Crustaceans show responses consistent with signs of pain and distress. [1-6] They also have the cognitive capacity to remember, and learn to avoid unpleasant stimuli. [7-9] As a result, RSPCA Australia considers that crustaceans should be captured, handled, transported, stored and killed humanely. This is true for all crustaceans, like crayfish, lobsters, crabs, Moreton Bay bugs, and yabbies, whether they are cooked or eaten raw (sashimi).
Killing involves loss of sensibility (ability to feel pain), followed by death. For killing to be humane, either:
A variety of methods are used to capture, hold, kill and process crustaceans. How it is done depends on the species, whether it is a commercial or noncommercial operation, and what the end product is. In each case, crustaceans should be killed by the most humane method.
The legal status of crustaceans in Australia varies between different states and territories. Crustaceans are protected by animal welfare laws in New South Wales, Victoria, the Northern Territory, and the Australian Capital Territory. In some states, this only applies to crustaceans that are meant to be eaten by people. Penalties may apply if crustaceans are not treated humanely.
Prawns are a delicious and popular seafood choice. However, they must be handled with care and killed humanely prior to cooking There are several recommended techniques to quickly and mercifully end a prawn’s life with minimal pain or distress. This guide covers the best practices for restaurants, fishermen, and home cooks alike when it comes to the ethical preparation of fresh prawns
Why Humane Killing Matters
While prawns do not have advanced nervous systems like mammals, research shows they likely experience some degree of sentience and feel pain. Killing them humanely minimizes suffering and shows respect for the lives of the animals we eat. Quick, precise killing techniques also preserve meat quality by preventing stress chemicals from building up in the muscles.
For commercial operations and restaurants, humane killing is not just ethical but makes good business sense. Consumers increasingly demand higher welfare standards for seafood. Regulators in some areas now require the humane killing of certain crustaceans. Adopting responsible killing methods is the right thing to do for the sake of the prawns, customers, and company reputation.
Recommended Techniques
Spike or Knife to Brain
The most widely recommended method is to swiftly and accurately stab the prawn in the head between the eyes with a thin, sharp spike or the tip of a knife. This severs the nerve cord and destroys the prawn’s brain, causing rapid death. The spike should be pointed, not rounded, to achieve the quickest kill.
Split Through the Head and Tail
Another technique is to take a large chef’s knife and cut the prawn in half lengthwise in one quick firm motion, neatly splitting it from head to tail through the centerline. This severs the head and destroys the internal organs killing the prawn rapidly.
Electric Shock
Some commercial operations or large restaurants use a special electric stunning device that applies a brief, high-voltage electric shock to the prawn This interrupts neurological function and renders them unconscious in under a second so no pain is felt They must then be spiked or split to finish killing them.
What to Avoid
Certain traditional methods of preparing live prawns cause unnecessary pain and suffering and should be avoided on ethical grounds.
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Plunging live prawns into boiling water causes extreme pain and distress as they are slowly cooked alive. They will writhe in agony for over a minute before dying. This method should never be used.
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Ripping the head off live often does not kill the prawn quickly. The body may continue moving afterwards, indicating ongoing sentience. Unless the spike or knife method is used accurately, this is an inhumane practice.
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Leaving prawns out of water to suffocate is also inhumane, as the slow oxygen deprivation causes significant stress and panic before death.
Handling Before Killing
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Store live prawns properly in clean, aerated water to reduce stress. Do not overcrowd the tank.
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Ideally, prawns should be killed only immediately prior to cooking to preserve freshness.
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Lightly ice prawns for 5-10 minutes before killing to sedate them and dull pain perception. Do not leave on ice too long or they will die slowly.
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Thoroughly dry the prawn so your hand does not slip when spiking or cutting.
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Immobilize the prawn on a firm, stable surface for an accurate killing cut.
For Restaurants
Restaurants should consider designating people who are experienced to humanely kill the prawns. This will not only allow for it to be done more humanely, but more efficiently as well. Some best practices include:
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Provide proper training to staff on the accepted killing methods and the rationale behind humane killing.
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Demonstrate proper technique and supervise new staff until skilled.
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Use appropriately sized spikes and knives to fit the prawns. Sharpness is critical.
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Work quickly, accurately, and decisively when killing. Avoid hesitation.
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Check that each prawn is dead via nerve cord destruction before cooking.
Why It Matters
Killing animals humanely requires care, precision, and respect. Following these recommendations allows prawns to be killed swiftly and painlessly, upholding good ethical standards. While the concept of humane killing may be unpleasant, it is a responsible approach for any restaurant, market, or home cook preparing fresh prawns. Doing it correctly makes a big difference in the welfare of these fascinating creatures.
Acceptable stunning and killing methods
This advice is based on the available scientific evidence. However, more research needs to be done before firm decisions can be made about whether stunning and killing crustaceans is cruel.
| Method | Suitable for | Comments |
|---|---|---|
| Stage 1: stunning | ||
| Crustastun (electrical stunning in a water bath) | All species | Requires specialised equipment |
| Chilling in an ice slurry | All tropical crustaceans and temperate species that are susceptible to cold temperatures | A saltwater ice slurry must be used for marine species Not recommended for temperate marine species that are adapted to colder temperatures |
| Chilling in air | Large crustaceans that are adapted to very cold temperatures | |
| Stage 2: mechanical killing | ||
| Splitting | Lobsters and similarly shaped species | |
| Spiking | Crabs | |
It is against the law to kill crustaceans mechanically without first making them unconscious in one of the ways listed below.
With enough electricity, crustaceans can become completely blind within one second of being shocked; this is called an immediate loss of sensibility. [11].
Only purpose-built electrical stunning equipment (the Crustastun) should be used, in accordance with the manufacturer’s instructions. [10] Failure to adequately electrically stun may have serious welfare consequences, including a high rate of autotomy.
Crustaceans are cold-blooded animals and reportedly enter a state of torpor at air temperatures of 4°C or below. They are rendered insensible when their body temperature is sufficiently reduced by chilling. [3].
Scientific proof of the association between chilling and absence of discomfort, stress or pain is limited. People generally think this method works, though, because crustaceans that are chilled don’t show the stress-related behaviors that happen when other methods are used, like boiling. [12] Further research is needed to fully understand the effects of different chilling methods on crustacean welfare.
One major benefit of chilling is that it reduces mobility. This makes crustaceans easier to handle and humanely kill, and also prevents individuals from injuring each other. [13].
Living things that are sensitive to cold, like tropical crustaceans and temperate species, could be stunned by being frozen in an ice slurry. When the temperature is the same, insensibility happens faster in an ice slurry than in air. This is because water absorbs heat much faster than air. [3, 15–16].
A saltwater ice slurry must be used for all marine species. Sea crustaceans should never be put in a slurry of freshwater ice, as this could cause osmotic shock.
Freshwater crustaceans should never be placed in a saltwater ice slurry.
Chilling in an ice slurry is not recommended for temperate marine species that are adapted to colder temperatures. When a saltwater ice slurry is used, the water in it loses some of its saltiness as the ice melts. If the animal is left in the slurry for too long, it could cause osmotic shock. This could happen before insensibility for cold-adapted species if the slurry’s salinity is not kept at a certain level. Monitoring and proper control of salinity of the slurry may help to overcome this potential welfare problem. [3].
Procedure: chilling in an ice slurry
- First, put crushed ice in a insulated container like an esky. Then, add water. For marine species, add salt water that is the same salinity (salt concentration) as sea water.
- For marine species, make sure that the ratio of ice to water (salt water) is 3:1. This will give the mixture the consistency of wet cement and a temperature of about -1°C. Make sure that there is enough ice to keep the right temperature throughout the chilling process.
- Place the crustaceans in the ice slurry. Check them often for signs of not being sensitive (see “Signs of insensibility” for more information). How long it takes to make an animal insensible will depend on its species, its size, and its metabolic state. For many species, at least 20 minutes is required.
- Once the crustaceans start to lose their senses, kill them mechanically right away to make sure they don’t come back.
Large crustaceans that are adapted to very cold temperatures may be stunned by chilling in air. Because heat moves more slowly through air than through water, cooling in air takes longer than cooling in ice slurry. [3, 14, 17].
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