Scientific surveys have periodically monitored stocks in the Gulf of Thailand for decades. They show a large reduction in fish stocks over time.
Other surveys of trawling efforts across the region show similar declines. Ask local experts about the state of fish stocks and most have a similar take: they are in poor condition. Some will be well-managed and healthy. It so happens that these tend to be richer countries: those across Europe, North America, Australia and Japan. This database covers over 1, of these fish stocks. In the chart we see how these stocks are doing.
It shows the biomass of fish populations. That is, essentially, the amount of wild fish there. The Maximum Sustainable Yield is the sweet-spot where we can catch as much fish as possible without reducing that fish population below the most productive level. Fish stocks are healthy across most of these regions. However, there are a few regions that are not doing so well. The Canadian East Coast has seen a large decline in recent years.
Assessed stocks in South America and Africa are struggling. The European Mediterranean is not doing well. This is reflected in the fact that the Black Sea is very overfished. Whether a fish stock is doing well or not is mainly determined by its fishing intensity: what fraction of the population is being caught each year.
In this chart we see levels of fishing intensity across the same regions. An optimal value is one. Fish stocks tend to be a lagging indicator to fishing intensity. So, if we hold fishing intensity too high above one — even if only slightly — then stocks will inevitably fall below one until fishing pressures are reduced. In the chart we see the same metric as before — fish stocks measured by biomass — across different types. Many of our most popular stocks are well-managed and have healthy populations.
A few groups are not faring so well. In recent years mackerels have dropped below the optimal level due to increased fishing intensity. And sharks are declining rapidly — a worrying trend.
The health of tuna populations has been a concern for decades. We often hear that tuna are being overfished to extinction. That we should avoid them if we want to eat sustainably. But many tuna populations are now well-managed. Previously we looked at the aggregate of tuna stocks; we can zoom in further and look at particular regional stocks. In the chart we see the health of fish stocks across three oceans: the Atlantic, Pacific and Indian Ocean.
The trend looks worse for those in the Indian Ocean. Its stocks have now fallen below one, and look to be continuing downwards. Atlantic and Pacific tuna might be a reasonable fish choice. Tuna from the Indian Ocean has less guarantee of being from a sustainable source.
But we can go even further and look at specific tuna species, such as bluefin or yellowfin. We see these stocks in the chart. Many tuna species have seen a significant recovery through improved management — especially in US and European waters. From the chart we see that most are above one: the maximum sustainable yield. Many of the tuna stocks that were the biggest concern have managed to turn things around. We see this in this chart, which now shows fish stocks measured as their total mass in tonnes , rather than relative to the maximum sustainable yield.
Throughout the s, 70s, 80s, and 90s we see a massive decline in tuna populations. The Western Pacific yellowfin fell by three-quarters. But, since the millennium, better management of fisheries and reduced overfishing means that many of these stocks are recovering. However, there are a few species that are still of concern. This is a positive sign. They are recovering but still need more time to return to sustainable levels. We saw previously that shark stocks were now below the maximum sustainable yield, and continue to decline.
We see this again in the chart here. Many more stocks have not been assessed — and these are likely to be in regions where monitoring is poor; and illegal catch is poorly regulated. There, shark populations might be in even poorer health. For general readers, this might be too detailed. But it could be useful for those with a background in this area to explore specific fish stocks.
One of the best ways to reduce our impact on the environment is changing what we eat. The research shows us that we can have the biggest impact by eating less meat and dairy. Or, substituting lower-impact meats such as chicken and pork for beef and lamb. Is that an environmentally-friendly option?
There are lots of types of seafood: not only different species, but also ways of producing them. We can catch them in the wild, or grow them in fish farms.
In a new study published in Nature , Jessica Gephart and colleagues conducted a meta-analysis of the impacts of fish and seafood across multiple environmental metrics. It covered over fish farms, and records from fisheries. These results look at the impacts on-farm and off-farm, up to the farmgate. That means, up to the point that harvested or caught fish are brought back to land.
It includes all of the inputs into production, such as fish feed, or fuel use on fisheries. It does not include post-farm processes such as transport to retail, packaging or cooking.
The impacts across the seafood products are shown in the charts. Comparing fish to other types of fish is useful. But we also want to know how seafood compares to other protein foods. Overall we see that seafood has a relatively low environmental impact among animal protein sources. Most farmed seafood needs less land and freshwater, and causes less nitrogen and phosphorus pollution. This is because fish tend to be more efficient than chickens in converting feed into meat: that means they need less feed per kilogram.
There are some exceptions though: wild flounders, lobsters, and shrimp, for example, can have a high carbon footprint. More than double that of chicken. Looking at the median footprints allow us to make quick, general assessments of the high- and lowest-impact species.
This makes little difference for some species, but for others it can have a large impact. In the chart we see the spread of greenhouse gas emissions among the different types of seafood.
The median of each — as we looked at above — is shown as the thick black line for each bar. The width of the bar shows us how variable this can be: it tells us what the largest and smallest impact can be for each species.
Wild-caught seafood is shown in blue; farmed seafood in red. 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. Supplementary notes. Other statistics on the topic.
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Single Account. The ideal entry-level account for individual users. Corporate solution including all features. Other divisions — based on large-scale marine ecosystems, for example — might appear to make more sense today. The 19 regions are in turn divided into three categories.
The first comprises areas where the catches have been fluctuating since The second consists of areas where catches have fallen over the years, and the third category covers areas where catches have continuously increased. Here again the FAO bases its analysis on the roughly fish stocks for which reliable stock calculations are available.
However, four of the 19 areas — the Arctic and the three Antarctic areas — are not considered in more detail below, either because there is little fishing in these regions or because few of the stocks are exploited for commercial purposes. In the past five years these areas provided, on average, 52 per cent of the total global catch volume. The most important area today is the Northwest Pacific.
Small pelagic fish such as the Japanese anchovy make up the largest proportion of the total catch. The Eastern Central Pacific and the Southeast Pacific are also prolific due to the nutrient-rich upwelling areas off the coast of South America. Catches are prone to huge fluctuations, sometimes from one year to the next. One reason for this is the large numbers of small schooling fish sardines and anchovies , stocks of which rely heavily on the current in the upwelling areas.
Nutrient-rich water rises to the surface from the depths, stimulating the growth and reproduction of the plankton on which fish feed. When the current weakens due to climatic fluctuations, there is less plankton and thus less food for the fish.
Compared with the general situation of world fish stocks, things are looking particularly grim in the Eastern Central Atlantic: 53 per cent of stocks in this area are considered overexploited, 43 per cent fully exploited and only 4 per cent non-fully exploited — off the coast of Senegal for example. The sardine Sardina pilchardus is the dominant species here. The Southwest Atlantic is also under heavy pressure. Important fish species are the Argentine hake and the anchovy off Brazil.
Both are thought to be overfished. However, according to experts, the latter appears to be recovering. In this area, 50 per cent of stocks are considered overexploited, 41 per cent fully exploited and 9 per cent non-fully exploited. The annual catch peaked here in the s. The largest proportion of the catch is made up of Alaska pollack, cod and hake.
Today 80 per cent of the stocks in this region are considered fully exploited and 10 per cent each are over-exploited and non-fully exploited. In some areas reduced catches were a result of fisheries management regulations, and stocks are expected to recover here. If the annual statistics indicate diminished catch volumes, this does not always mean that a stock is being depleted or has been overfished. In the Northeast Atlantic, for instance, the pressure on cod, plaice and sole has been reduced.
Management plans are in place for the most important stocks of these species. Fortunately the spawning stocks of the Northeast Arctic cod have increased again here — particularly in Apparently the stocks have recovered following the low levels of the s to s. The future is looking a little brighter for the Northeast Arctic pollack and the Northeast Arctic haddock, but other stocks of these species continue to be overexploited in some regions of the Northeast Atlantic.
Catches of blue whiting have decreased dramatically — from 2. This decline can be ascribed to the fisheries reacting too slowly to a sudden change in reproduction. Between the years of and the blue whiting for unknown reasons produced masses of young. During this period the species was fished intensively. But following a sudden drop in reproduction rates after , the fishing industry continued to exploit the species at the same rate as before. The marked reduction of catch volumes in recent years, however, has helped the stocks to regenerate.
In a harvest of almost , tonnes is expected. The situation of some deep-sea fish species is critical. All in all, 62 per cent of the stocks assessed in the Northeast Atlantic are fully exploited, 31 per cent overexploited and 7 per cent non-fully exploited.
Fish stocks also remain in a poor condition in the Northwest Atlantic. Cod and ocean perch, for example, have not yet recovered from the intensive fishing of the s, despite the Canadian authorities having completely banned the commercial fishing of these species. Experts ascribe the situation to adverse environmental conditions and competition for food Chapter 1.
Other stocks which are protected by fisheries management regimes appear to be regenerating. These include the spiny dogfish, the yellowtail flounder, the Atlantic halibut, the Greenland halibut and the haddock. Stocks in the Northwest Atlantic are considered 77 per cent fully exploited, 17 per cent over-exploited and 6 per cent non-fully exploited. Catch volumes in the Southeast Atlantic have declined considerably since the s, from a previous 3.
This can be ascribed partially to overfishing, and partially to catch reductions as a result of sustainable fisheries management. This applies in particular to the hake which is particularly important in this area. Thanks to the fishery measures introduced in , some stocks of hake such as the deep sea Merluccius paradoxus off South Africa and the shallow water Merluccius capensis off Namibia appear to be recovering. In contrast, stocks of the formerly prolific South African sardine appear to be overexploited following a phase of intensive fishing.
In the stock was classified as fully exploited. In the years since then, however, it has declined again as a result of adverse environmental conditions. This example highlights the speed at which a fully exploited stock can become overexploited, and the importance of forward-looking and sustainable fisheries management plans.
The condition of the mackerel off the coast of Angola and Namibia has also deteriorated, since being considered overexploited. Similarly, its situation is not particularly good. Of the stocks analyzed by the FAO, 50 per cent are overexploited, 33 per cent fully exploited and 17 per cent non-fully exploited. All stocks of the European hake Merluccius merluccius and the red mullet Mullus barbatus are classified as overexploited. Too little information is available about the condition of the sea breams and sole to categorize, but these are also suspected to be overexploited.
The most significant stocks of small pelagic fish sardines and anchovies are considered fully exploited or overexploited. Areas with increasing catches In only three of the FAO major fishing areas have catches been continuously increasing since the s.
Catch volumes in the Western Central Pacific have constantly increased since to a peak of The situation has changed in the meantime, however, and stocks are now in a critical condition. Most are assessed as fully exploited and overexploited — particularly in the western regions of the South China Sea.
But the FAO points out that the high catch numbers could be misleading. It is assumed that fish were counted twice during transportation. For this reason it is conceivable that flawed data is masking an actual trend reversal — i.
The annual catch in the Eastern Indian Ocean has also escalated over the years, and this trend is continuing. Between and alone, the catch volume increased by 17 per cent. In the Bay of Bengal and the Andaman Sea catch volumes are steadily increasing. This practice gives cause for concern because it is then impossible to assess the stocks of the different fish species in this heavily exploited region. Even when the total catch is increasing in one particular area, the trend for stocks of individual sub-areas can be the exact opposite.
As far as the protection of fish stocks goes, Australia and New Zealand are now regarded as models of best practice. The trigger was a ministerial decision which ended overfishing in the EEZ and made it possible for stocks to recover. The Western Indian Ocean has long been considered an area in which the catches have increased appreciably.
A temporary peak was reached in Since then, catch volumes have slightly decreased. The volume for was 4. Current investigations show that the widespread Narrow-barred Spanish mackerel Scomberomorus commerson found in the Red Sea, the Persian Gulf, the Gulf of Oman and off India and Pakistan, is overfished. Catch figures from these areas are incomplete, making it difficult to estimate the population.
Attempts are being made to gather valid data in other regions. The Southwest Indian Ocean Fisheries Commission responsible for the southwestern sub-area of the Western Indian Ocean carried out a systematic estimate of species in Overall, 65 per cent of the stocks in the Western Indian Ocean are fully exploited, 29 per cent overexploited and 6 per cent non-fully exploited.
Alien species add to the pressure Already weakened fish stocks in some maritime regions are faced with the additional threat of alien species. Predators which feed on the fish, eggs and larvae of weakened stocks are particularly problematic, and competitors for food can play further havoc with depleted stocks.
The situation becomes critical when the alien species thrives under its new living conditions and begins to reproduce vigorously. For example, alien species migrate from the Red Sea and through the Suez Canal into the Mediterranean. Some of them are apparently supplanting the native species of the eastern Mediterranean.
The anchovy and sprat stocks of the Black Sea collapsed in the s. This was due partly to overexploitation and partly to a type of fist-sized comb jellyfish introduced in the ballast water from ship tanks further undermining the already low fish stocks. The swarms of jellyfish ate the fish eggs and larvae en masse, biologists believe. Stocks have still not fully recovered. They are considered either fully exploited or still overexploited. A closer look at the different species Taking a closer look at the individual fishing areas of the world, it becomes clear that there is no simple response to the question of how the fish are faring.
Without doubt many stocks are overexploited or have collapsed. But others are recovering thanks to sustainable fisheries management regimes. By way of illustration, the following section describes some individual fish species and their status — including the most important species with the highest total catch volumes. Most of their stocks are considered fully exploited or overexploited. Tins of tuna generally contain the flesh of widespread species such as the skipjack tuna.
Nonetheless, consumers should ensure that the products they buy are from sustainable fisheries. The Peruvian anchovy — sometimes more, sometimes less The development of the Peruvian anchovy Engraulis ringens is interesting. In terms of catch, it is the most important fish in the world.
Large amounts are processed into fishmeal and fish oil to be fed to larger farmed fish in aquaculture operations. The largest volume ever caught, around 13 million tonnes, was landed in Today this would equate to a quarter of the global fish catch — excluding catches of other marine fauna such as mussels and squid. The stocks later recovered. A new annual record of This anchovy example clearly shows the extent to which stocks can fluctuate.
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