Integrated multi-trophic aquaculture (IMTA) use multiple species from different trophic levels for reducing wastes,
contributing to increase the sustainability of aquaculture. One of the most common IMTA systems consist of the integration
of seaweed cultures in land-based fish farms.
Cultures of Ulva spp. are currently being used in Integrated Multitrophic Aquaculture (IMTA) as biofiltration systems in fish farms,
both in open and recirculating systems (IMTA-RAS). Ulva ohnoi has been identified as ideal candidate for filtering fish effluents
due to their high growth rates and capacity to absorb and metabolize nitrogen
The integrated production of fish and seaweeds can improve the sustainability of the marine aquaculture industry. Seaweeds remove the nutrients dissolved in fish-farm effluents and can become a good source of proteins, carbohydrates and bioactive
compounds of commercial interest
The commercial production of Ulva spp. by aquaculture is gaining in importance due both to the qualitative and quantitative
increase in the use of the harvested biomass and its new applications in inland IMTA techniques. However, very little is
known about the specific culturing requirements and commercial quality of the different species of Ulva. The aim of this
work is to try from this point of view four Ulva species that could be grown in southern Europe: U. australis, U. fasciata,
U. ohnoi and U. rigida
Integrating seaweed production into land-based marine fish-farms allows removing dissolved nutrients and improves the sustainability of the coastal marine aquaculture. Free-floating seaweed culture in tanks, with suspension provided by tumbling, is the most usual cultivation technique used in this kind of facilities
Probiotics are a potential tool for bacterial control in aquaculture (Pintado et al. 2011), decreasing the use of disinfectants and
antibiotics and contributing to an ecosystem approach, which is more sustainable and respectful to the environment.
Among Integrated Multitrophic Aquaculture (IMTA) techniques, the integration of fish and macroalgae cultures in
Recirculating Aquaculture Systems (IMTA-RAS) is currently one of the most promising lines of action.
The effect of swimming fish on the average velocity and velocity profile of a circular tank was studied. Working with different inlet diameters and flow rates, nine different impulse forces (configurations) were evaluated. Each configuration was tested with and without fish, and the effects of two different fish sizes were compared.
The velocity profiles in experiments with fish presented a considerable reduction in velocity in the centre of the tank near the outlet, which was a consequence of the increase in the kinematic eddy viscosity due to the turbulence introduced by fish swimming. A flattening of the angular velocity profile was observed in the central area of the tank, which had a radius of about 0.3 m (18% of the total volume of the tank).
A previous model proposed by Oca and Masaló (2013) was modified in order to better describe the distribution of velocities in the central volume of a tank with swimming fish. The proposed modification was based on Burgers¿ proposal for a bathtub vortex, which implies the determination of the parameter (1¿e¿ar2)(1¿e¿ar2), where r is the radius and the a values were experimentally obtained for each tank configuration, in which they increased with the impulse force.
The average velocities in the tank were proportional to the square root of the impulse force in experiments with and without fish. Experiments with fish presented lower average velocities, which imply higher tank resistance coefficients. At similar stocking densities (14.6 kg/m3), the increase in the tank resistance coefficients obtained with small fish sizes (154 g) were slightly higher than those obtained with bigger fish sizes (330 g).
The measurement of total fish biomass is an essential practice in the aquaculture management. The method commonly used which involves removing a sub-sample of fish from a tank, weighing it and extrapolating the result to the whole tank, carries a large error, is intense labor and causes great stress. Here, we tested a laser scanning method to estimate the total fish biomass from the total fish volume of a sole population (Solea senegalensis) in a tank. The ratio FB/FLV of fish biomass (FB), weighing the 100% of soles, versus the fish layer volume (FLV) measured by the laser scanning, is calculated. Different fish size (small and large) and stocking densities (very low, low, medium and high) were tested. To test the method in the worst conditions, in very low stocking density, fish were 3.0 g ± 1.1 (individual mean weight ± SD); but in low, medium and high stocking density fish were 234.0 g ± 84.6 (individual mean weight ± SD). The fish layer volume included the fish biomass and the interstitial water present among them, which can be estimated from the ratio FB/FLV. In medium and high rearing densities with larger fishthe ratio takes values very close to 1 (0.957 ± 0.021 and 0.967 ± 0.011) giving percentages of interstitial water lower than 5%. But in very low stocking density (0.4 kg/m2) with smaller fish (3.0 g ± 1.1), the ratioFB/FLV was much lower, giving a non-realistic percentage of interstitial water estimation. The low ratios obtained at very low stocking densities are due to the resolution of the image catching process, which is aggravated when working with small fish, since the error of a pixel from a digital image represents a larger percentage of error than with larger fish and higher stocking density. It should be noted that the coefficient of variation (CV) obtained was very low (in all cases lower than 7.2%) and decreased as the stocking density increased achieving the lowest value (1.1%) at high stocking density. The laser scanning has proven to be a useful tool to estimate the total fish layer volume of flatfish, and thus fish biomass, in an aquaculture tank with a usual grow-out stocking density for sole, reducing the labor involved and the stress commonly associated to manual sampling.
Oca, J.; Pintado, J.; Cremades, J.; Masaló, I.; Ruiz, P.; Alamrousi, A.; Jimenez, P.; Machado, S.; Reig, L. Aquaculture, Nature and Society p. 566-567 Data de presentació: 2015-10 Presentació treball a congrés
Recirculating aquaculture systems (RAS) allow minimizing the water renewal flow rate needed in fish production by
increased Nitrogen (NO3
) and Phosphorous concentrations. Integrating seaweed production to RAS can improve its
performances and reduce soluble wastes, contributing to a more sustainable production system.
Cremades, J.; Pintado, J.; Oca, J.; Alamrousi, A.; Ruiz, P.; Masaló, I.; Reig, L.; Jimenez, P. Congreso Nacional de Acuicultur y Congreso Ibérico de Acuicultura p. 492-493 Data de presentació: 2015-10 Presentació treball a congrés
Circular tank geometry is very common in aquaculture because it provides more stable flow patterns, more homogeneous
distribution of oxygen and metabolites, better self cleaning features, and higher average velocities than rectangular tanks,
thanks to the rotating flow characteristics.
In sole (Solea spp.) culture, like in other flatfish culture, it is likely that a vertical gradient of dissolved oxygen (DO) occurs with the lower concentrations being at the tank bottom. This lower concentration at the tank bottom is a consequence of fish oxygen consumption and of the presence of the boundary layer. This fact generates lower DO concentrations in the near-bottom zone where soles are lying most of the time. The aim of this work was to study the hydrodynamic conditions that determine the oxygen gradient that occurs in the layer of water adjacent to flatfish.; Three flow rates were tested in a circular tank and in a rectangular or raceway tank. For each flow rate, water velocities, boundary layer thickness and Reynolds number were calculated. Results showed that the vertical gradient of dissolved oxygen diminishes when water velocity and Reynolds numbers (Re) increase. At the fish density used in this work (11.6 kg m(-2)), when Re decreased under 6000, a large increase in the DO gradient was observed. Guidelines are presented to determine in which situations, as defined by hydraulic parameters, Re >6000 is achieved and DO stratification avoided.; The present work shows that in raceways, the flow rate required to avoid DO stratification is higher than that typically needed to maintain water quality (oxygen, ammonia-nitrogen, carbon dioxide and suspended solids). In circular tanks, it can be easier to achieve velocities that are high enough to avoid stratification with low water inlet flow rates, by adjusting the area of the water entry orifices. (C) 2014 Elsevier B.V. All rights reserved.
The superior hydrodynamics of circular tanks over rectangular tanks are well known by aquaculturists; yet rectangular tanks are still widely used because of their easier handling. As a consequence, several studies have focused on the hydrodynamics of rectangular tanks, where rotating flow cells are generated by injecting water tangentially to the tank wall with the outlet placed in the center of the cell. In the present work, we evaluate the hydrodynamics in a rectangular tank with 4 rotating flow cells of 1m diameter, which is called multivortex tank. We also analyze baffle placement between two consecutive water inlets and the characteristics of the water inlet (flow rate and inlet velocity), which then allows us to determine the average velocities and the distribution uniformity of these velocities. The obtained results are compared with a circular tank having the same cell diameter and inlet configurations as the multivortex tank.
Baffle placement between two consecutive water inlets in the multivortex tank helps increase the average velocity, the uniformity of velocities and the symmetry in the rotating flow cells. In configurations without baffles, the combination of low flow rate and high impulse force present the lowest symmetry. Differences between intermediate and extreme cells were observed. In all configurations tested, velocities and uniformities were higher in extreme cells than in intermediate cells. In the circular tank the average velocities achieved were higher than in the multivortex tank with the same impulse force, but the uniformity of velocities were higher in the multivortex tank. Finally, the proportionality between the average velocity and the square root of the impulse force for a specific tank geometry has been corroborated in commercial scale models.