(Magallana gigas)
Pacific Oysters change sex at some point during their life, usually spawning first as a male and subsequently as a female. Environmental conditions may affect sex. When food supplies are plentiful, males tend to change into females, and vice versa when food supplies are in short supply.
Pacific oysters usually produce between 50 and 100 million eggs, which they release over several spawning bursts. The female discharges her eggs up to 30 cm from her body in the form of white clouds. The male oyster adds its sperm.
The Pacific Oyster can live and grow in water temperatures between 2 to 20°c but has higher growth rates in water temperatures of 12 to 15°c. Spawning is temperature-dependent and occurs in the summer months when water temperatures are typically warmer.
The overall growth varies by tidal height, season, and the area in which they grow. The Pacific Oyster prefers to attach itself to a hard surface and can be found on firm mud, sand, gravel, or a rock substrate in the lower intertidal zone, down to a depth of roughly 4.2 meters.
The Pacific Oyster was cultivated on Vancouver Island several hundred years ago. They are invasive. They were first introduced from the hulls of sailing ships and began to proliferate along our coasts. The cold nutrient waters were perfect for them. I can remember just how thick the oyster beds were. We used to have beach parties where we would break off large groups of oysters stuck together and place them on coals. Then we would wait with a fork in hand to stab the cooked meat and gobble the oysters down until we were full. Some beaches had been so thick with them that crushers were used to grind them down into Lyme.