An 8,000-year sequence of sh remains from Morro Bay, a shallow, 8.1km.2 coastal estuary in San Luis Obispo County, has been compiled during recent investigations. The sample, obtained from nine sites and 14 components (total excavation volume=275.86 m.3), includes 19,226 sh elements recovered via 1/8-inch dry-screening and 718 elements from 1/16-inch water-screened columns. The archaeological ndings are generally consistent with species inventories from the 1970s, although northern anchovies are under-represented in the prehistoric record. Remains show a consistent focus on the netting of small schooling shes in the calm backwaters of the bay. A signi cant decrease in bat rays is attributed to a shift in seasonality, although overexploitation cannot be ruled out. Remains show only modest changes between 8,000 and 950 cal B.P., but a dramatic spike in NISP/m.3 and sh/deer+rabbits during the Middle- Late Transition suggests an increased focus on marine prey during droughts of the Medieval Climatic Anomaly, when Morro Bay apparently served as a refugium. Fishing declined relative to terrestrial resources during the Late Period, when acorns and other plant foods increased in importance.