The oceans, upon which humanity relies for its survival, it is largely unexplored. Recent estimates establish that only 5% of the bottom of the sea has been explored. Of this small area, only one millionth is constituted by deep sea floor. Despite being largely unknown, the deep sea is becoming exceedingly exploited, especially by fisheries searching for new stocks.For all these reasons, understanding the functioning of the deep-sea environment is deemed crucial. This habitat has a pivotal role in the global conveyer belt, through regeneration of nutrients. This proposal (DEEMdeep) aims at expanding our understanding of the deep sea ecological and population dynamics through a strong multidisciplinary approach.The chosen taxon is the genus Molva, represented in the North Atlantic by two species, the common ling M. molva and the blue ling M. dypterygia.The novelty of this project is represented by its holistic multidisciplinary approach. State-of-the-art next-generation sequencing techniques will be simultaneously used with life-history traits, otolith microchemistry and stable isotopes analyses, parasitology and analysis of the fish gut microbiome in order to establish patterns of population connectivity and habitat interactions at the ecological level.Samples of common and blue ling will be collected throughout the North Atlantic in five sites (Norway, Iceland, Scotland, Greenland and Quebec) through scientific surveys. Basic traits will be recorded (length, weight and maturity), otoliths stored for microchemistry and stable isotopes analyses, gills removed for subsequent identification of the parasites and gut content sampled. Through enhancing our knowledge of the deep sea, this project will pave the way towards sound conservation (and management) of this resource.