Life History: Fertilized eggs develop into free-swimming larvae. After a period of growth, the larvae settle to the bottom, attach to a substrate, and develop into mature, sessile adult oysters. The oysters are usually males at first, but change between the sexes throughout their lifetime. When food is prevalent, they tend to be females, and when food is scarce they change into males. Hermaphrodites do occur on occasion. After one year, sexual maturity is reached (Nehring, 2006: 6; Pauley et al., 1988: 5-7).
Growth : Temperature radically affects the rate of development of the eggs. Most fertilized eggs develop to the shelled veliger stage within 48 hours. The resulting pelagic larvae grow over a period of 2 to 3 weeks. As the larvae grow, their length is 5-10 µm greater than their width. This condition persists until the larvae reach about 90 µm. At 100 µm, the length and the width are equal, but beyond 125 µm the width grows faster than the length. Growth of the free swimming larvae depends on many factors. The length of the larval period is dependent on the water temperature. Temperatures must be 20°C or greater for at least three weeks for optimal growth (Pauley et al., 1988: 5-7).
An eyespot, along with a foot containing a byssal gland, develops. Both remain throughout the free swimming stage. When the larvae reach a length of approximately 0.3 mm, their free swimming existence ends and they attach to the bottom or a hard substrate as spat. After the metamorphosis from free swimming larva to spat, the velum and foot disappear along with the anterior adductor muscle. The development of an enlarged set of gills begins. After settling, the juvenile oyster becomes a sessile animal (Pauley et al., 1988: 5-7).
Many factors affect the rate of growth in adults. They normally reach a length of 4-5 cm during their first year. Growth rate reduces significantly after 4 or 5 years. They exhibit compensatory growth, growing wider when lengthwise growth is physically deterred, and vice versa (Pauley et al., 1988: 5-7).
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