Oyster Life Cycle and Reproduction

For most of its life an oyster is fixed in one place, but it begins life as a tiny free-swimming larva. The transition from drifting plankton to permanently attached shellfish is one of the most important changes in its biology.

Spawning begins the cycle

Adult oysters release eggs and sperm into the water. Fertilization occurs externally, and the resulting embryos begin dividing rapidly.

Larvae live in the water column

Early oyster larvae are microscopic and planktonic. They feed, grow and are carried by currents while developing a shell and more complex swimming and sensory structures.

The pediveliger stage prepares for settlement

Late-stage larvae develop a temporary foot used to explore surfaces. At this point they are searching for a place where they can attach and remain for the rest of their lives.

Settlement creates spat

When a larva permanently attaches to suitable substrate, it metamorphoses into a juvenile oyster called spat. Old oyster shell is particularly useful settlement material because it provides hard surface in estuaries dominated by soft sediment.

Juveniles grow by feeding and building shell

Once settled, the oyster no longer swims away. It grows by filtering food from the surrounding water and adding shell at the margin. Growth depends on temperature, food, salinity, density and other site conditions.

Adults invest energy in reproduction

As oysters mature, energy shifts seasonally into reproductive tissue. Spawning can reduce body condition temporarily because energy and tissue are released into reproduction.

The cycle connects generations through habitat

Adult shell can become settlement surface for the next generation. That is one reason shell retention and reef structure can matter so much in native-oyster restoration.

Go deeper

Continue with Oyster Larvae and Settlement, Shellfish Hatcheries and Seed, and Olympia Oyster Restoration.