From ancient time until nowadays, most of the population in the world have been living near a source of water, these sources of water being rivers, lakes, ocean or seas. The connection between the land and the sea or ocean are the rivers, which permit to transfer food, supply, materials from the ocean or the sea to the continent, but also the reverse. To perform that, rivers were continually modified to fit the human needs. The cities were dependent on the rivers; most of the huge civilisations were living next to one. Therefore, the human activities affected the hydrosystem, modifying its delineation, influencing the aquatic communities that were living in. The case of the Seine River is interesting, because it is one of the most impacted rivers in France. It is mainly due to Paris conurbation (10.7 million of inhabitants in 2015). To assess this pressure through time, my work was to provide an historical analysis of the ecological continuity for the Seine River fishes since the 19th century. To answer this problematic, I determined the impact of the physical changes on the channel but also the evolution of water quality, parameters that might have affected the migration of fishes. With the help of ancient texts, data from the Montsouris Observatory and the National Archives, it was possible to understand and to identify the different periods that had affected the evolution of the Seine River ecosystem. The ecological continuity of the channel was decomposed into two different components; physical and chemical. To improve the navigation, the channel was modified and weirs/locks were built in the 19th century to help the ships to transit from the ocean to Paris. Then weirs modernisation and especially the one of Poses contributed to the fall in migratory fishes’ population due to its impassability. Besides that, the rejection of sewage waters from Paris into the river contributed to a loss in water quality (especially oxygen) downstream Paris through eras. In the era of the post war boom, the Seine became unsustainable for any type of fishes due to its low availability in oxygen. The identification of five key dates (1750, 1899, 1940, 1970, and 2018), representing main changing periods, were used to model connectivity evolution over time for some migratory species that have contrasted upwelling behaviours.