Effect of ice stunning versus electronarcosis on European sea bass (Dicentrarchus labrax) muscle structure, ultrastructure and quality traits

In recent years, the aquaculture industry has seen an increasing concern regarding the welfare of fish, particularly the slaughter and stunning processes, one of the most significant wellbeing issues. Despite the critical role of stunning methods in fish processing, studies examining their impact on the structural integrity of muscle tissue and the overall quality of fish have been relatively scarce. In this context, the current study subjected adult European sea bass with an average weight of 693.8 ± 71.6 to two distinct stunning methods prior to slaughter: immersion in ice water and electronarcosis (with a voltage of 40 V and frequency of 50 Hz for 15 s) to examine their effect on muscle and quality parameters. Immersion in ice water resulted in better and more preserved muscle organization. Electronarcosis exhibited higher K values (p < 0.05) and a softer texture (p < 0.05) with less gumminess (p < 0.05), including changes at electrolyte levels (P: p < 0.001; K: p < 0.036). No significant differences were found in plasma stress biomarkers, including cortisol (814 vs. 966 ng/mL for ice-water and electronarcosis, respectively), glucose (7.34 vs. 7.28 mmol/L), and lactate (9.12 vs. 10.12 mmol/L). In conclusion, stunning in ice water seemed to induce minimal effects on the muscle structure and ultrastructure and maintain product quality, while electronarcosis appeared to diminish quality traits.