Previous studies indicated that dart tags affect the migration pattern of kahawai (Australian salmon). Because kahawai cannot be held in experimental swim tunnels, we used rainbow trout Oncorhynchus mykiss as a surrogate species of similar physiology to test the effects of visible implant tags and dart tags on swimming performance. The critical swimming velocity (U-crit) of untagged rainbow trout, 2.93 +/- 0.12 (SE) body length/s, was unaffected by either tag type. Our findings suggest that altered migration of dart-tagged kahawai is not due to an acute tag-induced reduction in swimming performance. [References: 15]