The Nonlinear Library EA - 170 to 700 billion fish raised and fed live to mandarin fish in China per year by MichaelStJules
Jun 8, 2024
41:40
Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: 170 to 700 billion fish raised and fed live to mandarin fish in China per year, published by MichaelStJules on June 8, 2024 on The Effective Altruism Forum.
Summary
1. Around 1.2 to 1.9 trillion fish fry have been produced by artificial propagation (breeding) annually in China, and it seems those farmed for direct human consumption and pre-harvest mortality can only account for at most around 460 billion of them (more).
2. I estimate that 170 billion to 700 billion animals (my 80% credible interval) - probably almost all artificially propagated fish - are fed live to mandarin fish (or Chinese perch), Siniperca chuatsi, in China annually, with 9 to 55 billion of them (my 80% credible interval) alive at any time (more, Guesstimate model).
3. By contrast, the number of farmed fish produced globally for direct human consumption is around 111 billion per year, and 103 billion alive at a time, with another 35 to 150 billion raised and stocked per year (Šimčikas, 2020).
4. It's unclear how bad their deaths are as live feed to mandarin fish, but I'd guess they die by suffocation, digestion (stomach acid, enzymes), or mechanical injury, e.g. crushing, after being swallowed live, and probably a common way for aquatic animals to die by predation by fish in the wild (more).
5. It's unclear if there's much we can do to help these feed fish. There's been some progress in substituting artificial diets (including dead animal protein) for live feed for mandarin fish, but this has been a topic of research for over 20 years. Human diet interventions would need to be fairly targeted to be effective. I give a shallow overview of some possible interventions and encourage further investigation (more).
Acknowledgements
Thanks to Vasco Grilo, Saulius Šimčikas and Max Carpendale for feedback. All errors are my own.
Fish fry production in China
One of the early developmental stages of fish is the fry stage (Juvenile fish - Wikipedia). Šimčikas (2019, EA Forum), in his appendix section, raised the question of why hundreds of billions of fish fry were produced artificially (via artificial breeding, i.e. artificial propagation) in China in each of multiple years, yet only "28-92 billion" farmed fish were produced in China in 2015, "according to an estimate from Fishcount".
He found that if the apparent discrepancy were due to pre-slaughter mortality, then this would indicate unusually low survival rates. He left open the reason for the apparent discrepancy and recommended further investigation.
Before going into potential explanations for the discrepancy, I share some more recent numbers for the artificial propagation of fish: 1.9143 trillion fish fry in China in 2013 (Li & Xia, 2018) and 1.252 trillion freshwater fry and 167 million marine fish fry in China in 2019 (Hu et al., 2021). The 2019 numbers seem substantially lower than in 2013, so the trend may have reversed, one of these numbers is inaccurate, there's high variance across years or one of the years was unusual.
Li and Xia (2018) also plot the trend over time up to 2013, along with total freshwater aquaculture:
28 to 92 billion farmed fish produced in China in 2015 (Fishcount) from 1 to 2 trillion artificially propagated fish fry, would suggest a pre-slaughter/pre-harvest survival rate of 1.4% to 9.2% (from the fry stage on). Survival rates are typically at least 20% for the most commonly farmed species, including carps and tilapias (Animal Charity Evaluators, 2020, table 4), for which China accounts for most production. And Šimčikas (2019, EA Forum) notes:
Since hatchery-produced juveniles are already past the first stage of their lives in which pre-slaughter mortality is the highest, mortality during the grow-out period shouldn't be that high.
Under fairly generous assumptions for an explanation based on pre-harvest mortality, using ...
Summary
1. Around 1.2 to 1.9 trillion fish fry have been produced by artificial propagation (breeding) annually in China, and it seems those farmed for direct human consumption and pre-harvest mortality can only account for at most around 460 billion of them (more).
2. I estimate that 170 billion to 700 billion animals (my 80% credible interval) - probably almost all artificially propagated fish - are fed live to mandarin fish (or Chinese perch), Siniperca chuatsi, in China annually, with 9 to 55 billion of them (my 80% credible interval) alive at any time (more, Guesstimate model).
3. By contrast, the number of farmed fish produced globally for direct human consumption is around 111 billion per year, and 103 billion alive at a time, with another 35 to 150 billion raised and stocked per year (Šimčikas, 2020).
4. It's unclear how bad their deaths are as live feed to mandarin fish, but I'd guess they die by suffocation, digestion (stomach acid, enzymes), or mechanical injury, e.g. crushing, after being swallowed live, and probably a common way for aquatic animals to die by predation by fish in the wild (more).
5. It's unclear if there's much we can do to help these feed fish. There's been some progress in substituting artificial diets (including dead animal protein) for live feed for mandarin fish, but this has been a topic of research for over 20 years. Human diet interventions would need to be fairly targeted to be effective. I give a shallow overview of some possible interventions and encourage further investigation (more).
Acknowledgements
Thanks to Vasco Grilo, Saulius Šimčikas and Max Carpendale for feedback. All errors are my own.
Fish fry production in China
One of the early developmental stages of fish is the fry stage (Juvenile fish - Wikipedia). Šimčikas (2019, EA Forum), in his appendix section, raised the question of why hundreds of billions of fish fry were produced artificially (via artificial breeding, i.e. artificial propagation) in China in each of multiple years, yet only "28-92 billion" farmed fish were produced in China in 2015, "according to an estimate from Fishcount".
He found that if the apparent discrepancy were due to pre-slaughter mortality, then this would indicate unusually low survival rates. He left open the reason for the apparent discrepancy and recommended further investigation.
Before going into potential explanations for the discrepancy, I share some more recent numbers for the artificial propagation of fish: 1.9143 trillion fish fry in China in 2013 (Li & Xia, 2018) and 1.252 trillion freshwater fry and 167 million marine fish fry in China in 2019 (Hu et al., 2021). The 2019 numbers seem substantially lower than in 2013, so the trend may have reversed, one of these numbers is inaccurate, there's high variance across years or one of the years was unusual.
Li and Xia (2018) also plot the trend over time up to 2013, along with total freshwater aquaculture:
28 to 92 billion farmed fish produced in China in 2015 (Fishcount) from 1 to 2 trillion artificially propagated fish fry, would suggest a pre-slaughter/pre-harvest survival rate of 1.4% to 9.2% (from the fry stage on). Survival rates are typically at least 20% for the most commonly farmed species, including carps and tilapias (Animal Charity Evaluators, 2020, table 4), for which China accounts for most production. And Šimčikas (2019, EA Forum) notes:
Since hatchery-produced juveniles are already past the first stage of their lives in which pre-slaughter mortality is the highest, mortality during the grow-out period shouldn't be that high.
Under fairly generous assumptions for an explanation based on pre-harvest mortality, using ...