Foraging activity and habitat use throughout an annual migration of adult walleye (Sander vitreus) from the Trent River in eastern Lake Ontario

Mature walleye (Sander vitreus) that spawn in the Trent River conduct long-distance annual migrations into eastern Lake Ontario that begin and end in the Bay of Quinte. This scale of movement likely reflects seasonal spawning activity in the spring and a combination of temperature and foraging preferences at other times of the year. This study used a combination of acoustic transmitters and pop-off data storage tags to collect high-resolution data on temperature, depth, rate of vertical movement (ROVM), and rate of horizontal movement (ROHM) during these migrations. We tested the theory that post-spawn fish migrating to Lake Ontario experience colder water temperatures than those remaining in the upper Bay of Quinte, and offset this cost with greater foraging, as indicated by ROVM. We also documented the trends in these variables seasonally at the daily and hourly level. Temperature experienced by walleye in the lake (11.56 °C; SE ± 0.1) was on average 5.33 °C colder than in the upper bay (16.89 °C; SE ± 0.3), and there was a 15.5% increase in ROVM for fish in the lake. All the measured variables had significant seasonal trends, while only temperature, depth, and ROVM had significant hour of day trends. Sex based differences were limited to males having greater annual ROVM than females. There were differences in thermal habitat selection and vertical activity measures between the upper bay and Lake Ontario, which supported the current conceptual model of post-spawn walleye migration from the Bay of Quinte. Vertical activity peaked during crepuscular periods during the summer and fall when water temperatures promoted growth. This study demonstrates the value of combining tagging techniques to collect high-resolution data across multiple aspects of annual fish migrations.