Osmotic stress leading to drowning of lobsters

[Guest guest]

Hi,

Does anyone know exactly what severe osmotic stress is and what exactly

this

does to a sea (salt water) dwelling animal (eg putting lobsters in fresh

water?) re drowning?

Thanks,

Marguerite

 

http://www.maf.govt.nz/mafnet/press/archive/2000/140200lob.htm

 

maf > media centre > archive > 2000

Media Release

 

14 February 2000

 

Chill it, then split or spike it - the humane way to kill a lobster

The appropriate way to humanely kill a rock lobster is to chill it, then

kill it by either splitting or spiking it.

 

Chefs using this method can be sure that they are killing the lobsters

humanely, whilst preparing good quality lobster meat according to a

recent study by MIRINZ Food Technology and Research.

 

It's important because under the new Animal Welfare Act, which commenced

on the 1 January 2000, lobsters are classified as animals, and

accordingly, it is now an offence to kill a lobster inhumanely.

 

In New Zealand any animal killed for meat consumption must be killed

humanely. This means the animal must not be stressed when being handled,

should be held at the place of slaughter for only a short time under

appropriate conditions, and the killing method must not cause pain or

distress prior to death. It applies to animals killed in restaurants,

like lobsters.

 

Seafood shops and restaurants have recently come under growing scrutiny

concerning their methods for killing rock lobsters. One method, tailing

(where the body is severed between the fore half and abdomen with a

knife) received national media coverage and was condemned by the RNZSPCA

as inhumane.

 

The report's writers, Neville Gregory, MIRINZ scientist and member of

the National Animal Welfare Advisory Committee (NAWAC) and Dr Tim Lowe

found eight common procedures were being used in New Zealand seafood

restaurants to kill lobsters, usually with two or more methods combined.

 

These were chilling, drowning, spiking, chest spike, splitting, and

tailing, freezing, and boiling (definitions listed below).

 

" Not many lobsters are killed by freezing or boiling in New Zealand

restaurants because both methods affect the quality of the meat, " says

Dr Gregory, " Boiling lobsters alive tends to make the meat chewy, and

freezing makes the meat lose its fresh appearance. Boiling also causes

the lobster to shed its legs making it unsuitable as a garnish for

serving lobster meals, " he said.

 

The research found that lobsters should be chilled before being killed.

 

" It's the simplest way to make them insensible without damaging the

edible parts of the body. Being cold blooded, chilling the lobster helps

reduce nerve function and metabolic activity. To chill, place the

lobster in salt water or a refrigerator set at two to four degrees. When

it is fully chilled, the lobster will stop moving and no longer responds

to being handled, " Dr Gregory said. Chilling at a temperature above four

degrees does not guarantee complete insensibility, but a lobster can be

kept alive at this temperature for up to two days.

 

Dr Gregory says placing a lobster in unsalted tap water causes severe

osmotic stress leading to drowning. Drowning can cause the lobster meat

to turn soft due to it retaining water as part of the osmotic affect.

Regardless of water temperature, drowning is an inappropriate killing

method for lobsters.

 

The report recommends chilling a lobster before splitting it along its

length where it has two chains of nerve ganglia, with interconnecting

nerves along its body under the shell. Chilling beforehand prevents the

lobster from moving and mistakes during splitting occurring, otherwise

the manoeuvre requires skill to ensure a humane kill in an unchilled

animal. A lobster should also be well chilled before head spiking.

 

The report says that tailing and chest spiking do not cause immediate

unconsciousness in unchilled lobsters.

 

For further information concerning the research findings contact: Dr

Neville Gregory, Animal Welfare and Stress section, MIRENZ, Phone: 07

838 5321

 

For Animal Welfare Act information contact Kate Horrey, Animal Welfare

Policy Adviser, Ministry of Agriculture and Forestry, Phone: 04 474 4100

 

Common methods for killing lobsters in New Zealand seafood restaurants:

Chilling- animals are cooled in a cold room, fridge or slurry ice

 

Drowning - animals are placed in tap water

 

Head spiking - animals are spiked through the chest wall from the

underside

 

Splitting - the body is split along its length with a knife

 

Tailing - the body is severed between the fore half (cephalothorax) and

abdomen with a knife

 

Freezing - animals are frozen using a kitchen freezer

 

Boiling - animals are dropped into boiling water