Another Life: How far does pain extend in the living world?

Evidence mounts on ‘possibility of pain experience’ in fish and marine crustaceans

Human beings hate pain and mostly shrink from inflicting it, even at second hand. But how far does pain reach in the rest of the living world and how ready are people to care?

It’s a couple of years since the Swiss government banned the boiling of lobsters alive, along with their customary transport in ice. This recognised the creatures’ sentience, or awareness of feeling, in an improvement of animal welfare.

In Norway and New Zealand, too, there are new rules for the humane killing of decapod crustaceans such as lobsters, crabs, crayfish and Nephrops prawns. And in Britain there is pressure to include them, along with intelligent cephalopods such as octopuses and squid, in the new Animal Welfare (Sentience) Bill now in progress through the House of Lords.

In Ireland the issue has yet to find much of a voice, though “declawing” of live brown crabs at sea is well condemned officially. But Queen’s University Belfast has a leading figure in research into invertebrate sentience, which now extends even to insects.


Along with years of his own biological experiments, emeritus Prof Robert Elwood has examined the many studies by others into "the possibility of pain experience" in fish and marine crustaceans. In his latest review, published in Frontiers of Veterinary Science, he concludes that "both fish and decapods should be awarded consideration for their welfare".

A key objection in assessing potential pain in “lower” animals such as fish is that their responses to it could be simple mechanical reflexes, without actual awareness of feeling that could amount to pain.

In experiments with rainbow trout in Sweden, fish were injected in the lips with acid or bee venom. They rocked from fin to fin and repeatedly rubbed their lips on the sides of the tank and its gravel floor. This prolonged activity, with its echo of human rubbing of a sore spot, had “the largest impact on my own thoughts”, says Elwood.

He embarked on laboratory experiments of his own. He studied the behaviour of prawns that had acid brushed on to one antennae or had it pinched with forceps. They rubbed it, just like the trout. Both fish and prawns were also soothed by pain relievers such as morphine.

Brown crabs that had a claw removed “in the manner of fishery practice” showed behaviour directed at the wound and guarding it from other crabs competing for food or mates.

The most elaborate experiments by Elwood and his team involved hermit crabs, the small animals of the lower shore that slip their bodies for dark shelter into vacant gastropod shells, changing them as they grow. Using empty shells rigged to give electric shocks, they found the crabs learned avoidance of them, sacrificing shelter and feeding time, “consistent with the idea of pain”.

Elwood’s 13 published experiments that relate to the welfare of decapods (lobsters, crabs and others) have brought highly critical responses from the fishing industry. Some point to the animals’ lack of the pain-sensing areas in human brains. Others see the brains of fish and crustaceans as too small for the neural computation needed for awareness.

“There is complete denial,” says Elwood, “that very different brains can have similar functions as has been noted for visual ability in humans, cephalopods [octopuses and squids] and decapods.” He offers, also, the surprising complexity of the cognitive abilities of bees.

Elwood grants that there is “no conclusive proof of pain in any animal”, but “we must at least accept the possibility” from scientific evidence.

British Veterinary Association

Meanwhile, the British Veterinary Association now accepts that decapods are sentient and calls for electrical stunning before killing. An implement called the CrustaStun is already on the market.

While the issue of decapod welfare has yet to find many voices in Ireland – the Seanad might offer a first forum – the matter of “declawing” brown crabs at sea has already met with official disapproval.

In 2014, Susan Steele, chairwoman of the independent Sea-Fisheries Protection Authority, said: "The current practice of throwing clawless, defenceless crabs into the sea to be scavenged on by predators does not aid the fishery."

Bord Iascaigh Mhara points out that the crab-processing industry likes to buy the animals intact, then disassembles them for supermarket plastic. At major food-processing plants, says Elwood, crustaceans are commonly dismembered without being killed.

What, then, is the home chef meant to do with a live lobster, purchased, perhaps, on the Wild Atlantic Way? I must admit, years ago, to the mutual torture of the boil. Later, on advice, came a preliminary half-hour in the freezer, promising to stun the beast to sleep.

Live lobster, as it happens, no longer calls at our door. This has spared me a visit to YouTube, where chef and culinary guru Andrew Zimmern shows exactly, with a nerveless hand, where to plunge the knife.