An integrated approach for monitoring structural deformation of aquaculture net cages

The majority of present marine finfish production is conducted in flexible net cages which can deform when they are subjected to water movements generated by currents. The ability to monitor net deformation is important for performing cage operations and evaluation of fish health and welfare under changing environment. This paper presents a new method for real-time monitoring of net cage deformations that is based on an integrated approach where positioning sensor data is incorporated into a numerical model. An underwater positioning system was deployed at a full-scale fish farm site, with three acoustic sensors mounted on a cage measuring positions of the net at different depths. A novel numerical model with an adaptive current field was used to simulate net cage deformations, where the magnitude and direction of the current could be adapted by continuously assessing deviations between the simulated and the measured positions of the net. This method was found to accurately predict the pre-defined current velocity profiles in a set of simulated experiments. In the field experiment, a good agreement was also obtained between the simulated positions of the net and the acoustic sensor data. The integrated approach was shown to be well suited for in-situ real-time monitoring of net cage deformations by using a significantly reduced number of sensors.publishedVersio

Novel tag-based method for measuring tailbeat frequency and variations in amplitude in fish

The tailbeat frequency (TBF) together with tailbeat amplitude (TBA) of fish are tightly correlated with swimming speed. In addition, these parameters can be used as indicators of metabolic rate and general activity level, provided that appropriate calibration studies have been performed in the laboratory. If an implantable bio-logger could measure TBF and TBA, it would, therefore, have great potential as a tool to monitor swimming behaviours and bioenergetics over extended periods of time in free roaming fish within natural or farm environments. The purpose of this study was, therefore, to establish a method for deriving accurate TBF and variations in TBA from activity tags that log high-resolution acceleration data. We used 6 tagged Atlantic salmon (Salmo salar) of ≈1 kg and subjected them to two types of swim trials in a large swim tunnel system. Test speeds were either incrementally increased in 20-min intervals until steady swimming ceased, or constant speed of 60 cm s−1 was given in a 4-h sustained test. The TBFs were visually observed by camera and compared with computed values from the activity tags. In the incremental trials the TBF increased linearly with swimming speed, while it remained constant during the 4 h of sustained swimming. The TBFs measured by activity tags were within ± 0.1 beat s−1 of the visual measurements across the swim speeds tested between 30 to 80 cm s−1. Furthermore, TBF and its corresponding relative swim speed were consistent between trial type. The relative TBA increased with swimming speed as a power function, showing that the fish relies on changes in both amplitude and frequency of tail movements when swimming at higher speeds, while adjustments of amplitude only play a minor part at lower speeds. These results demonstrate that TBFs can be measured accurately via activity tags, and thus be used to infer swimming activities and bioenergetics of free roaming fish. Furthermore, it is also possible to estimate changes in TBA via activity tags which allows for more nuanced assessments of swimming patterns in free roaming fish.publishedVersio

System for Real-Time Positioning and Monitoring of Fish in Commercial Marine Farms Based on Acoustic Telemetry and Internet of Fish (IoF)

Website: www.isope.orgpublishedVersio

Under the sea: How can we use heart rate and accelerometers to remotely assess fish welfare in salmon aquaculture?

Recent advances in bio-sensing technologies open for new possibilities to monitor and safeguard the welfare of fishes in aquaculture. Yet before taken into practice, the applicability of all novel biosensors must be validated, and the breadth of their potential uses must be investigated. Here, we investigated how ECG and accelerometryderived parameters measured using bio-loggers, such as heart rate, acceleration and variance of acceleration, relate to O2 consumption rate (MO2) and blood borne indicators of stress and tissue damage to determine how biologgers may be used to estimate stress and welfare. To do this, we instrumented 13 fish with a biologger and an intravascular catheter and subjected them to a swimming protocol followed by a stress protocol throughout which the physiological parameters were measured and analyzed a posteriori. Additionally, based on the empirical data obtained, we calculated the mathematical relationships between the bio-logger data and the other parameters and tested the relationship between the calculated parameters using the linear regression algorithms and the measured parameters. Our results show that acceleration is a good proxy for swimming activity as it is closely related to tail beat frequency. In addition, we show that heart rate, acceleration and variance of acceleration all can be used as predictors for metabolic rate. Accelerometry based data, especially variance of acceleration, significantly explain some of the variation in venous partial pressure of O2, blood lactate and plasma cortisol concentration. Variance of acceleration also significantly explains some of the variation in pH and mean corpuscular hemoglobin concentration. These relationships are explained by variance of acceleration being a good indicator of the onset of burst-swimming activity, which is often followed by acid-base imbalances and release of catecholamines. The results herein indicate that bio-logger data can be used to extrapolate a range of stress-related physiological events when these are accompanied by increases in activity and highlight the great potential of biosensors for monitoring fish welfare. Biologger Acceleration Heart rate Stress MetabolismpublishedVersio

Tissue-Specific Orchestration of Gilthead Sea Bream Resilience to Hypoxia and High Stocking Density

Two different O-2 levels (normoxia: 75-85% O-2 saturation; moderate hypoxia: 42-43% O-2 saturation) and stocking densities (LD: 9.5, and HD: 19 kg/m(3)) were assessed on gilthead sea bream (Sparus aurata) in a 3-week feeding trial. Reduced O-2 availability had a negative impact on feed intake and growth rates, which was exacerbated by HD despite of the improvement in feed efficiency. Blood physiological hallmarks disclosed the enhancement in O-2-carrying capacity in fish maintained under moderate hypoxia. This feature was related to a hypo-metabolic state to cope with a chronic and widespread environmental O-2 reduction, which was accompanied by a differential regulation of circulating cortisol and growth hormone levels. Customized PCR-arrays were used for the simultaneous gene expression profiling of 34-44 selected stress and metabolic markers in liver, white skeletal muscle, heart, and blood cells. The number of differentially expressed genes ranged between 22 and 19 in liver, heart, and white skeletal muscle to 5 in total blood cells. Partial Least-Squares Discriminant Analysis (PLS-DA) explained [R2Y(cum)] and predicted [Q2Y(cum)] up to 95 and 65% of total variance, respectively. The first component (R2Y = 0.2889) gathered fish on the basis of O-2 availability, and liver and cardiac genes on the category of energy sensing and oxidative metabolism (cs, hif-1 alpha, pgc1 alpha, pgc1 beta, sirts 1-2-4-5-6-7), antioxidant defense and tissue repair (prdx5, sod2, mortalin, gpx4, gr, grp-170, and prdx3) and oxidative phosphorylation (nd2, nd5, and coxi) highly contributed to this separation. The second component (R2Y = 0.2927) differentiated normoxic fish at different stocking densities, and the white muscle clearly promoted this separation by a high over-representation of genes related to GH/IGF system (ghr-i, igfbp6b, igfbp5b, insr, igfbp3, and igf-i). The third component (R2Y = 0.2542) discriminated the effect of stocking density in fish exposed to moderate hypoxia by means of hepatic fatty acid desaturases (fads2, scd1a, and scd1b) and muscle markers of fatty acid oxidation (cpt1a). All these findings disclose the different contribution of analyzed tissues (liver >= heart > muscle > blood) and specific genes to the hypoxic- and crowding stress-mediated responses. This study will contribute to better explain and understand the different stress resilience of farmed fish across individuals and species

The New Era of Physio-Logging and Their Grand Challenges.

International audienc

NumSim - Numerical simulation of complex systems involving interaction between elements with large and varying stiffness properties

This report is a short summa ry of the research activity and results obtained in the project Numsim - Numerical simulation of complex systems involving interaction between elements with large and varying stiffness properties. Main focus of the project has been to develop numerical time-domain simulation models for fisheries and aquaculture systems. The numerical models build on the in-house time-domain simulation framework FhSim. The project has been financed by the Norwegian Research Council (grant 199574/070), The Norwegian Seafood Research Fund (FHF), Multiconsult AS and NOOMAS Sertifisering AS. Research partners in the project have been the Norwegian University of Science and Technology (NTNU), Dept. of Marine Technology and CNR-INSEAN, ltaly. This report covers the research activity at SINTEF Fisheries and Aquaculture.Norges ForsningsrådpublishedVersio

Controller Analysis in Real-Time Hybrid Model Testing of an Offshore Floating System

This paper presents an experimental study using Real-Time Hybrid Model (ReaTHM) testing of a moored floating cylindrical buoy, conducted in a wave basin. ReaTHM testing is a method for studying the dynamics of marine structures by partitioning the system into numerical and physical substructures that are then coupled in real-time using a control system. In this study, the floating cylinder buoy is modelled physically, and the mooring system modelled numerically. In this paper, the effect of selected controller parameters on the performance of the control system is studied, for both wave frequency and low-frequency ranges. The architecture/design of the control system is presented in the first part of the paper, while results from experimental tests with wave excitation on the physical substructure are presented in the second part of the paper.acceptedVersio

Kalman estimation of position and velocity for ReaTHM testing applications

Offshore wind power research is a rapidly growing field, because of the present climate crisis and increasing focus on renewable energy. Model testing plays an important role in the risk and cost analysis associated with offshore wind turbines (OWTs). The real-time hybrid model testing concept (ReaTHM testing) solves important challenges related to model testing of OWTs, such as achieving an accurate modelling of the wind field, and the occurrence of scaling issues when modelling wind and waves simultaneously. However, ReaTHM test set-ups are generally sensitive to noise, signal loss and inaccuracies in sensor values. The present study is focused on the design and implementation of a state estimator able to accurately estimate the position and velocity of floating structures, while taking disturbances into account. By combining the information received from several different sensors with mathematical models, the estimator provides smooth and reliable position and velocity estimates for ReaTHM testing applications. The main objective of the present study is to develop a kinematic state space model that could represent the motion of any floating structure in six degrees of freedom (6-DOF). The kinematic model is implemented in MATLAB, and acceleration time series obtained with numerical simulations are used as inputs. The computed outputs agree with the corresponding simulated motions. A Kalman estimator based on the state space model is designed, implemented and tested against virtual data from the numerical model, with artificially added disturbances. Sensitivity analyses addressing the robustness towards noise, time delays, signal loss and uncertainties are performed to identify the limits of the estimator. The estimator is demonstrated to be robust to most types of disturbances. Further, the state estimator is tested against physical data from laboratory experiments. Good agreement between the physically measured and the estimated states is observed.Kalman estimation of position and velocity for ReaTHM testing applicationspublishedVersio

Numerical Models in Real-Time Hybrid Model Testing of Slender Marine Systems

This paper presents a study of numerical models used in Real-Time Hybrid Model (ReaTHM) testing, conducted in a still water basin at SINTEF Ocean. ReaTHM testing is a method where a system is divided into physical and numerical substructures to study complex hydrodynamics on the physical system. Basin infrastructure limitations are handled by numerically modeling structural components with large geometrical extent. The numerical and physical substructures are coupled in real-time through a system of sensors and actuators. The emulated system under consideration in the study is a moored axisymmetric cylindrical buoy. The physical substructure is the buoy in model-scale ratio 1:144, while the numerical substructure is the full-scale mooring system consisting of twelve mooring lines. The time scale ratio requires the numerical models to run twelve times faster than real-time. To potentially reduce computational cost, a study is performed of three variations of numerical models, varying from low to high fidelity. The models are evaluated based on the sensitivity to jitter, induced time delays and clock drift imposed on the system