Various effective altruists have suggested that avoiding farmed fish is one of the most important things you can do to reduce the amount of suffering caused by your diet. Fortunately, an almost perfect substitute for farmed fish exists: wild-caught fish. It is very unclear whether eating more wild-caught fish is good or bad for fish. Replacing a food that’s very bad with a food that might be good or might be bad seems like progress.

However, it does not seem like there are any guides for how best to replace one’s farmed fish consumption with wild-caught fish.

I am offering a bounty of up to $500 for a well-written, easy-to-understand guide to replacing farmed fish with wild-caught fish. Questions that might be addressed by this guide include:

  • Which, if any, species of fish are always farmed?
  • Which, if any, species of fish are always wild-caught?
  • How likely are farmed fish to be mislabeled as wild-caught? Are there heuristics to use to avoid mislabeled fish?
  • If you don’t know whether a fish is wild-caught or farmed, how do you figure it out?
  • How likely is a fish of unknown origin to be wild-caught? Farmed? What factors affect whether it is wild-caught or farmed?
  • What are the cheapest ways to buy wild-caught fish?
  • What are the best wild-caught substitutes for commonly eaten farmed fish?
  • Which fish oil pills, if any, use wild-caught fish?

The full $500 will be paid out for a complete, well-researched, well-copyedited, easy-to-understand guide that is ready to be given to interested reducetarians. Incomplete or poorly edited reports will receive a portion of the bounty depending on my judgment of their quality. Reports with factual errors or which are otherwise very low-quality will not receive any money.

People interested in the bounty are encouraged to email me at ozybrennan@gmail.com so I can connect them to other interested people, for coordination and to avoid duplication of work.

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I doubt this makes a difference. Most of the market treats farmed and wild-caught fish as close substitutes, the supply of wild-caught fish is inelastic, and the supply of farmed fish is highly elastic. So if you switch from farmed to wild-caught fish, you are probably affecting market prices in a way which causes one other person to make the opposite change.

I agree with Jim's comment above. As the graph here suggests, the supply of wild fish appears to have been flat since the 90s, and the increase in demand has been met by the supply of farmed fish. So I think it's likely that consumption of wild fish will just cause someone else to consume farmed fish instead.

With regard to fish oil: Most of it originates from small wild fish such as anchovies. There's an entire industry dedicated to harvesting fish oil and fishmeal, and most of it is used as feed for carnivorous farmed fish like salmon. Fish oil seems to be mostly supply constrained as well, and the aquaculture industry is responding by feeding carnivorous fish more plant oils. I've written about this here and here, and should probably move these to the EA Forum now that less polished posts are encouraged.

Brian Tomasik has written about this here:

Substitution across fish types
The analysis becomes more complex when considering other wild fish species and fish farming. A decrease in the wild population of a given fish species may not reduce total fish consumption but might merely shift consumption to other fish.
Fishing down the food web
Big fish tend to be overexploited first, since they're easier to catch and take longer to mature. As populations of big fish decline, the result is fishing down the food web, i.e., harvesting smaller fish species. To produce the same amount of fish meat, more total fish will need to be harvested. Even if Fred weighs the badness of killing fish by the brain complexity of the fish killed, as long as Fred's brain-complexity function is less than linear in the mass of the fish being caught, then catching a given mass of smaller fish will be worse in Fred's eyes.c Assuming the total mass of fish harvested stays roughly the same now and into the long run, then eating more big fish and thereby reducing their long-term yields will have made things worse for Fred.
Fish farming
In addition to causing consumption of more small wild fish, overfishing of big species in the wild creates pressure to produce farmed fish. Some farmed fish are fed smaller wild-caught fish, which means fish farming can significantly increase total fishing. This would be prima facie bad in Fred's eyes.
However, there might be cases where fishing pressure on smaller wild-caught fish who are fed to bigger fish is sufficiently intense that populations of the smaller fish also decline. One example of this was the Peruvian anchovy fishery, which had supplied fish meal for livestock but which collapsed, leading to increased demand for soy protein instead.
Unfortunately, other fish-feed sources might be even worse than wild-caught fish, such as insects. Farming insects to feed farmed fish would significantly multiply the number of animals killed by humans. That said, fish feed may also include plant-based ingredients.
How much would substitution happen?
In rich countries, I would expect that demand for fish would remain pretty stable in the face of further fishery declines. As there become fewer big wild fish, prices of fish increase slightly, which slightly reduces the quantity demanded. And some eco-conscious consumers might cut back on fish in response to overfishing. But on the whole I expect the effect to be modest for affluent omnivores.
However, the effect might be more pronounced in poor countries, which may lack the resources to undertake aquaculture. According to the UN FAO:
In many areas of sub-Saharan Africa and South Asia, [...] fish consumption levels remain too low and they are failing to benefit from the contributions that fisheries and aquaculture are increasingly making elsewhere in terms of sustainable food security and income.
Given that up to 90% of US seafood comes from outside the US and that most rich countries import a lot of seafood from developing countries, increased consumption of fish in rich countries might indeed reduce long-term fishing by poor countries (to the detrmiment of indigent people in those countries).
Total fish production
One macroscopic perspective from which to assess the total impact of fishing is the following graph (compiled by Earth Policy Institute). [Graph here] I think the trends in the graph might be overstated if these figures include China, which is a major fish producer that's widely believed to overreport its fish numbers.d So the increase in fishing is possibly less dramatic than what's shown. But assuming the overall trend of wild + farmed fish is still an increasing one, then this is a bad sign from Fred's perspective, even if Fred only cares about fish in proportion to their mass (so that Fred wants to minimize the total biomass of fish caught). This is weak evidence that further demand for fish would make things worse for Fred, since most of the trend in the graph was probably driven by growing fish demand.
Of course, some fishery doomsayers might claim that the upward trend in the graph can't last forever (especially since fish farming often relies on wild-caught fish), and if they're correct, then drawing conclusions from the portion of the curve we can see now would give the wrong impression. But given that some fisheries are recovering, especially in the US, I'm personally skeptical about "end of fish" scenarios.
Conclusion
When considering substitution of fish consumers away from a declining fish species toward other species and fish farming, the effect of marginal big-fish consumption in the short run on total long-term fish harvesting becomes unclear. It's not obvious how much a reduction in populations of big wild fish reduces total fish consumption especially by the global poor (which could be good from Fred's perspective) versus how much it merely shifts consumption to other fish types (which could be quite bad from Fred's perspective).

That doesn't seem especially relevant to the question of whether first-world consumers should buy farmed or wild-caught fish; the amount caught form fisheries is set by regulations, not by demand, so consumer demand does not, on the margin, increase or decrease overfishing.

Enthusiastic +1 here. I'd also be willing to contribute to the bounty if there were an easy way to do that.

One complication is that tens of billions of fish are raised in hatcheries for a little bit, and then released into the wild, to enhance wild stocks, so that more fish could be caught later. You could say that they are farmed for a little bit. I am currently writing an article about that.

Note that this is also relevant for the question of whether eating more wild-caught fish is good for fish. If humans continuously restock waters with hatchery-produced juveniles to compensate for wild-caught fish, fishing might not affect wild fish populations in the same way.

It's not very clear how the WASR article you linked to in "whether eating more wild-caught fish is good or bad for fish" shows what you say it shows.

Can you briefly over the basic case for switching to wild caught fish? Is it just that wild caught fish tend to be predators?