Retention and mortality rates of 243 Rainbow Trout Oncorhynchus mykiss (73-119 mm) implanted with 8, 9, and 10 mm Passive Integrated Transponder (PIT) tags and 173 Brown Trout Salmo trutta (71-86 mm) implanted 8 and 10 mm PIT tags were examined in a hatchery setting. Retention rates were 95.9% for Rainbow Trout and 100% for Brown Trout over the study period. Only six Rainbow Trout ejected tags. With the 8 mm tags, two ejections occurred in the first seven days, one occurred between days nine and 15, and one occurred between days 22 and 50. One Rainbow Trout ejected a 9 mm between days 22 and 50, and another Rainbow Trout ejected a 10 mm tag in the first seven days. There were no significant differences in weight or length of fish that ejected their tags. Over the course of the study, survival was 100% for both species. This study documents that Rainbow Trout can be successfully tagged at a minimum TL of 73 mm and Brown Trout at minimum TL of 71 mm with no adverse effects on tag retention or survival.
Amanda Borchert, Jacob L Davis, Michael E Barnes