What's the kindest way to kill a lobster?

Lobsters may not exhibit recognisable symptoms of pain, but that doesn't mean they don't experience it, say some scientists

"Lobster is one of those rare foods that you cook from a live state," the recipe says.

"Quickly plunge lobsters head-first into the boiling water... Boil for 15 minutes," the recipe then instructs.

It's the tried-and-trusted method for many of us with any experience of cooking lobster - and there are dozens of similar recipes online.

But on Wednesday Switzerland banned the practice and ordered that lobsters be stunned before being despatched to our plates to avoid unnecessary suffering in the kitchen.

It comes amid growing scientific evidence that lobsters - and other invertebrates, such as crayfish and crabs - are able to feel pain.

So what's wrong with the traditional method? And what are the alternatives?

Can lobsters feel pain?

Animal welfare scientists define pain as "an aversive sensation and feeling associated with actual or potential tissue damage", explains Jonathan Birch, assistant professor in philosophy at the London School of Economics.

Defined like this, experiments suggest crustaceans do feel pain, Dr Birch explains in his article "Crabs and lobsters deserve protection from being cooked alive".

In a series of experiments at Queen's University in Belfast, crabs gave up a valuable dark hiding place after repeatedly receiving an electric shock there.

"They were willing to give up their hideaway in order to avoid the source of their probable pain," said Prof Robert Elwood, who led the team carrying out the experiments. He told the BBC that numerous experiments showed "rapid avoidance learning, and [crustaceans] giving up highly valuable resources to avoid certain noxious stimuli" - consistent with the idea of pain.

Crustaceans don't necessarily exhibit signs of pain that are easily recognisable to humans, say welfare activists. Stress-induced behaviours include thrashing, trying to escape and autotomy - where body parts are shed by the animal in response to damage or capture.

This might explain why they are excluded from many countries' legislation on animal welfare - though decapod crustaceans are protected in countries like Norway, New Zealand and Switzerland, and there are campaigns for change elsewhere.

So how should you kill them?

Humanely, say activists - whereby they are killed immediately or put into a state of continuous unconsciousness until death occurs.

But neither stunning nor killing crustaceans is necessarily a simple business when compared, for example, to fish.

This is because crustaceans have decentralised nervous systems, meaning that unlike fish, they can't be rendered unconscious with a single blow to the head.

To "spike" a lobster to death, again unlike fish, you have to pierce the body in more than one spot.

So the best ways to achieve a quick death are, according to animal welfare charity RSPCA Australia:

• Stunning it electronically with a device such as the Crustastun before killing or cooking - but with the device reportedly retailing at £2,500 ($3,400), this is unlikely to appeal to the domestic cook

• Stunning the crustacean by chilling it in cold air or an ice slurry - saltwater or freshwater, according to the species - for at least 20 minutes

• Once the lobster is stunned, it should be mechanically killed as quickly as possible, says the RSPCA, by splitting it along the longitudinal midline on its underside. This can be done without first stunning the animal, but it cannot be considered as entirely humane as it takes even the most experienced person several seconds to carry out

• Using the aquatic fish anaesthetic AQUI-S, which studies suggest kills without causing pain or distress

More details from RSPCA Australia

How shouldn't they be killed?

• Boiled alive and sentient (either in boiling water or cold water that is brought to the boil)

• By separating the tailpiece from the thorax without first destroying the nervous system (even if the lobster is unconscious)

• Cutting the animal up while sentient

• Microwaving or drowning

For Prof Elwood, the major concern is not the domestic cook or even restaurant kitchens, but major food processing plants, where animals are commonly dismembered without being killed.

He also says labelling crustaceans with relevant welfare information could help consumers make informed choices.