Dear MARMAMers, We are excited to share our latest publication https://doi.org/10.1016/j.scitotenv.2024.177164, which provides new insights into the effects of climate variability on the behavior of North Atlantic fin whales: <https://doi.org/10.1016/j.scitotenv.2024.177164> Baleen stable isotopes reveal climate-driven behavioural shifts in North Atlantic fin whales <https://doi.org/10.1016/j.scitotenv.2024.177164> Climate variability impacts the structure and functioning of marine ecosystems and can trigger behavioural responses in organisms. We investigated whe… doi.org Title: Baleen stable isotopes reveal climate-driven behavioural shifts in North Atlantic fin whales Authors: Marc Ruiz-Sagalés, Raquel García-Vernet, Josep Sanchez-Espigares, Sverrir D. Halldórsson, Valerie Chosson, Guðjón M. Sigurðsson, Morgana Vighi, Roger Lloret-Cabot, Asunción Borrell & Alex Aguilar Abstract: Climate variability impacts the structure and functioning of marine ecosystems and can trigger behavioural responses in organisms. We investigated whether such variability modulates diet and migration in the North Atlantic fin whale (*Balaenoptera physalus*). To reconstruct the dietary and migratory behaviours over time, we conducted stable isotope analysis of nitrogen (*δ*15N) and carbon (*δ*13C) along baleen plates from 29 fin whales sampled off southwestern (SW) Iceland in summer. We estimated a baleen growth rate of 16.1 ± 2.5 cm per year from the stable isotope oscillations observed along the baleens. We also assigned a deposition date for each baleen segment, thus obtaining isotopic sequential time series. We then assessed the potential association of these time series with the main climate patterns of the North Atlantic basin. Baleen *δ*15N and *δ*13C values are associated with the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO). During high AMO and low NAO periods, which tend to decrease krill abundance, there is an increase in both the mean and standard deviation of baleen *δ*15N values, suggesting that fin whales shift to higher trophic resources and expand their dietary niche. Additionally, high AMO periods, which relate to positive temperature anomalies, lead to a decrease in baleen *δ*13C values, suggesting that fin whales adjust their migratory routes and destinations towards higher latitudes. Significant variation in isotopic niche width between years also reflected these dietary and migratory behavioural shifts. This highlights the plasticity of the North Atlantic fin whale behaviour, a trait likely to strengthen the resilience of the species within the current context of rapid and intense climate variability. Cite: Ruiz-Sagalés, M., García-Vernet, R., Sanchez-Espigares, J., Halldórsson, S. D., Chosson, V., Sigurðsson, G. M., ... & Aguilar, A. (2024). Baleen stable isotopes reveal climate-driven behavioural shifts in North Atlantic fin whales. *Science of The Total Environment*, 177164. Please feel free to reach out at mruizisag@ub.edu if you would like to discuss our work further. Best regards, Marc Ruiz-Sagalés and coauthors Marc Ruiz-Sagalés, PhD student Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals Institut de Recerca de la Biodiversitat (IRBio) Facultat de Biologia Universitat de Barcelona Diagonal 643 08028, Barcelona Spain