Coley: the ideal robot fish

Research at NTNU shows that the cod is stubborn and capricious while the salmon is stupid. The coley, on the other hand, is the easiest to tame. IllustratIon: Elin Horn

Coleys are easily tamed. This is Professor Jens G. Balchen’s con-clusion after many years of experimenting with fish navigation.

By Arne Asphjell

– The cod is stubborn and capricious, and the salmon is stupid. The coley, on the other hand, is the ideal fish for our purposes, says Professor Jens G. Balchen at the Department of Engineering Cybernetics at NTNU. He has been occupied with fish navigation for more than thirty years, and his conclusion is that the coley is the fish that can most easily be trained.
– We like the coley a lot, it is a smart fish, says Balchen. At the moment he has a ‘fatted coley’ swimming around in the Atlantic Park at Ålesund. According to Balchen, it is as fat as a pig, and it weighs well over ten kilos. With all that stored food the coley can go without fodder for over a year.
Balchen has several ideas about what such a cyberfish can be used for. It can for example be equipped with a camera and monitor seabed pipelines. Another possibility is to use the robot fish as a ‘sheepdog’ for shoals of fish that are to be caught. Balchen says that he would like to hear from research groups and people in industry that might have interesting uses for such a ‘remote-controlled’ fish.

Testing the pet coley
A smart fish that can controlled for a whole year without refuelling is just what Balchen needs when he looks for a robot fish that can be given orders. The fat coley in Ålesund is ready for important testing at the end of October. It will be equipped with sophisticated electronics, and Professor Balchen will then be able to see whether the coley will obey his electronic orders about where to swim. Several methods have been tried out over a number of years while testing has been going on. Balchen and his staff have, among other things, tried to equip the fish with reins so that it could be steered like a horse, but this did not work particularly well. But now the research team has succeeded in making the fish move to port or to starboard on command.
– The fish does not like to be touched, and we make use of this fact so that it can be steered, explains Balchen. It is the gill cover that is especially sensitive to touch. Small motorized flaps on either side of the fish are activated by means of ultrasound, so that it can be persuaded to move to the right or to the left.

Tricking the fish
The most difficult thing has been to get the fish to move up and down. The method used is about to be patented, and Balchen is not willing to reveal too much. But he does disclose that he can trick the fish into believing that it is located at a different depth from what is actually the case, and it is thereby possible to make it dive into the deep or climb up towards the surface.
No doubt some of us will be worried by the idea of equipping a fish with high technology and making it perform certain tasks.
– We stay within the rules of professional ethics, says Balchen, who cannot see that his research can possibly be any less acceptable than is dog-training or horse-breaking.

Contact at NTNU: Jens G. Balchen
Tel: +47 73 59 43 82
Email: Jens.Glad.Balchen@itk.ntnu.no