My Year 7 class and I have been trying to find out whether sharks can swim backwards. Can anyone settle the issue please?
鈥� The forward motion of sharks is due principally, and in some large and fast-swimming species almost exclusively, to lateral beats of their tail fin. Numerous species of small, slender sharks also propel themselves in part by curving the rear two-thirds of their body from side to side in waves that flow towards their tails. So, when in contact with the walls of a crevice or the grasping hands of a human, dogfish and other small sharks can wriggle to escape, and this may involve some tailwards (or backwards) motion. Nevertheless, no shark can 鈥渟wim鈥� backwards in open water.
Some other types of fish can. These bony fish do so by rotating and beating their pectoral and pelvic fins. But sharks can鈥檛 rotate these fins, which are more like the fixed wings of an aircraft.
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鈥淪harks cannot swim backwards. They can鈥檛 rotate their fins, which are like fixed aircraft wings鈥�
Incidentally, it is not true that all sharks must keep swimming forwards to obtain oxygen (known as ram ventilation). Some sharks lie on the bottom facing into the current and can pump water over their gills by opening and closing their mouth. Some species can also draw water in through apertures, called spiracles, behind their eyes.
Oliver Crimmen, Senior fish curator, The Natural History Museum, London, UK
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