Effects of rested-harvest using the anesthetic AQUI-S™ on channel catfish, Ictalurus punctatus, physiology and fillet quality

Trials were conducted to determine effects of AQUI-S (TM) sedation during harvest (rested-harvest) on physiological responses and fillet quality of channel catfish, Ictalurus punctatus. Rested-harvest is defined as application of an anesthetic immediately before harvest to reduce fish activity associated with a normal harvest. Doses of 25-35 ppm AQUI-S (TM) were effective for rested-harvest of catfish (loss of equilibrium in 3 to 10 min and 100% survival following recovery). Time to loss of equilibrium and time to recovery following sedation with 35 ppm AQUI-S (TM) increased as water temperature decreased from 30 degrees C to 10 degrees C. Catfish exposed to 25 ppm AQUI-STM, 35 ppm AQUI-STM, 100 ppm trincaine methanesulfonate, and 8 ppm metomidate had lower blood lactate, cortisol, and glucose and higher blood pH than unsedated fish exposed to a low-water stress. Rested-harvest (RH) catfish had higher muscle and blood pH, lower blood and muscle lactate, and higher muscle ATP levels than catfish exposed to a 45 min low-water stress. Rates of muscle pH decrease, ATP decrease, and lactate increase accelerated as storage temperature decreased from 15 degrees C to 5 degrees C in RH fish acclimated to summer temperatures (33 degrees C), conversely these rates accelerated as storage temperature increased from 5 degrees C to 15 degrees C in RE fish acclimated to winter temperatures (7 degrees C). Based on physiological response (higher muscle pH, lower blood lactate, delayed time to rigor), post-sedation euthanasia by CO2 was superior to post-sedation euthanasia by AQUI-STM overdose (150 ppm), nitrogen gas, or electrical stunning. Compared to fillets from fish exposed to simulated industry transport conditions, fillets from RH/CO2 euthanised fish had higher pH 1 h post-slaughter, and less drip-loss and lower L* and a* color values during 7 days of iced storage. RH/CO2 and control fillets were not different for shelf-life based on bacterial counts. Rested-harvest with AQUI-STM followed by CO2 euthanasia has potential to improve catfish fillet quality, but AQUI-S (TM) approval, development of rested-harvest strategies, and demonstration of economic benefits of rested-harvest will be required for adoption of rested-harvest to commercial catfish production. (c) 2006 Elsevier B.V. All rights reserved.