Evaluation of Nile tilapia in monoculture and polyculture with giant freshwater prawn in biofloc technology system and in recirculation aquaculture system.

Abstract: Biofloc technology system (BFT), recirculation aquaculture system (RAS) and polyculture promote efficient use of water, area and nutrient recycling, which are essential practices for sustainable aquaculture development. The aim of this study was to evaluate the growth, feed efficiency, biofloc composition and water quality of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) in monoculture and polyculture with giant freshwater prawn Macrobrachium rosenbergii (De Man, 1906) in BFT and RAS, over a period of 30 days. Fish (n = 128; 7.29 +/- 0.67 g) were distributed randomly in 16 experimental tanks (8 fish/tank). Prawn (n = 96; 0.50 +/- 0.09 g) were allocated in 8 experimental tanks (12 prawn/tank) in a polyculture. The experimental design was completely randomized with four treatments with four replicates each, in a factorial design 2 x 2 (BFT and RAS vs. monoculture and polyculture). The experimental diet (28% of digestible protein; 3100 kcal kg(-1) of digestible energy) was used both to fish and prawn in BFT and RAS. There was significant effect (p < 0.01) of the system and the culture for weight gain, apparent feed conversion and protein efficiency ratio. The average weight gain and apparent feed conversion of tilapia in monoculture (30.04 g and 1.39) and in polyculture (36.44 g and 1.27) were superior (p < 0.01) in BFT than in monoculture (23.64 g and 1.74) and in polyculture (24.14 g and 1.61) in RAS. Weight gain and survival of giant freshwater prawn was superior (p < 0.01) in BFT (0.43 g and 87%) compared to RAS (0.26 g and 79%). The data showed that BFT provides better growth performance responses in monoculture for Nile tilapia and in polyculture with giant freshwater prawn compared to RAS

Comparação do desempenho produtivo da tilápia-do-nilo em sistema bioflocos e com filtro biológico.

O desafio atual para o aprimoramento dos sistemas intensivos de produção está baseado na diminuição do uso da água para renovação e manutenção de sua qualidade e redução da emissão de efluentes, que consequentemente proporciona menor impacto ambiental. O sistema bioflocos (BFT) atende estas premissas, permitindo alta produção sem renovação de água. O objetivo desse trabalho foi avaliar o desempenho produtivo da tilápia no sistema bioflocos e sistema com filtro biológico durante 60 dias. O delineamento experimental foi inteiramente casualizado com dois tratamentos e quatro repetições. Foram utilizados 64 alevinos de tilápias peso inicial (7,29±0,67 g), distribuídos em oito aquários experimentais com volume útil de 150 L (8 peixes/aquário). No final do ensaio de desempenho mensurou-se o ganho de peso, o consumo de ração, a conversão alimentar aparente, a taxa de crescimento específico, a taxa de eficiência proteica, retenção proteica, e a sobrevivência. Diariamente, registrou-se o valor de temperatura (°C), pH e oxigênio dissolvido (mg L-1) e, semanalmente, os compostos nitrogenados. Os dados experimentais foram submetidos análise de variância (ANOVA), e quando significativo, aplicou-se o teste t a 5% de probabilidade. Os peixes no sistema bioflocos obtiveram melhores respostas (P<0,05) para GP 67,37±7,41, CAA 1,02±0,15, e TEP 2,79±0,45 , quando comparado ao sistema sem bioflocos. O sistema bioflocos melhora as respostas de ganho de peso, conversão alimentar aparente e taxa de eficiência proteica, indicando que a tilápia pode utilizar bioflocos como alimento suplementar de alto valor biológico. The current challenge to improve the aquaculture intensive systems is based on the reduction of use of water to renovation and maintenance of its quality and reduction of the effluent emission that consequently provided less environmental impact. Biofloc technology meets this demand, allowing high production without water renewal. The objective of this work was to evaluate the growth performance of tilapia in biofloc system and without biofloc (biological filter) for sixty days. Sixty four tilapia fry with initial mean weight of 7.29 ± 0.67 g were used, distributed in eight experimental aquariums with a useful volume of 150 L and at a density of 8 fish / aquarium. The experimental design was completely randomized with two treatments (biofloc system and without biofloc) and four replications. At the end of the growth test, weight gain, feed intake, apparent feed conversion, specific growth rate, protein efficiency ratio, protein retention, and survival were measured. The temperature (°C), pH and dissolved oxygen (mg L-1) were recorded daily and the nitrogen compounds weekly. The experimental data were submitted to analysis of variance (ANOVA), and when significant, the t test was applied at 5% probability. The fish in the biofloc system obtained better responses to GP 67.37 ± 7.41, CAA 1.02 ± 0.15, and TEP 2.79 ± 0.45 than in the system without bioflocs Fish in the biofloc system obtained better responses for WG 67.37 ± 7.41, AFC 1.02 ± 0.15, and PER 2.79 ± 0.45 compared than those cultured in the system without biofloc. Thus, it was observed that the biofloc system improves the weight gain, apparent feed conversion and protein efficiency rates, indicating that tilapia can be use the biofloc as a supplementary feed of high biological value

Influence of surface atomic structure demonstrated on oxygen incorporation mechanism at a model perovskite oxide

Perovskite oxide surfaces catalyze oxygen exchange reactions that are crucial for fuel cells, electrolyzers, and thermochemical fuel synthesis. Here, by bridging the gap between surface analysis with atomic resolution and oxygen exchange kinetics measurements, we demonstrate how the exact surface atomic structure can determine the reactivity for oxygen exchange reactions on a model perovskite oxide. Two precisely controlled surface reconstructions with (4 × 1) and (2 × 5) symmetry on 0.5 wt.% Nb-doped SrTiO3(110) were subjected to isotopically labeled oxygen exchange at 450 °C. The oxygen incorporation rate is three times higher on the (4 × 1) surface phase compared to the (2 × 5). Common models of surface reactivity based on the availability of oxygen vacancies or on the ease of electron transfer cannot account for this difference. We propose a structure-driven oxygen exchange mechanism, relying on the flexibility of the surface coordination polyhedra that transform upon dissociation of oxygen molecules.Austrian Science Fund (SFB “ Functional Oxide Surfaces and Interfaces ” - FOXSI, Project F 45)European Research Council Advanced Grant (“OxideSurfaces” (Project ERC-2011-ADG_20110209))National Science Foundation (U.S.). Division of Materials Research (CAREER Award Grant No. 1055583

The Chemical Evolution of the La0.6Sr0.4CoO3−δ Surface Under SOFC Operating Conditions and Its Implications for Electrochemical Oxygen Exchange Activity

© The Author(s) 2018Owing to its extraordinary high activity for catalysing the oxygen exchange reaction, strontium doped LaCoO3 (LSC) is one of the most promising materials for solid oxide fuel cell (SOFC) cathodes. However, under SOFC operating conditions this material suffers from performance degradation. This loss of electrochemical activity has been extensively studied in the past and an accumulation of strontium at the LSC surface has been shown to be responsible for most of the degradation effects. The present study sheds further light onto LSC surface changes also occurring under SOFC operating conditions. In-situ near ambient pressure X-ray photoelectron spectroscopy measurements were conducted at temperatures between 400 and 790 °C. Simultaneously, electrochemical impedance measurements were performed to characterise the catalytic activity of the LSC electrode surface for O2 reduction. This combination allowed a correlation of the loss in electro-catalytic activity with the appearance of an additional La-containing Sr-oxide species at the LSC surface. This additional Sr-oxide species preferentially covers electrochemically active Co sites at the surface, and thus very effectively decreases the oxygen exchange performance of LSC. Formation of precipitates, in contrast, was found to play a less important role for the electrochemical degradation of LSC.Fonds zur Förderung der wissenschaftlichen Forschung (FWF)212921411

Reproductive and morphometric traits of Macrobrachium amazonicum (Decapoda: Palaemonidae) from the Pantanal, Brazil, suggests initial speciation

The palaemonid shrimp Macrobrachium amazonicum shows an unusually large geographic range (ca. 4 000km across) living in coastal, estuarine, and limnic inland habitats of the upper Amazon, Orinoco, and La Plata basins. This raises doubts whether allopatric, ecologically diverse populations belong to the same species. While shrimps from estuarine and Amazonian habitats have been studied in great detail, very little is known about hololimnetic inland populations. In the present study, biological traits related to growth (maximum body size, fresh weight, morphometric relationships) and reproduction (sex ratio; occurrence of male morphotypes; minimum sexable size; minimum size of ovigerous females; fecundity; egg size), were studied in M. amazonicum collected from a pond culture and two natural freshwater habitats (Rio Miranda; Lagoa Baiazinha) in the Pantanal of Mato Grosso do Sul, Brazil. In total, 2 270 shrimps were examined (603 males; 1 667 females, 157 of these ovigerous). Sex ratio (males:females) was at all sampling sites strongly female-biased, ranging from 0.2-0.6. Maximum body size was larger in natural habitats compared to the pond culture, suggesting reduced growth or a shorter life span under artificial mass rearing conditions. Maximum fecundity observed in our material was 676 eggs, reached by the largest female (TL=65mm; Lagoa Baiazinha). A significant difference between slope parameters of linear regressions describing fecundity, either in terms of numbers of eggs laid or of larvae released, in relation to female fresh weight, indicates egg losses. This may be due in part to a 2.4-fold increase in egg volume occurring during the course of embryonic development, while the available space under the abdomen remains limited. Size-weight relationships differed significantly between males and females, indicating sexspecific morphometric differences. Males appear to have a more slender body shape than females, reaching thus lower weight at equal TL. When reproductive and morphometric traits are compared with literature data from estuarine and inland populations living in the Amazon and Orinoco plains, shrimps from the Pantanal show conspicuous peculiarities differing from other populations: (1) maximum body size is far smaller, suggesting shorter longevity; (2) females are consistently larger than males; (3) different male morphotypes are absent; (4) minimum sexable size and (5) minimum size of ovigerous females are smaller. These traits suggest a heterochronic shift (predisplacement) of sexual maturation and r-selection. In summary, our data show biologically relevant differences in life-history traits of shrimps from the Pantanal compared to M. amazonicum populations in other regions. All these differences persist also in long-term cultures maintained under constant conditions. Altogether, our data support the hypothesis that M. amazonicum in the Paraná-Paraguay drainage basin has phylogenetically diverged from allopatric populations that are hydrologically separated by continental watersheds, implying an at least incipient vicariant speciation. Rev. Biol. Trop. 61 (1): 39-57. Epub 2013 March 01