Retention and effects of miniature transmitters in juvenile American eels

•Transmitter effects for a micro (0.088g) acoustic transmitter were evaluated in juvenile American eel.•Swimming performance and tag loss were evaluated in yellow stage American eel (113–175mm).•Swimming performance was not impaired for any size groups implanted with a transmitter.•Tag loss was observed and occurred from day 14 to the end of the holding period (38days).