From tradition to innovation: Effects of manual and automated ikejime on welfare and product quality of rainbow trout and hybrid striped bass

Ensuring humane slaughter is essential for ethical and high-quality fish production. Ikejime is widely regarded as rapid and quality-preserving, yet its manual application is labour-intensive and anatomy-dependent, limiting scalability. An automated, AI-guided ikejime system could overcome these constraints, but its welfare efficacy is unvalidated. We provide the first neurological evaluation of manual and automated ikejime for rendering rainbow trout ( Oncorhynchus mykiss , ∼0.3–0.5 kg) and hybrid striped bass ( Morone chrysops ♀ × M. saxatilis ♂, ∼1.1–2.1 kg) insensible, using visually evoked responses (VERs) on the electroencephalogram (EEG). Results are compared with manual percussion and asphyxiation, together with exploratory product-quality analyses. Asphyxiation caused prolonged distress lasting up to 13–16 min in both species. In contrast, both ikejime methods rendered all trout irreversibly insensible within 2 min, although neither reliably achieved immediate insensibility. Efficacy declined in bass, with ∼25–43 % of individuals remaining sensible after application. These findings demonstrate that ikejime , whether manual or automated, should be preceded by a stunning step ensuring immediate loss of sensibility. Reduced effectiveness in larger and more robust species underscores the need for species-specific refinements, including optimized spike dimensions and insertion techniques. While exploratory product-quality assessments indicated potential effects of slaughter method and effectiveness on rigor mortis and drip loss, these patterns should be validated in future studies using larger sample sizes and broader replication. Together, these data provide critical evidence to guide the refinement of slaughter methods aiming to enhance fish welfare while ensuring product quality. • First neurophysiological validation of manual and automated ikejime efficacy • Fish size and morphology influence ikejime and percussion efficacy • AI-driven ikejime prototype shows promise for humane fish stunning and killing • Improved fish welfare during slaughter linked to enhanced product quality • Ongoing innovation and validation are key to advancing fish slaughter methods