Current methodological issues in archaeomalacological studies

Abstract

Shell midden sites along the upper Gulf coast of Baja California contain abundant evidence of Indigenous subsistence practices and land use strategies reflecting the long history of local fisheries. Many of these sites contain well preserved faunal remains indicating people utilized a variety of littoral and marine habitats and exploited seasonal runs of the now endangered totoaba (Totoaba macdonaldi). We analyze totoaba otoliths recovered from eight archaeological sites along the upper Gulf coast with adjusted accelerated mass spectrometry (AMS) radiocarbon date ranges spanning ~5700 to 125 cal BP. Integrating geochemical, biological, oceanographic, and archaeological datasets, this study investigates ~5700 years of Indigenous fishing practices and past marine environments by examining totoaba biogeography, population dynamics, season of harvest, and changes in water chemistry. Otolith morphometrics indicate that most (~78%) of the Indigenous catch consisted of yearlings and juveniles, reflecting more sustainable practices than commercial fisheries, which target larger, older, and more reproductively viable fish. Stable isotope results reveal slight oscillations in water chemistry between the Middle and Late Holocene and suggest shifts in salinity due to the extensive damming of the Colorado River in the past century. Our results contribute to regional paleoenvironmental reconstructions, the natural history of totoaba, and the growing body of data that suggest many Indigenous people engaged in localized sustainable fishing practices over thousands of years.