178
R.A. BOWLER, D.S.C. YANG AND A.J.E. SMITH
Pearl River estuary. Oysters imported into Hong Kong from Shajing could thus be of variable origin.
Two types of commercial oyster are recognised by the oyster farmers but further studies are needed to determine whether the two forms are different species.
Traditional bottom-laying culture techniques based on lumps of rock are still practised but concrete tiles, posts and blocks are more often used in the shallow intertidal beds. Cultches are re-planted 2-3 times a year and, following storms, oysters have to be lifted within 72 hours to avoid suffocation. Deep water beds are also cultivated, making use of divers. Rafts are used on the Chinese side of Deep Bay to suspend the oysters above the sea bed and so avoid siltation problems.
The productivity of the oyster beds is extremely difficult to ascertain. The net production of wet-weight oyster flesh may be in the range of 0.45-0.67 kg/m2/year. If allowance for access paths and other non-productive areas is taken into account, the gross productivity may be as low as 0.105 kg/m2/year.
No organised marketing system exists, but demand is greatest in the colder winter months (October to March). Informal transactions take place with sometimes whole beds of oysters changing hands. The oyster industry estimates that around 70% of oysters produced go to restaurants.
This paper presents some information which has, for a number of reasons, been difficult to obtain. Many questions remain unanswered and the information has, in most cases, been impossible to verify. Nevertheless, it is hoped that this somewhat sketchy background will stimulate further interest and possibly detailed research work. Apart from scientific interest over the species of the commercial oyster, improved culture techniques would benefit a traditional industry and possibly help it to withstand the increasing effect of urbanisation.
Acknowledgement
The authors are grateful to the Hong Kong Government,
!
178
R.A. BOWLER, D.S.C. YANG AND A.J.E. SMITH
Pearl River estuary. Oysters imported into Hong Kong from Shajing could thus be of variable origin.
Two types of commercial oyster are recognised by the oyster farmers but further studies are needed to determine whether the two forms are different species.
Traditional bottom-laying culture techniques based on lumps of rock are still practised but concrete tiles, posts and blocks are more often used in the shallow intertidal beds. Cultches are re- planted 2-3 times a year and, following storms, oysters have to be lifted within 72 hours to avoid suffocation. Deep water beds are also cultivated, making use of divers. Rafts are used on the Chi- nese side of Deep Bay to suspend the oysters above the sea bed and so avoid siltation problems.
The productivity of the oyster beds is extremely difficult to ascertain. The net production of wet-weight oyster flesh may be in the range of 0.45-0.67 kg/m2 year. If allowance for access paths and other non-productive areas is taken into account, the gross pro- ductivity may be as low as 0.105 kg/m2 year.
No organised marketing system exists, but demand is greatest in the colder winter months (October to March). Informal transac- tions take place with sometimes whole beds of oysters changing hands. The oyster industry estimate that around 70% of oyster produced go to restaurants.
This paper presents some information which has for a number of reasons been difficult to obtain. Many questions remain unan- swered and the information has in most cases been impossible to verify. Nevertheless it is hoped that this somewhat sketchy back- ground will stimulate further interest and possibly detailed re- search work, Apart from scientific interest over the species of the commercial oyster, improved culture techniques would benefit a traditional industry and possibly help it to withstand the increas- ing effect of urbanisation.
Acknowledgement
The authors are grateful to the Hong Kong Government,
!
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