Do Fish Produce CO2? 23 Fish Species’ Carbon Dioxide (Fish Carbon Footprint)

Georgette Kilgore headshot, wearing 8 Billion Trees shirt with forest in the background.Written by Georgette Kilgore

Animals | March 15, 2024

Diver underwater looks at a fish producing co2 cloud, and asks Do Fish Produce CO2 and What's a Fish Carbon Footprint?

Cows produce methane and chickens produce carbon dioxide….in fact, all animals do, so many people ask, do fish produce CO2?

Fish do produce CO2 during respiration, which means that the water taken into their mouths passes through the gills situated behind their heads.13

During this process, oxygen is absorbed from the water, while CO2 is released and the water is then eliminated.

This type of CO2 production is known as natural CO2 production, as opposed to man-made CO2 production.

But, what exactly is a fish carbon footprint? And, where does natural carbon dioxide come from?

This complete guide explains how much carbon dioxide a fish produces (along with the carbon footprint of X species of fish) and more.

How Can I Tell How Much CO2 Is in My Water?

Natural carbon dioxide (atmospheric) releases occur when the ocean out-gasses itself, volcanoes erupt, natural wildfires occur, large masses of vegetation is left to decompose, and animals such as cows belch.

An optical sensor is used to measure the level of infrared absorption, which measures the CO2 level in water.

Even though these natural CO2 releases have a detrimental effect on the atmosphere, there are natural carbon sinks on Earth to help offset the resulting CO2 emissions. These come in the form of photosynthesis, ocean absorption, and the existence of soil.

Natural carbon dioxide releases have occurred over millions of years, and during the past ice ages, the level of CO2 in the atmosphere has been kept at 300 ppm.

With the advent of human activity, the level of CO2 has risen close to over 416 parts per million, and is at the highest level it’s ever been.14

The below table indicates just how fast and constantly the level of CO2 has risen between 1999 and 2021.1

Year The Concentration of CO2 in Water, Parts Per Million
2021 416.45 ppm
2020 414.24 ppm
2019 411.66 ppm
2018 408.72 ppm
2017 406.76 ppm
2016 404.41 ppm
2015 401.01 ppm
2014 398.87 ppm
2013 396.74 ppm
2012 394.06 ppm
2011 391.85 ppm
2010 390.1 ppm
2009 387.64 ppm
2008 385.83 ppm
2007 384.02 ppm
2006 382.09 ppm
2005 379.98 ppm
2004 377.7 ppm
2003 375.98 ppm
2002 373.45 ppm
2001 371.32 ppm
2000 369.71 ppm
1999 368.54 ppm

Chart that shows concentration of CO2 in PPM.

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Do Fish Need Carbon Dioxide?

After answering the question, do fish produce CO2 the next logical question is, do fish need carbon dioxide?

CO2 plays an important role in the ultimate lifespan of fish. The balance should be just right because too little CO2 or too much CO2 could lead to fish dieoff.

So, do fish produce enough CO2 for plants?

Fish have the ability to produce enough CO2 for plants if said plants happen to be moderate light and grow underwater in an aquarium.15

Highlight plants or highlighted aquarium plants will most likely require extra CO2 to grow properly. Without adequate CO2, algae will start to bloom in an aquarium.

So then how much CO2 is needed in a planted aquarium?

A thriving aquarium requires sufficient light, enough nutrients, and adequate carbon dioxide. But the CO2 levels must also be monitored as too much carbon dioxide can kill the fish in the aquarium.

The typical CO2 level is between 15 and 25 parts per million. Anything over 30 ppm can be fatal for fish, therefore it is best to cap the CO2 at 25 ppm.2

Do you really need CO2 for aquarium plants?

Carbon Dioxide is the most vital element in most planted aquariums, but this does not mean that some aquarium plants cannot thrive without it.15

Setting up an aquarium tank without CO2 will require low-energy plants.3 But, fish add CO2 to the aquarium.

If it becomes clear that even the low-light and low-energy plants inside the aquarium require a CO2 boost, extra fish can be added.16 Fish can produce enough carbon dioxide to keep low energy plants healthy, while many fish can even keep medium-energy plants alive.

Do Fish Produce CO2? (Do Fish Produce Carbon Dioxide?)

The above information makes it clear that the answer to the question, do fish produce CO2, is yes they do.

But exactly how much do they produce after being caught?

How Much CO2 Do Fish Produce?

Once caught, how much CO2 do fish produce?

The below table indicates the GHG emissions released by different types of fish and seafood.4

Type of Fish / Seafood CO2 Per Kg
1. Farmed bivalves 1.40 kg
2. Wild bivalves 11.40 kg
3. Farmed carp 6.95 kg
4. Farmed catfish 7.77 kg
5. Cod/haddock 5.13 kg
Man holding a catfish

(Image: Justin Miller26)

Type of Fish / Seafood CO2 Per Kg
6. Wild flounder 20.31 kg
7. Wild herring/sardines 3.88 kg
8. Wild jack fish 9.67 kg
9. Wild lobster 19.44 kg
10. Farmed milkfish 6.43 kg
Caught wild flounder on wood deck.

(Image: Brian Yurasits23)

Type of Fish / Seafood CO2 Per Kg
11. Farmed freshwater fish 18.91 kg
12. Farmed marine fish 11.60 kg
13. Wild redfish/bass 9.91 kg
14. Farmed salmon 5.10 kg
15. Wild salmon 6.88 kg
Wideshot of farmed fish in sea.

(Image: PublicDomainPictures25)

Type of Fish / Seafood CO2 Per Kg
16. Farmed seaweed 1.09 kg
17. Farmed shrimp 9.43 kg
18. Wild shrimp 11.96 kg
19. Farmed bighead 3.51 kg
Wide shot of farmed bighead fish in water.

(Image: U.S. Fish and Wildlife Service27)

Type of Fish / Seafood CO2 Per Kg
20. Wild squid 8.18 kg
21. Farmed tilapia 10.68 kg
22. Farmed trout 5.41 kg
23. Wild tuna 7.63 kg
Wild squid under the sea.

(Image: MartinStr25)

Graph of CO2 emissions of fish or seafood per kg.

Read More About: How These Animals Live in Trees Is Changing How People Live in Houses

Do Fish Produce CO2? Fish Carbon Footprint

The fish carbon footprint is explained as follows:17

One serving of fish equal to 100g is the equivalent of 1.34 kilograms of CO2 emissions. This can be compared to driving 6.8 kilometers in a gasoline car and 0.73 m3 or CO2 gas emissions.

The below table indicates the percentage of production and emissions of the nine major aquaculture species including marine fish in China:5

Species Production % Emissions %
Marine Fish 0.78 1.90 1.65
Marine Bivalves 12.33 30.04 12.70
Marine Shrimp 1.11 2.70 7.48
Freshwater Shrimp 2.16 5.26 12.99
Other Fresh Water Fish 3.01 7.34 10.84
Cyprinids 19.51 47.53 46.82
Catfish 0.40 0.97 1.10
Tilapia 1.65 4.02 6.31
Fresh Water Bivalves 0.10 0.24 0.11
Total 41.05 100% 100%

Do Fish Produce CO2?

Following the question, do fish produce CO2, is the question, where do fish rank when it is compared to lobster, lamb, beef, and dairy?

A 2021 study found that wild fish, and other types of seafood, produced only a sixth of the emissions of beef, a fifth of the emissions of lamb or mutton, and half of the emissions of cheese.18

Also, in 2021 it was established that the production of meat-based food is responsible for around 60% of all food production emissions.

The below table indicates the estimated GHG emissions per 1 kg of food produced, including animal-based foods such as beef and lamb, as well as fish and plant-based foods:

Type of Food GHG Emissions Per Kg of Food Produced
Beef (herd) 60 kg of carbon emissions per 1 kg of food
Lamb & Mutton 24 kg of carbon emissions per 1 kg of food
Cheese 21 kg of carbon emissions per 1 kg of food
Beef (dairy) 21 kg of carbon emissions per 1 kg of food
Chocolate 19 kg of carbon emissions per 1 kg of food
Stack of different kinds of cheese.

(Image: VMonte1325)

Type of Food GHG Emissions Per Kg of Food Produced
Coffee 17 kg of carbon emissions per 1 kg of food
Farmed Prawns 12 kg of carbon emissions per 1 kg of food
Palm Oil 8 kg of carbon emissions per 1 kg of food
Pork 7 kg of carbon emissions per 1 kg of food
Poultry 6 kg of carbon emissions per 1 kg of food
A poultry farm with chickens eating.

(Image: Magda Ehlers24)

Type of Food GHG Emissions Per Kg of Food Produced
Olive Oil 6 kg of carbon emissions per 1 kg of food
Farmed Fish 5 kg of carbon emissions per 1 kg of food
Eggs 4.5 kg of carbon emissions per 1 kg of food
Rice 4 kg of carbon emissions per 1 kg of food
Wild Fish 3 kg of carbon emissions per 1 kg of food
Wide shot of olive oil poured into a small bowl.

(Image: stevepb25)

Type of Food GHG Emissions Per Kg of Food Produced
Milk 3 kg of carbon emissions per 1 kg of food
Cane Sugar 3 kg of carbon emissions per 1 kg of food
Groundnuts 2.5 kg of carbon emissions per 1 kg of food
Wheat and Rye 1.4 kg of carbon emissions per 1 kg of food
Tomatoes 1.4 kg of carbon emissions per 1 kg of food
Milk poured into a glass.

(Image: Couleur25)

Type of Food GHG Emissions Per Kg of Food Produced
Corn 1.0 kg of carbon emissions per 1 kg of food
Cassava 1.0 kg of carbon emissions per 1 kg of food
Soymilk 0.9 kg of carbon emissions per 1 kg of food
Peas 0.9 kg of carbon emissions per 1 kg of food
Bananas 0.7 kg of carbon emissions per 1 kg of food
Closeup of a bunch of yellow bananas.

(Image: _Alicja_25)

Type of Food GHG Emissions Per Kg of Food Produced
Root Vegetables 0.4 kg of carbon emissions per 1 kg of food
Apples 0.4 kg of carbon emissions per 1 kg of food
Citrus Fruit 0.3 kg of carbon emissions per 1 kg of food
Nuts 0.3 kg of carbon emissions per 1 kg of food
Different nuts on wood chopping board.

(Image: ExplorerBob25)

The main takeaway from the above table is that while fish production produces far less CO2 emissions compared to meat such as beef and lamb, it is not as low on CO2 emissions as plant-based foods.6

How Does a Carbon Dioxide Unit Work?

A carbon dioxide unit or CO2 sensor works by monitoring infrared absorption at a wavelength of 4.3 μm. If infrared light is observed as being absorbed, it indicates the presence of CO2. Whenever infrared light is not absorbed, it indicates a lack of CO2.

Carbon dioxide levels can also be measured using photoacoustic spectroscopy and electrochemical CO2 sensors.

Furthermore, a carbon dioxide unit also refers to a unit of measurement – CO2 is typically measured in ppm (parts per million).

Carbon Footprint of Animals by Species

When looking at the carbon footprint of animals by species, the below table indicates the GHG emissions of livestock as estimated in MMT of CO2e.19,7

Livestock Animals CO2 Emissions in MMT of CO2e
Cattle 5,024 MMT of CO2e
Chickens 829 MMT of CO2e
Pigs 819 MMT of CO2e
Buffalo 766 MMT of CO2e
Small ruminants 596 MMT of CO2e
Other poultry 82 MMT of CO2e

Graph of the different livestock emissions in MMT of CO2e.

Furthermore, global livestock is responsible for 7.1 gigatons of CO2 emissions every year, which constitutes 14.5% of anthropogenic greenhouse gas emissions.

  • Cattle (herds of dairy and beef) are responsible for the highest amount of emissions, around 65% of the total livestock emissions (globally).20
  • The production of feed from ruminants produces 45% of CO2 emissions, while enteric fermentation produces around 39% of CO2 emissions. The storage and production/processing of manure produce 10% of CO2 emissions.
  • The use of fossil fuels for supply chain purposes accounts for around 20% of global livestock emissions, while milk from beef and cattle produces around 41% and 20% of emissions respectively.
  • Following this is pork with 9% of CO2 emissions, buffalo meat/milk with 8% of CO2 emissions, and chicken/eggs with 8% of CO2 emissions.
  • Small ruminant meat/milk adds 6% of CO2 emissions and the remainder of the emissions is made up of poultry and non-edible product emissions.

Emission intensity per product

  • Beef – 300 kilograms of carbon dioxide equivalent per kilogram of protein.
  • Ruminants (meat/milk) – 165 and 112 kilograms of carbon dioxide equivalent per kilogram.
  • Dairy milk (cow), chicken, and pork are all below 100 kilograms of carbon dioxide equivalent per kilogram.8

Carbon Footprint of Meat

The carbon footprint of meat is indicated in the below table and compares the CO2 equivalents to other foods. This table also indicates the CO2 equivalents of miles traveled by car.9

Bar graph of carbon footprint of meat per CO2 with its equivalent in miles traveled by car.

Food Type CO2 kg Equivalent Car Miles Equivalent
Lamb 39.2 kg of CO2e 91
Beef 27.0 kg of CO2e 63
Cheese 13.5 kg of CO2e 31
Pork 12.1 kg of CO2e 28
Lamb meat with bone.

(Image: ReinhardThrainer25)

Food Type CO2 kg Equivalent Car Miles Equivalent
Turkey 10.9 kg of CO2e 25
Chicken 6.9 kg of CO2e 16
Tuna 6.1 kg of CO2e 14
Eggs 4.8 kg of CO2e 11
Dressed chicken on a spit with some vegetables next to it.

(Image: RitaE25)

Food Type CO2 kg Equivalent Car Miles Equivalent
Potatoes (Image26) 2.9 kg of CO2e 7
Rice 2.7 kg of CO2e 6
Nuts (Image29) 2.3 kg of CO2e 5
Beans/tofu 2.0 kg of CO2e 4.5
A sack of potatoes on the ground.

(Image: Couleur25)

Food Type CO2 kg Equivalent Car Miles Equivalent
Vegetables (Image26) 2.0 kg of CO2e 4.5
Milk 1.9 kg of CO2e 4
Fruit (Image26) 1.1 kg of CO2e 2.5
Lentils 0.9 kg of CO2e 2
Some vegetables inside a container.

(Image: JillWellington25)

Carbon Footprint of Chicken

The carbon footprint of chicken is explained as follows:

  • 1.39 kg of CO2 emissions per 21 grams of protein
  • This is equal to a square footprint of 17.48 square feet
  • It is also equal to a water footprint of 17.80 gallons.

Overall, the environmental impact of chicken is almost 10 times lower than that of beef.21

  • In total chicken produces 6.6 times less CO2 emissions.
  • Chicken uses 16.6 times less land than beef.
  • Chicken requires 4 times less water than beef.

This means that the cradle-to-grave CO2 chicken footprint is estimated to be 12.27 kilograms of CO2e per kilogram.10

Carbon Footprint of Vegan Diet

The carbon footprint of vegan diet has been touted for a long time as being the smallest out of all the types of diets which can help promote a globally green environment. It has been estimated that a meat-based diet produces at least 2 times the carbon ‘foodprint’ compared to a vegan diet.

The different diets are compared as follows (based on the average American diet):

  • Meat-based diet- 3.3 tons of CO2 emissions per year
  • Meat-less diet- 1.9 tons of CO2 emissions per year
  • Vegetarian diet- 1.7 tons of CO2 emissions per year
  • Vegan diet- 1.5 tons of CO2 emissions per year

The below chart indicates the carbon intensity of different foods including meat-based, and plant-based foods.11

Chart that shows CO2 intensity of food.

Studies have also shown that wild seafood, including wild fish, has a lower CO2 footprint than beef (red meat), dairy (cheese), and chicken (poultry).

It has also been estimated that because marine fisheries provide food security for millions of people around the world, a concerted effort to restore global ocean’s could provide food for a billion people while lowering the CO2 footprint of food production.22

The below chart indicates the comparison of the CO2 footprint of wild fisheries and aquaculture compared to other types of foods:12

Graph that shows emissions per source of protein.

It is clear that aquaculture and wild fisheries are at the lower end of the carbon footprint scale.

It is also easy to see that the question, do fish produce CO2, has a far more complicated answer than just ‘yes’ when looking at the above information and statistics.

Frequently Asked Questions About Do Fish Produce CO2

Do Fish Produce CO2?

Fish produce CO2 as a by-product of breathing. The processing of fish and seafood products also emit CO2.

How Does Carbon Dioxide Affect the Fish?

While CO2 in water can help boost the health of fish, too-high levels of CO22 can cause fish to suffocate.

Read More About About Do Fish Produce CO2


References

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