Estuarine food webs in the Upper San Francisco Estuary vary in primary producer importance to fishes across different habitats and seasons. A study found that fishes in tidal wetland, turbid backwater, and open-water channels rely on a mix of submersed aquatic vegetation and phytoplankton for food. Fishes use multiple food sources and show little separation between pelagic and littoral food webs. Primary producer availability changes with seasons and spatial scales, helping food webs adapt to environmental changes. Restoring a variety of primary producers can enhance ecosystem resilience in estuarine habitats.