Salmon run plankton. At this point the baby salmon are called "fry". At the end of the summer the fry develop into juvenile fish called "parr". Parr feed on small invertebrates and are camouflaged with a pattern of spots and vertical bars. They remain in this stage for up to three years. As they approach the time when they are ready to migrate out to the sea the parr lose their camouflage bars and undergo a process of physiological changes which allows them to survive the shift from freshwater to saltwater. At this point salmon are called "smolt". Smolt spend time in
First Life (TV series) animals first appeared in the oceans around 540 million years ago, an event known as the Cambrian Explosion. Trace fossils of multicellular organisms from an even earlier period, the Ediacaran biota, are also examined. Attenborough travels to Canada, Morocco and Australia, using some of the latest fossil discoveries and their nearest equivalents amongst living species to reveal what life may have been like at that time. Visual effects and computer animation are used to reconstruct and animate the extinct life forms. "Attenborough's Journey", a documentary film profiling the presenter as he journeyed around the globe filming "First Life", was shown