We will cover that in much more detail in a follow-up article. But the headline summary is that the status of wild fish stocks is mixed.
Effective management of fisheries across Europe, and North America means that many of these fish stocks are stable and no longer in decline.
That matters for where you source wild-caught fish from: sourcing from European or American fisheries might be a safer choice if you want to ensure they are sustainable.
The issue of wild fish stock depletion is not an issue for farmed seafood. As these fish tend to also have a low carbon and land footprint, farmed fish can be a low-impact source of protein. But dredging — sometimes referred to as bottom trawling — has the largest negative impact.
Bottom trawling drags a structure along the seabed — at various depths in the sediment depending on the specific method — to dislodge organisms such as crustaceans.
But it usually comes at an environmental cost. In this article we look at how much of the seafloor is trawled; what the consequences are; and what we can do to reduce its impacts. Improved satellite and GPS tracking technologies mean that scientists can now map trawling patterns at high-resolution. In a paper published in Nature , Enric Sala and colleagues estimate that around 5 million square kilometers km 2 of seabed is trawled each year.
The total ocean seabed spans million km 2. That means 37 million km 2 of seabed is within our scope. That is shown by the second bar. Our 5 million km 2 of trawled seabed — shown as the bottom bar — is therefore equal to around Many have compared this area to the Amazon Rainforest.
But we should be careful about using this comparison. Trawling does not have the same impacts as cutting down a primary rainforest. As we will soon see, trawling does kill a lot of life on the seabed, but recovery times can be very quick: in the order of a few months to years.
When we cut down primary rainforest we are locking ourselves into a recovery period of many decades. Maybe even longer. If that were true, within 5 years almost all of the shallow seabed would be trawled. The extent of trawling varies a lot from region-to-region. Others experienced a lot. One-quarter of the shelf in the Irish Sea was. You can see these rates by region here. Passing a trawl over the seabed can have quite a severe impact on the organisms that live there.
How much of the biota is affected depends on a couple of factors, including the type of gear used; the type of sediment; and what lifeforms live there. We might imagine that a coral that sticks out from the seabed will be flattened, while organisms deeper in the sediment might survive. Researchers have carried out studies to see what impact trawling has on wildlife — either through experimental methods, or observing real-world impacts.
We see that in the chart below, which shows the impact of four types: otter trawling; beam trawling; towed dregs; and hydraulic dredging. On the y-axis we have the share of organisms that are removed or killed by a single pass of a trawl over the seabed. On the x-axis we have the depth into the ocean sediment that the trawl reaches. What we see clearly is that the deeper the trawl digs into the sediment, the more biota we kill.
Otter trawls have the lowest impact: it digs just 2. Towed dredges dig twice as deep, and one-fifth of organisms are killed off. Once this area has been affected by trawling, how long does it take for its biodiversity to recover?
The differences here were dependent on the method used — the shallower otter trawls caused less damage and recovered more quickly than the deep hydraulic trawling — and the environmental context such as the type of seabed. This finding was consistent with previous studies, finding recovery to be in the range of years [ this study , for example, reports a year recovery time across multiple commercial trawling sites].
If we cut down the Amazon rainforest, it is decades if not centuries before it gets back to its previous state if it gets there at all. Thankfully these seabed communities recover orders of magnitude quicker.
But, of course, they do only recover if we leave them alone. Globally, bottom trawling rapidly increased through the second half of the 20th century. But it has not changed much since the s. We see this in the chart. We catch between 25 and 30 million tonnes each year. What has changed is where bottom trawling is happening. Trawling rates were very high across Europe in the s, 60 and 70s.
However, growing concern about the depletion of wild fish stocks has led to a significant reduction in recent decades, to allow populations to recover. The case of the UK, Portugal and Spain are shown in the chart. Bottom trawling has been growing elsewhere, though. It has been growing rapidly in China and India since the s.
Although these rates have stabilized — or even declined — in the last few years. Since most methods of trawling create environmental damage, you might suggest that the best option is to eliminate it completely. But in reality, it is still the most efficient method of catching seafood — which is why so many countries continue to use it.
We can limit the use of trawling and, in fact, many countries have. We just saw examples of this across Europe and Japan. But this will come at the cost of catch and income for communities that rely on it.
The types of gear used for trawling can have very different impacts. Some are much more damaging than others. One option is therefore to ban specific types of gear rather than banning the practice completely. Another option is to modify the types of gear used to limit their damage to the seabed.
For example, the doors on otter trawls are very destructive; newer designs now limit the amount of impact these doors have with the seafloor. In some cases, they eliminate this contact completely.
Finally, we can ban trawling in specific locations where the habitat is particularly sensitive. For example, not allowing trawling in areas with coral reefs, or important biodiverse habitat such as seagrasses. This would allow trawling activity to continue but would protect important areas of our ocean at the same time. Fish farming — also known as aquaculture — has boomed over the last 50 years. Production has increased more than fold. In fact, we now produce more seafood from aquaculture than we do from wild catch.
This has been good news for the health of global fish stocks. Global demand for seafood might have increased, but wild fish populations are finite. If we push beyond the limits of how quickly fish populations recover, this becomes unsustainable.
Aquaculture has therefore been an ingenious solution: rather than relying on wild fish, we can produce our own. Nearly all of the growth in seafood production in recent decades has come from aquaculture; wild fish catch has changed very little. But there has been one concern about the rise of aquaculture in relation to wild fish stocks. Like any type of animal farming, we need to feed them. Sometimes we feed them fishmeal and fish oils.
Not all aquaculture species are fed from animal sources, but many are. Many have questioned whether aquaculture is really the solution that it seems. If it is partly fed by wild fish, perhaps more fish farms means more pressure on wild fish stocks?
In this article I take us through the numbers to understand how much of wild fish catch really goes towards animal feed; how this is changing over time; and whether this undermines the benefits of aquaculture. In the chart we see the breakdown of global fish catch in In the second bar we see global aquaculture production. We produce around million tonnes of farmed seafood a year. We should be careful not to interpret this as the total input and output of feed for fish farming.
That would massively overstate the efficiency of fish farms. First, fishmeal is just one of many things that we need to fish, so there are other inputs. Second, many aquaculture species are not fed fishmeal or oils at all. But aquaculture production has grown quickly. If we want to understand how sustainable this is, we need to know how the use of fish for feed has changed over time. In the chart we see global fish catch since First, we see that global fish catch has been relatively stable since When we look at the breakdown we also see that the amount that is allocated to fishmeal and oil animal feed has also not changed much since It increased a lot from the s through to the s.
But since , it has actually declined. This decline is seen even more clearly in this chart, which shows the amount of wild fish used as animal feed in blue and aquaculture production in red. To produce one fish you needed several fish as feed inputs. This is for several reasons.
First, the feed conversion and efficiency of fish farms has improved. Meanwhile fish catch used for feed actually declined. If you have a FIFO greater than 1, you need more fish inputs than you get back from your fish farm. So a ratio of 2 means you need two fish equivalents of fishmeal and oil to be able to produce one fish in return. On the flip-side, a ratio of 0. In the chart here we see the FIFO ratio across all of the most common aquaculture species.
This shows the change in FIFO in the two decades from the red markers to blue markers. In , aquaculture used fish feed very inefficiently. The overall ratio was 1. This has improved massively in the decades since then. In this ratio was 0. The FIFO improved for all aquaculture species.
Today, this ratio for the most common species — carp, tilapia, and catfishes, shown at the top — is incredibly low. They use very tiny amounts of fishmeal as inputs. On the other hand, farmed salmon, trout, and eel still have unfavourable ratios. This has improved significantly in recent decades, but is still well above 1. Hopefully this ratio continues to fall. Overall, aquaculture is an important solution to meet growing demand for seafood. But with massive improvements in efficiency, it is now a net producer of seafood.
Fears that a growing aquaculture industry would put more and more pressure on wild fish stocks has not come true. When fishers go out to catch fish, it would be great if they only caught the fish that they needed. Unfortunately this is not the case. Fishers sometimes bring by-catch back to land, to eat or sell. But often they will throw these unwanted fish back into the water. The animals they throw back are called discards.
Discards can be dead or alive, but the survival rate is low. Some hardy shellfish might survive, but most discarded fish are dead. There are various reasons why fishers might not want these fish. They might be too small; inedible; damaged; or not give them a good return in the market. Fishers might also have strict quota restrictions on how much they can bring back each day.
Discards are obviously negative. Killing for no reason. Second, this is an issue that is often hidden from official statistics. Discards are not reported. Maintaining sustainable fish stocks relies on us understanding how quickly fish populations regenerate, and balancing this with how much fish we catch.
Hidden catches could tip this out-of-balance. Thankfully we are not completely blind. Marine scientists do reconstruct and estimate discards. The UN Fisheries Division also carries out periodic — around once every per decade — assessments to understand the magnitude of the problem. In , this was 8. We see this in the chart, which shows global fish catch since Researchers Dirk Zeller, Daniel Pauly, Maria Palomares, can reconstruct this data from estimates of how much discards are captured from different fishing methods.
Their web platform — Sea Around Us — is an excellent resource to understand global fisheries. The world caught around million tonnes of marine animals in The UN Fisheries Division did an independent assessment of discards and found a similar result.
That was The amount of fish we discard has declined a lot in recent decades. We see this in the other chart which plots discards since In the early s we were throwing around 5 million tonnes of fish away. This increased to 14 million tonnes in Since then, discards have fallen to around 8 or 9 million tonnes. This is back to levels in the late s.
Some fishing methods generate much more discards than others. Indeed, most discards come from large fisheries. Small-scale fisheries contribute very little. Researchers gather data on how much catch is discarded when different types of fishing gear are used. This gives us what is called the discard rate — what percentage of the total catch is thrown back into the water.
The average results across different fishing methods is shown in the chart. Unsurprisingly, bottom trawling has the highest discard rate. Some forms are even higher — half of catch from shrimp trawls is thrown back in. The fact that trawling tends to have a high discard rate, and it is the method used to catch a lot of our fish, means that around half of global fish discards come from bottom trawling.
There are no big winners when it comes to discards. Fish are killed needlessly; and the fact that these fish are not sold or eaten means that no one benefits from more income or food. Reducing discards is a good thing. As we saw earlier, discards have fallen since the s. Why have they declined, and can we learn to replicate it? One factor has been a rising market value of fish — even the species that fishers do not intend to catch. Fishers are therefore incentivized to bring more of their bycatch to land and sell it.
That means that even if bycatch did not decline, the amount of discards would. Some countries have implemented a no-discard policy — a ban on discards at sea. This policy is implemented by the European Union, and was a core part of its Common Fisheries Policy reform in If fishers have a quota or limit on how much fish they can catch, they have to be much more careful about by-catch — these unwanted fish will still count towards their quota for the day.
Improved gear has led to much more selective fishing practices. Over time, gear has been adapted to reduce by-catch. Many of the effective solutions to reduce discards relies on effective monitoring and enforcement of fishery policies.
This means that countries that have been successful so far tend to be those with strong fisheries policies. Eliminating by-catch completely might be unrealistic. But the fact that discards have been falling means that we can do something about it.
Marine protected areas MPAs are areas of ocean — which includes the water column and seafloor — that have been reserved by law or other effective means to protect part or all of the enclosed environment. Regulations in marine protected areas can vary but includes interventions such as no fishing zones; restrictions on fishing such as the type of gear that can be used; bans or restrictions on activities such as mining; and regulations on inputs to the ocean from rivers and industrial effluents.
The world has set long-term targets on the extent of marine protected areas. In the chart we see the amount in each zone that is protected and unprotected. As of , 7. In the charts here we see the share of territorial waters that are protected in each country. Fish production How much fish does the world produce? Methods of fishing What methods do we use to catch fish? Fish consumption and nutrition How much fish do people eat across the world?
Employment in fishing How many people are employed in fishing? Fish stocks and overfishing What does sustainable fishing mean? Environmental footprint of fishing What is the carbon, water, and pollution footprint of fish? Dredging and trawling How much of the seabed is trawled each year? Aquaculture fish farming How much fish feed comes from wild fish? Learn about our use of cookies, and collaboration with select social media and trusted analytics partners here Learn more about cookies, Opens in new tab.
Fish and shellfish are especially important in low-income areas where total protein intake is low and diets are less diversified. Fishing companies—businesses that catch fish or other seafood in the wild—will play a major role in sustaining food security and supporting fishing communities. But in their quest to capture enough fish to satisfy soaring demand, they are exerting unprecedented pressure on marine and freshwater ecosystems.
It now takes five times the effort in kilowatt-hours to catch the same amount of fish as it did in , because the targeted species are now in scarce supply. Yannick Rousseau et al. This shortage not only jeopardizes commercial prospects for fishing companies but also greatly threatens the ability of endangered ocean species to reproduce and maintain their numbers.
Balancing fishery interests with environmental concerns is not easy, but advanced analytics AA —the use of sophisticated methods to collect, process, and interpret big data—might represent an untapped solution to this problem.
While fishing companies, regulators, and environmentalists now apply these tools, their use is typically limited to small-scale pilots. But we may have reached the point where advanced analytics will take off within the fishing sector. In addition to the development of new technologies that support analytics in this field, both policy makers and fishing-company leaders have an increased sense of urgency because of dwindling fish stocks. Further, people entering the fishing industry or participating in regulatory development are more tech savvy than their predecessors, giving them a greater understanding of advanced analytics and other digital tools.
Even fishermen from emerging markets can access information on these technologies—and their benefits—through a simple smartphone search.
The growth of advanced analytics could promote the development of precision fishing—the use of advanced tools and technologies to optimize fishing operations and management. Christopher Costello et al. This article attempts to paint a picture of the current situation in the fishing industry, focusing on the challenges that are making it more urgent to adapt advanced analytics and associated tools.
It also discusses several of the most popular use cases that have emerged for advanced analytics, as well as others that show great potential. Finally, the article provides a practical guide to next steps for all industry stakeholders. The appetite for tuna, salmon, shrimp, and other ocean creatures is nothing new. Demand has increased an average of 3. Consumers also increasingly prefer healthy food choices, and many view fish as a good alternative to red meat.
As boats across the world search for a good haul, wild-fish capture has been slowly declining. Since the mids, the amount of wild fish processed has fallen by about 0. Aquaculture production comprises entities that breed, rear, and harvest all types of fish as well as other organisms that live in water.
To cope with the decreased catch in their traditional fishing grounds, commercial fishing companies have considerably expanded their footprint on the oceans. David Tickler et al. Thanks to technological improvements, fishing companies have also penetrated further depths to target deepwater animals such as grenadiers and blue lings.
Fishing these species is rarely sustainable because many have slow reproduction rates, which limits spawning and population growth. In the past, targeting such fish has often resulted in ecological disasters. In the s, for instance, the deep-sea orange roughy almost suffered extinction through overfishing until researchers discovered that it was slow growing and exceptionally late to mature. As fishing companies expand their reach, they are putting extreme pressure on the ocean environment.
This phenomenon is particularly apparent with large fish at the top of the food chain, including sharks, tuna, and billfish. Jonathan L. Payne et al. The loss of these apex predators has cascading effects that disrupt the equilibrium of ocean ecosystems. James A. Estes et al. Take the decline of some shark populations, which has been known to trigger sudden and undesirable population changes in species living in the same habitat.
The number of shellfish or herbivores might collapse, for instance, or a large algae bloom could develop. Other perils also loom. By , oceans could contain million metric tons of plastic—one per every three tons of fish—unless companies and other stakeholders institute some mitigation measures.
Jenna R. Jambeck et al. The accumulation of plastic debris may reduce the fish-survival rate, lowering stocks. Climate change, and its accompanying acidification, warming, and deoxygenation processes, is already affecting the oceans and will have profound implications for marine ecosystems, including reduced biodiversity and shifts in habitat. According to some scenarios, these shifts could decrease fishing revenues by 35 percent by Vicky W.
Lam et al. Recognizing the growing threat to fish stocks, some countries and regions have acted to improve resource management, with mixed results. Daniel Ricard et al. For instance, the United States has increased the proportion of stocks fished at biologically sustainable levels from 53 percent to 74 percent from through , an increase that may be partly attributed to the Magnuson-Stevens Fishery Conservation and Management Act.
Similarly, around 69 percent of stocks managed by the Australian Fisheries Management Authority were sustainably fished in But these regional gains are negated by overfishing in other markets, illegal fishing, and excessive waste.
Since regulations alone cannot eliminate overfishing, fisheries need other solutions to stay on a sustainable trajectory while minimizing their environmental impact.
For most issues, including catch reporting, trade-information sharing, subsidies, tariff policies, and regulation enforcement, greater national and international collaboration will help. But fisheries and the public could also benefit from the increased use of advanced analytics Exhibit 3. These algorithms have become popular across industries over the past few years as technological improvements have increased data availability, facilitated the deployment of information, and expanded data-ingestion capabilities.
Many industry stakeholders have already incorporated advanced analytics into all components of the value chain. Sensors for collecting data have become more common, compact, and less expensive over the past few years. At the same time, the variety of platforms on which these devices can be deployed has considerably expanded, allowing them to capture data more rapidly and over greater distances. Sensing platforms that are particularly important within the fishing industry include the following:.
Public organizations such as the National Oceanic and Atmospheric Administration and the Copernicus Marine Environment Monitoring Service have increased the effective usage of data obtained from satellite sensors by freely publishing them. Many start-ups and other companies also offer various products related to sensing platforms, including output from satellite sensors and data-collection systems designed for commercial fisheries.
The growth of the Internet of Things IoT , land- and satellite-based mobile networks, and smartphones makes it much easier for fisheries to transmit data from vessels for analysis.
For instance, vessels can use IoT to monitor and transmit data on fuel consumption in real time. The resulting data are then sent ashore through wireless mobile networks, including 3G and 4G, when close to shore.
At further distances, vessels rely on satellite networks for transmission. Computational power has increased substantially, making it easier to process and analyze information using sophisticated algorithms.
Across industries, some of the most important advances relate to the rise of artificial intelligence and machine learning, which can identify hidden relationships in large amounts of data. In particular, image-recognition and object-detection tools, powered by deep learning, have made a significant leap forward during the past decade. For instance, onboard cameras, assisted by image-recognition software, can provide fishermen with important information on the content of their catch in real time, including species, volume, and fish size.
Fishing-industry stakeholders are already transforming their operational and business processes by incorporating AA into all parts of the value chain, including fishery management, detection and capture, processing, reporting, and surveillance and control Exhibit 4. We have found that in some of the most important use cases involving AA and fishing, the following actions have been taken. Now we see that not only are there large differences in the median between each.
There are also large differences in how variable emissions can be. In general we tend to see that the impacts of farmed seafood are much less variable than wild-caught; the red bars are much thinner than the blue.
The median emissions for farmed and wild-caught salmon are similar; farmed has a slightly lower footprint of 5. But the big difference comes from the spread of emissions: wild-caught can range anywhere from 1.
Farmed salmon only ranges from 4. If you choose wild-caught salmon you could be picking a low-carbon, or a high-carbon protein source.
It might even be lower than farmed salmon. But if you pick farmed salmon you are almost guaranteed that it will be relatively low-carbon. We see this across other species too: see shrimp, for example. The same is true in our comparison to chicken.
Chicken has a very low variation in footprint. Some choices that will guarantee a relatively low footprint are farmed bivalves mussels, oysters and scallops and seaweed — these are filter-feeding organisms which also sequester carbon and nutrients in their shells.
That is partly why they have such low emissions; and they need no additional land either. Farmed salmon, trout, carp and catfish are also good choices.
Again, we should be clear that the most effective way to reduce the impact of your diet is to eat less animal-sourced products overall. On the basis of total protein and calories, plant-based foods such as legumes and soy still have a much lower impact. But for those who do not want to eliminate animal products completely, seafood can be a good choice.
Many types of seafood have a lower impact than chicken. This means they have a much lower impact than foods such as beef or lamb. The sustainability of wild fish stocks is not something that we discuss here, but is a crucial metric to consider. We will cover that in much more detail in a follow-up article. But the headline summary is that the status of wild fish stocks is mixed.
Effective management of fisheries across Europe, and North America means that many of these fish stocks are stable and no longer in decline.
That matters for where you source wild-caught fish from: sourcing from European or American fisheries might be a safer choice if you want to ensure they are sustainable. The issue of wild fish stock depletion is not an issue for farmed seafood.
As these fish tend to also have a low carbon and land footprint, farmed fish can be a low-impact source of protein. But dredging — sometimes referred to as bottom trawling — has the largest negative impact.
Bottom trawling drags a structure along the seabed — at various depths in the sediment depending on the specific method — to dislodge organisms such as crustaceans. But it usually comes at an environmental cost. In this article we look at how much of the seafloor is trawled; what the consequences are; and what we can do to reduce its impacts.
Improved satellite and GPS tracking technologies mean that scientists can now map trawling patterns at high-resolution. In a paper published in Nature , Enric Sala and colleagues estimate that around 5 million square kilometers km 2 of seabed is trawled each year.
The total ocean seabed spans million km 2. That means 37 million km 2 of seabed is within our scope. That is shown by the second bar. Our 5 million km 2 of trawled seabed — shown as the bottom bar — is therefore equal to around Many have compared this area to the Amazon Rainforest. But we should be careful about using this comparison. Trawling does not have the same impacts as cutting down a primary rainforest.
As we will soon see, trawling does kill a lot of life on the seabed, but recovery times can be very quick: in the order of a few months to years. When we cut down primary rainforest we are locking ourselves into a recovery period of many decades. Maybe even longer.
If that were true, within 5 years almost all of the shallow seabed would be trawled. The extent of trawling varies a lot from region-to-region. Others experienced a lot. One-quarter of the shelf in the Irish Sea was. You can see these rates by region here. Passing a trawl over the seabed can have quite a severe impact on the organisms that live there.
How much of the biota is affected depends on a couple of factors, including the type of gear used; the type of sediment; and what lifeforms live there.
We might imagine that a coral that sticks out from the seabed will be flattened, while organisms deeper in the sediment might survive. Researchers have carried out studies to see what impact trawling has on wildlife — either through experimental methods, or observing real-world impacts.
We see that in the chart below, which shows the impact of four types: otter trawling; beam trawling; towed dregs; and hydraulic dredging. On the y-axis we have the share of organisms that are removed or killed by a single pass of a trawl over the seabed. On the x-axis we have the depth into the ocean sediment that the trawl reaches. What we see clearly is that the deeper the trawl digs into the sediment, the more biota we kill.
Otter trawls have the lowest impact: it digs just 2. Towed dredges dig twice as deep, and one-fifth of organisms are killed off. Once this area has been affected by trawling, how long does it take for its biodiversity to recover? The differences here were dependent on the method used — the shallower otter trawls caused less damage and recovered more quickly than the deep hydraulic trawling — and the environmental context such as the type of seabed.
This finding was consistent with previous studies, finding recovery to be in the range of years [ this study , for example, reports a year recovery time across multiple commercial trawling sites]. If we cut down the Amazon rainforest, it is decades if not centuries before it gets back to its previous state if it gets there at all.
Thankfully these seabed communities recover orders of magnitude quicker. But, of course, they do only recover if we leave them alone. Globally, bottom trawling rapidly increased through the second half of the 20th century. But it has not changed much since the s.
We see this in the chart. We catch between 25 and 30 million tonnes each year. What has changed is where bottom trawling is happening. Trawling rates were very high across Europe in the s, 60 and 70s. However, growing concern about the depletion of wild fish stocks has led to a significant reduction in recent decades, to allow populations to recover.
The case of the UK, Portugal and Spain are shown in the chart. Bottom trawling has been growing elsewhere, though. It has been growing rapidly in China and India since the s. Although these rates have stabilized — or even declined — in the last few years. Since most methods of trawling create environmental damage, you might suggest that the best option is to eliminate it completely. But in reality, it is still the most efficient method of catching seafood — which is why so many countries continue to use it.
We can limit the use of trawling and, in fact, many countries have. We just saw examples of this across Europe and Japan. But this will come at the cost of catch and income for communities that rely on it. The types of gear used for trawling can have very different impacts. Some are much more damaging than others. One option is therefore to ban specific types of gear rather than banning the practice completely.
Another option is to modify the types of gear used to limit their damage to the seabed. For example, the doors on otter trawls are very destructive; newer designs now limit the amount of impact these doors have with the seafloor.
In some cases, they eliminate this contact completely. Finally, we can ban trawling in specific locations where the habitat is particularly sensitive. For example, not allowing trawling in areas with coral reefs, or important biodiverse habitat such as seagrasses. This would allow trawling activity to continue but would protect important areas of our ocean at the same time.
Fish farming — also known as aquaculture — has boomed over the last 50 years. Production has increased more than fold. In fact, we now produce more seafood from aquaculture than we do from wild catch. This has been good news for the health of global fish stocks. Global demand for seafood might have increased, but wild fish populations are finite.
If we push beyond the limits of how quickly fish populations recover, this becomes unsustainable. Aquaculture has therefore been an ingenious solution: rather than relying on wild fish, we can produce our own. Nearly all of the growth in seafood production in recent decades has come from aquaculture; wild fish catch has changed very little. But there has been one concern about the rise of aquaculture in relation to wild fish stocks. Like any type of animal farming, we need to feed them.
Sometimes we feed them fishmeal and fish oils. Not all aquaculture species are fed from animal sources, but many are. Many have questioned whether aquaculture is really the solution that it seems. If it is partly fed by wild fish, perhaps more fish farms means more pressure on wild fish stocks? In this article I take us through the numbers to understand how much of wild fish catch really goes towards animal feed; how this is changing over time; and whether this undermines the benefits of aquaculture.
In the chart we see the breakdown of global fish catch in In the second bar we see global aquaculture production. We produce around million tonnes of farmed seafood a year. We should be careful not to interpret this as the total input and output of feed for fish farming. That would massively overstate the efficiency of fish farms. First, fishmeal is just one of many things that we need to fish, so there are other inputs.
Second, many aquaculture species are not fed fishmeal or oils at all. But aquaculture production has grown quickly. If we want to understand how sustainable this is, we need to know how the use of fish for feed has changed over time. In the chart we see global fish catch since First, we see that global fish catch has been relatively stable since When we look at the breakdown we also see that the amount that is allocated to fishmeal and oil animal feed has also not changed much since It increased a lot from the s through to the s.
But since , it has actually declined. This decline is seen even more clearly in this chart, which shows the amount of wild fish used as animal feed in blue and aquaculture production in red. To produce one fish you needed several fish as feed inputs. This is for several reasons. First, the feed conversion and efficiency of fish farms has improved.
Meanwhile fish catch used for feed actually declined. If you have a FIFO greater than 1, you need more fish inputs than you get back from your fish farm. So a ratio of 2 means you need two fish equivalents of fishmeal and oil to be able to produce one fish in return.
On the flip-side, a ratio of 0. In the chart here we see the FIFO ratio across all of the most common aquaculture species. This shows the change in FIFO in the two decades from the red markers to blue markers. In , aquaculture used fish feed very inefficiently. The overall ratio was 1. This has improved massively in the decades since then. In this ratio was 0. The FIFO improved for all aquaculture species. Today, this ratio for the most common species — carp, tilapia, and catfishes, shown at the top — is incredibly low.
They use very tiny amounts of fishmeal as inputs. On the other hand, farmed salmon, trout, and eel still have unfavourable ratios. This has improved significantly in recent decades, but is still well above 1. Hopefully this ratio continues to fall. Overall, aquaculture is an important solution to meet growing demand for seafood. But with massive improvements in efficiency, it is now a net producer of seafood. Fears that a growing aquaculture industry would put more and more pressure on wild fish stocks has not come true.
When fishers go out to catch fish, it would be great if they only caught the fish that they needed. Unfortunately this is not the case. Fishers sometimes bring by-catch back to land, to eat or sell. But often they will throw these unwanted fish back into the water.
The animals they throw back are called discards. Discards can be dead or alive, but the survival rate is low. Some hardy shellfish might survive, but most discarded fish are dead. There are various reasons why fishers might not want these fish.
They might be too small; inedible; damaged; or not give them a good return in the market. Fishers might also have strict quota restrictions on how much they can bring back each day.
Discards are obviously negative. Killing for no reason. Second, this is an issue that is often hidden from official statistics. Discards are not reported. Maintaining sustainable fish stocks relies on us understanding how quickly fish populations regenerate, and balancing this with how much fish we catch. Hidden catches could tip this out-of-balance.
Thankfully we are not completely blind. Marine scientists do reconstruct and estimate discards. The UN Fisheries Division also carries out periodic — around once every per decade — assessments to understand the magnitude of the problem.
In , this was 8. We see this in the chart, which shows global fish catch since Researchers Dirk Zeller, Daniel Pauly, Maria Palomares, can reconstruct this data from estimates of how much discards are captured from different fishing methods.
Their web platform — Sea Around Us — is an excellent resource to understand global fisheries. The world caught around million tonnes of marine animals in The UN Fisheries Division did an independent assessment of discards and found a similar result.
That was The amount of fish we discard has declined a lot in recent decades. We see this in the other chart which plots discards since In the early s we were throwing around 5 million tonnes of fish away. This increased to 14 million tonnes in Since then, discards have fallen to around 8 or 9 million tonnes.
This is back to levels in the late s. Some fishing methods generate much more discards than others. Indeed, most discards come from large fisheries. Small-scale fisheries contribute very little. Researchers gather data on how much catch is discarded when different types of fishing gear are used.
This gives us what is called the discard rate — what percentage of the total catch is thrown back into the water. The average results across different fishing methods is shown in the chart. Unsurprisingly, bottom trawling has the highest discard rate. Some forms are even higher — half of catch from shrimp trawls is thrown back in. The fact that trawling tends to have a high discard rate, and it is the method used to catch a lot of our fish, means that around half of global fish discards come from bottom trawling.
There are no big winners when it comes to discards. Fish are killed needlessly; and the fact that these fish are not sold or eaten means that no one benefits from more income or food. Reducing discards is a good thing. As we saw earlier, discards have fallen since the s. Why have they declined, and can we learn to replicate it? One factor has been a rising market value of fish — even the species that fishers do not intend to catch.
Fishers are therefore incentivized to bring more of their bycatch to land and sell it. That means that even if bycatch did not decline, the amount of discards would. Some countries have implemented a no-discard policy — a ban on discards at sea. This policy is implemented by the European Union, and was a core part of its Common Fisheries Policy reform in
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