top of page

Why stop using eyestalk ablation?

What is Eyestalk Ablation?

Eyestalk ablation (ESA) involves one or more of the animal’s eyestalks being removed through crushing, cutting, burning, or tying it off. This increases spawning and shortens the maturation time. However, it disturbs the health and welfare of breeding animals and their offspring. Also, ESA affects the quality of the animals and their survival. This then affects production and can lead to lower financial profits for farmers. 

Eyestalk ablation and welfare

Scientists label decapods (including shrimps and prawns) as sentient beings. ‘Sentience’ means that the animals can feel pain and distress. It also means they have negative and positive feelings. Researchers discovered that when shrimps are subjected to ESA, they try to escape it. They also flick their tails and rub their eye area. When the wounds are covered or medicine is given, the shrimps calm down. This suggests that the ablation caused them pain and distress. Any practice that causes or might cause pain, fear, and or distress should be minimised if not eliminated.

The X-organ-sinus-gland complex in the eyestalk of crustaceans produces and stores hormones. There is one hormone in particular called gonad-inhibiting hormone (GIH) that controls the reproductive organs and when they mature. It also affects when spawning happens. Removing the gland speeds up their maturation and makes them spawn sooner.

Another hormone affected is the moult-inhibiting hormone (MIH). Following ablation, moulting increases. This process uses a lot of the animal's energy. They become exhausted and stressed. It is harder for them to reproduce, especially in intensive farming settings. Shrimps that have recently moulted have softer bodies. Other shrimps eat them because they can't defend themselves without a hard shell.

Other important hormones are not released properly, which leads to hormonal problems.

This causes lower survival rates of breeding animals, reduced quantity and quality of offspring, physical harm, health issues, reproductive exhaustion, weight loss and stress.

Studies on breeding animals with either one or both sides of their body ablated have shown major differences in mortality rates.

Ablated females' offspring are less tolerant of stress. They are also more likely to get diseases. There are many possible stress factors for animals in aquaculture. These include handling, crowding, high stocking densities and poor water quality. Eyestalk ablation is one more thing that worsens their welfare.

Impact on aquaculture outcomes

Studies show that animals who have not been ablated can have the same productivity levels as those who have. This is still true when the shrimps are raised in intensive farming conditions. The offspring show similar performance. They may even resist stress better than offspring from ablated females. A few studies have found that non-ablated females produce more eggs (> 20%) and nauplii (> 16%) per day. This is when we compare them with the ablated females. Several studies show that there is no big difference in hatching rates between ablated and non-ablated female shrimps.

The evidence suggests that there are many other factors that affect productivity. These could include environmental conditions during spawning, variation in fertilisation rate and general animal health. Eyestalk ablation is not the only thing that affects animal productivity.

Animals who have had their eyestalks removed succeed more in mating and spawn more often. But this comes at a cost. They have almost double the mortality rate and lower reproductive productivity in the long-term.

Juveniles that come from non-ablated breeding animals do much better. They have higher survival rates when affected by common shrimp diseases such as Early Mortality Syndrome and White Spot Syndrome Virus that are common shrimp diseases in aquaculture.

The use of non-ablated breeding animals has many benefits. These include lower mortality rates for breeding animals, better animal welfare, higher productivity in the long-term, and less losses for producers.

It is clear that ablating breeding animals has no significant long-term advantages. Farmers should replace it with the use of non-ablated breeding animals. Changes in husbandry should be made to compensate for the lower mating rate of non-ablated animals.

The way forward

Producers should consider using closed-cycle breeding as a beneficial alternative to ESA. This means that producers breed successive generations of high-quality animals. This replaces the need to rely on wild breeding animals for losses.

But it is very important to maintain the welfare of closed breeding cycle animals. Breeding animals should be used for a limited number of generations. To achieve similar or better production without ESA, producers should focus on the following: providing breeding animals with good quality nutrition during the pre-growth stage; maintaining a sex ratio of 1:2 male to female instead of the usual 1:1; and creating optimal environmental conditions.

The nutritional, behavioural, health, environmental and mental needs of the animals are very important. Farmers should make these a priority, whether they use ablated or non-ablated animals.

Consumer demand

Consumers are becoming more aware of animal welfare practices in shrimp farming and aquaculture. Their concern is growing. It is therefore in the best interests of producers to move towards ablation-free farming. This is necessary to meet the demands of consumers and the strict requirements of certification bodies and laws in certain countries.

Shrimp Welfare Project recommends the use of ablation-free stock in shrimp farming. We discourage sourcing animals from ablated breeding animals. Several maturation facilities in countries such as Brazil, Colombia, Ecuador, Mexico and Thailand have stopped this practice and have successfully transitioned to non-ablation methods.

bottom of page