In this day and age, we are all becoming increasingly informed about how single-use plastics are a terrible pollutant. Whilst many of us are now aware that we should reduce / reuse / recycle drinks bottles, food packaging, tooth picks, electronics cases, beverage cups, party plates and plastic cutlery, there are other sources of plastics that most of us have absolutely no control over. In our oceans, plastic netting and other fishing gear which breaks loose and is left to roam across the seas is now becoming a huge environmental issue. So what is this "ghost fishing" gear? How much if it is there? And is it really a problem for sharks and rays?
Getting Ghosted
Abandoned, lost and discarded fishing gear is a huge environmental issue all over the world. “Ghost fishing gear" are nets or equipment no longer under the control of the fishing professionals, which passively drift across oceans and continue to entangle marine animals. It is estimated that around 6.4 million tonnes of marine debris find their way into our oceans every year and of this number, 10% is ghost gear (Stelfox et al, 2016; Gilman, 2015).
If the animal is lucky, entanglement by ghost fishing may just lead to injury and/or stress, but more commonly it causes immobilisation, and ultimately death by predation, starvation or suffocation. This most problematic ghost fishing gears are gillnets, trammel nets, longlines, and pots and traps. To learn more, see If You Love Me, Let Me Go (Gilman, 2015).
Ghost fishing has become increasingly common in our oceans as our fishing industry has expanded. We now have more fleets reaping our oceans, venturing further afield than ever before. Therefore, it only makes sense that more and more fishing gear is being lost at sea (Matsuoka et al, 2005; Gilman, 2015).
Exacerbating the problem, fishing gear has transitioned from more biodegradable materials like ropes, to be made from more durable synthetic materials, like plastics. When these gears are lost they are buoyant, so they can often be carried far in currents and they are very slow to break-down. This means nets hold their shape for many years, so they can continue entangling marine organisms like sharks, potentially for decades! (Matsuoka et al, 2005; Gilman, 2015).
Giving Up the Ghost
There are many different reasons why fishing gear may end up roaming free in our oceans. Gear can be accidentally lost when it becomes snagged on rocks or corals, or it becomes entangled in passing vessels. It may also be misplaced when tracking systems malfunction or if currents are especially strong. It is also common for gear to be lost in bad weather conditions, as the equipment may be washed away or it may be too dangerous for the fishers to go out to retrieve it. Poorly designed gear or equipment that is poorly maintained and worn out is also commonly lost at sea (Matsuoka et al, 2005; Gilman, 2015).
There are also more disturbing reasons why fishers may discard their gear. In some cases fishers will choose to set an excessive amount of gear in the hopes of increasing their catch. They will then use the boat’s hold to carry their bounty back to shore and throw the nets overboard so they don’t take up valuable space. Some fishers may also choose to abandon their gear when they have been fishing illegally (without a permit or in another country’s Exclusive Economic Zone or within a protected area) and want to avoid detection and potential prosecution (Gilman, 2015).
Ghost Town
Ghost gear can continue fishing for many years, indiscriminately killing many marine animals, including turtles, birds, fish, sharks, rays and dolphins. It is completely wasteful. If a trapped animal is lucky, and does manage to escape, they may still suffer sub-lethal effects, like lost mating and/or foraging opportunities. The stress and the injuries sustained may also eventually lead to their demise, as they suffer from infections or are too weak to evade predators (Matsuoka et al, 2005; Stelfox et al, 2016; Gilman, 2015).
Discarded gears can also damage the physical environment. The vast majority of ghost gear sinks to the bottom, where it can damage delicate structures. Nets can smother reefs and block vital refuge crevices in rocks. If it is accidentally dragged by currents or boats, lost gear can also scour and damage vital “benthic habitats” like seagrasses and corals. Lost equipment can also entrap sediments and alter water flows. It can even aid in the transport of “invasive species”; seriously disrupting local communities and even leading to localised extinctions (Gilman, 2015).
You might think that it is a massive relief when ghost fishing gear eventually breaks down as a result of wind and wave erosion, but that is not the case! Synthetic materials break down into microplastics, which can build up in animals’ digestive tracts and tissues, leading to blockages, starvation and even death. These plastics also degrade into harmful chemicals, which spread through the water. These toxins can build up in an animals system, causing illness, and can also disrupt hormone production and affect breeding (Andrady, 2015; Kühn et al, 2015).
Ghost fishing also causes major problems for fisheries managers. As the gear is indiscriminately killing without being monitored, it is very challenging to estimate which species and how many animals they kill. This means that stock assessments can be inaccurate, driving vital stocks to collapse, with devastating economic and social impacts (Matsuoka et al, 2005; Gilman, 2015).
Net Infested Waters
Sharks are particularly vulnerable to ghost fishing because they often bite objects in the water to investigate them (we call this “mouthing”) and curiosity of novel objects like nets may cause entanglement. Sharks and rays can become entangled in any marine litter, but reviews of the scientific literature show that of all shark and ray entanglements, 74% are in ghost fishing gears (Matsuoka et al, 2005; Stelfox et al, 2016; Parton et al, 2019).
Ghost fishing is indiscriminate, taking anything in its path, but particular species of “elasmobranchs” (sharks, skates and rays) are more susceptible to entanglement than others. Ghost fishing gear is more commonly found in oceanic environments (as opposed to near the coast), so “pelagic” shark species are more likely to encounter them. Sharks with an elongated body shape with protruding fins (like those of the Carcharhiniformes family) are also more likely to become trapped compared to those which are “dorso-ventrally flattened” (like rays and skates). Whatsmore, animals with appendages are more likely to get tangled. For example, the sawfishes (Family Pristidae) boast a magnificent toothed "rostrum" that sticks out of the front of their faces. This is very easily ensnared in fishing nets, which is one reason why these creatures have been driven so near to the brink of extinction (Stelfox et al, 2016; Parton et al, 2019).
Ghost Busters
Ghost fishing represents a significant threat to certain groups of sharks, many of which are already considered vulnerable to extinction, BUT, not only should we be concerned about the unnecessary losses this causes, but we need to recognise that ghost fishing is an animal welfare issue. Entanglement causes sharks (and other marine animals) considerable pain and distress, and if they do eventually die as a result, it is an extended, cruel death (Gilman, 2015; Stelfox et al, 2016).
We have been aware of the ghost fishing problem since the 1980s and in recent years the issue has received increasing political attention. Governments now know that we need better regulations for fishers, which are effective on an international scale. Thankfully, we are starting to see legislation come into place (Matsuoka et al, 2005; Gilman, 2015). For instance, the entire country of Belize has taken a huge stance on the issue - completely banning all gillnet fishing in their waters, to reduce their contribution to ghost fishing! To learn more you can head over to You’d Better Belize It.
The situation is bad, but we can always improve it! We just have to make the effort! We have a moral obligation to clean up the mess that we have created - ensuring that all fishing gear is responsibley removed from our oceans and that we have better systems in place to ensure that continued littering is kept to a minimum.
What can you do to help!?
If you would like to help, you can attend (or even organise your own!) beach clean-up effort.
If you don't have the time or energy for that, you can still become a part of the movement for ocean clean-up by joining 4ocean. They pull plastic from the ocean to save our marine life, including sharks.
Donate to clean-up charities.
Only buy seafood which is marked with a sustainability logo.
Why not even lobby your government!? A single internet search will expose who your local environmental minister is - write them a letter or an email to petition them to make changes!
References
Andrady AL (2015). Persistence of plastic litter in the oceans. In: Bergmann M, Gutow L & Klages M (Eds.). Marine Anthropogenic Litter. Springer, Cham Switzerland. pp 57-72. Access online.
Gilman E. (2015). Status of international monitoring and management of abandoned, lost and discarded fishing gear and ghost fishing. Marine Policy, 60, 225-239. Access online.
Kühn S, Bravo Rebolledo EL & van Franeker JA (2015). Deleterious effects of litter on marine life. In: Bergmann M, Gutow L & Klages M (Eds.). Marine Anthropogenic Litter. Springer, Cham Swutzerland. pp 75-72. Access online.
Matsuoka T, Nakashima T & Nagsawa N (2005). Review of ghost-fishing: Scientific approaches to evaluation and solution. Fisheries Science, 4:71, 691-702. Access online.
Parton KJ, Galloway TS & Godley BJ (2019). Global review of shark and ray entanglement in anthropogenic marine debris. Endangered Species Research, 39:4, 173-190. Access online.
Stelfox M, Hudgins J & Sweet M. (2016). A review of ghost gear entanglement amongst marine mammals, reptiles and elasmobranchs. Marine pollution bulletin, 111:1-2, 6-17. Access online.
By Sophie A. Maycock for SharkSpeak
