Time to tide up - Fishing debris in Australian oceans
Lost and discarded fishing gear has been an international environmental issue for over 50 years. Globally, over 6.4 million tonnes of fishing gear is accidentally lost, abandoned or deliberately dumped in the ocean each year (Maefadyen et al. 2009). The Australian marine environment has similar problems (Jones 1995). Not a shock really, I mean the oceans are all connected! Fishing debris has been found in our deep seas, throughout our estuarine systems and washed up on our usually pristine beaches. Since Jones’ paper there has been very limited literature in this area in Australia and the exact amount of lost fishing gear is currently unknown. A recent CSIRO paper estimated that 2% of debris found on beaches came from fishing sources, but this doesn’t include the gear that is found in open water (Hardesty et al. 2017). There are a load of stats relating to the contribution that lost fishing gear has on the ‘plastic problem’ flying around at the moment. Most of these are inaccurate and the hard stats behind the overall contribution of lost fishing gear is still undetermined.
It is known, however, that lost fishing gear, can have devastating consequences for marine life. It creepily drifts through the currents, tangling and often killing marine organisms, in a sort of floating grave yard, hence its common name ‘ghost gear’ (Wilcox et al. 2015). Any net, long line, fish trap or other man-made fishing equipment can turn into ghost gear if left unattended. Unsurprisingly, something which was designed with the sole purpose of catching fish, will still end up catching them whether there is someone pulling them out of the water or not!
Every year ghost nets are responsible for entangling, trapping and ultimately killing many, marine organisms. This includes fish, whales, birds, rays, dolphins, turtles and sharks (Stelfox et al. 2016). Animals become trapped in the nets, and in a desperate struggle to release themselves often suffocate, starve or exhaust themselves to death. Unfortunately, the cycle doesn’t end here, as the dead animals act as bait for other predators, whom then may also get entangled in the nets. These floating, ghostly graveyards can drift through currents for years, travelling vast distances and leaving a trail of death behind them.
In the past couple of months there have been several reports of incidents surrounding ghost gear in Australian waters. Firstly the huge three tonne net pulled out of the Sir Joseph Banks Group Conservation Park near Port Lincoln in South Australiathree weeks ago. This 50 metre net is thought to have been there for nearly a year, and disturbingly was found in a protected area, an area where marine life should be safe. Secondly, on the weekend a humpback whale calf was rescued from a shark net on the Gold Coast. Although not technically ‘ghost gear’ this highlights the danger that nets have to marine mammals. Luckily this calf was spotted as it was close to the shore, but other animals who get caught further away from land may not be as lucky.
Image credits
Seal in net: https://ensia.com/features/fishing-gear-recycling/
References
Hardesty, BD, Lawson, TJ, van der Velde, T, Lansdell, M, Wilcox, C (2017) Estimating quantities and sources of marine debris at a continental scale.Frontiers in Ecology and the Environment 15, 18-25.
Jones, MM (1995) Fishing debris in the Australian marine environment. Marine Pollution Bulletin 30, 25-33.
Maefadyen, G, Huntington, T, Cappell, R (2009)Abandoned, lost or otherwise discarded fishing gear. UNEP Regional Seas Reports and Studies
Stelfox, M, Hudgins, J, Sweet, M (2016) A review of ghost gear entanglement amongst marine mammals, reptiles and elasmobranchs. Marine Pollution Bulletin 111, 6-17.
Wilcox, C, Heathcote, G, Goldberg, J, Gunn, R, Peel, D, Hardesty, BD (2015) Understanding the sources and effects of abandoned, lost, and discarded fishing gear on marine turtles in northern Australia. Conservation Biology 29, 198-206.