The Five Threats
How does overfishing affect sharks and rays?
When fishermen catch fish, there are inevitably fewer fish left in the sea. If it weren’t for the ability of fish to reproduce relatively quickly, fishermen would simply ‘mine down’ the resource and there would be nothing left. But fishing has been sustained for many millennia because fish can reproduce and recover their numbers. This source of potentially endless protein is what makes our fish stocks one of our most valuable renewable resources.
How overfishing affects sharks & rays
The rate at which fish reproduce varies and thus so does the rate at which they can be fished sustainably. Some – like sharks and rays – reproduce more slowly than others, making them more vulnerable to fishing pressure. If we kill sharks more quickly than they reproduce, we are overfishing; their numbers will dwindle and we won’t be able to catch many sharks in the future. Overfishing is a problem for both sharks and us.
Sharks and rays are generally subjected to ubiquitous and relentless fishing pressure – a pressure so great that it’s the leading threat to these animals. Sharks are caught in directed fisheries, where fishermen aim to catch them for their meat, fins, liver oil, skin (for leather), cartilage (for medicine) and teeth and jaws (for curios). They are also taken as incidental by-catch, when fishermen target other species like tuna and swordfish but accidentally end up with a shark in their net or on their line. Because sharks are a valuable catch, fishermen often keep them. Yet even if they return a shark to the sea, it is often so traumatised that it dies shortly afterwards. Finning – the practice of removing a shark’s fins and throwing the rest of the fish back into the ocean – contributes to the problem of overfishing and is now illegal in most countries. It’s a cruel and wasteful practice that is driven by the demand for shark-fin soup.
Scientists estimate that each year 100 million sharks are removed from our oceans and much of this haul is illegal, unreported and unregulated. The fishing pressure on sharks, combined with their slow rate of reproduction, means that they are being overfished. The solution would seem simple: reduce the number of sharks and rays we kill.
But a major obstacle to conservation efforts is our limited understanding of sharks. We simply don’t properly understand their behaviour, breeding habits or migration patterns. For most shark species, we don’t even know how many of them there are! Without this basic knowledge, we can’t accurately calculate fishing limits and develop other effective conservation measures to conserve them. That’s why the Save Our Seas Foundation funds the basic research into sharks that is so desperately needed.
Frequently asked questions about the overfishing of sharks and rays:
What is overfishing?
Fishing is the practice of catching wild fish from fresh or salt water and humans have been doing it for a long time. For centuries, people around the world have relied on fish as a source of food and nutrition – and they still do. Catching fish is not necessarily bad for the marine environment, but it becomes a problem when we do it unsustainably.
Overfishing occurs when we take too many fish and too fast. Fish are a ‘renewable’ resource in that they reproduce and so constantly replenish their own populations, so in theory if some members of the population are lost, they will be replaced by new offspring. But if we harvest fish at such a rate that individuals are removed more quickly than they can be replaced, the balance between gains and losses is skewed. The population of that species in the place where it is being fished – known in commercial terms as a ‘stock’ – will begin to fall. If the stock is not given time to recover, it can collapse and eventually become completely depleted, which can then impact the global population.
Overfishing only really became a problem in the last century, as large-scale, industrial fishing methods boomed to meet the burgeoning demand of a rapidly growing human population. It is estimated that between 1990 and 2018 alone, global fish consumption rose by 122%. This demand has seen the development of more intensive fishing methods, including trawling, long-lines and gill nets. It has also had severe consequences for marine life: the percentage of fish stocks considered biologically sustainable has dropped from 90% to 65.8% over the past 30 years. And today, 90% of our fish stocks are said to be overfished or at capacity – meaning they are close to reaching the maximum level at which they can be harvested before collapsing.
What are the causes of overfishing in sharks and rays?
While we may associate fishing with bony fish like salmon and cod, there are shark and ray (elasmobranchs) fisheries around the world. These species are directly targeted for numerous reasons. Sharks’ meat is an increasingly popular source of protein that is sold in the USA, Europe, Japan and Australia. Their skin is made into leather and their teeth are sold as trinkets or curios. Oil from their liver (squalene) is used in cosmetics and pharmaceuticals and their cartilage in medicine. In particular, the shark-fin trade is a major driver of overexploitation. Fins are highly valuable in the global market for their use in shark-fin soup. Rising demand for these products has led to an 18-fold increase in fishing pressure, which has been linked to a 71% decline in the global abundance of oceanic sharks and rays. Long-line nets pose the biggest threat, as they catch the greatest number of sharks annually (WWF, 2021a). These are extremely long nets with hundreds or even thousands of baited hooks set at intervals to attract the target species. They are commonly used in the fin trade, but are also notorious for capturing sharks by accident, as ‘by-catch’.
As well as being targeted directly, sharks are also fished indirectly as by-catch. This term refers to non-target marine life that is caught – either by neglect or by accident – in nets made for other commercially fished species. These unwanted animals are either thrown back into the sea (where they commonly die due to trauma) or are killed on board. Because sharks tend to be valuable species, fishermen often keep them to sell. In addition, sharks are threatened by the habitat destruction that follows intensive fishing methods such as bottom trawling, which is essentially like taking a huge plough to the seabed. The loss of vital habitats, like coral reefs, reduces the amount of vital prey species for predatory sharks.
So, while only some species are fished commercially, many more suffer the effects of overfishing in indirect ways.
Why should we worry about the overfishing of sharks and rays?
Recent studies suggest that three-quarters of oceanic shark and ray species are threatened with extinction, with overfishing as the primary cause. Elasmobranchs are particularly vulnerable to exploitation; they are typically long-lived and slow to reproduce and they have fewer pups per litter. This means it takes a long time for the individuals that have been caught to be replaced – much longer than relatively short-lived, fast-reproducing species like mackerel.
But does this matter? Are sharks important? The answers to these questions are complicated, but the short answer is: yes.
Marine food webs are highly complex, so it can be difficult to predict what will happen if some shark species disappear. But many of the shark species targeted are apex predators, which means they are at the ‘top’ of the food chain and play a key role in how an ecosystem operates. If they are removed it can have a cascade-like effect across the whole marine ecosystem; the very function of the ecosystem can change. This can carry implications for some of our most important marine systems. For example, scientists at the Scripps Institution of Oceanography (USA) and the Integrative Ecology Group (Spain) found that predatory sharks play a vital role in the health of coral reefs in the Caribbean. Without them, the number of grouper fish – a prey species of Caribbean sharks – has exploded. Groupers prey on parrotfish, a species that clears coral of a harmful type of algae, and this could explain why Caribbean coral reefs are now degraded. Other studies also support the critical part that sharks play in ecosystem health, but there are many more species whose role we do not quite understand. Research into this area is therefore crucial.
Aside from ecological impacts, losing sharks and rays could have severe consequences for coastal communities, with a disproportionate impact in low-income and developing countries and island nations. Many of these communities have fished for sharks over generations and these fish remain a vital source of protein and nutrition, as well as employment.
What is being done about overfishing?
Since the late 1980s, when the collapse of global fish stocks became only too apparent, a number of conservation measures have been put in place to prevent overfishing. Several nations have signed international treaties, like the EU common fisheries policy and the Paris Agreement, to voice their commitment to the sustainable use of our oceans. Fisheries are also encouraged to stick to certain quotas – set limits defined by the maximum number of fish that can be taken before the stock begins to decline – and to cease fishing for specific periods of time and in designated areas, known as ‘no-fishing’ or ‘no-take’ zones, to allow stocks to recover. There have also been a number of improvements in fishing gear and techniques to reduce by-catch.
But these measures aren’t working. The existing regulations are often not strong enough and in the overwhelming majority of countries are not effectively enforced. The problem with our oceans is that they are notoriously difficult to police. Illegal, unreported and unregulated (IUU) fishing is pervasive and is estimated to account for 30% of the total global catch for high-value species. This is exacerbated by government subsidies (financial support given to the fishing industry). Experts suggest that 85% of subsidies go to large-scale fishing fleets and perpetuate IUU by encouraging the industry to take more than we actually need.
What should be done to stop overfishing?
There is no clear or easy answer to the problem of overfishing. The simplest solution is also the hardest: to shut down fisheries. Although this may have an immediate effect, it would result in economic devastation for coastal livelihoods. Fisheries are a major source of employment; in 2018 it was estimated that 200 million jobs are connected with the fisheries sector, 54% of which are based in developing nations.
We can start by having stricter regulations – based on precautionary, science-based knowledge – and more effective enforcement. The elimination of the subsidies that contribute to IUU fishing and overfishing could also be a big stepping-stone, alongside substantial penalties for countries that do not adhere to international law. As marine life does not typically stay within regional borders, these measures only work if everyone is on the same page. Additionally, more protected areas with tighter regulations are desperately needed. Currently only 1.5% of our oceans is protected and in many of the protected areas fishing is still allowed.
But that is just the tip of the iceberg. Solutions can’t only be ‘top-down’; we must also support sustainable fisheries at a community level. Ninety per cent of the world’s fishermen and fisherwomen are in small-scale fisheries, but they account for just 30% of the global catch. Eliminating harmful subsidies would free up funding to invest in developing sustainable livelihoods for coastal communities and the creation of alternative sources of income. Education about the detrimental effects of overfishing – present and future – is also crucial in encouraging producers and consumers to make more sustainable choices.
Is aquaculture the solution to overfishing?
Aquaculture is the practice of breeding and farming fish for food rather than taking them from wild populations. It has been touted as the solution to overfishing and has dramatically increased around the globe, employing millions of people. However, environmental and animal welfare concerns have been raised regarding the intensive nature of industrial aquaculture. Research is being conducted to raise standards – perhaps once we learn more, aquaculture will become a viable alternative.
What can I do about overfishing?
There are a few small changes we can all make at home. Firstly, be conscious of your shopping choices. If you are buying fish, check the label (or ask your fishmonger) if it has been sustainably sourced and caught using ‘shark-friendly’, less damaging methods such as pole and line, hook and rod, and fish traps. Avoid fish caught using trawling methods, gill-netting, long-lines, purse-seine nets and blast or cyanide fishing. These methods are unselective, environmentally damaging and intensive. Shop locally where you can and support small-scale artisanal fisheries. Also, be careful of cosmetics. Squalene is a popular component of many products, but check the label to see whether it comes from shark liver oil or from plants. The latter is a better choice. If you are unsure, consider putting that product back on the shelf.
We can also use our voices for change. There are so many conservation organisations and campaigns you can get behind – just like the Save Our Seas Foundation! Communicate the dangers of overfishing on social media and help support projects that are working towards more sustainable fisheries – whether that be through a financial donation or by sharing the word. Finally, you can write to your government and ask it to commit to tackling overfishing and conserving our oceans. Your voice really matters and you can make a big difference!
Food and Agriculture Organization of the United Nations, 2020. The state of fisheries aquaculture 2020’ Interactive story, FAO.org.
World Wildlife Fund, 2021a. Species-Shark, worldwildlife.org
Dulvy et al., 2017. ‘Challenges and priorities in shark and ray conservation’, ScienceDirect.
Pacoureau et al., 2021. ‘Half a century of global decline in oceanic sharks and rays’, Nature.
J Bascompte et al., 2005. ‘Interaction strength combinations and the overfishing of a marine food web’, Pnas.org.
World Wildlife Fund, 2021b. Threats – Overfishing’, Worldwildlife.org