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Stunning and killing of edible crabs ( Cancer pagurus )

By B. Roth, S. Oines

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Abstract

The stunning and killing efficiency of ice, superchilling (N2 gas), freezing (-37 degrees C), gradual heating (40 degrees C), boiling, piercing of ganglia, salt baths (NaCl and KCl), gas (CO2) and electricity (50 Hz AC) on edible crabs was studied. Results showed that electricity was the most efficient stunning method, whereby edible crabs could be rendered insensible within I s using electric field strengths of 400 V m-1 and above. Prolonging the electrical current to 10 s resulted in less potential difference (220 V m-1) required to stun the crabs. Applying a two-stage stun with 530 V m-1 for I s followed by 170 V m-1 for 2 min resulted in a state of prolonged unconsciousness and 60% mortality. Failure to stun the crabs with electricity resulted in massive autotomy, where all appendages were lost. Behavioural responses were lost in approximately 30% of crabs after 100 min of chilling on ice, while freezing did not render the crabs unconscious until temperatures of subzero were reached. The exposed chelipeds stiffened, and once frozen, irreversible damage was caused. Placing crabs into heated seawater (40 degrees C) led all responses to be lost after 5 min, while the internal temperature exceeded an average of 26 degrees C, representing approximately 2.5 min of boiling. Gas, in the form of CO2, NaCl, and a low concentration of KCl (5%), failed to render the animals insensible within 12 min. Using 20% KCl saw all animals lose all behavioural responses within 3 min. The piercing of single ganglions failed to kill the animal; both ganglia must be pierced in order to kill the animal. We conclude that electrical stunning is recommended prior to boiling or carving, while piercing can alternatively be carried out by trained personnel.

Date 2010
Publication Title Animal Welfare
Volume 19
Issue 3
Pages 287-294
ISBN/ISSN 0962-7286
Language English
Author Address Nofima-Norconserv A/S, Box 327, N-4002 Stavanger, Norway. bjorn.roth@nofima.no
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Tags
  1. Animal rights
  2. Animal slaughter
  3. Animal welfare
  4. Aquacultural and fisheries
  5. Aquatic Biology and Ecology
  6. Aquatic organisms
  7. Arthropods
  8. Cancer
  9. Crustaceans
  10. Diseases
  11. Electricity
  12. Electronarcosis
  13. Employees
  14. Freezing
  15. Ganglia
  16. Heat
  17. Invertebrates
  18. Mammals
  19. mortality
  20. peer-reviewed
  21. personnel
  22. Primates
  23. shellfish
  24. staff
  25. stunning
  26. temperatures
  27. water
Badges
  1. peer-reviewed