35-150 billion fish are raised in captivity to be released into the wild every year


  • Fish stocking is the practice of raising fish in hatcheries and releasing them into rivers, lakes, or the ocean.

  • 35-150 billion finfish are stocked every year.

  • Fish are stocked to:

    • increase the catch in commercial fisheries (probably tens of billions of stocked fish annually),

    • increase the catch in recreational/sport fisheries (billions of stocked fish annually),

    • restore a population of threatened or endangered species (the number of stocked fish seems to be lower)

  • Fish can be stocked when they are anywhere between the egg stage and multiple years old. The mean time spent in hatcheries/farms seems to be somewhere between 6 days and 4 months. Fish stocked to enhance recreational fisheries tend to be released when they are older than those stocked to enhance commercial fisheries.

  • Usually, fish are stocked to maximize economic outputs so we shouldn’t expect fish welfare to be given sufficient consideration. It’s unclear how much hatcheries are incentivized to breed healthy and unstressed fish that would have higher survivorship after the release. Bigger fish may also starve and suffer after their release due to their lack of survival skills.

  • I was unable to find any animal advocacy organization that is working on reducing the suffering caused by fish stocking. I found very few articles that talk about fish stocking from an animal welfare perspective.

  • Possible interventions include lobbying to decrease the number of fish stocked for recreational fishers and requiring better conditions in hatcheries. I am very uncertain if such interventions would be cost-effective compared to ACE’s recommended charities.

  • Fish stocking has various ecological effects (e.g., a decrease in the genetic diversity of wild populations) that would need to be well-understood before seriously considering trying to reduce the number of stocked fish.

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Rodents farmed for pet snake food

In this article, I first estimate the number of animals raised for pet snake food in the world. Then I discuss some welfare concerns of these feeder rodents by comparing the conditions in which they are raised to the ones recommended for pet mice. Finally, I brainstorm about possible interventions.

Some key findings:

There are between 4.2 million and 7.8 million pet snakes in the world.

  • 160 million to 2.1 billion vertebrates are killed for pet snake food every year. Most of the vertebrates seem to be farmed mice.

  • Feeder mice are killed when they are anywhere between 48 hours and more than 9 months old. Most seem to be slaughtered when they are less 3–4 weeks old.

  • Farming of feeder animals seems to involve considerable suffering because they are often living in cramped and possibly unsanitary conditions, which don’t have shelters to hide in, lack daylight and activities.

  • I haven’t figured out what possible interventions in this space could be particularly promising. It’s possible that the problem is not very tractable.

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Will companies meet their animal welfare commitments?

Multiple animal organisations are now focusing on securing corporate commitments to improve animal welfare. And they have been very successful: Chicken Watch lists 1672 such commitments, 1007 of which are set to be fulfilled between 2020 and 2026. However, there is some reason to worry that some of these commitments may be broken:

  • Some industry sources doubt whether U.S. cage-free commitments will be fully met. Insufficient consumer demand and lack of funds led to producers slowing down or even shutting down their cage-free conversion plans. What is more, only 27% of U.S. companies included in CIWF’s EggTrack report disclosed their progress towards cage-free commitments.

  • So far, most animal welfare commitments were met. However:

  • Sainsbury’s broke their broiler commitment.

  • MarriottBurger KingSmithfield Foods and Woolworths pushed back the date of their commitments.

  • Bennet, Dussman, Au Bon Pain, Hilton Hotels & Resorts, and The Walt Disney Company did not report progress to CIWF for cage-free commitments that have already passed their due date.

  • In the past, some companies gave themselves some wiggle room in the phrasing of their commitments, which they could later use to get out of their commitments with less damage to their reputation.

Based on this, I suggest that it would be valuable to put more effort in ensuring that companies keep their promises, and I list some ways in which it could be done.

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Detecting Morally Significant Pain in Nonhumans: Some Philosophical Difficulties

Other humans merit moral concern. We think many nonhumans merit moral concern too. But how do we know? And which nonhumans? Chimpanzees? Chickens? Bumblebees? Protozoa? Roombas? Rocks? Where and how do we draw a line?

What would it take to justifiably believe that some nonhuman experiences pain (or pleasure) in a morally significant way?1 This is a tough question, but it is incredibly important to get right. Humans constitute a very, very small fraction of the animal kingdom. If other vertebrate animals experience morally significant pain, then much of our engagement with these animals is deeply immoral. If invertebrate animals experience morally significant pain, then, given the sheer number of invertebrates,2 an almost incomprehensible amount of morally significant suffering occurs beyond the ken of normal human attention. And if the capacity to experience morally significant pain is not restricted to organic entities, then human civilizations of the future may be capable of producing exponentially more sentient entities than presently exist.

On the other hand, if many, most, or all nonhumans do not experience morally significant pain, then it could be a waste of resources to try to change their condition. Given that there are millions of humans currently experiencing morally significant pain (for whom these resources would be a great aid), the opportunity cost of wasting time, talent, and money on nonhumans appears tremendous.

Figuring out where and whether to allocate resources to help nonhumans is of significant interest to Rethink Priorities. This post is our first in a series on morally significant pain in invertebrates.

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Animal Equality showed that advocating for diet change works. But is it cost-effective?

Animal Equality and Faunalytics put together a field study testing individual video outreach on belief and diet change. They found statistically significant results on both. Together with the Reducetarian study, we now think there is sufficient evidence to establish that individual outreach may work to produce positive change for nonhuman animals. However, evidence in this study points to an estimate of $310 per pig year saved (90% interval: $46 to $1100), which is worse than human-focused interventions even from a species neutral perspective. More analysis would be needed to see how individual outreach compares to other interventions in animal advocacy or in other cause areas.

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What is Animal Farming in Rural Zambia Like? A Site Visit

Factory farming in the United States and other developed countries is no doubt terrible. And while other developing countries are catching up in their sophistication, it is not clear yet what factory farming is like in the least developed parts of the developing world where most aid is focused. Instead, most rural livestock in the developing world is kept in a pastoral farming system that is relatively “free range”. However, little information is publicly available on the internet about what this is like or how much animal suffering is involved relative to the developed country horror of factory farming.

One such site visit exploring what this looks was seen in GiveWell’s 2012 Kenyan site visit (for example, this photo). To gather a bit more qualitative information on what animal farming could be like, I commissioned a different site visit to Zambia. Using Vipul Naik as an intermediary, I paid $570 to Sebastian Sanchez (“Sebas”) to visit and report on farming in Zambia1 during the course of his already pre-planned trip to Africa. This money was to compensate Sebastian for his time and his costs of travel and doing business. I explained the project to Sebas as “consisting in visiting facilities and qualitatively assessing farming and agricultural practices for nonhuman animals”. Sebas arranged his visits with the help of a local guide. His guide also connected him with a taxi driver. Both of these people were compensated by Sebas via the money I provided.

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