200 Y.H. CHEUNG, K.Y. TAI, S.W. TSAO AND L.B. THROWER
Discussion
Arguably, the traditional kei wai has two attractive economic features. The first is that it provides a method for controlled exploitation of recently-deposited alluvium. Probably, rearing of fish is the most feasible procedure for exploiting such sites and the construction of a kei wai requires much less equipment and labour than digging deep fish ponds. The second feature of the kei wai is that it facilitates exploitation of the nutrient-rich waters of an estuary to produce animal protein in a variety of forms.
An estuary has been defined as “an area in which sea water is appreciably diluted by fresh water from rivers” (Stewart, 1972). Therefore sources of energy and nutrients produced in terrestrial communities are carried by the rivers to the estuary, where tidal movement assists recycling of nutrients from consumer back to producer. This characteristic structure and function of an estuary has led to it being called a “nutrient trap” (Odum, E.P., 1971). The importance of supplements of energy and nutrients moving to the estuary from terrestrial communities has been shown clearly by Odum W.E. (1971) and Odum & Heald (1975) for a system in southern Florida. There an estuary is receiving material from an extensive mangrove community, and measurements showed that material to be more important as a basis for economic productivity than was photo-synthesis.
In considering the productivity of the waters of Hau Hoi Wan, it is relevant that Vrijmoed (1975) found that the weight of fouling organisms (invertebrate animals) accumulating on blocks of pine wood submerged for several months in Hau Hoi Wan was the greatest among the five sites she investigated within Hong Kong's coastal waters; this result reflects the high nutrient content of the water.
The inherently nutrient-rich water of the estuary is then impounded in the kei wai where it is further supplemented with nutrients and energy by the plant material that enters it. Microorganisms play an important part in fragmenting the plant material and converting much of the structural carbohydrates to protein. Consequently, the higher trophic levels have available material
200 Y.H. CHEUNG, K.Y. TAI, S.W. TSAO AND L.B. THROWER
Discussion
Arguably, the traditional kei wai has two attractive economic features. The first is that it provides a method for controlled ex- ploitation of recently-deposited alluvium. Probably, rearing of fish is the most feasible procedure for exploiting such sites and the construction of a kei wai requires much less equipment and labour than digging deep fish ponds. The second feature of the kei wai is that it facilitates exploitation of the nutrient-rich waters of an estuary to produce animal protein in a variety of forms.
An estuary has been defined as “an area in which sea water is appreciably diluted by fresh water from rivers” (Stewart, 1972). Therefore sources of energy and nutrients produced in terrestrial communities are carried by the rivers to the estuary, where tidal movement assists recycling of nutrients from consumer back to producer. This characteristic structure and function of an estuary has led to it being called a “nutrient trap" (Odum, E.P., 1971). The importance of supplements of energy and nutrients moving to the estuary from terrestrial communities has been shown clearly by Odum W.E. (1971) and Odum & Heald (1975) for a system in southern Florida. There an estuary is receiving material from an extensive mangrove community, and measurements showed that material to be more important as a basis for economic productivi- ty than was photo-synthesis.
In considering the productivity of the waters of Hau Hoi Wan, it is relevant that Vrijmoed (1975) found that the weight of fouling organisms (invertebrate animals) accumulating on blocks of pine wood submerged for several months in Hau Hoi Wan was the greatest among the five sites she investigated within Hong Kong's coastal waters; this result reflects the high nutrient content of the water.
The inherently nutrient-rich water of the estuary is then im- pounded in the kei wai where it is further supplemented with nutrients and energy by the plant material that enters it. Microor- ganisms play an important part in fragmenting the plant material and converting much of the structural carbohydrates to protein. Consequently, the higher trophic levels have available material
No comments yet.
Private notes are available after approval.