The ICES Planning Group on Commercial Catch, Discards and Biological Sampling (PGCCDBS) identified the need of the Horse Mackerel, Mediterranean Horse Mackerel and Blue Jack Mackerel (Trachurus trachurus, T. mediterreaneus and T. picturatus) otolith exchange to take place in 2015. It was the forth exchange. The IFREMER institute and the COISPA Tecnologia & Ricerca, Italy, coordinated this exchange. A total of 550 fish was sampled from the Atlantic Ocean (Eastern Channel, Celtic Sea, Bay of Biscay, Azores, Portuguese waters and Tenerife) and the Mediterranean Sea (Alboran Sea, South Adriatic Sea and Ligurian Sea). 19 readers from 8 countries (France, Germany, Spain, Ireland, Italy, Portugal, Netherlands and Norway) participated to this exchange. Among three Trachurus species, all data showed the very low precision with the percent agreement between 47 and 56% and the CV from 29 to 69%. The precision analysis showed the same level of precision between otolith sections and whole otoliths from the Ligurian Sea.