American oyster

Introduction

Oysters have been a favourite of food lovers and romantics throughout the centuries. The oyster has maintained a timeless mystique when it comes to passion. When Aphrodite, the Greek goddess of love, sprang forth from the sea on an oyster shell and promptly gave birth to Eros, the word "aphrodisiac" was born. Roman emperors literally paid for them by their weight in gold. The dashing lover Casanova also started his evening meal by eating dozens of oysters. Please read the DFO fact sheet entitled, Oysters: ‘Myths’ and Facts for more information regarding the passions associated with oysters.

It is rumoured that oysters were the first sea animal to be transported from one area to another and cultivated as food. Commercial-scale oyster farming began early in the 20th century on both coasts, where cultivation consisted of collecting wild seed and spreading them on beds where they could be protected from public harvest and predation. Oyster farmers require a reliable source of spat, or seed, for grow-out. In the 1950s, the industry started collection of wild juvenile oysters on "spat collectors". Spat refers to fertilized shellfish larvae that settle on uneven, rough surfaces placed within the spat collectors until it is time to remove it. Spat size ranges between 5 and 25 mm depending on the species and the number of months spat remained on the collector. Some shellfish species are also produced in hatcheries where broodstock are spawned and the larvae raised under controlled growing conditions.

In both cases, when the juveniles are large enough to be transferred to grow-out sites they are removed from the collectors and transferred to a grow-out system: either oyster "beds" (sites that have been prepared for the spreading of juvenile oysters on the ocean floor); or, to various types of off-bottom (suspension) systems such as floating bags, bags in cages or on tables until the oysters reach market size. Held in suspension, oysters grow more rapidly and develop plumper meats than on the bottom because better water circulation increases the availability of food. However, as a result of rapid growth, their shells tend to be thin. In order to produce shell qualities of the shape and thickness desired by Canadian consumers, the oysters need to be held for an additional year or two on the bottom or on suspended trays.

Canadians can enjoy fresh oysters twelve months of the year. Oyster aquaculture complements the supply of oysters at your local seafood counter when wild, commercially-harvested oysters are not available. Oysters are generally harvested at the time of year when they are in peak condition, when their meat is at its "fattest". Oysters need a period in the spring to recuperate from the winter before they reach a condition ideal for the retail market. Also, oysters spawn in the summer, which can alter their flavour and texture.

Cultured American oysters are usually available for retail sale live in the shell and are sold per count, or by weight, in varying sizes . Practices vary to region and market demand. Two forms of American oyster are marketed from the Maritime Provinces: the traditional size oyster, the "cocktail oyster".

Traditional-sized oyster

These oysters are farmed or wild harvested American oysters that measure over 76 mm (3 inches) in length from the hinge to the tip of the shell. Fisheries and Oceans Canada set this length as a conservation measure to permit oysters in the wild to spawn over at least two seasons prior to harvest. It can take between three and four years for cultured eastern oysters to grow to market size and quality. There are three grades of oysters: choice, standard and commercial – with choice being the highest valued product. Shell and meat conditions are both taken into account for these rankings. They are available year round.

Most wild American oysters from the commercial fishery are harvested between September 15 and November 30 and are sold at sizes varying between 76 and 127 mm (3–5 inches). Many larger farmed oysters are also marketed late in the year, as there is a major demand for oysters in the Maritimes and Europe, particularly France, around December.

The "cocktail" oyster

Cocktail oysters are American oysters that are less than 76 mm (3 inches). Larger oysters can either be commercially harvested from the wild or cultured but these sources cannot be sold under the "cocktail" oyster category for farmers producing their oysters from seed.

The cocktail oyster policy was introduced in 1996 to permit oyster growers to sell their produce at a smaller size than that set to protect the commercial fishery. This license requires farmers who wish to market oysters less than 76 mm (3 inches) in length to have grown their oyster from seed size. This condition reflects the added investment and work required to do this and is designed to minimize conflict with the commercial fishers or farmers who stock their sites with larger oysters to cut down the grow-out period to traditional market size. Cocktail oysters take two-and-a-half to three years to grow from seed.

DFO Research Activity

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