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.
Aquaculture needs to obtain the most out of the resources in order to be efficient and sustainable. For this purpose it is
essential to provide an environment that guarantees a level of welfare allowing the fish to grow at their full potential and
maintain a good health.
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 Presentation's date: 2015-10 Presentation of work at congresses
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 Presentation's date: 2015-10 Presentation of work at congresses
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.
Oca, J.; Masaló, I.; Duarte, S.; Sanchez, P.; Almansa, C.; Reig, L. II Simposi d'Aqüicultura de Catalunya: Investigació, desenvolupament i transferència en aqüicultura des de Catalunya a Europa p. 33 Presentation's date: 2009-10-15 Presentation of work at congresses
Evaluating flatfish activity can be a useful tool for studying fish behavior and welfare. The aim of this
workwas to obtain a quantitative index for measuring flatfish activity using image analysis. Accordingly,
motor activity of a sole population was recorded by digital video for three nights, bearing in mind the
nocturnal lifestyle of the species. Subsequent image analysis was done by image subtraction of
consecutive frames. The result was a ‘‘difference frame’’ showing the changes in the image area due to
fish movement. Using these data, an image processing activity index (IPAI) was determined by
measuring the percentage of area altered due to fish movement and by taking this percentage as an
indicator of fish activity. Typical sole behavioral acts (take-off and surface swimming) were recorded by
direct observation during the same intervals in order to calibrate the IPAI. A direct observation activity
index (DOAI) was determined by weighting each kind of attitude according to its average duration.
Results obtained from image analysis (IPAI) were compared with results obtained by direct observation
(DOAI). A linear relationship between the two indexes was found with a correlation coefficient of
r2 = 0.80 for 92% of coverage area tank and r2 = 0.90 for 210% of coverage area tank. Thus, this digital
video-based index can be a highly reliable and accuratemethod for objectivelymeasuring activity levels
in sole with a low consumption of labor and time. Nevertheless, the application to farm conditions would
need further research and an accurate calibration for other species.