Ghost nets
Lost and abandoned fishing gear, including "ghost nets" pose a major threat to marine animals when they become entangled in the gear and drown or die of exhaustion or starvation.
Ghost nets are fishing nets that have been either lost or abandoned at sea. Sometimes nicknamed 'walls of death' they drift on ocean currents indiscriminately catching a wide range of marine animals, including turtles, dugong, sharks and dolphins.
For thousands of years the Gulf of Carpentaria has acted as a catchment for marine debris for the Indo-Pacific region. In the past currents sweeping into the Gulf carried debris like canoes, organic fibre nets, tree logs and other organic material. Over the last few decades however the composition of the debris has changed dramatically. Nets woven from natural fibres have given way to synthetic nets that are so resilient that they can persist in the marine environment for hundreds of years.
Once inside the Gulf, the nets - often still buoyed by floats - become trapped in the clockwise spin of the Gulf of Carpentaria Gyre that is fed by the north-west monsoon pattern. The nets will remain in an endless cycle of washing ashore in storms and back into the spin of the gyre unless they are collected when they are washed ashore. The growing weight of dead animals in the nets can outweigh the buoyancy of the floats and force the net out of circulation for a while. However, after the trapped dead animals break down or get eaten the net's buoyancy returns and it is set adrift to start the cycle all over again.
The Carpentaria ghost net programme, led by indigenous communities in the Gulf, commenced in 2004 with the assistance of federal government NHT funding. In a 50 month period up to July 2009 almost 90,000m of ghost netting had been collected from the Gulf. The largest nets found to date in the Gulf were Taiwanese gill nets which stretched out to approximately 4km in length with a drop of 12m.