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

Seasonal dynamics of Aedes aegypti (Diptera: Culicidae) in the northernmost state of Brazil: a likely port-of-entry for dengue virus 4

Roraima is the northernmost state of Brazil, bordering both Venezuela and Guyana. Appropriate climate and vector conditions for dengue transmission together with its proximity to countries where all four dengue serotypes circulate make this state, particularly the capital Boa Vista, strategically important for dengue surveillance in Brazil. Nonetheless, few studies have addressed the population dynamics of Aedes aegypti in Boa Vista. In this study, we report temporal and spatial variations in Ae. aegypti population density using ovitraps in two highly populated neighbourhoods; Centro and Tancredo Neves. In three out of six surveys, Ae. aegypti was present in more than 80% of the sites visited. High presence levels of this mosquito suggest ubiquitous human exposure to the vector, at least during part of the year. The highest infestation rates occurred during the peak of the rainy seasons, but a large presence was also observed during the early dry season (although with more variation among years). Spatial distribution of positive houses changed from a sparse and local pattern to a very dense pattern during the dry-wet season transition. These results suggest that the risk of dengue transmission and the potential for the new serotype invasions are high for most of the year