American Eel Tracking and Tag Detection Efficiency in High Flow Environments

A collaborative, multi-year, acoustic telemetry project was developed to investigate fish movements in and near the FORCE in-stream tidal energy test site within Minas Passage, Bay of Fundy, NS. This presentation addresses two sets of data: 1) results of a directed investigation of acoustic receiver detection performance under high flow conditions, and 2) results of two seasons of American eel tracking. Forty-five (45) eels were acoustically tagged during the fall of 2011 and 2012. Twenty-one (21) eels were detected within Minas Passage, of which eight (8) were detected within the FORCE site. Presence within Minas Passage occurred over a short time frame due to the single passage nature of eel out-migration.  Little selectivity was shown for a specific migration pathway. Depths of transit through Minas Passage were highly variable among individuals, ranging between surface and 110m. Patterns in movement through Minas Passage, with regards to time of day and tidal stage, that might help inform when eels could be most at risk during the installation and testing of TISEC devices, were not well resolved. Detection efficiency is significantly reduced in high flow environments; therefore, cautious interpretation of animal detection data, in light of instrumentation limitations and flow considerations, is advised.