~ 211 ~ International Journal of Fisheries and Aquatic Studies 2020; 8(3): 211-216 E-ISSN: 2347-5129 P-ISSN: 2394-0506 (ICV-Poland) Impact Value: 5.62 (GIF) Impact Factor: 0.549 IJFAS 2020; 8(3): 211-216 © 2020 IJFAS www.fisheriesjournal.com Received: 16-03-2020 Accepted: 18-04-2020 Nguyen Thi Ngoc Anh College of Aquaculture and Fisheries, Can Tho University, Vietnam Le Van Thong College of Aquaculture and Fisheries, Can Tho University, Vietnam Nguyen Phuong Lam College of Aquaculture and Fisheries, Can Tho University, Vietnam Thach Thi Kim Lien College of Aquaculture and Fisheries, Can Tho University, Vietnam Nguyen Van Hoa College of Aquaculture and Fisheries, Can Tho University, Vietnam Corresponding Author: Nguyen Thi Ngoc Anh College of Aquaculture and Fisheries, Can Tho University, Vietnam Effects of water levels and water exchange rates on growth and production of sea grape Caulerpa lentillifera J. Agardh 1837 Nguyen Thi Ngoc Anh, Le Van Thong, Nguyen Phuong Lam, Thach Thi Kim Lien and Nguyen Van Hoa Abstract Study on cultivation of sea grape (Caulerpa lentiliifera) in the 1 m 2 - lined ponds, a 2×2 factorial experiment with two water levels (40 and 80 cm) and two water exchange rate (25% and 50%/week) was randomly designed in triplicate. Sea grape was cultivated at salinity of 30 ppt with continuous aeration, initial stocking rate of 1 kg /m 2 and fishmeal was used as nutrient source for sea grape, and cultivation lasted for 60 days. Results showed that a significant interaction effect (p<0.05) between water level water exchange rate was only observed for the growth rate of sea grape after 45 and 60 days of cultivation. Water level significantly influenced (p<0.05) frond (edible portions) production of sea grape, while the effect of water exchange rate on frond production was not significant (p>0.05). Water level and water exchange rate did not affect morphometric frond properties (commercial frond length, ramuli density and ramuli size) and sensory properties. It can be suggested that cultivation of sea grape C. lentillifera at water level of 80 cm combined with 50% water exchange per week could be the appropriate factors to obtain highest growth rate (1.95%/day) and frond production (12.21 kg/m 2 ). Keywords: Water level, water exchange rate, growth rate, frond production 1. Introduction The edible sea grape (Caulerpa lentillifera J. Agardh 1837) is rich in protein, minerals, dietary fibers, vitamins, unsaturated fatty acids as well as bioactive compounds that act as anti-cancer, anti-oxidative, anti-diabetic, and also help with cholesterol reduction, prevents cardiovascular diseases (Matanjun et al., 2010; Saito et al., 2010; Paul et al., 2014; Sharma and Rhyu 2014) [13, 16, 15, 17] . Therefore, this seaweed has been considered to be beneficial in various help issues and called green caviar, one of the favored species of Caulerpa due to its soft, succulent texture and refreshing taste. It is a popular seafood delicacy eaten as raw dip in vinegar or used in fresh salads with other seafood and vegetables (Paul et al., 2014; Chen et al., 2019) [15, 2] . Sea grape C. lentillifera is naturally distributed in tropical and subtropical regions, such as Southeast Asia, Japan, Taiwan and Oceania (Shokita 1991; Paul et al., 2014) [18, 15] . This species has high economic value and high biomass production potential in monoculture, and has been cultivated in some Asian countries in for a long time (Shokita 1991; FAO 2003; Paul et al., 2014; Chen et al., 2019) [18, 6, 15, 2] . In Vietnam, sea grape C. lentillifera was transplanted from Okinawa island, Japan, successfully cultivated in the central areas in recent years and has been considered high economic product (Dai et al., 2006, 2009; Minh et al., 2019) [3, 4, 14] . This seaweed has been commonly cultivated in ponds, open lagoons or in cages, but these methods are greatly affected by the weather conditions as they bring low productivity and uncontrolled quality of product. Previous studies found that sea grape Caulerpa spp. cultivated in tanks gave high productivity, free from pollution sources and the products of this seaweed satisfy the criteria for food hygiene, safety and high nutrition (Paul et al., 2014; Zuldin et al., 2018) [15, 23] . Growth rate and production of C. lentillifera were not only affected by environmental conditions such as salinity, temperature, light intensity (Shokita 1991, Wang 2011; Guo et al., 2015a; Chen et al., 2019) [18, 21, 8, 2] but also by technical factors and culture conditions (Paul et al., 2014; Wang et al., 2017; Minh et al., 2019) [15, 20, 14] . The aim of this study was to determine the suitable water level and water exchange rate for cultivating sea grape.