Fish welfare is a major component of sustainable fish farming and research to gain an in-depth understanding of the factors affecting the welfare of farmed fish is of high priority . Guidelines from the World Organisation for Animal Health and European Food Safety Authority of economically important aquaculture species are available, including harvest and slaughter, however, there is still a need to develop efficient humane slaughter methods (Hastein, 2007) . Existing m ethods for European sea bass consider to be inhumane and not conclusive (de la Rosa et al., 2021) . Therefore, there is an urg ent need to develop and evaluat e stunning/slaughter methods that will ensure immediate loss of brain function, insensibility to pain and maintenance of flesh quality. The aim of the study was to evaluate the impact of different stunning methods prior to slaughter on the onset of rigor mortis, muscle pH and stress indicators in European sea bass .
Materials and Methods
European seabass (Dicentrarchus labrax) ranging in weight from 250 to 300 grams were used to evaluate the effect of three different stunning methods: chemical (Group Benzocaine), electronarcosis ( Group E/A: electrical stunning, 1.5 V/cm), and thermonarcosis ( Group Ice Slurry: immersion in ice-slurry without prior anaesthetization). Following crowding, all fish were captured by net and slaughtered by immersion in ice-slurry. Capture of fish by hook and line and immediate slaughter by pithing (ikijime), was used as control (Group Ikigun). M uscle pH and r igor m ortis were performed at regular intervals between 0- and 4-hours post-mortem. Blood samples were taken to determine haematological (haematocrit), biochemical (g lucose, lactate , osmolality) and hormonal indicators (cortisol). All data are expressed as means with the standard error of the means (SEM, n = 10 per group). Data analyses were based on ANOVA or Duncan’s multiple range test and significance ascribed to differences at the 0.05 level.
Development of humane stunning/slaughter methods for farmed Mediterranean fish species is of high priority . E/A has shown a great potential as an alternative stunning method in European sea bass (Zampacavallo et al., 2015). Our results show that handling stress prior to stunning significantly enhances the stress response and has a negative impact on quality indicators (RI% and muscle pH). Electrical stunning delays the time needed to reach full rigor mortis and maintain muscle pH in comparable levels with those obtained in sunning/slaughter fish in ice-slurry. Chemical anaesthesia is also stressful for the fish and affects negatively flesh quality. Finally, the study confirmed that pithing , used by experienced staff, does not evoke an increase in stress indicators and ensures rapid insensibility.
de la Rosa I, Castro PL, Ginés R. Twenty Years of Research in Seabass and Seabream Welfare during Slaughter. Animals . 2021; 11(8):2164. https://doi.org/10.3390/ani11082164
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Zampacavallo G, Parisi G, Mecatti M, Lupi P, Giorgi G, Poli BM. Evaluation of Different Methods of Sunning/Killing Sea Bass (Dicentrarchus labrax) by Tissue Stress/Quality Indicators. J Food Sci Technol. 2015 May;52(5):2585-97. doi: 10.1007/s13197-014-1324-8. Epub 2014 Apr 8. PMID: 25892757; PMCID: PMC4397339.
Research funded by the European Maritime and Fisheries Fund – Operational Programme for Greece (2014 - 2020) . Project Code: MIS 5010690.