Biomarkers Used in European Aquaculture: Overview on Fish Nutrition, Stress and Health

Biomarkers are increasingly recognized as essential tools for assessing fish nutrition, stress, health, and environmental interactions in aquaculture, yet little is known about their awareness, use, and perceived value among European stakeholders. This study aimed to characterize current knowledge, applications, barriers, and future needs through a questionnaire-based survey distributed to researchers, industry professionals, and other aquaculture stakeholders across Europe. The survey, conducted via Google Forms, gathered responses from 38 participants representing 17 countries and diverse production systems. Results showed high familiarity with biomarker concepts, particularly those related to stress and health assessment, and identified blood biochemistry, histology, cortisol, oxidative stress markers, and gene expression as the most commonly used indicators, mainly in trout, seabass, and seabream. Although biomarker data occasionally informed decisions—especially regarding health treatments and feed adjustments—their wider adoption was constrained by high analytical costs, limited technical capacity, and lack of standardized protocols. Respondents emphasized the need for training, user-friendly diagnostic tools, funding support, and harmonized methodologies to enhance implementation. Overall, findings reveal strong interest and clear potential for expanded biomarker integration in European aquaculture, while highlighting critical gaps that must be addressed to support evidence-based and sustainable farm management.