52 SEPTEMBER 2014 • WORLD AQUACULTURE • WWW.WAS.ORG The oyster Crassostrea lugubris (Fig. 1) is a major source of food, industry and tourism for the coastal area of central Vietnam. In this area, oysters are harvested from Lang Co Bay, Thua Thien Hue Province (500 t/ yr), An Hoa Lagoon, Quang Nam Province (500 t/yr), Thi Nai Lagoon, Binh Đinh Province (12-15 t/yr) and O Loan Lagoon, Phu Yen Province (12-15 t/yr), Nha Phu Lagoon, Khanh Hoa Province (25-30 t/yr) and Nai Lagoon, Ninh Thuan Province (3040 t/yr). These oysters are also found in Thailand, Philippines and Hong Kong (Angell 1986, Lam et al. 2004). Enhancement of oyster stocks has been proposed as a restoration strategy to improve water quality. Oysters absorb nutrients from the water column and release biodeposits in the form of feces and pseudofeces. This process decreases water turbidity and stimulates growth of microphytobenthos, such as diatoms and cyanobacteria. Nutrients and organic matter from bivalve wastes are then mineralized by sediment microbes. Developing oyster aquaculture is a management strategy to protect biodiversity in lagoons. Oyster culture may also improve productivity of other organisms, such as crustaceans, by providing a complex habitat. Furthermore, small fringing oyster reefs can be used to protect shorelines in low-energy environments. Therefore, the development of oyster aquaculture has been identified as an important goal for enhancing the Nha Phu Lagoon ecosystem. Biological Characteristics of the Oyster Crassostrea lugubris in Central Coastal Vietnam Cao Van Nguyen, Nguyen Tac An and Ho Van The To obtain ecological benefits from oyster aquaculture, the basic requirements of appropriate water quality and substrate must be met. However, there have been no published studies of oyster populations and the potential development of oyster aquaculture in Nha Phu Lagoon. Nha Phu Lagoon is 12 km north of Nha Trang along the central coast in Khanh Hoa Province (Figs. 2 and 3). The lagoon has an average depth of 1.5-2 m and a water surface area of 5000 ha at high tide and 3000 ha at low tide. The total intertidal area is 1900 ha. We measured survival, growth and reproduction of oysters in Nha Phu, while considering water quality. The study was intended to provide preliminary data that can guide future development efforts in the coastal areas of central Vietnam. Water Quality of Nha Phu Lagoon There were two monsoon seasons: the winter monsoon (rainy season) from the northeast between September and December and the summer monsoon (dry season) from the southwest between January and August. The minimum temperature (24 C) occurs at the end of the winter monsoon. Maximum temperature (30 C) occurs in May and June; the average annual average temperature was 27 C. Average annual rainfall was about 1500 mm, and 70-80 percent occurred in the rainy season. Dissolved oxygen FIGURE 1. Crassostrea lugubris. (Photo: Cao Van Nguyen) LEFT, FIGURE 2. Nha Phu Lagoon in relation to Nha Trang city, central coast of Vietnam. RIGHT, FIGURE 3. Nha Phu Lagoon, indicating the location of the farm for cultured oysters Crassostrea lugubris, near Hon Nua Island.
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