Understanding how oysters procreate explains how this prize shellfish moves or travels to form colonies--referred to as beds, bars or reefs. Edible oysters fall into two different categories: Eastern oysters (Crassostrea Virginica) and Pacific oysters (Crassostrea gigas). Only for the short first part of an oyster's life does it move; beginning several days after birth, it stays put in its bed for the rest of its life.
The Birth of an Oyster (Ostreidae)
Oysters are hermaphrodites, meaning that they are born male and within a few years become female. It is almost impossible to tell which sex an oyster is. Once the oyster becomes a female and the water temperate reaches approximately 60 degrees, it releases eggs.
An Oyster's Method of Travel
The eggs are buoyant in nature. At this stage, they are swimming larva and move with the current of the ocean. Once they start to develop their hard shell, they settle to the bottom of the ocean. While on the bottom of the ocean, they begin to move or travel as do most mollusks: by foot. This foot is released in the front of the shell and grabs the floor of the ocean; the creatures then pull themselves along. At this point, oysters seek a spot to attach themselves to. Items like debris on the ocean floor or empty oyster shells are suitable places for them to make their new home. Once they attach themselves, they no longer move. The next time an oyster moves is when it is dredged up by humans to be consumed.
The oyster is a member of the mollusk family, and is a bivalve. Bivalves include oysters, clams, scallops and mussels. They feed through two tubes. One tube sucks in the nutrient-filled water and the other discards it. Some bivalves, such as clams and scallops, use these tubes as a means to move about, but oysters do not.