Welfare cost and alternatives to pre-sale purging in Chinese carp farming

commitment: 8 hrs/week
flexibility: No mentee proposal

mentored by

The project

Carp are the most farmed fish on earth — on the order of 1⁠5⁠–⁠2⁠0 billion individuals a year in China alone. Almost all of it is sold live into the domestic market, so there's no export or certification lever and very little outside attention. Before sale, carp are commonly held for 3⁠0⁠–⁠4⁠5 days with no feed at five to six times normal stocking density. The practice has been described in passing but nobody in animal welfare is working on it.
There's a promising crack in it. Removing the muddy off-flavour compounds that ostensibly drive the practice (geosmin and 2-MIB) appears to take days, while the multi-week protocols are doing a different job — improving flesh texture and quality. Our own work has already ruled out another of the stated rationales: the purge cannot be functioning as a drug withdrawal period, on both regulatory and arithmetic grounds. If what remains is discretionary quality work rather than technical necessity, the practice becomes far more challengeable — and at least one documented alternative already exists in the literature.
The mentee will produce the first clear-eyed assessment of the practice, to inform whether and how Myrias intervenes. The review will:

Establish, with sources and evidence grades, why the purge is done and how its prevalence and duration vary by region and by tier of the supply chain
Synthesise what it costs the animal — the welfare effects of prolonged fasting combined with crowding
Assess the alternatives on both welfare gain and commercial plausibility

There's a second layer. Myrias is building a structured, AI-assisted database of farmed animal welfare interventions and their evidence base, jointly with a US partner organisation — a "second brain" for intervention research. This review will be the first body of work written directly into it, which means the evidence is structured and graded to a shared schema from day one rather than written up as prose and retrofitted later. The mentee helps shape that schema by being its first real user, and sees how a research process becomes reusable infrastructure rather than a document that gets filed.
Deliverable: a standalone review plus a short prioritisation memo, with the underlying evidence entered as structured, graded records. No coding or domain expertise required — research synthesis, clear writing and honest evidence-grading matter most.

The mentee's role

The mentee owns the review end-to-end, with weekly guidance from me. Sample tasks:

Pin down what the purge is actually for — off-flavour removal, flesh-quality improvement, gut clearance before transport, or some combination — and how far each stated industry rationale survives scrutiny. I'll hand over what we've already established, so you start from the open questions rather than from zero.
Establish where the practice happens (farm, wholesaler, distribution centre, retail tank) and for how long, since that determines whether this is a month-long or a two-day problem.
Synthesise the welfare evidence on extended fasting and on high-density holding in carp, flagging clearly where findings are carp-specific and where they're inferred from other species.
Assess documented alternatives — shorter clean-water depuration, low-salinity depuration, feed manipulation, upstream control of off-flavour compounds — for whether they deliver the same commercial outcome.
Enter evidence as structured, graded records as you go, rather than writing prose first and extracting later.
Write it up as a review plus a memo ranking which alternative is most tractable to push, and what would have to be true for it to work.

On Chinese-language sources: a substantial share of the relevant literature and nearly all of the industry practice sits in Chinese. I work in Chinese daily and will supply translated material and summaries — you don't need the language, but expect to work partly from material I've brought across rather than finding everything yourself.

Who I'm looking for

Must-haves: strong research and synthesis skills; clear, concise writing; the discipline to source claims and grade evidence honestly rather than overstate; comfortable writing "the evidence here is thin" and leaving it there; able to work independently between weekly calls.
Nice-to-haves: ability to read Chinese — a real advantage, though not a barrier, as I can supply translated material; quantitative literacy for rough scale estimates; familiarity with EA-style cause prioritisation or the ITN framework; existing interest in aquaculture, fish welfare or neglected farmed species; some tolerance for structured data work, since you'll be entering records against a schema rather than only writing prose.
No coding or formal science background needed. I'd rather have a rigorous generalist who can be sceptical about their own conclusions than a subject expert who can't.

Questions for applicants

Pick any claim you believe about animal welfare and tell me how strong you think the evidence for it actually is, and why.
Roughly how many hours per week can you commit, and are there weeks in the Aug–Nov window where you'll be unavailable?

Support offered

Shaping direction and scope, and structuring the review and prioritisation logic
Grading evidence and stress-testing conclusions
Drafting and editing feedback on the written output
Domain context on Chinese freshwater aquaculture — supply chain structure, regulation, industry economics — plus translated source material and access to industry contacts
Access to Myrias's internal research on carp welfare across the supply chain, so the mentee starts from the current state of knowledge rather than rebuilding it
If the work is strong: a route into how Myrias evaluates and potentially funds interventions, plus introductions within the animal welfare and EA research ecosystem

format: Research & writing · Project scoping
topic: Neglected animal groups · Tools for advocates · Near-term impact

Jo Han

Myrias

I'm a researcher and project manager at Myrias, an EA-aligned venture studio targeting the largest and most neglected sources of farmed animal suffering. My work covers Chinese freshwater aquaculture — principally carp and crucian carp — and duck welfare, combining literature research, industry data and direct outreach to producers and processors.
Over the past months I've built a stage-by-stage welfare opportunity map for the major farmed freshwater species in China, running from farming through harvest, holding, transport, pre-sale purging and slaughter, and stress-tested the industry's own justifications for each practice against the regulation and the cost arithmetic. That work established, among other things, that the anaesthetics used for humane slaughter elsewhere have no legal route to market in China under the veterinary drug positive-list system, and that one widely-repeated commercial rationale for the long pre-sale purge doesn't survive contact with the numbers.
Before moving into animal advocacy I worked in investment research in Hong Kong, and that training still shapes how I work: verify the source, check whether the cost logic actually holds, and make the case to industry in the metrics they already use — FCR, mortality, downgrade rates — rather than in welfare language. I also host 《有点豆腐》(Slightly Tofu), China's only animal rights and veganism podcast, and advise the China Vegan Society.
I'm most useful to a mentee who wants to learn how a rigorous, evidence-graded process turns a hunch into a decision — and who'd value a mentor with direct access to the Chinese-language sources and industry contacts this question actually depends on.