References of "Becco, Christophe"
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See detailFish lateral system is required for accurate control of shoaling behaviour
Faucher, Karine ULg; Parmentier, Eric ULg; Becco, Christophe ULg et al

Conference (2010)

In teleost fishes, the lateral system is assumed to contribute, among other roles, to maintaining schooling behaviour. Sight is also assumed to play a role in schooling, as fish with a cut lateral line do ... [more ▼]

In teleost fishes, the lateral system is assumed to contribute, among other roles, to maintaining schooling behaviour. Sight is also assumed to play a role in schooling, as fish with a cut lateral line do not stop schooling unless they are also blinded. This conclusion, however, was based on experiments where only the trunk lateral line was inactivated, leaving the head lateral system intact. Here the aim was to test how inactivation of the whole lateral system affects the fish shoaling behaviour. Groups of firehead tetras, Hemigrammus bleheri, were video-recorded before and after inactivation of their whole lateral system with aminoglycoside antibiotics (and also in sham-treated specimens). Shoaling behaviour was characterized by: nearest distance to the first, second, and third neighbour, shoal radius, shoal order parameter, and the number of collisions between individuals. SEM observations showed damage to most superficial neuromasts as a result of antibiotic treatment. Importantly, the antibiotic-treated fish proved unable to maintain a shoal. After the end of the treatment, however, they recovered both a normal tissue morphology and normal shoaling behaviour within about a month. The lateral system is thus more crucial to shoaling behaviour than previously believed. [less ▲]

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See detailFish lateral system is required for accurate control of shoaling behaviour
Faucher, Karine ULg; Parmentier, Eric ULg; Becco, Christophe ULg et al

in Animal Behaviour (2010), 79

In teleost fishes, the lateral system is assumed to contribute, among other roles, to maintaining schooling behaviour. Sight is also assumed to play a role in schooling, as fish with a cut lateral line do ... [more ▼]

In teleost fishes, the lateral system is assumed to contribute, among other roles, to maintaining schooling behaviour. Sight is also assumed to play a role in schooling, as fish with a cut lateral line do not stop schooling unless they are also blinded. This conclusion, however, is based on experiments where only the trunk lateral line was inactivated, leaving the head lateral system intact. We investigated how inactivation of the whole lateral system affects fish shoaling behaviour. Groups of firehead tetras, Hemigrammus bleheri, were videorecorded before and after inactivation of their whole lateral system with aminoglycoside antibiotics (and also in sham-treated specimens). Shoaling behaviour was characterized by nearest distance to the first, second and third neighbours, shoal radius, shoal order parameter and the number of collisions between individuals. Scanning electron microscope observations showed damage to most superficial neuromasts as a result of antibiotic treatment. Importantly, the antibiotic-treated fish proved unable to maintain a shoal. After the end of the treatment, however, they recovered both a normal tissue morphology and normal shoaling behaviour within about a month. The lateral system is thus more crucial to shoaling behaviour than previously believed. [less ▲]

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See detailOntogeny of swimming movements in the catfish Clarias gariepinus
Mauguit, Quentin ULg; Gennotte, Vincent ULg; Becco, Christophe ULg et al

in The Open Fish Science Journal (2010), 3

The swimming movements of C. gariepinus larvae were recorded with a high-speed camera (400, 500 and 800 fps) from 0 to 336 hours post-hatching. Movements of adult fish were also recorded to provide ... [more ▼]

The swimming movements of C. gariepinus larvae were recorded with a high-speed camera (400, 500 and 800 fps) from 0 to 336 hours post-hatching. Movements of adult fish were also recorded to provide information on the last developmental stage. Seven landmarks positioned on the fish midline were used during tail beating to determine various parameters during ontogeny and, on the basis of these parameters, to describe the first appearance of swimming movements and their development and efficiency during growth. Larvae were unable to swim at hatching (4 mm total length). Swimming movements were established at 48 hours posthatching when the fish measured between 7 and 8 mm total length and the yolk sac was more than 95% absorbed. At this stage, lateral excursion of the head appeared strongly reduced (from 13% to 6% of the total length). The efficiency of swimming movements increased throughout ontogeny, as did the homogeneity of the speed of the propulsive wave. Spontaneous swimming speed of 1 to 10 TLs-1 were observed in early stage (8-12 hPH). The various speed induced significant variations in parameters such as the amplitude of lateral head movements, swimming efficiency, and body rigidity. No major change was observed at the theoretical flow-regime transition. [less ▲]

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See detailA video multitracking system for quantification of individual behavior in a large fish shoal: Advantages and limits
Delcourt, Johann ULg; Becco, Christophe ULg; Vandewalle, Nicolas ULg et al

in Behavior Research Methods (2009), 41(1), 228-235

The capability of a new multitracking system to track a large number of unmarked fish (up to 100) is evaluated. This system extrapolates a trajectory from each individual and analyzes recorded sequences ... [more ▼]

The capability of a new multitracking system to track a large number of unmarked fish (up to 100) is evaluated. This system extrapolates a trajectory from each individual and analyzes recorded sequences that are several minutes long. This system is very efficient in statistical individual tracking, where the individual’s identity is important for a short period of time in comparison with the duration of the track. Individual identification is typically greater than 99%. Identification is largely efficient (more than 99%) when the fish images do not cross the image of a neighbor fish. When the images of two fish merge (occlusion), we consider that the spot on the screen has a double identity. Consequently, there are no identification errors during occlusions, even though the measurement of the positions of each individual is imprecise. When the images of these two merged fish separate (separation), individual identification errors are more frequent, but their effect is very low in statistical individual tracking. On the other hand, in complete individual tracking, where individual fish identity is important for the entire trajectory, each identification error invalidates the results. In such cases, the experimenter must observe whether the program assigns the correct identification, and, when an error is made, must edit the results. This work is not too costly in time because it is limited to the separation events, accounting for fewer than 0.1% of individual identifications. Consequently, in both statistical and rigorous individual tracking, this system allows the experimenter to gain time by measuring the individual position automatically. It can also analyze the structural and dynamic properties of an animal group with a very large sample, with precision and sampling that are impossible to obtain with manual measures. [less ▲]

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See detailAdvantages and limits of a video multitracking system for quantification of individual behavior in a large fish shoal
Delcourt, Johann ULg; Becco, Christophe ULg; Vandewalle, Nicolas ULg et al

in Spink, A.; Ballintijn, M. R.; Bogers, N. D. (Eds.) et al Proceedings of Measuring Behavior 2008 (2008)

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See detailSchool fish behaviour
Becco, Christophe ULg; Vandewalle, Nicolas ULg; Delcourt, Johann ULg et al

Conference (2006, September)

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See detailDense bubble flow in a silo: An unusual flow of a dispersed medium
Bertho, Y.; Becco, Christophe ULg; Vandewalle, Nicolas ULg

in Physical Review E (2006), 73(5, Pt 2), 56309

The dense flow of air bubbles in a two-dimensional silo (through an aperture D) filled with a liquid is studied experimentally. A particle tracking technique has been used to bring out the main properties ... [more ▼]

The dense flow of air bubbles in a two-dimensional silo (through an aperture D) filled with a liquid is studied experimentally. A particle tracking technique has been used to bring out the main properties of the flow: displacements of the bubbles, transverse, and axial velocities. The behavior of the air bubbles is observed to present similarities with nondeformable solid grains in a granular flow. Nevertheless, a correlation between the bubble velocities and their deformations has been evidenced. Moreover, a new discharge law (Beverloo like) must be considered for such a system, where the flow rate is observed to vary as D-1/2 and depends on the deformability of the particles. [less ▲]

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See detailExperimental evidences of a structural and dynamical transition in fish school
Becco, Christophe ULg; Vandewalle, Nicolas ULg; Delcourt, Johann ULg et al

in Physica A: Statistical Mechanics and its Applications (2006), 367

We have developed a video tracking system in order to determine all the trajectories of young fish (Oreochromis niloticus L.) within a school. Both individual and collective behaviours have been studied ... [more ▼]

We have developed a video tracking system in order to determine all the trajectories of young fish (Oreochromis niloticus L.) within a school. Both individual and collective behaviours have been studied as a function of the number of fish per unit area. By studying distributions of distances between fish and distributions of relative orientations, structural effects and cooperative motions have been evidenced. Signatures of a phase transition have been found, as predicted by some numerical models. This work opens new perspectives in the study of collective phenomena in biological systems since it is the first time that such measurements are possible. [less ▲]

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See detailComparing the EthoVision 2.3 system and a new computerized multitracking prototype system to measure the swimming behavior in fry fish
Delcourt, Johann ULg; Becco, Christophe ULg; Ylieff, Marc ULg et al

in Behavior Research Methods (2006), 38

Coming from the framework of unmarked fry tracking, we compared the capacities, advantages, and disadvantages of two recent video tracking systems: EthoVision 2.3 and a new prototype of multitracking. The ... [more ▼]

Coming from the framework of unmarked fry tracking, we compared the capacities, advantages, and disadvantages of two recent video tracking systems: EthoVision 2.3 and a new prototype of multitracking. The EthoVision system has proved to be impressive for tracking a fry using the detection by gray scaling. Detection by subtraction has given less accurate results. Our video multitracking system is able to detect and track more than 100 unmarked fish by gray scaling technique. It permits an analysis at the group level as well as at the individual level. The multitracking program is able to attribute a number to each fish and to follow each one for the whole duration of the track. Our system permits the analysis of the movement of each individual, even if the trajectories of two fish cross each other. This is possible thanks to the theoretical estimation of the trajectory of each fish, which can be compared with the real trajectory (analysis with feedback). However, the period of the track is limited for our system (about 1 min), whereas EthoVision is able to track for numerous hours. In spite of these limitations, these two systems allow an almost continuous automatic sampling of the movement behaviors during the track. [less ▲]

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See detailA new automatic video multitracking system able to follow a large school
Delcourt, Johann ULg; Becco, Christophe ULg; Vandewalle, Nicolas ULg et al

in Noldus, L.P.P.J.; Grieco, F.; Loijens, L. W. S. (Eds.) et al Proceedings of Measuring Behavior 2005 (2005)

The study of shoaling behaviours is tackled by scientists by three approaches: the field, laboratory and computer modelling approach. The field studies are complicated and permit rarely an analysis of ... [more ▼]

The study of shoaling behaviours is tackled by scientists by three approaches: the field, laboratory and computer modelling approach. The field studies are complicated and permit rarely an analysis of individual positions. The third approach, consisting of development of mathematic models, is artificial. It requires a comparison with empiric results to validate and to determine the explications’ degree of each model. Thanks to the developments of digital imaging techniques, the laboratory studies on fish are able to measure the behavioural parameters with precision, impossible to realize with manual recording. Multitracking systems are rare and of recent development. These are insufficient to study the real size of shoals, often composed of hundreds of .shes. We have developed a new system of multitracking thanks to collaboration with the G.R.A.S.P. The G.R.A.S.P. has before realised other multitracking systems to follow some hundreds physical objects. Our video multitracking system is able to detect and to track more than a hundred unmarked fishes by gray scaling technique during some minutes. It permits an analysis as well at the group level as at the individual level. The multitraking program is able to attribute a number at each fish and to follow each one during the whole duration of the track. Our system permits the analysis of the movement of each individual, even if the trajectories of two fishes cross each other. It is possible thanks to the theoretical estimation of trajectory of each fish, compared with the real trajectory (analysis with feedback). The human eye is always necessary to detect the errors in identification but reediting is possible. However, if the fishes don’t move too rapidly, a rate of 25 images /s gives very good results, without too much visual expertise from the experimenter. If the fishes are too fast (i.e. escape response), it is better to use a high speed camera. [less ▲]

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