Physical activity and stress during a harvest process, before slaughter, is known to have significant negative impacts on muscle quality. These negative impacts can be attributed to increased anaerobic metabolism during the harvest that leads to decreased muscle energy stores, a rapid decline in muscle pH and accelerated degradation of muscle proteins. These changes in muscle pH and proteins results in muscle having unfavourable colour, soft texture, gaping, blood spotting, reduced water holding capacity, reduced shelf life, and overall poor consumer acceptability.
Different harvest methods commonly used in aquaculture tend to reflect the value of the species. For example, high value or physically larger species such as salmon and tuna require harvest procedures that pay individual attention to fish in an aim to maximise muscle quality. Smaller species such as perch, carp, tilapia, catfish, etc., do not to have the same level of individual care and are processed in larger numbers with subsequent impacts on the final product.
Low-stress harvesting of fish, also known as RESTED HARVEST, is widely known to significantly improve product quality post-harvest. Rested harvesting can be applied to all species in all types of operations. For a true rested harvest, fish are sedated/anaesthetised during the harvest process thus completely removing the stress response and the animals escape response. By reducing the escape response, energy is retained in the muscle which increases the time to rigor mortis and subsequently increases shelf life. The muscle from a rested harvested fish has a better texture, less gaping, less bruising and less blood spotting and where the fish is sold whole, the overall appearance is improved with less scale loss and other evident physical damage. This all results in higher consumer acceptability and higher profit margins.