Hepatic heat shock protein 70 and plasma cortisol levels in rainbow trout after tagging with a passive integrated transponder

This study examined the potentially stressful effects of tagging juvenile rainbow trout Oncorhynchus mykiss with passive integrated transponder (PIT) tags by measuring short-term (<120-h) changes in plasma concentrations of cortisol and hepatic heat shock protein 70 (hsp70). In a laboratory experiment, plasma cortisol levels were measured in fish before they were tagged (0 h) and at 2, 6, 24, and 120 h after being tagged. Hepatic hsp70 levels were measured at 0, 24, and 120 h. All results were compared with those for fish that were handled but not tagged. Plasma cortisol levels were significantly higher in both treatment groups (tagged and handled but not tagged) at 2 h than in the pretreatment groups (0 h). Plasma cortisol levels in the treatment groups returned to near pretreatment levels by 6 h. However, there was a significant difference in plasma cortisol levels between treatment groups at 6 h. There were no significant differences in hepatic hsp70 levels among the two treatment groups, and hepatic hsp70 levels did not change through time. Our results suggest that PIT tagging is a low-impact tagging procedure for juvenile salmonids. ?? Copyright by the American Fisheries Society 2008.