Both lobsters and crabs have highly developed nerve centres called "ganglia", each centre capable of experiencing pain, not merely the one in the head. Destroying these centres cleanly and quickly takes great skill.
At present there is no way of killing these creatures without causing them pain and distress, but in the hands of professional chefs they will at least be dispatched relatively quickly. In the hands of less experienced people the suffering could well be prolonged further, and this after the animals have been taken home in often wholly inadequate conditions.
If consumers still feel the need to eat shellfish, they should ensure that adequate provision has been made for the welfare of these animals. The least cruel method at present recommends that they are frozen to minus 20C for two hours in a deep-freeze cabinet, and boiling, cutting or grilling should be done immediately afterwards. This renders the animal unconscious so that they feel no pain when boiled, cut up or grilled.
The prototype of a stunning tank is at present under review, and if successful, will cause unconsciousness in a fraction of a second.
While the Shellfish Network would prefer to see all the shellfish free to live out their lives in their own environment, until such time their welfare should be of the first consideration.
The Shellfish Network
East Horsley, Surrey