Salmon jump to clear obstacles in their path while travelling to their spawning grounds. Salmon hatch in freshwater rivers and then swim downstream to reach the ocean, where they mature. When they reach adulthood, the salmon swim back upstream to reach the spawning grounds where they hatched. To travel upstream, salmon have to jump up and over obstacles, such as waterfalls and rapids.
Salmon also jump for reasons that scientists do not completely understand. One possible reason is that the salmon are trying to rid themselves of parasitic sea lice through the friction created when they re-enter the water. Other scientists believe that it serves a role in helping the salmon to maintain buoyancy. Unlike a number of other species that have closed swim bladders, salmon have open swim bladders. To keep the swim bladders full of air, the salmon must gulp air from the surface. Their jumping behavior may aid them in swallowing air.
Some salmon have been documented jumping obstacles that are 12 feet high; however, they cannot clear all objects that lie in their path. Sometimes, humans build dams or other structures that block the fishes’ path back to their spawning grounds. Salmon do not usually eat while swimming back up stream, and can only survive by living off their fat reserves.