Hey you ! Here is a riddle !: How do we organise ourselves, in a school (a group) ? And why do we swim in this or that configuration ? Yes, we know you can answer part of the question. You will say that we do so to defend against predators, by diluting the chance of individual capture [1], and to boost the group’s foraging (feeding) success [2], because we have a lot of eyes looking for food and when one fish shows feeding behaviour, we follow. In fact, these motions and reactions of the school are the result of complex social interactions, depending on our needs and way of living. What you might not know, is that we swim together also to optimise hydrodynamic interactions, so we spend less energy compared to swimming alone. [3] [4] [5]. It is exactly like team cyclists who want look to minimise wind resistance ! Although these kind of cohesive organisations have been discussed since years and many observations, models and simulations have been performed, none of you guys understands exactly the formation of swimming fish groups, like ours. Héhé ! But wait… Actually, there is someone from FDV studying the question… Hanaé ! She is working in one of the ESPCI’s labs, with a Phd student named Intesaaf. They study the basic mechanisms of the formation of stable swimming groups with 4 to 5 red nose tetra fish Hemigrammus bleheri. How ? With this specific and ‘’home made’’ setup, below. They place gently a group of 4 or 5 fish in the channel / test section, with specific and different uniform water flows corresponding to different swimming velocities (speeds) of the fish, and they capture films from 3 cameras; one on each side and another on top : With these videos, they are able to track the fish using MATLAB, to measure the distances and angles of each fish to nearest neighbours, and observe synchronisation. So far, Intesaaf and Hanaé have only performed experiments, and have not started to analyse their data. Experiments with our cousins, the red nose tetra fish, are not easy because they get stressed and tired easily ! Here is a video, from the top camera, showing a group of 5 swimming together in the channel, in a relatively stationary position: Before Hanaé arrived in the lab, Intesaaf has been working on the phase locking and pattern formation of 2 swimming red nose tetra fish, using the same setup and tracking analysis. He concluded that 2 fish synchronise more at higher swimming velocities (they look synchronised when they swim in phase IP or out of phase OP - see image bellow) and that they do so to save energy and communicate efficiently. Check out his poster about this study ! [6]:
REF: [1] Article: An individual based model of fish school reactions: predicting antipredator behaviour as observed in nature - Published October 1997: http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2419.1997.00037.x/full [2] Article: Fish in larger shoals find food faster - Published December 1981: http://link.springer.com/article/10.1007/BF00300175 [3] Article: Energy savings in sea bass swimming in a school: measurements of tail beat frequency and oxygen consumption at different swimming speeds - Published August 1998: http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8649.1998.tb00986.x/full [4] Article: Burst-and-coast swimming in schooling fish (Notemigonus crysoleucas) with implications for energy economy - Published in 1991: http://www.sciencedirect.com/science/article/pii/030096299190382M [5] Article: Hydromechanics of Fish Schooling - Published in January 1973: http://www.nature.com/nature/journal/v241/n5387/abs/241290a0.html [6] Poster: Phase locking and pattern formation in tandem fish swimming - 2016: http://nonlineaire.univ-lille1.fr/SNL/media/2016/resumes/ASHRAF_intesaaf.pdf
3 Comments
Maryam
5/11/2016 09:08:16 am
Hi Bradshaw !
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Hanae
7/11/2016 03:22:07 am
Ahhh hydrodynamic interactions is indeed an interesting thing to discuss ! I could explain it in my next post, thanks for the idea !
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Maryam
7/11/2016 10:38:40 am
Yeah I think it could be interesting, you're welcome ;) Leave a Reply. |