Pre-Slaughter Stunning Phase 2: Foundational Research Reports and Next Steps

Summary

As part of the first phase of our project to investigate and possibly implement pre-slaughter stunning in India, we commissioned three research reports to assess general viability. These reports have now been finished, and we are linking to them below.

Based on the findings from these reports, we are proceeding with the project through two parallel tracks:

1. Trialing chill killing.

2. Investigating manual percussive stunning and killing methods.

Update July 31, 2025: Since the publication of this post, we’ve reconsidered our approach to manual percussive stunning and have ultimately decided not to continue pursuing it right now. Our decision stems from the limited potential for meaningful welfare improvements within India’s current aquaculture context, specifically:

• Mass Harvest Limitations: Most farmed fishes in India are killed through mass asphyxiation, making it implausible that farmers, workers, or traders could be incentivized to manually stun thousands of fishes individually.

• Limited Welfare Improvement in Wet Markets: For fishes sold alive in wet markets, manual percussive stunning would only spare approximately 30 seconds of intense suffering per animal, according to our preliminary research. Given the challenges related to scalability and the difficulty of consistently effective stunning practices, this modest reduction in per-fish suffering, in our view, does not justify the resource cost compared to other projects we could undertake.

This decision does not affect our ongoing plans regarding chill killing, which we continue to pursue actively.

We remain hopeful that manual percussive stunning will eventually become a more widespread and effective practice in India’s fish markets. However, the current conditions suggest that today is not yet the right moment for this approach.

Context

In October 2024, we announced our project to assess the feasibility of pre-slaughter stunning for farmed fishes in India. Stunning, we believe, would constitute a significant welfare improvement for farmed fishes in India, as they are currently mostly killed via air asphyxiation. Based on our anecdotal observations during farm visits, it seems that this method causes these animals to take anywhere from 30 minutes to 2 hours to die.

Indian major carps, still alive, at a “harvest” in June 2025.

Unfortunately, there are significant challenges to implementing pre-slaughter stunning in this context. For instance, would consumers be interested in paying for it? Or could we even reliably bring stunning machines to the rural farms where these fishes are currently killed?

Because of these challenges, we have opted for a phased approach. That means that each phase must be completed and resolved positively before we proceed to the next one. 

Our first phase—conducting foundational research on viability—is now complete, and we are excited to share the results with you.

Phase 1: Foundational Research on Viability

This phase took the form of a request for proposals (RFP) process, in which we solicited proposals for a 3-month research project to address the following questions:

1. Target Population: Which stakeholder groups within India’s aquaculture sector are most likely to adopt pre-slaughter stunning technology?

2. Incentives and Barriers: What economic, logistical, cultural, or market-driven factors could incentivize or hinder the adoption of stunning technology?

3. Pathway to Scalability: What strategies or adjustments will be required to scale stunning technology across the aquaculture industry?

We received 16 proposals and selected two to fund. Additionally, one of our internal departments—the Exploratory Programs, or “ExPros” team—ran their project independently. The motivation behind running three projects concurrently was to maximize our chance of success, particularly given that each team had different approaches and areas of expertise.

The following are the completed reports from the three teams:

Report	Methodology	Key Findings and Recommendations
Hornbill AgriTech (2025)	Desk review of stunning technologies and meat quality literature 14 interviews with processors, researchers, and NGOs Two-day Andhra Pradesh field visit Online survey of 60 Indian fish consumers	There is limited consumer awareness and interest in the practice of stunning. Furthermore, the domestic seafood market in India, where nearly all farmed fishes are sold, is highly price-sensitive. European stunners are likely to be expensive and have not been validated for use with Indian species. Recommendations: Partner with a mission-driven fish cooperative, as collaboration with such an organization could help promote the adoption of more humane practices Consider chill killing, as it could offer a more economically feasible solution and lead to quicker deaths for the fish, even though it is not technically stunning. Engage with premium seafood brands to conduct market research, which could yield valuable insights into consumer preferences and market dynamics. Long timelines: They think it will be a 15-25 year journey, and we might as well get started now, as the market is unlikely to change anytime soon.
FWI's ExPros Team (2025)	35-paper literature review 24 key-informant interviews 70 farmer surveys Multi-state field visits (Andhra Pradesh, Jammu and Kashmir, Maharashtra)	The findings are similar to those of Hornbill AgriTech. Recommendations: Prioritize engaging with exporters, as they may demonstrate some interest in adopting more humane practices. Note: We’ve since looked more into exporters, and it appears there are very few. Explore chemical stunning, as it could be a promising option, though it faces challenges related to consumer acceptance and regulatory barriers.
Murthy &. Bardhan (2025)	40-paper review on chemical anaesthetics 4 farmer focus groups (47 total participants) in West Bengal 9 expert interviews (academics, veterinarians, regulators) Stakeholder landscape mapping and preliminary regulatory analysis	Focus on chemical stunning: This report was generally limited in scope to chemical stunning. Regional focus: It was also limited in scope to just one state, West Bengal, which is one of the largest fish farming states in India. Importance of freshness: Consumers in India, and particularly in West Bengal, really value freshness, and want to see the fishes alive before they buy them. Local hesitations with chemical use: Locals are very hesitant about anything involving “chemicals”. Significant regulatory partnerships and approvals would likely be needed before proceeding here. Recommendations: They’re proposing additional studies to test the efficacy of chemical stunning.

Do note that sometimes the reports are contradictory—for instance, Murthy & Bardhan (2025) recommend chemical stunning, while Hornbill AgriTech (2025) found no viable regulatory pathway for it. We believe this is a consequence of pre-slaughter stunning in India being a novel field.

FWI staff member Subrata visiting a tilapia cage farm in Maharashtra as part of our internal report.

Phase 2: Investigating Chill Kill and Manual Mechanical Stunning and Killing

When we commissioned these foundational reports, our hope was to uncover a clear opportunity for stunning in India—a pocket of the market where fishes are sold to buyers (ideally exporters) willing to pay a premium for stunned fishes. We hoped to find farming systems where stunning could realistically be deployed at scale, using methods already proven effective for that species. Unfortunately, the research didn’t reveal any scenario that ticks all those boxes.

After reviewing these three commissioned reports, we spent significant time considering whether we wanted to proceed with this project. After all, as per our original phased approach, we were prepared to end the project here if we didn’t see any sufficiently promising avenues forward.

We have decided, however, that we do see enough promise in stunning—or, perhaps to be more precise, more humane killing methods—to warrant the continuation of this project. We are now planning to do so in two ways, in parallel:

1. Trialing chill killing.

2. Investigating manual mechanical stunning and killing methods.

We explain more on each below.

Chill Kill

One of the recommendations from Hornbill AgriTech (2025) (page 30) was that we explore chill killing. Chill killing—or the process of killing fishes via submerging them in an ice slurry bath—is actually widely used to slaughter seabass and seabream in southern Europe. However, because it does not result in immediate loss of consciousness, it is also widely considered an inhumane killing method (e.g., by the World Organization for Animal Health), and European animal advocates have lobbied against it.

Despite not being considered a “humane” slaughter method, we believe chill kill may still constitute a significant improvement over open-air asphyxiation. For instance, our evidence suggests Indian major carps take up to two hours to asphyxiate in the open air; via chill kill, they may lose consciousness much quicker (though still not instantaneously).

Another benefit of chill kill is that it seems to be the only plausible improvement that could be implemented in the sort of mass harvests commonly practiced in India. Ice, which is used to transport the fishes, is already brought to the farms via the transport trucks (though two to five times more ice would likely be needed here). Additionally, advanced electronic machines are probably not economically or technologically feasible for these rural individual farms at the moment.

Key remaining uncertainties here still include:

• How much (if any) of a welfare improvement does this chill kill constitute?

• How difficult, logistically speaking, is it to execute a chill kill harvest? For instance, how much ice would be needed, and what adjustments would need to be made to the current harvest procedure?

• Will traders and/or consumers be willing to pay a price premium for chill-killed fishes?

Our specific plan here is to develop and implement a trial of chill kill, with the possibility of conducting additional trials later. We aim to have the first trial completed by the end of September. Personnel-wise, we are exploring contracting this project to Hornbill AgriTech, one of the authors of the foundational research reports listed above, with the support of our internal team.

Manual Mechanical Stunning and Killing

Whereas chill kill focuses more on species harvested en masse, we intend manual mechanical (or percussive) stunning to focus on “higher value” species, particularly when those are killed individually for the consumer. Some such stunning is already happening in India, for instance, via the use of a club-like object to stun trout in Jammu and Kashmir (Fish Welfare Initiative, 2025). Manual percussive stunning also appears to be practiced in wet markets, though in both cases, the primary motivation seems to be the ease of processing the fish.

We are also interested in exploring more humane killing methods. For instance, we are aware of a separate trout farm that claims to practice iki jime as a slaughter method.

We are excited by these approaches because, like chill kill, they do not rely on expensive technology and may thus be more suitable to the Indian context. In the best-case scenario, manual percussive stunning could be scaled to many wet markets, in which fishes are sold alive, across the country.

Key remaining uncertainties still include:

• How much (if any) of a welfare improvement does manual percussive stunning entail? This is likely a bigger question here than for chill kill, because for fishes processed individually, they are generally killed immediately after they would have been stunned anyway.

• How much training is required to reach a sufficiently effective stun rate?

• Could such an approach of relying on individual stunning (or killing) ever be scalable and cost-effective?

Our specific plan here is to spend the next three months investigating these questions, via desk and field research. We aim to publish a report by October with the results of our investigation, along with a decision on whether, and if so, how we will proceed. Personnel-wise, we expect our internal Exploratory Programs team, led by Subrata, to take the lead on this project.

Ruled Out Approaches

We elected not to further investigate the following stunning methods:

• Electrical: For various reasons, we believe that electrical stunning does not make sense to pursue in the Indian context right now. These reasons include: a) the vast majority of Indian farmed fishes are sold domestically to a market with little demonstrated interest in paying for more humane practices, and b) there are currently no electrical stunners designed for the most commonly farmed species in India. We hope and believe that electrical stunning will materialize in India, but we think it prudent to wait until both the technology develops further in Europe and India’s middle class becomes increasingly affluent.

  
  

• Chemical: Ruling this out was a more difficult choice, particularly as there was some disagreement between our foundational reports on its viability. Ultimately, we were primarily persuaded not to investigate chemical stunning further for two reasons: a) it seems challenging at scale, and b) there are serious regulatory approvals required here that would likely take ~5 years to obtain.

A Note on Ethics

At FWI, we’re used to working near suffering: We regularly observe fish harvests firsthand, and sometimes the studies we run do cause certain fishes to suffer more (for example, our Welfare Assessment Protocol requires handling fishes outside the water). However, projects aimed at developing more humane stunning and killing procedures will likely involve more moral tradeoffs that go beyond what we are used to. Such studies will likely involve the killing of fishes—for instance, our planned chill kill trial will involve killing fishes via this method (although, as this will likely happen at a regularly scheduled harvest, these animals would have likely faced a worse fate anyway).

Obviously, we do not take this issue lightly, both for the ethical implications as well as for the impact such studies have on our staff—people who spend all their working hours advocating for these animals. 

We will continue to reckon with the ethical trade-offs here and think about what enables us to improve the lives of fishes the most. As usual, we plan to express our decision-making on this transparently, and we always welcome external input.

Learn More

As always, we will keep our blog updated. The next update on this project should come at the end of September, by which time (hopefully!) we will have conducted our first chill kill trial and published a report on the viability of manual mechanical stunning and killing methods.

Those interested in diving more into the weeds of how we made these decisions may also find this internal document interesting, which discusses our decision process for moving between Phases 1 and 2.