快猫短视频

Swimming in schools has massive energy-saving benefits for fish. A study in 鈥渨ater tunnels鈥� has found that fish use half as much energy swimming at high speeds if they are in a school rather than alone, and they also recover in nearly half the time.

This helps explain why so many fish species swim in schools, write and at Harvard University.

It has long been thought that swimming in schools reduces energy use in addition to various other benefits such as protection from predators. But measuring energy use in free-swimming fish is tricky, not least because as fish swim faster they can no longer generate enough energy using only the oxygen they take in via their gills 鈥� aerobic respiration 鈥� and start using energy reserves stored in muscles 鈥� anaerobic respiration.

Zhang and Lauder put giant danio (Devario aequipinnatus) in long, narrow sealed aquariums where the speed of the water flow can be precisely controlled. They then measured oxygen consumption while individual danios or schools of around eight fish swam at a wide range of speeds.

Crucially, the pair kept measuring oxygen consumption for at least 19 hours after the fish swam at a certain speed. The more energy reserves fish use for anaerobic respiration, the more oxygen they consume to replenish those reserves after exercise.

Previous studies have measured oxygen consumption only during swimming, which reflects only aerobic energy use. Post-exercise oxygen consumption provides a measure of anaerobic respiration as well, allowing the total energy used during swimming to be estimated.

Zhang and Lauder found that at low speeds 鈥� between 0 and 3 body lengths per second 鈥� there was little difference in energy use between shoals and single fish. But at higher speeds fish in schools used a lot less energy.

At 7 body lengths per second, for instance, on average each fish in a school used 53 per cent less energy than solitary fish. At this speed the schooling fish were still getting 50 per cent of their energy from aerobic respiration, whereas the solitary fish were getting just 20 per cent, relying on anaerobic sources for the other 80 per cent.

鈥淲e鈥檝e known for a long time that there are energetic benefits for fish swimming in schools, but this study is exciting because it shows an indirect but overlooked benefit of these energy savings 鈥� that fish are less likely to need to engage in costly anaerobic metabolism to support swimming at intermediate to high speeds,鈥� says at the University of Glasgow in the UK.

This means fish have more energy to spend searching for food, digesting meals or avoiding predators, says Killen.

鈥淚 think they did a great job,鈥� says at the University of Alberta in Canada, whose team has in fish as an alternative way of estimating anaerobic respiration.

Overall the results are in line with his expectations. But what is surprising, says Tierney, is that Zhang and Lauder found that fish in schools beat their tails at the same frequencies as solitary fish swimming at the same speeds, but use half as much energy per beat. 鈥淰ery cool.鈥�

快猫短视频 contacted Yangfan Zhang.