Module 1
04.
Lesson 4 : What’s Ahead: Overview of Upcoming Modules
Lesson 4 provides a preview of what to expect in the upcoming modules.
How slaughter and handling practices affect shrimp welfare during harvest?
What does it mean for a shrimp to be unconscious, paralyzed, or dead, and how can we be sure the killing method is humane?
How the living environment — including water quality, enrichment, density, and social interactions — could influence shrimp behavior, welfare, and overall health?
What you will find in this lesson
References such as “Dupont et al., 2015” or “Martin & Durand., 2015” refer to the authors of the scientific publications on which the presented information is based. They ensure the accuracy and traceability of the data.
Handling at slaughter
Slaughter practices
Several practices exist to kill shrimp but some of them have been proved to be inhumane. In the next lesson, we will focus on 2 main practices:
- Immersion in an ice slurry bath: shrimp are harvested and immersed in an ice slurry bath for a certain time with a temperature between 0 and 4°C. Salinity might vary depending on the quantity of ice needed and if the water used is from the pond or freshwater.
- Electrical stunning before ice slurry bath: shrimp are harvested and go through a stunner designed to stun them with electricity before going to the ice slurry bath. Currently, 2 stunners are on the market: the in-water stunner and the out-of-water stunner.
In the next lesson, we will discuss these two slaughter practices in regards with shrimp welfare.
The case of the pump
No matter the slaughter practice, harvest can be done either manually (operators in the water collecting the shrimp at the exit gate and filling baskets) or with a pump. No research has focused on a comparison between the two methods in terms of animal welfare, but it seems obvious that, when using a pump, it is better to avoid the elbows often seen with the tubes. Concerning the manual method, it should be recommended to avoid charging too much the basket to avoid having shrimp being crushed.
Definitions
A humane killing is a method that ensures an animal is either killed instantly or that involves rendering an animal insensible to pain until death ensues.
Before talking about the best method to kill shrimp, here are some definitions:
- Uncousciousness: there is an anaesthetization, the animal does not feel pain nor distress or any stimuli caused by the process
- Death: the animal does not move and is dead
- Paralyzis: the animal can feel everything but can not move
Here is an example of a dialogue with operators in Central America after the ice slurry bath (+/- electrical stunning):
- Scientist: “Do you think the shrimp are dead?”
- Operators: “Yes”
- Scientist: “How do you know that?”
- Operators: “Because they are not moving anymore.”
The scientist decided to immerse the shrimp into warm water after the ice slurry bath (no matter if there was electrical stunning or not).
- Scientist: “Look, the shrimp start swimming again.”
- Operators: “Oh… So they were not dead?”
- Scientist: “No, they were not dead. But we do not know for now if they were not moving because they were unconscious (and not sensible) or because they were parylized (and feeling everything without moving).”
Indicators of unconsciousness
In terrestrial animals or in some fish, there are clear indicators indicating that animals are unconscious (see beside an exemple of signs of recover in fish with the eye roll reflex). In terrestrial slaughterhouses, operators must check that the signs of consciousness are absent or that the signs of unconsciousness are present before bleeding.
In shrimp, there are not yet validated indicators to evaluate the unconsciousness. Update will be done as soon as more research will be available.
(Picture from HSA. Signs of revover in fish - the eye roll reflex, Adapted from 'Protocol for assessing brain function in fish and the effectiveness of methods to stun and kill them'. SC Kestin, JW van de Vis, DHF Robb. The Veterinary Record, March 9 2002.)
What living environment is suitable for shrimp?
In this module, we will discuss different topics around shrimp living environment.
- Introduction to the concept of enrichment and substrate to allow shrimp to express more natural behaviours.
- Discussion on the water quality with the best parameters for shrimp welfare.
- Field experiment feedback on feeding improvement, in terms of frequency.
- A frequently asked question around optimal density linked to the shrimp sociality and the concepts of territorialiy, hierarchy and cannibalism.
As for the slaughter process, a lot of information is missing on the best living environment for shrimp and we are still waiting for more research to come.
While you wait, feel free to watch this beautiful video we recorded in a raceway in Central America.
What to remember
- Focus on two methods to kill shrimp:
- Ice slurry bath (immersion in water at 0–4 °C).
- Electrical stunning before the ice bath (in-water or out-of-water stunner).
- Handling during harvest (pumping or manual collection) can affect shrimp welfare: it is important to handle them gently, to avoid the elbow for the pump and to avoid crushing them.
- Distinguishing unconsciousness, paralysis, and death in shrimp is not easy. Classical signs used for other animals are not validated, and some shrimp may appear dead while they are only unconscious or paralyzed.
- The living environment is a key factor for welfare: water quality, enrichment, density, social interactions, feeding… but many questions remain unanswered and will be addressed in the following modules.
- Focus on two methods to kill shrimp:
💡 In summary: this lesson lays the groundwork for considering shrimp welfare during harvest and in their environment, introducing concepts that will be explored in more detail in the upcoming lessons.