Evaluating passive integrated transponder tags for tracking movements of round gobies

The round goby (Neogobius melanostomus Pallas) is an invasive species in North America and Europe. We evaluated the efficacy of passive integrated transponder (PIT) tags for marking round gobies and tracking their movements with a portable underwater antenna in shallow areas (<= 1 m) of a lake. Tagging did not markedly decrease growth of fish < 105 mm; however, growth decreased unexpectedly for tagged fish >= 105 mm during the final sampling period. Nevertheless, tagging did not increase mortality regardless of size class, and tag retention was 100% for caged fish. Tagged round gobies in a 20 x 20-m(2) block net avoided detection by the portable underwater antenna, and a high proportion of fish probably escaped from the net, suggesting that round gobies may be more mobile than previously reported. In conclusion, PIT tags are a viable method for individually marking round gobies, but detecting tagged round gobies with a portable underwater antenna, given current technology, does not appear promising in shallow areas with low habitat complexity.