Why blind farmed shrimp?
Why only the females?
Question: why do shrimp farms blind their female shrimp?
Answer: because captive sighted female shrimp do not develop ovaries. If you’re a shrimp hatchery with no reproducing shrimp you’ve just invested in a really expensive aquarium.
Welcome to Costs Matter, a series that asks different questions all of which have the same answer: to better manage costs. The costs are frequently economic though not always. The series focuses narrowly on the impact of costs. It does not claim these costs are the sole cause. To read more in the series, visit https://medium.com/galileo-onwards/costs/home.
The practice of shrimp blinding, technically called eyestalk ablation, began in the 1970s and it enabled the commercialization of shrimp farming. It made the industry more predictable — an important consideration for a business.
Wikipedia describes eyestalk ablation in quite some detail. The ethics of these practices do not fall under the ambit of Costs Matter so are not discussed here.
The Alternatives section in Wikipedia says there are two alternatives to ablating shrimp eyestalks:
- giving high quality, nutritious feed to broodstock in pre-maturation stage
- changing the sex ratio in breeding tanks from 1:1 to 1:2 (male-to-female)
⑴ is simple proof of Costs Matter. Giving high quality feed will increase costs. ⑵ is interesting because you’d think a shrimp hatchery, like a chicken hatchery, is already interested in only keeping a predominantly female brood. If you’re wondering why hatcheries are interested in high female populations, see “Why are rotisserie chickens always hens?”
Why don’t all hatcheries only keep a high female to male ratio? That will be discussed in a future Costs Matter post.
Why do blind shrimp develop ovaries?
It’s all good to know why shrimp farmers blind them but why, you ask, do blinded shrimp develop their ovaries?
Sorry, but that answer is out of scope for the Costs Matter department. Wikipedia has some speculations on the matter.