Arnau Rodríguez Illamola stayed from 14th December 2020 to 19th March 2021 in Vigo (Spain) in the laboratory of Fish Physiology of Dr. Jesús M. Míguez at the University of Vigo. In this term, he work in the analysis of neuropeptides arginine vasotocin and isotocin using very specific HPLC techniques, which he had settled before in that laboratory, in samples of plasma and pituitaries of male trout from experiments performed in the Research Institute of Fish Culture and Hydrobiology (Faculty of Fisheries and Protection of Waters) of the University of South Bohemia in Vodňany. During the stay he has also started agreements for possible future collaborations between the laboratory of Reproductive Physiology of Dr. Serhii Boryshpolets at the Research Institute of Fish Culture and Hydrobiology and the laboratory of Fish Physiology of Dr. Jesús Míguez Miramontes at the faculty of Biology of the University of Vigo, with the objective of extending this research field in future.