Performance of Nile tilapia Oreochromis niloticus fingerlings in a hyper-intensive recirculating aquaculture system with low water exchange

The aim of this paper was evaluate the performance of Nile tilapia fingerlings (Oreochromis niloticus) raised at hyper intensive stocking density in a recirculating aquaculture system (RAS) with minimum water replacing. The experimental system was performed in a single-batch nursery system to obtain 50 g fish size in 60 days. Fish (2.07 ± 0.04 g) were stocked in triplicate at 400 (T1), 500 (T2) and 600 (T3) fish m-3 (0.84, 1.05, 1.22 kg m-3). RAS functioned with 12,000 L of recirculating water and 252 L day-1of water replacing (2.1% daily). The efficiency of the biofilter for removing the total ammonia nitrogen (TAN) was 48 ± 12.5 mg L-1. Stocking density did not affect significantly the survival (89.5 to 93.6%). The growth rate of T1 (0.96 g day-1; 5.01% day-1) and T2 (0.92 g day-1; 4.95 % day-1) was significantly higher than T3 (0.83 g day-1; 4.80% day-1). The specific growth rate (SGR) of T1 was 41% influenced by temperature. For T2 and T3 the SGR were influenced by the variation of dissolved oxygen (DO) that explained 47 and 44% of the fish weight variation, respectively. The SGR from T3 was also affected by the concentration of ammonia nitrogen (31%). The high stocking density affected the overall size of fish and the size homogeneity, but had no negative effect on the length-weight relationship (L-W). Data support the conclusion that fingerling stocked at 400 and 500 fish m-3 shows high performance during 9-weeks when the biomass not exceed 37 kg m-3. At this time fish have reached the desired final nursery weight (50 g) for transfer to grow-out facilities

PDMS Microfluidic Device with an Integrated Optical Sensor for Determination of Zinc (II) in Pharmaceuticals: Toward the Production of Miniaturized Green Chemistry Analytical Systems

A simple miniaturized system was fabricated in general laboratory from polydimethylsiloxane (PDMS) according to a prototype casting and molding process permitting the construction of three-dimensional (3D) microchannel (100 mu m i.d.) with T-type network, together with an integrated optical sensor for on chip detection. The fabricated device has been successfully applied as a green chemistry-compatible miniaturized analytical system for the determination of zinc (II) in pharmaceutical samples taking the advantage of the colorimetric reaction of zinc (II) and xylenol orange in acetate buffer at pH 5.5. The microfluidic device is a convenient way to quantify zinc (II) over a wide dynamic range, 0.2-2.5 mu gmL-1, with good linearity (R2 0.9940)

Vibrio fortis sp nov and Vibrio hepatarius sp nov., isolated from aquatic animals and the marine environment

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