BRIAN MORTON & P. S. WONG
power. There is thus an advantage for an oyster farmer to possess a large family. Usually every member of the family participates in the work. Male members usually handle the more laborious procedures such as the laying of the cultch, the transfer of the oysters from one bed to the other and the harvesting of the oysters for resale. Female members may also participate in this work especially those young and strong enough--but more often they are in charge of separating the oysters from the cultch and the shucking and selling of the oysters. Younger members of the family assist with domestic chores.
In Deep Bay, the oysters are cultivated in the traditional manner i.e. by bottom-laying (*). This method involves the laying of cultch (*) on the muddy bottom to collect the oyster spat (#). The set oysters are then left to grow for one or two years in the breeding ground (*) before being transferred to the deeper fattening ground (†) for an additional period of one or more years prior to harvesting (#).
Elsewhere in the world various materials are used as cultch for the collection of spat. These include stones, shells, bamboo sticks (Cahn, 1950), lime coated roofing tiles or egg-crate fillers, cement dipped wood veneer rings or old fish nets (Needler, 1941; Quayle, 1969) and even sticks of the mangrove, Aegiceras majus (Roughley, 1922). In Hong Kong some ten years ago, rocks and shells (Plate 14; A, B) were most commonly used as cultch. The supply of rock from nearby shores has, however, been virtually exhausted. Consequently stones are now being replaced by concrete tiles (*) (Plate 14; C, D) or concrete posts (Plate 14; E, F). Stones and oyster shells of appropriate size and thickness are still collected and reserved as cultch whenever available. The oyster shells are first cleaned and placed in the sun for weathering prior to being used. Concrete slabs are made artificially at a cost of HK$500/10,000 (in 1974). Old concrete slabs or posts which remain unbroken after the oysters have been detached can be reused. They are cleaned to remove all fouling organisms and then dried in the sun.
The most important and labour intensive stage in the bottom-laying method of oyster culture is the collection of the spat (**). In Deep Bay oysters spawn from March to September when temperatures are high and salinities are low (Mok, 1973). As a consequence the cultch has to be laid within this period. However,
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