Each winter, thousands of spider crabs rise up from the depths of Bass Strait to gather for one of the world’s most extraordinary natural spectacles. For many years these mass aggregations went on relatively unknown to the wider public until in recent years films, such as David Attenborough’s Blue Planet 2, shed light on to the wildlife spectacle. Nature photographer Justin Gilligan jumped into the cold waters in Port Phillip bay to capture the event during which the crabs moult their tough exoskeletons. This makes them easy bait for predators such as Australia’s largest stingrays. But since last year's march the crabs are facing another threat - from fishers who could potentially end this spectacle. This Episode of Talking Australia is hosted by Angela Heathcote (Digital Producer at Australian Geographic) and produced by Ben Kanthak (www.beachshackpodcasts.com).You can also follow us on Instagram @australiangeographicSee omnystudio.com/listener for privacy information.