Two pike species occur in France: the ubiquitous northern pike Esox lucius and the endemic Aquitanian pike Esox aquitanicus living in small tributaries and coastal catchments in South-West of France. For this last species, there are few knowledges. So, tools and data are needed for its management and stock assessment such as length–weight relationships (LWRs). This study provides the first LWR for E. aquitanicus and compares it with data of French E. lucius. Data for both pike species were collected from 1981 to 2022 during the monitoring of the Departmental Angling Federations and the French Agency of Biodiversity (OFB). Data from 3,657 Aquitanian pikes and 5,413 northern pikes were then provided with average sizes and weights respectively 10.7 cm for 20.2 g and 30.2 cm for 339.8 g. Our study highlights that Aquitanian pike is smaller than northern pike, certainly due to the surface area of habitat and the warmer temperature. The a and b parameters are significatively smaller for the Aquitanian pike than those of E. lucius. This should be explained by the poor environments where it lives (sandy substrates, few aquatic vegetation, low biomass) conferring a lower primary productivity.