AbstractBackgroundLesser sandeel (Ammodytes marinus) is widely distributed in North Sea ecosystems. Sandeel acts as a critical trophic link between zooplankton and top predators (fish, mammals, sea birds). Because they live buried in the sand, sandeel may be directly affected by the rapid expansion of anthropogenic activities linked to their habitat on the sea bottom (e.g., hydrocarbon extraction, offshore renewable energy, and subsea mining). It is, therefore, important to understand the impact of cumulative environmental and anthropogenic stressors on this species. A detailed description of the ontogenetic timeline and developmental staging for this species is lacking limiting the possibilities for comparative developmental studies assessing, e.g., the impact of various environmental stressors.ResultsA detailed description of the morphological development of lesser sandeel and their developmental trajectory, obtained through visual observations and microscopic techniques, is presented. Methods for gamete stripping and intensive culture of the early life stages are also provided.ConclusionThis work provides a basis for future research to understand the effect of cumulative environmental and anthropogenic stressors on development in the early life stages of lesser sandeel.