Fasting before harvest influences the sensory quality of farmed fish through interacting biological processes that affect taste, odor, texture, and safety. Guidance from the Food and Agriculture Organization of the United Nations FAO highlights that pre-harvest feed withdrawal primarily aims to clear the digestive tract to reduce contamination, improve fillet appearance, and lower waste in holding facilities. Research on fish stress and flesh quality by Fiona A. Huntingford Institute of Aquaculture University of Stirling connects handling, feeding status, and postmortem changes that shape final flavor.
Physiological mechanisms
Fasting promotes gut clearance, which reduces the presence of digesta that can carry bitter or muddy off-flavors and fuel bacterial growth during evisceration. At the same time, fasting shifts metabolism from recent dietary substrates toward stored glycogen and lipids. Glycogen depletion alters postmortem muscle pH, influencing texture and the release of flavor precursors. Mobilization of fats during prolonged fasting can increase free fatty acids that accelerate lipid oxidation, producing rancid notes if fish are stored improperly. The optimal balance is species-dependent: carnivorous fish with high lipid content respond differently than lean, temperate species.
Trade-offs and practical guidance
Short-term fasting before harvest is widely used because it reduces gut-derived microbial load and improves packing and transport hygiene, a point emphasized in FAO post-harvest handling recommendations. NOAA Fisheries National Oceanic and Atmospheric Administration also notes that managing feeding and minimizing stress around harvest support both product quality and animal welfare. However, extended feed withdrawal can lower fillet quality by promoting muscle catabolism, color changes, and potential flavor deterioration, and raises ethical concerns in small-scale operations where economic pressures lengthen fasting periods. Cultural practices matter: coastal communities that value whole, unprocessed fish may prioritize gut clearance differently from processors selling fillets into distant markets.
Consequences extend beyond flavor: better-managed fasting reduces pond pollution during harvest, lowering environmental impacts on local water bodies, while poor fasting practices can increase post-harvest spoilage and food safety risks. Integrating species-specific fasting periods, careful handling to limit stress, and prompt cooling after harvest aligns with evidence-based recommendations from institutions such as FAO and NOAA Fisheries and with academic findings on stress–quality links from the Institute of Aquaculture.