Gulf of Lion

Along the Gulf of Lion's Languedoc shore, merchants and fishers needed different kinds of access to the sea. Fishing traps caught fish moving between lagoons and open water, while commercial vessels struggled with silting channels. In 1719 Aigues-Mortes requested work at Grau-du-Roi chiefly to protect revenues from its fisheries and saltworks. Fish went to neighbouring towns, and salt moved toward the Rhône.

Harbour building gradually changed this coast. Early projects at Sète in 1599–1605 and Brescou in 1634–1654 failed through rapid silting and inadequate maintenance. A new Sète harbour began in 1666 with two jetties southeast of Mont Saint-Clair; regular maintenance was contracted in 1690. Further works stabilised lagoon entrances at Agde, La Nouvelle and Le Grau-du-Roi. The same openings that encouraged commerce needed protection: after the English landing at Sète in 1710, military concerns remained, and battery redoubts and signals were placed along the shore from 1743.