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Humane slaughter of African sharptooth catfish (Clarias gariepinus): Effects of various stunning methods on brain function

Brijs, Jeroen and Sundell, Erika and Hjelmstedt, Per and Berg, Lotta and Sencic, I and Sandblom, E. and Axelsson, M. and Lines, J. and Ellis, M. and Saxer, A. and Gräns, Albin (2021). Humane slaughter of African sharptooth catfish (Clarias gariepinus): Effects of various stunning methods on brain function. Aquaculture. 531 , 735887
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Abstract

Common slaughter procedures for African sharptooth catfish (Clarias gariepinus) include asphyxiation, ice chilling and exsanguination, which may all cause substantial suffering over prolonged periods of time before death. Therefore, comprehensive evaluations of potentially more humane slaughter procedures for this species are urgently needed. Here, we use a non-invasive electroencephalographic (EEG) method to assess the state of sensibility in African sharptooth catfish in response to various stunning methods (e.g. ice chilling, electrical stunning, electrical stunning followed by exsanguination, percussive stunning, and immersion in isoeugenol). Based on the abolition of visually evoked responses (VERs) on the EEG, ice slurry immersion induced insensibility between 2.6 and 7.6 min, during which catfish exhibited aversive behaviours. Once VERs were lost, they remained absent so long as catfish remained immersed in the ice slurry. Electrical stunning (i.e. exposure to similar to 1.7 A dm(-2) at a water conductivity of similar to 997 mu S cm(-1)) induced insensibility immediately but not irreversibly. Depending on the duration of the stun (i.e. from 1 to 10 s), catfish either regained VERs immediately or within 4.9 min after the completion of the electrical insult. However, when a 10 s electrical stun was immediately followed by exsanguination and immersion in an ice slurry, the duration of insensibility was sufficient to humanely kill catfish. When administered correctly, manual percussive stunning with a fish priest induced insensibility immediately and irreversibly. However, 36% of catfish regained VERs, which is likely explained by the difficulty associated with administering an accurate manual percussive stun of sufficient force on a live and struggling catfish. Catfish appeared to be sedated following immersion in isoeugenol (i.e. catfish were calm and easy to handle), yet VERs remained present at doses exceeding that recommended for euthanasia in salmonids, which indicates that this substance may not be suitable for stunning catfish. However, the potential for using isoeugenol as a pre-stunning sedative for improving handleability and reducing handling stress of this species warrants further investigation. In conclusion, this study clearly demonstrates that when singularly administered, none of the abovementioned stunning methods could reliably induce insensibility immediately and/or irreversibly without welfare implications. Yet, our findings indicate that these shortcomings can be resolved by using a combination of methods. This could include an electrical or percussive stun to immediately induce insensibility that should be immediately followed by exsanguination and immersion in an ice slurry to maintain insensibility until death.

Authors/Creators:Brijs, Jeroen and Sundell, Erika and Hjelmstedt, Per and Berg, Lotta and Sencic, I and Sandblom, E. and Axelsson, M. and Lines, J. and Ellis, M. and Saxer, A. and Gräns, Albin
Title:Humane slaughter of African sharptooth catfish (Clarias gariepinus): Effects of various stunning methods on brain function
Series Name/Journal:Aquaculture
Year of publishing :2021
Volume:531
Article number:735887
Number of Pages:11
Publisher:ELSEVIER
ISSN:0044-8486
Language:English
Publication Type:Journal article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Fish and Aquacultural Science
Keywords:Electrical stunning, Ice chilling, Percussion, Isoeugenol, EEG, VERs, Insensibility, Unconsciousness
URN:NBN:urn:nbn:se:slu:epsilon-p-109495
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-109495
Additional ID:
Type of IDID
DOI10.1016/j.aquaculture.2020.735887
Web of Science (WoS)000595052000014
ID Code:21199
Faculty:VH - Faculty of Veterinary Medicine and Animal Science
Department:(VH) > Dept. of Animal Environment and Health
Deposited By: SLUpub Connector
Deposited On:12 Jan 2021 07:03
Metadata Last Modified:12 Jan 2021 07:11

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