Stable isotopes demonstrate the importance of freshwater fisheries in Late Holocene native Californian diets in the California Delta

•New historical ecological data for extirpated California Delta faunal species.•Faunal collagen stable isotope data used to model human paleodiets.•Human paleodiets 1000 to 400 years ago heavily dependent on local fisheries.•Sacramento perch are currently extirpated but were major source of dietary protein.