Fishes barely register in public conversations about animal experimentation. Mice? Rats? Rabbits? People picture them immediately.
Fishes disappear.
A new analysis of the European Union’s main chemical safety law suggests around 382,000 fishes have already been used, are being used, or have been approved for use in REACH toxicity testing. And changes to the rules could require hundreds of thousands more.
REACH requires chemicals to be assessed for their effects on human health and the environment. Animal experiments remain the basis of many of those assessments. For fishes, that means experiments testing short-term toxicity, long-term toxicity, bioaccumulation and endocrine disruption. Around 281,900 fishes, roughly three quarters of the total identified by researchers, are associated with long-term toxicity tests alone. And this could get dramatically worse.
A 2022 amendment expanded requirements for long-term fish toxicity testing and removed the most commonly accepted reason for avoiding these experiments. Researchers estimate this could generate another 940 to 1,240 tests involving 520,000 to 680,000 fishes. Potentially more fishes than the entire historical total.
They Are Not Lab Equipment
The moral absurdity becomes harder to ignore the more we learn about fishes.
Rainbow trout, one of the species used in toxicity testing, have been studied extensively for their capacity to experience pain. Researchers examining air asphyxiation estimated that an individual rainbow trout may experience 1.9 to 21.7 minutes of moderate to intense pain before losing consciousness. The evidence incorporated behavioural, neurological and physiological responses.
Another recent study found cleaner wrasses rapidly behaving in ways researchers interpreted as mirror self-recognition. Six of nine attempted to remove marks visible only through a mirror within four hours, with the first attempt occurring after around 20 minutes. The researchers argue the results suggest the fishes already possessed a sense of self rather than developing one through mirror exposure.
These are thinking, feeling individuals. But even the legal definition can erase them. Long-term toxicity experiments begin with fertilised eggs, but EU law does not classify fishes as protected animals until they become capable of independent feeding. Researchers estimated that around 24,000 fishes may already have died after hatching but before reaching the legally protected stage, meaning they are excluded from the official animal count despite the researchers noting that suffering may occur during this period.
Convenient.
Stop Looking for Better Ways to Use Them
REACH itself says animal testing should be a last resort. For short-term toxicity testing, researchers say a genuinely non-animal approach already exists using computer modelling alongside a fish-cell assay. But it has not been incorporated into REACH guidance in a way that requires or incentivises its use.
For long-term toxicity testing, validated replacements are still needed.
So develop them.
Because fishes do not become disposable simply because they are small, underwater, difficult for us to relate to or conveniently excluded from public concern.
The question should not be how many fishes we can justify using. It should be why we are still designing systems that require us to use them at all.