Oanh, D.T., T.Q. Phu (2008). Control of phytoplankton growth in shrimp (Penaeus monodon) rearing tanks by precipitating phosphorus compounds. Scientific Journal of Can Tho University, Specific Issue on Aquaculture and Fisheries 2008(1): 23-32. (Full paper in Vietnamese).

Abstract:

A study was conducted to investigate the capacity in precipitating phosphorus of CaSO4, Ca (OH)2 and Al2(SO4)3 to control growth of phytoplankton. At the same time, possible effects of these chemicals on shrimp were also evaluated. The results showed that all of these chemicals have high potential in precipitating phosphorus. Application of these chemicals in the shrimp tanks resulted in decreased phytoplankton densities as compared to the control. Mean densities of phytoplankton in CaSO4, Ca(OH)2 and Al2(SO4)3 treatments were 730.154±377.367 cell.L-1, 752.065±335.024 cell.L-1, 793.157± 346.607 cell.L-1, respectively. The mean density of phytoplankton in the control was 923.940±506.438 cell.L-1 and significantly higher than that of other treatments (P<0, 05).

Ngan, P.T., T.C. Tam, T.Q. Phu (2008). Effects of vegetable oil supplementation on the diversity of bacteria in bio-filter system. Scientific Journal of Can Tho University, Specific Issue on Aquaculture and Fisheries 2008(1): 33-43. (Full paper in Vietnamese).

Abstract:

The aim of this study was to investigate the effects of vegetable oil on the nitrification and denitrification processes in aquaria system. The experiments were designed in freshwater and seawater systems. Each system had two treatments including the control and bio-filter module connected with a membrane tube as a bioreactor. Water parameters such as pH, DO, NO2 and NO3 were monitored continuously in the aquaria (70 L). Nitrification and denitrification processes were observed after adding ABIL (ammonia binding inoculum liquid) and vegetable oil into the bio-filter module. The results showed that in the module treatment in freshwater system, pH slightly decreased at the end of experiment. DO was always lower in the module treatment. Nitrate removal rate was faster in the module treatment than in the control from date 9 onwards. Nitrification process took place faster in the third pulse than in the first and the second pulse. The microbial community in the module treatment was more diverse than that of the control. Similarly, in seawater system pH also decreased at the end of experiment. DO in the module treatment was lower than in the control. Nitrate removal rate in the module treatment was faster than in the control. However, the diversity of microbial community was similar in both treatments.

Long, N.T., V.T. Toan (2008). Study on the accumulation of nitrogen and phosphorus in intensive shrimp (Penaeus monodon) ponds. Scientific Journal of Can Tho University, Specific Issue on Aquaculture and Fisheries 2008(1): 44-52. (Full paper in Vietnamese).

Abstract:

A study on nutrient mass balance in the shrimp intensive culture system was conducted in Bac Lieu province. The aim of the study was to determine the accumulation and dispersal levels of nitrogen and phosphorus in this culture model. Two shrimp stocking densities (27 PL/m2 and 35 PL/m2) were designed in two earthen ponds (2,000 m2/pond) with two replicates each. The results indicated that all measured parameters were fluctuating during the culture period (168 days). However, these values varied within the acceptable ranges. The quality of culture water reduced towards the end of the culture period in both treatments. Concentrations of TAN, NH3, NO2-, NO3-, TKN, chlorophyll-a and TSS increased during this period. DO concentration at 6 AM was decreasing after one month of culture period. There were no significant differences in yields between treatment 1 (4,953±413 kg/ha/crop) and treatment 2 (4,842±850 kg/ha/crop), however, survival rate in treatment 1 (78.62±4.55%) was significantly higher than that in treatment 2 (46.79±4.51%) while daily weight gain in treatment 1 (0.15±0.00 g/shrimp/day) was significantly lower than that in treatment 2 (0.17±0,01g/shrimp/day) (p<0.05). FCRs in two treatments were high but no significant difference found between treatment 1 (1.82±0.14) and treatment 2 (1.79±0.06) (P>0.05). Nitrogen accumulated in shrimp, water and sediment was 16%, 29% and 28%, respectively. Similarly, 9%, 2% and 40% were found for phosphorous in these sources, respectively. In addition, significant uncountable amounts of nitrogen and phosphorus considered loss were 27% and 49%, respectively. Results of nutrient mass balance asl indicated that to produce 1 ton of shrimp, approximate 118÷120 kg N of nitrogen and 30÷33 kg of phosphorus were released into the environment.

Luong, V.C. (2008). Ecopath modeling for natural food web management in cove aquaculture. Scientific Journal of Can Tho University, Specific Issue on Aquaculture and Fisheries 2008(1): 53-60. (Full paper in Vietnamese).

Abstract:

This study was conducted at Truong Dang Cove in Tri An Reservoir with an extensive polyculture system of marble goby, common carp, silver carp, bighead carp and grass carp. An attempt to construct a steady-state model was made using the Ecopath 5.0 approach and software to average the trophic flows and biomasses over the production period. In application aspect, a steady-state model for a rapidly developing culture system should be possibility and reality to saving the time and input data. In this model, the energy flows of terrestrial plant, detritus, phytoplankton, periphyton, zooplankton, benthos, small wild fish, prawns, and five cultured fish species were quantified. This study demonstrated that the cove’s natural food web and fish stocking densities can be managed by Ecopath model.

Lien, N.T.K., T.T. huy, N.T. Phuong (2008). Culture of rotifer (Brachionus rotundiformis) (super small type) using Chlorella and Baker’s yeast as feeding diets. Scientific Journal of Can Tho University, Specific Issue on Aquaculture and Fisheries 2008(1): 67-74. (Full paper in Vietnamese).

Abstract:

A study was conducted at College of Aquaculture and Fisheries, Can Tho University to investigate food preference for Rotifer (Brachionus rotundiformis-SS) culture. One experiment was designed in a room with controlled conditions including temperature (28-30oC), salinity (25 ppt) light intensity (2,000 lux) and continuous aeration. Two treatments were randomly set up in 100 L composite tanks with 3 replicates each, consiting of (i) Chlorella (40,000 cells. rotifer-1. day-1) and (ii) baker’s yeast (0.3 gr. million rotifer-1. day-1). Rotifers were stocked at a density of 200 ind.mL-1. The results showed that the rotifer densities in both treatments were similar. After 8 days of culture period, rotifers in the Baker’yeast and Chlorella treatments obtained a final mean density of 893±50 ind. mL-1 and 873±50 ind.mL-1, respectively. At the same time, specific growth rate of 0,2±0,16 and 0,1±0,15 were found for both treatments, respectively. Egg ratio observed in Baker’ yeast treatment was 25,5±7,32% and similarly in Chlorella was 26,0±6,91%.

Dinh, T.D., N.T. Phuong, Mohd Azmi Ambak & Anuar Hassan (2008). Population dynamics of the goby (Pseudapocryptes elongatus) in coastal areas of Soc Trang and Ca Mau. Scientific Journal of Can Tho University, Specific Issue on Aquaculture and Fisheries 2008(1): 75-80. (Full paper in Vietnamese).

Abstract:

Population parameters of the goby Pseudapocryptes elongatus distributed in the coastal mud flat areas of the Mekong Delta were investigated to obtain the information required for sustainable use of the fish stock. The parameters of von Bertalanffy growth function fit to length frequency data were L∞ = 25.5 cm, K = 0.71/year and to = - 0.09 year. The longevity (tmax) was determined to be 4.2 years. Recruitment of young fish to the adult populations occurred in February and June. Length at first capture (Lc) was 10.31 cm. The fishing mortality (F=1.92) accounted for 56% of the total mortality (Z=3.45). Relative yield-per-recruit and biomass-per-recruit analyses also gave Emax = 0.66 and E0.1 = 0.56. The results show that the fish stock was growth-over exploitation; therefore, the mesh sise of the fishing gear should be increassed

Thuong, N.V. (2008). Classification of the Pangasianodon hypophthalmus in the Mekong River. Scientific Journal of Can Tho University, Specific Issue on Aquaculture and Fisheries 2008(1): 84-89. (Full paper in Vietnamese).

Abstract:

Pangasianodon hypopthalmus (Tra catfish) are characterized by a laterally compressed body, a short dorsal with one or two spines, a well developed adipose, a long anal fin, strong pectoral spines, and two pairs of barbels (maxillary and mandibulary). The position of the mouth is decribed as being terminal. There are 6 branched dorsal fin rays and the pelvic fins have 8-9 soft rays. The gill rakers are described as being normally developed, with small gill rakers being interspersed with larger ones.Pangasianondon hypophthalmus have the swimbladder with a single chamber extending posteriorly above anal fin.
The natural range of Pangasianodon hypophthalmus is limited to the lower Mekong Basin, includes Cambodia, Lao PDR, Thailand and Viet Nam, and the Chao Praya River in Thailand.
Over their native range, Tra catfish are divided into two distinct populations: stocks in the Mekong River in Cambodia and Viet Nam belong to one population (southern stock); and stocks above Khone Falls in Lao PDR and Thailand form a separate population (northern stock). The southern stock is subject to more intensive fishing than the northern stock, and is larger in s