Use of Acoustic Telemetry to Evaluate Lake Trout Spawning on Constructed Reefs

In 2010-2011, 29 reefs were constructed in Thunder Bay, Lake Huron, to mitigate degradation of a natural spawning reef and improve spawning success of lake trout.  Reefs were designed to study characteristics that may attract spawning lake trout and maximize egg incubation success, including size, height, and orientation.  Reef attraction, compared with two degraded reefs and a large area of natural reefs, was evaluated for four years post-construction by assessment of adult, egg, and fry density.  Forty lake trout were implanted with acoustic tags and tracked in fall, 2012-2014, within a VEMCO positioning array of 27 receivers encompassing all of the study reefs.  Lake trout movements in all three years were focused on a small area of the large natural reef, but virtually no fish were detected on the degraded reefs.   Frequency of positions on the constructed reefs increased over the three years, and was positively correlated with reef size and with adjacency to the natural reef. Telemetry data identified lake trout preferences for individual reefs and identified new potential spawning areas with more precision, encompassing a much wider area, than was possible with egg, fry, or adult collections.