Transport of jundiá Rhamdia quelen juveniles at different loading densities: water quality and blood parameters

Abstract

Fish transportation is a common practice on fish farms and is considered to be a stressor that could negatively affect fish health. The objective of this study was to evaluate several physiological responses of stress in jundiá caused by transport at different loading densities. Jundiá juveniles were placed in plastic bags on a mechanical transport simulator for four hours at four different loading densities (75, 150, 250 and 350 g L-1) and then transferred to sixteen 80-L plastic boxes for 96 hours after transport. Water samples were collected before and after transport to measure dissolved oxygen, temperature, pH and ammonia levels. Blood samples were taken at departure and arrival, as well as at 24 and 96 hours after transport to monitor cortisol, glucose, ammonia, chloride and hematocrit levels. Water ammonia levels were found to increase gradually as loading densities increased. Plasma ammonia was higher after transport in fish from all treatments. Compared to initial values, substantial increases in plasma cortisol and ammonia levels were detected mainly in those fish submitted to the highest loading density. Blood glucose appeared to be positively influenced by the increase of transport densities. No statistical differences were observed in any of the other blood parameters. The costs in fish culture, as in other animal production systems, must be minimized and fish producers depend on optimal techniques to ensure better profit. Therefore, based on fish survival and the physiological indicators determined in the present study, especially during recovery, the best density at which to transport jundiá in plastic bags for four hours is about 350 g/L.