The West African Mangrove oyster (Crassostrea tulipa) is a tropical oyster found in estuaries along the West and Central coast of Africa from Senegal to Angola. The growth, reproduction and survival of the oyster is dependent on prevailing environmental conditions (i.e, salinity, temperature, and pH) of its habitat. Globally, 85% of oyster reefs have been lost over the last few decades, while the landings of the C. tulipa have reduced about three-folds since the last 75 years. The decline is mainly attributed to a number of human-induced stressors including overfishing and harmful harvesting practices, water quality degradation, climate change, mangrove, degradation and disease outbreaks. To understand how C. tulipa fishery has changed in response to these stressors, our study used stable isotope composition of shells excavated across the equatorial coast West Africa to constrain past salinity regime of the oyster. We further assessed pre- historic against growth performance of the C. tulipa within the sub-region to inform a sustainable management of its fishery. Results show decline in salinity regimes, size, and growth rate in modern-day shells relative to pre-historic shells.