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Stunning and killing of edible crabs (Cancer pagurus)

Published online by Cambridge University Press:  01 January 2023

B Roth  and
S Øines
B Roth*
Affiliation:
Nofima-Norconserv A/S, Box 327, N-4002 Stavanger, Norway Department of Biology, University of Bergen, Box 7800, N-5020 Bergen, Norway
S Øines
Affiliation:
Nofima-Norconserv A/S, Box 327, N-4002 Stavanger, Norway
*
* Contact for correspondence and requests for reprints: bjorn.roth@nofima.no
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Abstract

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The stunning and killing efficiency of ice, superchilling (N2 gas), freezing (-37°C), gradual heating (40°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 1 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 Vm−1 for 1 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°C) led all responses to be lost after 5 min, while the internal temperature exceeded an average of 26°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.

Keywords

animal welfareedible crabselectricitykilling edible crabsstunningtemperature
Type
Research Article
Information
Animal Welfare , Volume 19 , Issue 3 , August 2010 , pp. 287 - 294
Copyright
© 2010 Universities Federation for Animal Welfare

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