Evaluation of transportation procedures on water quality and fry performance in red porgy (Pagrus pagrus) fry

摘要

The effect of stocking density (10, 20, 30, 40 kg/m(3)), water renewal (0% or 100% renewal rate per hour), hauling temperature (14, 19, 24 degreesC), salinity (20, 25, 30, 35, 40 psu), and use of anaesthesia (0, 10, 20, or 50 ppm ethynelglycol-monophenylether) prior to transportation on red porgy's fry performance, liver glycogen, and water quality parameters was tested to evaluate transportation procedures in a promising candidate for aquaculture. Simulated transport was performed in plastic containers (volume 60 1) for 48 h. Water samples were taken at 4-h intervals after transport for the determination of pH, carbon dioxide (CO2) un-ionised ammonia (NH3) and ammonium (NH4+). Additionally, liver samples were collected at 4 and 48 h for glycogen determination. There were no statistically significant fluctuations in dissolved CO2 concentration in all tested conditions. Stocking density did not affect NH3 and NH4+ average values and hepatic glycogen content in groups exposed to a water renewal rate of 100%, while increasing NH3 and NH4+ average values with increasing stocking density was observed in groups with no water renewal. Under the same stocking density, a significant change in NH3 and NH4+ fluctuations over the duration of the experiment was observed with concentrations increasing, with a mean exponential rate (+/- SD) of 0.060 +/- 0.005 (NH3) and 0.062 +/- 0.005 (NH4+) per hour in groups with no water renewal, and -0.033 +/- 0.004 (NH3) and -0.024 +/- 0.007 (NH4+) per hour in groups with 100% water renewal. Water temperature affected significantly the hepatic glycogen content and survival during transport. There was no significant effect of salinity and anaesthetic (except at a dose of 50 ppm) on fry survival and on the water quality parameters. It is suggested that red porgy should be transported in stocking densities of 20-25 kg/m(3) and at a hauling temperature similar to that kept at the exporter's fish rearing tanks (preferable 19 degreesC). Besides, it is recommended to avoid temperature differences between the hauling water and the water used for renewal during fry transportation.