Harvesting procedures, welfare and shelf life of ungutted and gutted shortfin pompano (Trachinotus falcatus) stored in ice

Shortfin pompano (Trachinotus falcatus) were harvested from a floating cage culture. Handling stress (blood pH, white muscle pH, and rigor mortis) and welfare (“eye roll”) were determined for two harvesting methods: (i) batch netting and transfer to ice-slurry where the fish were killed and chilled (commercial method) and, (ii) transfer of fish to a tub immersed in the cage before it was lifted onto a barge where the fish were euthanised by an AQUI-S™ overdose. Half of the ice-slurry fish were gutted. All fish were subsequently stored for 18 d in ice for assessment of freshness (total bacterial counts, TBC and Quality Index Method, QIM) as well as skin and eye color. A modified QIM scheme for European sea bass was used with demerit points ranging from 0 to 18. Due to excessive swimming during crowding, both ice-slurry and AQUI-S™ fish were harvested in an exhausted condition. Upon sampling, none of the fish exhibited “eye roll”, indicating they were either unconscious or dead. Since the ice-slurry fish were not stunned immediately, the welfare of the fish might have been compromised. During rapid chilling, the fish developed cloudy eyes. The asset of using AQUI-S™ was possibly better fish welfare during the stunning and euthanising phase since exposure to ice-slurry was associated with escape swimming behaviour and slow death. Shortly after harvesting there were some significant differences between harvesting methods in terms of skin color. They were, however, largely offset by storage for one day. Only a few minor changes in skin color took place during further storage. Changes in eye color were more prominent than for skin. After storage for more than a week, the TBCs of gutted fish were significantly higher compared with ungutted fish (P <0.05). AQUI-S™ fish (ungutted) exhibited the lowest TBCs for about the first two weeks indicating exposure to the anesthetic reduced bacterial growth. After 18 d, none of fish from all treatments had yet reached the generally accepted spoilage level of 7 log cfu g−1. At this point, the fish had not reached the maximum attainable QI score of 18. High linear correlations (R ≥ 0.972, P < 0.001) were achieved for development of QI during ice storage where the ungutted and AQUI-S™ treatments were practically similar. The modified QIM scheme was considered suitable for pompano. The shelf life was tentatively considered to be approximately 18 d, although this should to be verified by other, supplementary methods. To prolong shelf life, it is recommended that pompano is not gutted before they are subjected to chilled storage.