Female prawns in prawn farms have their eyes sliced open or cut off
A Meat and Dairy Industries Article from All-Creatures.org

FROM AnimalsAustralia.org
November 2020

Eyestalk ablation: a hatchery technique of macerating or destroying the eyestalk gland in female broodstock prawns to encourage spawning.

You may have heard about the horrors inflicted on pigs and chickens inside factory farms but it might come as a surprise to learn of the cruel procedure that is happening in almost all prawn farms around the world.

It's called 'eyestalk ablation' and this is the definition from the Australian Prawn Farming Manual:

eyestalk ablation: a hatchery technique of macerating or destroying the eyestalk gland in female broodstock prawns to encourage spawning.

In short, female prawns have their eye sliced open or cut off — usually without pain relief — to make them reproduce faster.

This illustration shows one method of the gruesome procedure:

Eyestalk ablation illustration from the Food and Agriculture Organisation of the United Nations' Shrimp Hatchery manual.

Along with cutting and squeezing the prawn's eye, other methods including cauterisation (cutting the eyestalk with a heated blade or forceps) and ligation (tying a thread or wire around the eyestalk causing it to fall off after a few days).

Female prawns have a gland behind their eyes which tells their ovaries when to mature. In the wild this could be influenced by things like breeding season or environmental factors but prawn farmers have found that the stressful and crowded conditions on farms can make prawns reluctant to reproduce. By destroying this gland, farmers rapidly force ovary growth, denying female prawns the natural instinct to only reproduce when the conditions are right.

Research has found that, given the right environment, female prawns in farms will breed without having their eye cut off. One of Latin America's largest group of prawn farms, SeaJoy, has already phased out this gruesome procedure.

Does it hurt?

A study into the pain experienced by prawns whose eye was sliced open and crushed or ligated found that both procedures caused prawns to become disoriented, flick their tail (an escape reflex) and rub the traumatised area — all behaviours associated with pain. The ablated prawns were also less likely to seek shelter following the procedure, which researchers believe to indicate a degree of stress amongst these animals. The study concluded that:

These procedures are traumatic not only because of the surgical treatment or ligation but also due to the subsequent discomfort and hormonal changes.

Scientist Dr Robert Elwood has also studied the way prawns react to negative stimulus and concluded that their behaviour was "consistent with the interpretation of pain experience."

What's more, studies have found that prawns and other crustaceans are able to see polarized light, which humans can't. This superior vision helps them with navigating through water, seeing transparent or silvery prey, and avoiding predators. Destroying a prawn's eye not only destroys the hormonal gland moderating their reproduction, but impacts their vision as well. In a crowded farm environment, impaired vision is likely to increase the stress on these animals.

Prawns travel in 'schools' and communicate with one another using snapping, clicking sounds. Some species have been known to form mutually beneficial relationships with other sea animals. Studies have found that prawns are able to innovate and solve problems to get food. 

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