The Silent Killers
Ghost nets are commercial fishing nets that have been lost, abandoned, or discarded at sea. Every year they are responsible for trapping and killing millions of marine animals including sharks, rays, bony fish, turtles, dolphins, whales, crustaceans, and birds. Ghost nets cause further damage by entangling live coral, smothering reefs and introducing parasites and invasive species into reef environments.
In addition, ghost nets affect the sustainability of well-managed fisheries by damaging boats and killing species with economic value. They also impact the beauty of shorelines, resulting in expensive cleanup costs and financial loss for the tourism and diving industry.
The deadly effects of ghost nets can be felt far from their point of origin. Ghost nets drift with ocean currents for years, or even decades. As they travel huge distances, they continuing to catch and kill marine animals in a process called “ghost fishing”.
Entanglement in ghost nets can lead to exhaustion, suffocation, starvation, amputations of limbs, and, eventually, the death of a marine animal. Entangled fish often act as bait, attracting larger predators such as turtles, sharks, and dolphins, which may themselves become entangled.
The Cycle of Devastation
A drifting ghost net might eventually become so heavy due to its catch that it sinks to the bottom of the ocean. On the seabed, smaller ocean dwellers start feeding on the entangled marine animals, which, along with natural decomposition, reduces the weight of the net to the extent that it floats back up to the surface. Once the ghost net is again drifting with the ocean currents, it starts its cycle of ghost fishing, sinking and floating back up all over again. Due to the durability of modern fishing nets, this circle of devastation can continue for decades.
Why Do Ghost Nets End Up In The Ocean?
Research is ongoing to better understand why ghost nets end up in the ocean. However, the cause and magnitude of the negative impact of ghost nets on the economic and ecological resources in the Indian Ocean remain unknown.
The Olive Ridley Project focuses on identifying the key factors contributing to ghost nets in the Indian Ocean, some of which are:
- Bad weather conditions;
- Catch overload;
- Snagging on the bottom;
- Poor gear maintenance;
- High cost of retrieval;
- Fishery conflicts or vandalism;
- Poor or no access to disposal or recycling facilities;
- Illegal or unregulated fishing activities;
- Destructive fishing techniques.
Problematic Fishing Techniques Cause Ghost Nets
Many fishing techniques and practices are destructive to the marine environment. They may for example cause over-fishing, massive by-catch, damage to the sea bottom and coral reefs, and ghost fishing. Trawling and the use of gillnets, purse seine and FADs (Fish Aggregating Devices) are some of the problematic fishing techniques that create ghost nets. On the other hand, pole and line, the primary fishing technique in the Maldives, is a low impact and sustainable fishing technique.
The dominant fishing gear in the Indian Ocean is gillnets. Gillnets contribute as much as 30-40% of the total catch in artisanal and semi-industrial fisheries.
Gillnets are sets of panels of uniform mesh size, which form a large net-wall hanging vertically in the water. Suspended in the top- or mid-depths of the water (a drift gillnet), or anchored to the seafloor (bottom gillnet), gillnets trap fish by their gills. They are very effective – and particularly destructive.
Trawling involves dragging a large fishing net with heavy weights behind a boat, either mid-water or across the bottom. The net indiscriminately catches or crushes everything in its path. Consequently, by-catch is extremely high and nets are often lost due to snagging on the bottom.
Trawling is a common fishing technique in India and Sri Lanka.
Purse seine is a long wall of netting deployed around a school of fish and pulled tight, thus enveloping the school of fish (and any other animals) in a purse-like structure.
Purse seines target pelagic fish of all sizes, including tuna, and are therefore frequently used in the western Indian Ocean, often in combination with FADs (see below).
Fish Aggregating Devices (FADs)
Fish Aggregating Devices (FADs) are man-made objects used to improve a vessel’s catch by attracting fish beneath them. FADs are usually a square of bamboo with netting and buoys attached. Sometimes a solar-powered GPS tracker is also on board to allow the boat that deployed it to track it. The devices are either in a static location or deployed in the open ocean as drifting devices (dFADs).
dFADs frequently drift with the currents in Maldivian waters. Some have even been traced back to specific boats operating in the Western Indian Ocean.
Actively Fighting Ghost Nets
The Olive Ridley Project is actively fighting ghost nets in the Indian Ocean on several fronts:
- Between July 2013 and December 2018, we physically removed 1400 ghost nets from the Indian Ocean
- During the same period, we documented 671 turtle entanglements in the Maldives
- Our Community Outreach Officers and Field and Project Coordinators focus on educational outreach and organise talks and workshops in local communities and schools
- Our Marine Turtle Rescue Centre in Baa Atoll has treated more 66 turtle patients since opening in February 2017
- We work with fisheries to prevent ghost nets from entering the Indian Ocean in the first place and to develop ways to minimise ghost gear and reuse fishing gear
In addition, we are carrying out research trying to find answers questions such as:
- What is/are the major source(s) for the nets we find in the Indian Ocean?
- Can we age ghost gear to determine how long it has been drifting?
- What are the socio-economic impacts of ghost gear in the Indian Ocean?
- Why are Olive Ridley turtles, and particularly juveniles, at such a risk?
- How can we prevent these fishing nets from entering the Indian Ocean in the first place?
- How can we recycle and re-purpose all the recovered ghost gear?
The ultimate goal of our research is to provide recommendations on how to manage and mitigate the ghost gear issue. We also hope that our research results will prompt changes in fishing net and gear designs, as well as influence fishing legislation.