a phenylpyrazole pesticide widely used to protect sugar-cane crops from insect pests. After reaching the environment, this insecticide may have several fates. This research aimed to propose a kinetic model to describe the fate of commercial fipronil Regent 800WG in the sediment-water interface of the Oleo Lagoon in the Mogi-Guaçu river floodplain, situated within the Jataí Ecological Station, by means of a microcosm scale experiment. Results showed that a small fraction of the pesticide is quickly dragged to the sediment while most of it remains in the water column. Biodegradation proves to be an important fipronil degradation route, especially when microorganisms capable of using fipronil as sole carbon source increase their population, as a function of exposure time. Biodegradation rates were higher in the sediment than in the water column.

Composição da ictiofauna em função da fisiografia de um riacho costeiro de Floresta Atlântica - Brasil

Os riachos costeiros apresentam grande diversidade de peixes, apesar dos impactos a que sao submetidos. O conhecimento da estrutura e da composicao da ictiofauna constitui importante esforco para levantamento de parâmetros de avaliacao que possam proporcionar atitudes para a conservacao destes ambientes. A composicao da ictiofauna relacionada a caracteristicas fisiograficas de riachos costeiros do sul do Brasil constitui-se uma contribuicao para a interpretacao da dinâmica destes ecossistemas. Foram realizadas coletas de peixes em cinco pontos amostrais do Rio do Pinto, localizado no municipio de Morretes, Parana, Brasil. As coletas foram realizadas entre os meses de maio de 2006 a novembro de 2007, utilizando a tecnica de pesca eletrica, com um esforco amostral de 50 m/hora em cada localidade. Os animais coletados foram fixados em formaldeido 10%. Cada localidade foi classificada em relacao ao tipo de substrato, profundidade, velocidade de correnteza e largura media. Foi possivel observar a relacao direta entre o tipo de substrato e a composicao da ictiofauna. Em regioes onde a granulometria era maior, tais como matacoes e seixos, prevaleceram os Siluriformes. Por outro lado, em regioes onde o sedimento apresentava menor granulometria, tais como areia grossa associada a cascalho, ocorreram especies de Characiformes.

Parâmetros reprodutivos do curimbatá no rio Mogi-Guaçu

Com o objetivo de obter informacoes sobre parâmetros da biologia reprodutiva da populacao de curimbata, visando ao gerenciamento da especie voltado para sua conservacao, foram realizadas coletas mensais de peixes no periodo de fevereiro de 2003 a setembro de 2004 em dois pontos do rio Mogi-Guacu. Foram capturados 176 femeas e 140 machos. Os parâmetros analisados foram relacao peso-comprimento, fator de condicao (K), indice gonadossomatico (IGS), proporcao sexual e abundância relativa. Os individuos adultos de curimbata do rio Mogi-Guacu tem crescimento alometrico negativo. Os maiores valores do fator de condicao (K) e de IGS ocorreram durante o periodo reprodutivo, quando a proporcao sexual foi de 1:1. O periodo de reproducao de curimbata ocorre entre os meses de outubro e janeiro, com picos em novembro e dezembro. Os machos de curimbata apresentam antecipacao da maturacao gonadal em relacao as femeas.

Cultivo consorciado do pirarucu com a tilápia

Abstract: With the purpose of studying the growth of arapaima (Arapaima gigas) and tilapia (Oreochromis niloticus) in an intercropping, a pond area of 190 m2, has been excavated in Gleissolo Haplico populated with individuals of 10 A was used . gigas measuring 21.5 cm in average length and weighing an average of 54.21 g. The tilapia was introduced as food, totaling 6840 individuals (36 fish m-2) measuring 5.4 cm on average, and an average weight of 3.2 g, and six couples tilapia with 12.4 cm and 32.46 g of total average length and average total weight, respectively. Tilapia were fed diet of chicken mash with 23% crude protein in quantities of 2% of the initial biomass throughout the growing season, just to maintain basic needs. The growth of A. gigas, submitted to foraging fingerlings of O. niloticus in captivity, was estimated monthly by: relative increase in length relative increase in weight growth curve fitted to the data length, weight / length, and growth curves were obtained by weight deductive method of conjunction between weight / length ratio and the growth curve in length, the survival curve of tilapia was obtained by curve fitting the monthly data of densities and biomass for the curves conjunction between the survival curves of the growth and weight. The results showed that tilapia should be offered as food less than 15 cm and fish densities above 36 m 2 per 10 pirarucus throughout the cultivation period size. From 15 cm, tilapia is hardly consumed by arapaima and may be available to the fish farmer to consumer.