Seafood when do we

The most widely-eaten fish include salmon, tuna, snapper, mackerel, cod, trout, carp, catfish and sardines. Most of these are caught in the sea or in lakes and rivers, but edible fish are also raised in ponds. In Chinese aquaculture , fish like the grass carp have been raised for nearly four thousand years, but the first known example of aquaculture is a complex of ponds and canals built by the Gunditjmara people of Australia over eight thousand years ago to farm eel , a long, thin, snake-like fish that's still eaten today.

Many other sea creatures can also be eaten, including some with an outer shell you have to remove before getting to the soft flesh inside. This type of seafood includes lobsters , crabs, crayfish , prawns and shrimp, a smaller relative of the prawn. 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.

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. Use your eyes, hands, and nose when selecting fresh fish or shellfish. Your purchase should feel cold to the touch. Be aware of temperatures—of the air, of your refrigerator and freezer, of cooking. Keep foods out of the danger zone 40 degrees F- degrees F.

Be aware of time—limit how long the fish and shellfish are refrigerated. Finally, to help keep your seafood safe, keep it clean, keep it cool, and keep it moving! By abiding by these rules and adopting the following guidelines, you can be confident that your efforts and the HACCP program are working together to keep seafood safe.

The storage life of seafood depends on how well you take care of it, whether a whole fish or a live oyster. When your seafood purchase arrives home, store it immediately in your refrigerator or bury it in ice. When purchasing fresh-frozen seafood, place it in the freezer immediately. The shelf life of fish depends on the variety and its quality at the time of purchase.

In general, you should use fish quickly—within one to two days. Buy live shellfish from reputable dealers, or ask to see the certification tags that indicated the shellfish were harvested from safe waters. Store live shellfish, such as oysters and mussels in the shell, in a shallow dish covered with damp towels or moistened paper towels.

Never put live shellfish in water or in an airtight container. Scrub shells with a stiff brush just prior to shucking or cooking. Mussels live in the shell should be used within two to three days; clams and oysters in the shell, within seven to ten days.

If some shells open during storage, tap them. They will close if alive; if not, discard them. Store shrimp, squid, and shucked shellfish in a leak-proof bag or container. Squid and freshly shucked clams have a shelf life of one to two days. Finfish should be stored in the refrigerator and used within 1 to 2 days after purchase. Shellfish , such as mussels, clams and oysters that are purchased live in their shells, should be put in a shallow pan no water , covered with moistened paper towels and refrigerated.

Mussels and clams should be used within days and oysters within days. Shucked shellfish can be placed in a sealed container and frozen. Live lobsters and crabs should be cooked the day they are purchased. Frozen seafood should be kept frozen, and it is a good idea to date packages of frozen seafood so you can use the older seafood first.

Frozen seafood must be thawed properly. Other thawing methods include: immersing frozen seafood in cold water for a short time in a sealed plastic bag, or microwaving on a defrost setting until the fish is pliable but still icy.