🐟 Fishing series: How fishing plays a part in the collapse of our climate

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Hering fishing with a “super trawler” boat.

There’s not a lot of room for everyone in the world to increase their consumption of fish.
The “Food and Agricultural Organization” of the United Nations (FAO) estimates[1] that:

  • 60% of world fisheries are fully-fished.
  • 33% of fisheries are overfished.
  • 7% of fisheries are under-exploited.

If some fisheries can be sustainably managed it is important to take the type of fish, mollusk or crustacean you are buying as well as the fishing technic into account as it might impact the environment much more than you think…

Overall emissions

Emissions from fisheries, at 179 million tonnes of CO2[1], account for approximately 4% of the emissions of the food sector. If these numbers do not sound critical it is important to reconsider them in another context. In 2011 alone, fishing vessels used up an estimated 40 billion litres of fuel, which represents the equivalent of 16% of the total CO2 emissions of airplanes. Putting all other environmental impacts aside (which are many), fishing is not to be forgotten when following a climate conscious diet.

Compared to other sources of animal protein however, products of the fishing industry create relatively low GHG emissions. In comparison to beef 🐄 or lamb 🐑, wild fish often has a relatively small climate footprint, with the main source of emissions being the fuel burned by fishing boats. One recent analysis[2] found that a number of popular wild fish — anchovies, sardines, herring, tuna, pollock, cod, haddock — have, on average, a lower carbon footprint than chicken or pork.

On the other hand, crustaceans such as wild shrimp and lobster can have a much larger impact on the environment than chicken, pork or cheese, they today account for 22% of the total emissions of the fishing industry. Indeed, crustaceans are often the product of trawling boats which burn tremendous amounts of fuel[3] and permanently impacts the sea bed. Since 1990, emissions from fishing overall have grown by a striking 28%, despite production staying the same, simply because of more intensive use of fuel required by crustaceans fishing. The increasing demand however makes the prices skyrocket which leads fishermen/women to fish at greater distance and for longer periods of time. On these grounds, buying shrimp, prawns or lobster simply accentuates the effects of their fishery on the environment.

Protein rich products[4]
(for a 100g protein)
GHG emissions
(kg CO2 equivalent[5])
Land use
(m2 year)
(kg SO2eq.[7])
(g PO2eq.)
Use of water
(kL equivalent)
Beef (meat) 🐄 50 164 0,189 0,177 871
Lamb & Mutton 🐑 20 185 0,087 0,060 1082
Beef (dairy) 🐄 17 22 0,209 0,209 1650
Crustaceans 🍤 18 2 0,060 0,098 1394
Cheese 🧀 11 41 0,149 0,089 4735
Pig meat 🐖 7,6 11 0,083 0,044 1073
Fish 🐟 6,0 3.7 0,025 0,092 1315
Poultry meat 🐓 5,7 7,1 0,064 0,030 402

The difficult case of Aquaculture, also known as “fish farms”

An “aerator” powered by electricity, increasing the level of oxygen of the water to allow the farming of shrimps.

The question of the energy

It can be surprising but, in some cases, livestock production uses less energy than some forms of seafood aquaculture. The production of catfish, shrimp and tilapia for instance, demands a constant circulation and oxygen enriched water powered by electric pumps and aerators which are extremely costing in terms of electricity. Catfish aquaculture alone demands a similar amount of greenhouse gases that of cattle. But in the long run, the impacts of farmed fish are also dependent on the nature of the national energy supply; a factor which is often outside of the control of fish farmer.

Pellets of fish meal to grow sturgeons

The question of the feed

Almost 50% of Chinese carps, 80% of tilapia and 93% of shrimp farmed in Aquaculture are today raised on “compound feed”. This feed is often constituted of fibers[9] but also from “fish meal” and “fish oil”, which enriches the feed in fat, calories and protein. These two products are, however, also a product of the fishing industry. Fish meal is obtained from the drying and grinding of either small fishes (like Anchovetas) harvested for this very purpose, fish trimmings considered as waste, or other kinds of marine species resulting from the by-catch of industrial fishing. Fatty fishes will be pressed beforehand to extract fish oil.

As of 2010, about 56% of fish meal was used to feed farmed fish, about 20% was used in pig feed, about 12% in poultry feed, and about 12% in other uses, such as fertilizers[10].This part of the industry is, alone, responsible for 15% of the global emissions of the fishing sector[11].

Fish meal and fish oil is, all in all, the product of the Capture fishing industry. 99% of Anchovetas, the formerly largest fished species in world[12], are still transformed to produce fish meal and oil. If farmed fishes are fed with fish meal and fish oil[13], and even though fish converts a greater proportion of the food they eat into body mass[14], the exponential business of farmed fish places heavy demands on the fishmeal and fish oil industry, ergo on capture fishing and ultimately on the environment.

Unless appropriate substitutes are found, the growth of the aquaculture sector is likely to push prices of fishmeal and fish oil production higher. These higher prices can create incentive for overfishing in poorly regulated fisheries. It also encourages industrial fisheries not to limit their quantities of by-catch (the other species caught in their nets), which impacts marine ecosystems. Between mid-2005 and mid-2008, the prices of fishmeal and fish oil rose by 50% and 130%, respectively.

The question of the water

For a large part, farming ponds tend to be filled and drained once per year with water. Water is also added periodically to counterbalance water lost through leakage and evaporation. While one might consider this as water use, one could also argue it to be a form of water storage and that leakage represents a service to the ecosystem as it can serve to recharge groundwater reserves that are deep enough for the soil to act as a natural filter. The latter argument only holds, however, if leakage does not stream into rivers and lakes, as it could be contaminated by nitrogen and phosphorus wastes from processed feeds.

The detrimental aspects of offshore marine aquaculture

Offshore marine aquaculture pens

A part of the aquaculture industry is also based on offshore marine farms. Mainly seen on the coast of Chile and the fjords of Norway, this method involves the use of large cages (also known as pens) of roughly 1000m2 large, which are left to float a few kilometers away from the coast.

Just as for livestock farming on land, these structures often create a stressful, overcrowded environment for fish to grow into. Other than the production of low quality fish, marine farms produce gigantic amounts of waste which falls on the sea bed, polluting the surrounding areas and potentially spreading diseases to wild species. Worst still, since the antibiotics poured into the water to help fight diseases among fish populations aren’t fully absorbed, they often get leaked back into the water and carried away by streams. Another issue comes from the questionnable durabilty of the material used in building the cages which can break and lead farmed fish to escape by the thousands, later competing for ressources with wild species and disrupting the ecosystem.

Least climate impactful species

Because capture fisheries do not rely on fertilizer, they consistently score lower than both aquaculture and livestock production. Conjointly, in addition to using very little energy, mollusk aquaculture actually absorbs excess nutrients that are harmful to ecosystems. Farmed mollusks also produced the least amount of air pollution, with small capture fisheries and salmon aquaculture close behind.

⚠️  Disclaimer:  ️️⚠️
Buying local seafoods, produced by small scale, soft fishing[15] producers will, of course, be less costing to the environment than fishes industrially farmed at the other side of the world. The following paragraph, however, describes which species are the least climate costing on a global scale, as a point of reference. Best choices for low-carbon fish protein are:[16]

🐚  Farmed mollusks such as:

  • Oysters
  • Mussels
  • Scallops

🐟  Small capture fisheries such as:

  • Anchovy
  • Herring
  • Sardines

🐟  Whitefish such as:

  • Pollock
  • Cod
  • Haddock

Small capture fisheries like anchovies and sardines account for a huge part of the world fish landings[17] (15%), but produces only 3% of overall fisheries emissions, because of their more fuel-efficient capture methods; often using the ”purse net”, a giant net left stationary in mid-water then brought up to the surface and closed.[18]


  1. 1.0 1.1 Numbers given by the FAO in its 2018 report (numbers are often referring to 2016). Click here for report
  2. “The environmental cost of animal source foods”
  3. “Fuel use and greenhouse gas emissions of world fisheries” Nature Climate change
  4. Includes production of food to feed the animals
  5. Including methane for instance
  6. The acidity of a soil is defined by its hydrogen potential (pH). Below a certain threshold (~ 6 on the pH scale), the soil is too acidic for most cultivated plants: it limits biological activity (fertility) and its structure is degraded. Indeed, acidity influences the uptake of nutrients and trace elements by a plant, as well as the presence of deep roots or earthworms that structure and aerate the soil.
  7. soils or waters (ex: ocean acidification due to fish and crustacean water farming)
  8. Excessive intake of nutrients into the water, resulting in overgrowth, oxygen depletion and ecosystem imbalance. e.g. nitrogen + phosphorus
  9. These fibers can come from various sources such as soy, rice, corn, wheat etc…
  10. Numbers of the Fishmeal information network
  11. Estimation for the year 2011
  12. The production of Anchovetas was 3 times more developed than any other species before 2014. Due to the impact of Hurricane El Niño as well as strong regulations, the production was divided by 3 in 3 years, putting Anchovetas on the second step of the podium in 2016.
  13. Farmed Salmon feed contains 16% of fish oil
  14. Fish, have cold blood require less energy than mammals to live, as they do not need to keep their blood warm
  15. See article for more information
  16. See study here
  17. Amount of fish fished
  18. The targeted fish being small, fishermen/women can make use of a net with small eyelets which prevents the fishing of larger species and saves in processing.