Quantifying shifting fish migration phenology across the Great Lakes

The timing of major life cycle events (reproduction, flowering, feeding) is set by seasonal environmental cues in many organisms.  Migratory fish in the Great Lakes are largely spring spawners, and they move into tributary rivers as the water warms in March-June.  There is growing evidence that the timing of these migrations is shifting under climate change, creating ever-earlier migrations.  These changes in timing may profoundly change which species are present in rivers at a given time, potentially unraveling critical ecological linkages during the dynamic spring warming period.  We are analyzing historical data on migration timing of six species across the Great Lakes basin, using Bayesian statistical modeling to maximize power to detect shifts from a patchwork of migration records in space and time.  Looking forward, we have partnered with the Shedd Aquarium and Lake Superior National Estuarine Research Reserve to launch a new citizen science-monitoring network along the shores of Lakes Michigan and Superior.  We hope to continue this into the future, and link it with the USGS National Phenology Network.

The goals of this project are:

• Understanding which fish species may have reproductive cycles disrupted by climate warming.
• Assessing whether critical species interactions are eliminated by differential shifts in phenology.
• Maintaining healthy populations of native and introduced migratory fishes to support recreational, subsistence, and commercial fisheries
• Public awareness of migratory fishes, and the impact of climate change on their ecology.

Preliminary results indicate some species are showing clear shifts in the timing of spring spawning migrations, while others are not.  Monitoring of sucker migrations in 2016 and 2017 spring seasons indicates high responsiveness to temperature cues, which were unpredictable and fluctuating in both years.