video transcript

STORY: Every year, markets like this one all over the Czech Republic sell carp - it's a Christmas dinner tradition. But this year, researchers studied the fish before they ended up on a plate. Scientists wanted to prove that carp possess a capacity to perceive geomagnetic fields, always orienting themselves north-south. The research was initially carried out in ponds and lakes, but that proved tricky and the results were inconclusive. Until one of the team's leading scientist, Vlastimil Hart, had a dream. SOUNDBITE: PROJECT LEADER SCIENTIST VLASTIMIL HART SAYING (Czech): "For several nights I had a dream about Christmas, when the carp are sold from the tubs in streets. When I woke up, I thought this is a great idea [for our research] and we have to put this into practice. I discussed it later with colleagues and we decided that we would try to observe the carp in the tubs around Christmas time." The scientists photographed and analysed the positions of the carp in the plastic tubs and the research included over 14,000 fish in 25 markets. Hart says one of the reasons the vats work so well, is because there are no corners or flat surfaces to block the carp and the circular bins allow the fish to move naturally. The result? The majority of fish aligned themselves along the north-south axis. SOUNDBITE: PROJECT LEADER SCIENTIST VLASTIMIL HART SAYING (Czech): "Most of the fish were positioned in the north-south axis; a few of them were in a different position which is a statistical variance and does not negatively influence the result, which shows that the north-south direction is the primary one." The researchers found that disturbances like city lights and sounds did not interfere with the carps' choice of direction. And neither did the absence of common orientation stimuli, like the flow of water. Leading authors to conclude that carp most likely align themselves to geomagnetic cues. Head of the research team, Hynek Burda says the findings reveal that carp rely on this magnetic perception for their basic survival and the ability to orient affects entire schools of fish. SOUNDBITE: CHIEF SCIENTIST PROFESSOR HYNEK BURDA SAYING (Czech): "This enables synchronization of the movement of the whole group, the whole school of fish. They must choose a direction to float or swim or perhaps escape from a predator. And their magnetic sense, this tendency and preference of specific magnetic direction should enable them to do this. This 'compass' can also be important for fish that are moving in muddy waters over short distances." And though the carp at these markets may not know it, this year they have offered Science a tasty Christmas treat.