The French seaweed industry, primarily driven by Brittany, plays a crucial role in local employment and alginate production. Traditionally, depending on Laminaria digitata, the local alginate sector now faces significant challenges. The late decline of L. digitata populations due to climate change and competition with other kelp species—mainly Saccorhiza polyschides—poses a serious threat to its harvesting sustainability. Additionally, increasing variability in the seaweed landing composition has been observed in recent years, worrying local alginate processors. In the short term, ensuring a high proportion of L. digitata is thus required to maintain high-quality alginate production. In response to these recent changes, this study aims to assess the quality of L. digitata landings and identify the factors influencing their variability. It also examines the past and present exploitation of L. digitata while exploring potential short- and long-term solutions to sustain the local alginate production. Results indicate that landing composition varies significantly, with L. digitata biomasses sometimes representing less than 50% of the total harvest. Two main factors seem to drive these variations: (1) sea conditions, with lower quality observed when wave heights exceed a certain threshold, and (2) differences among vessels, as some seaweed harvesters consistently deliver lower quality landings. This requires implementing best practices for harvesters, combined with systematic visual inspections when necessary. In the mid-term, as L. digitata resources will continue to decline, yet reducing reliance on this species will be necessary to support its conservation. Promoting alternative sources of alginate will be required, and a shift toward other species such as Laminaria hyperborea, L. ochroleuca, or even S. polyschides has to be considered.