Ashley LaRoque

Critical life stages of freshwater fish are heavily influenced by changes to lake temperature. Spawning phenology is driven by temperature cues, therefore, species with fixed spawning locations only begin to spawn when their temperature threshold is reached. As lake temperatures change, many fish species are forced to alter their reproductive phenology. We aimed to understand how spawning phenology has shifted due to temperature changes within a variety of lakes in Minnesota. Using a Process-Guided Deep Learning (PGDL) model, estimates of lake temperature were generated from preexisting observations and patterns for 638 lakes. Our dataset used 602 of those lakes and applied three thermal guild parameters to them. Each parameter corresponded to the average temperature for three guilds of spawners; warm-summer, cool-spring, and cold-fall. The date in which our thermal parameters were reached were used to evaluate change. Over the course of 39 years, spawning has delayed an average of 2.35 and 4.89 days in warm-summer and cold-fall spawners, respectively. Cool-spring spawners are cued to begin spawning an average of 3.27 days earlier. Our results indicate that while total change in days is related to temperature, there are other variables to factor in. Overall, changes in lake temperature are occurring among Minnesota lakes which have led to shifts in the phenology of freshwater fish spawning.