Response of European whitefish embryos to thermal conditions diverges between peri-alpine populations

Peri-alpine lakes are vulnerable to climate warming. Water temperature in these lakes has increased and will likely continue in the coming decades, questioning the fate of inhabiting aquatic populations. Understanding how coregonine fishes respond to these changes is of great importance as these are economically and ecologically valuable populations. Considering the diversity of European whitefish from the Coregonus genus in peri-alpine lakes, we can assume that their response to rising temperatures could be diverse. We conducted an experiment to explore how embryos from four European whitefish populations from three lakes − Bourget, Geneva, and Constance − responded to contrasting incubation temperatures (7.0 °C vs. 9.0 °C) in terms of incubation duration and survival. In Constance, both pelagic and littoral populations were considered separately. Survival from the eyed-egg stage to hatching at 7.0 °C in all populations was high, ranging from 89% to 98%. At 9.0 °C, increased mortality−compared to the 7.0 °C treatment−was the lowest in Bourget (33%) and the highest in the Constance littoral (62%) population. Mortality was intermediate for the Constance pelagic (44%) and Geneva (45%) populations. The impact of warmer incubation temperature on hatching dynamics also contrasted among populations, as both Constance populations hatched more precociously in the warm treatment relative to the cold treatment (–4.6 and −2.7% Accumulated Degree Days for littoral and pelagic populations, respectively), suggesting they are more stressed than populations from Geneva and Bourget (–1.2 and +1.1%, respectively). These data indicate populations may possess the ability to respond differently to warming temperatures.