Dear Marmam, On behalf of my co-authors, I am pleased to announce the publication of the following article in Limnology and Oceanography: Methods: *Alkenones as a temperature proxy in fin whale (Balaenoptera physalus) tissues* *Rita, D.; Borrell, A.; Aguilar, A (2020) *Alkenones as a temperature proxy in fin whale (Balaenoptera physalus) tissues. Limnol. oceanogr.: Methods. DOI:10.1002/lom3.10375 *Abstract*: Alkenones are a group of extremely resilient molecules produced by cosmopolitan haptophyte organisms. The unsaturation index (Uk’37) of di- versus tri-unsaturated C37 alkenones (C37:2·(C37:2+C37:3)-1) can be used to estimate the temperature of the water in which the alkenone-producing organisms grew. Alkenones have been widely used in palaeoceanography, but they have received little attention in other fields. In this study, a method to detect alkenones in fin whale (*Balaenoptera physalus*) tissues is developed to adapt this technique to the marine ecology field. Five replicas of five tissues (stomach content, external blubber, internal blubber, muscle and liver) were analysed using gas chromatography coupled to mass spectrometry. Alkenones were present in both blubber tissues (66 ±57 ng·g-1 in external blubber and 145 ±89 ng·g-1 in external blubber), and in the stomach content (3126 ±2643 ng·g-1). The calculated Uk’37 index was very similar in the three tissues: 0.54 ±0.03 in the external blubber, 0.55 ±0.08 in the internal blubber and 0.71 ±0.06 in the stomach content. These indexes are equivalent to a sea surface temperature estimates of 17.79 ±0.68ºC in the external blubber, 17.84 ±1.84ºC in the internal blubber and 21.07 ±1.23ºC in the stomach content, which are very similar to the expected temperature for the region. The results of the current study indicate that alkenones biodilute in the trophic web, which could hinder the analyses of alkenones in species with a high trophic level. However, it is shown that alkenones can be detected in fin whale tissues and can be used to approximate the environmental water temperature where these animals feed. The paper can be accessed using the following link: https://aslopubs.onlinelibrary.wiley.com/doi/abs/10.1002/lom3.10375 Or send me an e-mail (diegorita@ub.edu) for the full text. Best regards, Diego Rita