True Oysters are bivalve mollusks in the Ostreidae Family that have irregularly shaped shells that have two solid valves that differ in size and shape (inequivalve). The left valve is cemented to solid substrate and shapes to match that substrate. The right valve is convex and smaller than the left. Like scallops, these shells have a single adductor muscle. Most True Oysters are gray in color.

The True Oysters are suspension feeders consuming phytoplankton and detritus from the drift. In turn they are preyed upon by carnivorous mollusk and sea stars. True Oysters are found globally in all tropical and temperate seas. Oysters can be found in brackish water and are considered oligotrophic being able to survive in low nutrient level environments.

There are forty species in the Ostreidae Family of which eleven are found along the coastlines of the Baja Peninsula. True Oysters are edible, commercially fished and farmed, and have been consumed by humans for hundreds of years.