It is our pleasure to announce the organization of the second 3Days MESSH `Mathematics for bio-Economics and Sustainability of fiSHeries', in January 17-18-19, 2024 in Brest, France. This event is mainly supported by the IMPT (Mathematics of Planet Earth), AMURE, LMBA, CEREMADE and CEE-M as well as the GDR OMER and GDR-Jeux.

Aligned with the first 3Days MESSH successfully held this year in Sete, the format of these 'MESSH 3 Days ' in Brest will be again a combination of a Symposium and a School, with keynote lectures planned every morning. A running thread throughout the 3 days this year in Brest will be on `Complexity in bio-economics of marine fisheries'. External keynote speakers include this year Carlos Chávez, (Facultad de Economía y Negocios, Talca, Chile & Environment for Development Initiative EFD) and Rudi Voss (Kiel University & German Centre for Integrative Biodiversity Research iDiv).

These 3 days constitute steps towards a more perennial international network we would like to launch next year on the topic 'mathematics of bio-economics and biodiversity'.