Research on environmental status of some pacific oysters (Crassostrea gigas Thunberg, 1793) and estuarine oysters (Crassostrea rivularis Gould, 1861) farming areas in Quang Ninh

Abstract

Pacific oysters (Crassostrea gigas Thunberg, 1793) and estuarine oysters (Crassostrea rivularis Gould, 1861) are raised in open ocean environments, therefore they are strongly affected by changes in environment. Research on the current state of farming of pacific oysters and estuarine oysters is necessary to serve the sustainable development of aquaculture of these objects. Research location inluded Van Don district and Quang Yen town. Implementation period was from June 2020 to May 2021. Environmental indicators monitored included: Salinity, temperature, DO, alkalinity, COD, BOD, TSS, flow rate, clarity, algae, total Vibrio sp. count in water. Samples were sampledperiodically once a month, at each district investigation was conducted in 2 communes, at each commune, 3 mollusk farming were investigated in a total 144 samples samples were conlected. Research results show that most environmental indicators were in the safe limits for marine aquaculture. Some environmental factors exceed the safe limits value and have may impact on the health of oysters such as salinity elevated up to 30‰ in December and not suitable for the development of estuarine oysters, in December the low algae densityshowed a lack of natural food condition and high total Vibrio sp. counts exceeds 10³ cfu/l were coccured in  October, November, March, April.