Underwater view of spawning salmon in Katmai National Park, Alaska, USA (@ Paul Souders/Corbis)

Underwater view of spawning salmon in Katmai National Park, Alaska, USA (@ Paul Souders/Corbis)

comments,

• It looks like you\ve joined us in the middle of rush hour.""Everyone\s racing against the biological clock
• The fish are under constant threat here from a brown bear population estimated at 2,000.""Humans also face danger - as which Grizzly Man famously discovered?
• You\ll find these fish in a US national park that covers 16,564,09 km2.""That\s roughly the size of which country?
• We\re swimming with the fishes today.""Don\t panic - there\s plenty of life left in us yet