Thank you for sharing this, Nunik! 
It seems the post you link is right to caution that lumping the low mercury and PCB claim together for small pelagics as is often done (even in our own post - prior to the update we just made!) is misguided. 
I tried to do further research and it seems to me the following is true (I'm new to the topic, so please say if you know otherwise):

1. PCB concentrations are extremely geographically and temporally variable. Areas like the Baltic sea or SF Bay are very high in PCBs, but levels in the open oceans are much lower. Also, PCBs have been banned from the 80's and levels in fish have been declining as more of the PCBs sediment to ocean floors, so it is becoming less of a concern.
2. PCBs are hydrophobic, thus they do accumulate in fishes, particularly their fat. As sardines/anchovies are fatty, they contain higher PCBs than less fatty fishes like Cod.
3. PCBs like most contaminants biomagnify. Predators consuming sardines will absorb the PCBs in their fat, increasing their PCB levels. Thus, sardines/anchovies may be less contaminated than equally fatty but longer-lived/higher trophic level fishes.

It really does seem PCB levels can be a health concern, something I was not as aware of before. However, health authorities still lean heavily towards promoting the consumption of oily fishes, often even singling out sardines/anchovies as top choices. I suppose the trade-off of higher PCBs but higher EPA/DHA + other nutrients is still a positive one, but I would love to explore this deeper! Let me know if you have any insights on this topic :)

I agree with your point on catch volumes. Though I do hope I'll find a fisheries expert to evaluate this quota claim properly, as it seems so critical. 

Regarding your second point, I don't share all your concerns about the second-order consequences. Sardines and anchovies are currently used primarily as low-value inputs for fishmeal. The margins of sardines and anchovies for human consumption exceed that of fishmeal, so reallocating catch to human diets would likely not change the price.

Frozen sardines in the UK are currently priced slightly below chicken per gram of protein while also providing valuable EPA/DHA (canned sardines are a bit pricier due to packaging and processing costs).

For salmon or shrimp, their dependence on fish meal would make them more expensive were sardines/anchovies to shift to human consumption, making them less appealing substitutes.

Thanks for all your input :) Really appreciate it!

Thanks for sharing your thoughts, Michael! I believe the key reason wild fish ingredients in aquaculture have yet to be eliminated is due to EPA/DHA (omega 3s) which as far as I know are only derived from algae or the marine creatures which consume it. Thus, insect meal might be able to replace some of the fish meal, but certainly not the fish oil. Currently, both insect meal and, especially, algae oil seem to be expensive, so even if producers were to switch to these ingredients, salmon prices would rise, likely decreasing demand. But I agree that if insect and algae farming become more efficient this could be a concern in the future. 

Also, thanks for sharing the information on krill, I've updated my thoughts thanks to you :)

Thank you so much for your thoughtful feedback, Sagar, and especially for pointing out the issue with the stress duration. That's very helpful. We really aren't experts on this matter. We've tried to research this issue as thoroughly as we could and made a real effort to seek out input from marine biologists and fish welfare researchers. That said, we weren't able to find anyone with specific expertise on sardines and anchovies. As a result, there's still a lot of question marks for us, which is why we are so keen to get the feedback of people like yourself. :) 

It seems with net hauling we mistakenly based our numbers on a study citing net setting times, without realising that this did not include haulage. We looked into the study your shared as well as more recent studies and it seems the 90 to 120 minutes time from net set to loading on board is a good estimate to go for, though it seems it can sometimes even exceed this time if slippage is required or the boat is overloaded. We have updated our claims and would love to hear your thoughts on the uncertainty this may introduce in the trade off between deaths in the wild vs from fishing!

We personally think the direct suffering experienced by the sardines and anchovies may not be the most important consideration, especially as they appear to have a very low moral weight. Instead, the environmental impacts of different protein sources and their indirect effects on wild animal populations might dominate the overall animal welfare implications.

We also think it’s important to add that what we're really trying to explore with this post is not only whether sardines and anchovies might be a good option for people who are resistant to going vegan, but also whether they could be a meaningful and defensible choice for people who already consider themselves vegan. That is, of course, a more controversial angle, and one where the nutritional considerations play an especially important role.

Regarding larger pelagic forage fish like mackerel and herring, we did not consider them for several reasons:

• They are higher in the food chain and longer-lived, which increases the risk of heavy metal and microplastic accumulation.
• Their more complex hunting behaviours likely indicate a higher welfare range, which increases the potential for direct suffering, though this might change if stunning technologies could be implemented (thanks for raising this interesting point!).
• Unlike sardines and anchovies, which feed on rudimentary, brainless planktonic organisms, mackerel and herring prey on more complex animals, including small fish like sardines and anchovies. Building on this post (thank you, Bella!), reducing mackerel/herring populations could increase sardine/anchovy numbers, and if those species lead net-negative lives, this could worsen overall outcomes. We don't think this consideration applies to planktonic organisms.
• Due to their higher trophic level and longer life spans, mackerel and herring stocks may be less resilient to fishing pressures, raising concerns about scalability.
• Pelagic trawling, which is more commonly used to catch mackerel and herring, likely results in higher GHG emissions and slightly higher bycatch than purse seining/ring netting.
• Sardines and anchovies are heavily used as feed in salmon farming, which is less the case for herring and mackerel. So eating sardines/anchovies might simply shift them from feed to food use, potentially displacing part of the salmon industry (yay!), whereas the same effect is less likely with mackerel or herring.

That said, our thinking on mackerel and herring is based on limited exploration. We haven't looked into these species in detail, and we'd be really curious to hear your thoughts on whether any of these assumptions seem off.

Agreed. However, I think the issue with my Muslim friend was not the foreignness of this idea but rather that it was illustrated with a particularly off-putting (for her) example of pigs. In this case, I think something as simple as changing the animal to one that does not automatically invoke disgust in certain religious groups (i.e. Judaism and Islam) would increase the diversity of those taking the intro EA programme.

While taking the introductory EA virtual programme, I shared my experiences with my Muslim roommate. She was very sympathetic to the idea of ea. Big BUT: when I mentioned one of the exercises on moral decision making which weighed the expected value of deworming children with lobbying for farmed pig welfare (and ultimately led to comparing the value of human life with a pig), she was horrified. I’m thrilled to see that Ahmed is planning to develop a Muslim EA fellowship! In the meanwhile, perhaps a Muslim EA could review the introductory EA virtual programme and see if there are any examples such as this one which could be altered to make EA principles seem less hostile to Islam while retaining the community’s intellectual honesty?

Vegan EPA and DHA supplement: https://www.vegetology.com/supplements/omega-3