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Collection of Marine Research Works, Vol. XV, 2006

Publish year: 2006
Category: COLLECTION OF MARINE RESEARCH WORKS

CONTENTS
 
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SOME CHARACTERISTICS OF WIND STRESS AND ROTATION OF
WIND STRESS IN THE SOUTHERN CENTRAL VIET NAM
   

Bui Hong Long, Pham Sy Hoan
Institute of Oceanography (Nha Trang)
 
ABSTRACT: This paper presents some statistic calculating results  of primary characteristics on spatial distribution and temporal variation of wind stress and rotation of wind stress in the Southern Central Vietnam (from 5oN and 105oE to 15oN and 115oE). Here, the average of daily, monthly and annual wind stress and rotation of wind stress was calculated basing on wind field and remosensing data during the time from 07/1999 to 03/2006. The most interesting results are as follows:
- The wind stress and rotation of wind stress had a seasonal change as monsoon change.
- The strongest module value of wind stress and rotation of wind stress was always found in the area from Vung Tau to Nha Trang. The strongest module value of wind stress was about 5 dyn/cm2 and rotation of wind stress was about 70x108 dyn/cm3.
- The values of rotation of wind stress were often negative in the winter monsoon and positive in the summer monsoon. As a result, features of air rotation motion were clockwise in winter monsoon and counterclockwise in summer monsoon.
- Values of rotation of wind stress were positive at Southern Truong Sa archipelagos while winter monsoon was very strong (December and January). This area was not very large and existed for a short time.

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THE ANNUAL VARIATIONS OF OCEANOGRAPHIC PARAMETRIZED STRUCTURES IN THE SURFACE LAYER OF VIETNAMESE SEA
AND ADJACENT WATERS
 
La Van Bai
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Studying the time variation of water structures in the surface layer of the East Sea, is  met with difficulties because the strong influency of  hydro-dynamical  formated factors.  This paper presents an using approximation of vertical structure of  surface layer by polynom of Chebusev in order to simplify the indentificational procedure on the calculated “digital  field”. Spatial distribution of coefficients A0, A1 and anomaly of studied elements was well described as having the features of hydrological structures of surface layer of Vietnamese Sea (SLVNS) in the annual cycle. “The calculated structures” of temperature, salinity and dissolved oxygen in SLVNS may be to assess the size of spatial distribution and the annual variations, giving out the comment on “stable trend” of the hydrological structures of SLVNS in oder to serve for forecast.

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FEATURES OF SHORELINE CHANGE IN THE DAI MOUTH (HOI AN) AREA
FROM 1965 TO 2003
 
Le Dinh Mau
Institute of Oceanography (Nha Trang)
 
ABSTRACT: The paper considered the extent, rate and feature of erosion-deposition in the Dai mouth (Hoi An) area for both long-term and short-term periods; Study results showed that from 1965 to 2003 shorelines in the Dai mouth area moved towards southeast direction with distance of approximately 900 m. That means the rate of southeastward moving was approximately 23 m per year. The extent of erosion-deposition in the northern and southern shoreline during wet season was larger (around 1.5 to 2 times) than that of dry season. River bank was eroded during wet season, whereas it was slightly accreted in dry season. Cua Dai Cape was strongly accreted in wet season, whereas, it was eroded in dry season. In general, shoreline has been changed in the Dai mouth area in the recent years showing that northern shoreline was slightly eroded, southern shoreline was in the accretion process, and river bank was in the erosion process. The short-term effects of storms primarily caused the unusual shoreline changes in the Dai mouth area.

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CHARACTERISTICS OF SEDIMENTARY LAYERS CONTAINING PINATUBO ASH  IN THE CENTRAL BASIN OF EAST VIETNAM SEA 
 
Nguyen Dinh Dan
Institute of Oceanography (Nha Trang)
 
ABSTRACT: The studied results showed that the sedimentary layer containing Pinatubo ash is mainly constituted of mud and sandy mud with highly sorted rate. The composition of this ash layer greatly consists of biological relics such as foraminera, and volcanic materials. In addition, the significant difference in sedimentary composition obviously observed can divide the central basin into 2 separate regions, the West and the East, with a boundary at the divergent rift of East Sea. Furthermore, manganese mineralization was chemically observed in this layer.
It can be concluded that this ash layer is a strategically marked layer, and the findings of this study play a vital role in further geological studies in the future.

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LANDSCAPE AND EXPLOITATION OF NATURAL RESOURCES ON THE ALLUVIAL SAND BARS IN THE LOWER REGIONS OF CO CHIEN ESTUARIES  (TRA VINH PROVINCE)
  
Trinh The Hieu, Pham Ba Trung
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Based on data of the field trips at alluvial sand bars in the lower regions of Co Chien estuaries – Tra Vinh province in September 2004, October & November 2005 and February – March 2006, the paper indicated that:
1. General characteristics of the alluvial bars were that the top parts of these bars (in the parts of rivers) were being eroded rather strongly while deposition was occurring at the bed (in the estuarine parts of the sea). The deposed materials were mainly derived from the estuarine erosion.
2. The general development of these bars is through land reclamation, upgraded land and expanded islands to the sea. As the same as the developing processes of the Mekong Delta, alluvial bars in Tra Vinh province developed from warp bars to islets and then to islands.
3. These days, the exploitation of natural sources, such as sand and minerals, has been proposed in the master plan of the province. However, there are still some problems in the management of the plan. For example, there are many people who harvest sand without permission and unsuitable land conversion such as cutting down mangrove forest to build shrimp ponds. These activities might cause a change in the state of alluvial bars.

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SOME DATA ON THE WATER ENVIRONMENT IN XUAN TU - RAN TRAO AREA, KHANH HOA
 
Le Thi Vinh
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Collected data at dry season (May) and rainy season (October), 2004 in Xuan Tu-Ran Trao area indicated that:
Concentrations of ammonia and nitrite were very low, concentration of nitrate  was intermediate. There is no significant difference of these nutrient concentrations  between two surveys.
Phosphate, silicate and organic P concentrations in October were usually higher  than that in May while organic N concentration in October was lower than that in May.
 Suspended solid value and organic matter concentration in water and suspended solid were not high.
Sedimentation rate was  relatively high.
In May, N/P average ratio = 17.4. This value was comparatively similar to Redfield ratio while nitrate acted as limiting nutrient in October (N/P average ratio =6.4). N/Si ratios were always under 1 in both investigations.
 According to current fishery water standards, water quality in Xuan Tu-Ran Trao was still relatively good concerning nutrients in studied time. Concentrations of ammonia, nitrite, nitrate and suspended solid value were still within acceptable levels, only phosphate concentration exceeded the maximum allowable concentration at some stations in October.

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CONCENTRATION OF HEAVY METALS Pb, Cd and Cr IN SEA GRASS AND MOLLUSC AT MY GIANG, VAN PHONG BAY
 
Le Thi Vinh
Institute of Oceanography (Nha Trang)
 
ABSTRACT: The studied results on the concentration of Pb, Cd and Cr in sea grass and mollusc obtained in Mygiang in  2005 indicated that:
Mean concentration of heavy metals in sea grass (leaves) Enhalus acoroides and Thalassia hemprichii was rather low, ranged from 0.32 to 1.15 µg/g dry weight for Pb, 0.11 to 0.27 µg/g dry weight for Cd, 0.59 to 2.27 µg/g dry weight for Cr.
Mean concentration of heavy metals in the bodies of mollusc (snail Turbo bruneus and Lambis lambis; and oyster Saccostrea cucullata) was not high, ranged from 1.2 to 9.5 µg/g dry weight for Pb, 0.4 to 3.1 µg/g dry weight for Cd, 1.0 to 5.8 µg/g dry weight for Cr.
There was no significant difference of heavy metal concentration in sea grass and mollusc collected from My Giang compared to those from Cam Ranh, Nha Trang, and Xuan Tu.
Concerning seafood safety, the metal contents of Pb, Cd and Cr in the mollusc samples from My Giang did not exceed the maximum permissible levels set up by the Ministry of Public Health of Vietnam and Hong Kong.
 
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THE IMPACT OF Zn AND Cu IN NIX GRAINS FROM HYUNDAI -VINASHIN SHIPYARD UPON ENVIRONMENTAL QUALITY OF MYGIANG, VANPHONG BAY
 
Le Thi Vinh, Pham Van Thom, Nguyen Hong Thu,
Duong Trong Kiem, Pham Huu Tam
Institute of Oceanography (Nha Trang)
 
ABSTRACT:  In order to assess the impacts of Zn and Cu in NIX grains from the Hyundai -Vinashin Shipyard (HVS) on the environment of Mygiang (2005), samples were collected in zone near HVS and zones far HVS (Mui Du, Cam Ranh,  Xuan Tu and Nha Trang). The  initial results showed that Zn and Cu in NIX grains from the HVS led to:
Increase concentration of Zn and Cu in suspended particles, mud fraction of the sediment in My Giang compared to Mui Du.
Increase concentration of Zn and Cu in sea grass (leaves) Enhalus acoroides compared to Cam Ranh and Xuan Tu.
Increase concentration of Zn and Cu in the bodies of mollusc (snail Turbo bruneus and Lambis lambis, and oyster Saccostrea cucullata) in My Giang compared to Nha Trang, Mui Du. Especially, the content of these metals in oysters was higher than the critical value for food safety set up by Ministry of Public Health of Vietnam.
Increase concentration of Zn and Cu in well water, suspended particles, mud fraction of well sediment near HVS compared to far HVS.
To reduce and eliminate negative impacts of Zn and Cu in NIX grains, it is necessary to cover NIX grains stored inside and outside the shipyard; to move local residents affected by dusts of NIX grains; to inform local residents about the toxic effect of heavy metals in mollusc on human health; to study the safety measures to treat effectively used NIX grains.

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SOME ENVIRONMENTAL ELEMENTS AND DISTRIBUTION OF PHYTOPLANKTON IN VAN PHONG AND CAM RANH BAYS,
KHANH HOA, VIET NAM
 
Thai Ngoc Chien 1, Rune Rosland 2, Knut Barthel 3, Bui Hong Long 4,
Nguyen Tac An 4
       1 Research Institute for Aquaculture No.3, Vietnam
           2 Biological faculty, Bergen University, Norway
           3 Geographical Institute, Bergen University, Norway
     4 Institute of Oceanography in Nha Trang, Vietnam
 
ABSTRACT: The sampling data from NUFU project in 2004 and 2005 showed that Van Phong and Cam Ranh bays are different in neurotic phytoplankton community, which regarding species composition, production, seasonal development and environmental conditions. Phytoplankton in the shelf water is largely dominated by diatoms, but diatoms density in Cam Ranh is more abundant due to turbulence, while dinoflagellates and flagellates in Van Phong are more abundant due to stratified water. The phytoplankton biodiversity in Van Phong bay is higher (192 species) and 166 species recorded in Cam Ranh bay. 67 % species are similar from two bays. The biomass of diatoms and dinoflagellates in Cam Ranh bay is 48 mg C m-3 and 7 mg C m-3, respectively. While these biomasses are 26 mg C m-3 and           4 mg C m-3 in Van Phong bay. The biomass is correlated with  the rainfall and wind schemes, increased from August to December. Both nutrient concentrations and phytoplankton biomass in Cam Ranh bay are higher (63.0 mgC m-3) than that in Van Phong bay (30.7 mgC m-3). The ratio of DIN:DIP in Van Phong and Cam Ranh bays is 9 and 14, respectively.
Key words: Phytoplankton, diatoms, dinoflagellates, flagellates, DIN, DIP, environment, aquaculture.

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WATER ENVIRONMENTAL QUALITY IN THI NAI LAGOON – QUY NHON BAY
 
Nguyen Huu Huan, Le Lan Huong,
Vo Duy Son, Le Tran Dung, Le Hoai Huong
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Based on data collected during 2001-2005, the water quality in Thi Nai lagoon - Quy Nhon bay was described and discussed. The results showed that the water quality in Thi Nai lagoon - Quy Nhon bay was in range of environmental standards. However, in details, there are some matters of great interest as:
The water quality in Quy Nhon bay is better than in Thi Nai lagoon. These areas are strongly developing socio-economic activities in Binh Dinh province. Thus, it is necessary to build the managing resolutions of socio-economic activities as well as environmental quality in order to ensure sustainable development of economy and safe protection of ecological environment in Thi Nai lagoon - Quy Nhon bay.
The heavy metals, pesticides, hydrocarbon and bacteria (coliform and vibrio) presented in the water with remarkable concentrations or over the standards of aquacultural environment in some sites of Thi Nai lagoon - Quy Nhon bay. Because the characteristics of polluted components are easy to outbreak on population, quickly spread (vibrio and coliform), have the high and stable eco-toxicity (heavy metals, pesticides, petroleum), it is necessary to make reasonable strategies of monitoring and controlling in order to prevent the waters from ecological risks.

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PHYTOPLANKTON IN NHAPHU LAGOON, KHANH HOA, VIETNAM
 
Nguyen Ngoc Lam, Nguyen Thi Mai Anh, Doan Nhu Hai, Ho Van The
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Qualitative samples of phytoplankton were collected by a net (25 µm mesh) hauling from bottom to surface, while 1,000 ml of sea water were collected by Niskin bottle for the quantitative researches during twelve months from April 2004 to May 2005. Results showed that there was high diversity of phytoplankton species in the shallow lagoon. 232 species were identified, in which diatoms were dominant with 150 species occupying 65% of total, and dinoflagellates were 75 species occupying 32%. There was no difference in species composition between sampling months. Index of species diversity was high from mid- /end of dry season and low in rainy season. Cell concentration reached a pick in the beginning of rainy season, in the period of intermonsoon. The bloom of Alexandrium pseudogoniaulax was observed and there were no effects on the growth of cultured Tiger shrimp.
 
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DINOFLAGELLATES OF BINH THUAN COASTAL WATERS
 
Ho Van The, Nguyen Ngoc Lam
Institute of Oceanography (Nha Trang)
 
ABSTRACT: This paper presents the results of variation in biomass, cell density, and species composition of Dinoflagellates in Binh Thuan. A list of 97 species in 6 orders, 17 families, and 24 genera were recorded. Cell density greatly varied in time with the lowest in February (700 cells/L) and the highest in October (3,600 cells/L). There were two peaks of cell density and carbon biomass in southwestern monsoon (May – 2,900 cells/L and August - 2,400 cells/L) and one peak of cell density in northeastern monsoon (October, 3,600 cells/L). Average carbon biomass ranged between 0.32 – 5.90 µgC/L.
Keywords: Binh Thuan, carbon biomass, cell density, Dinoflagellates.
 
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EFFECT OF ENVIRONMENTAL ELEMENTS TO THE DEVELOPMENT OF CAULERPA LENTILLIFERA
 
Nguyen Huu Dai, Nguyen Xuan Hoa, Nguyen Xuan Vy
Pham Huu Tri, Nguyen Thi Linh
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Caulerpa lentillifera also called “green caviar” or “sea grapes”. It is a good source of iron, iodine, calcium and vitamin A and C. It has been cultured in Japan, Philippines, Thailand…In Vietnam this species was transplanted from Japan, is growing in botanical laboratory of the Institute of Oceanography in Nha Trang.
The main reproduction is vegetative reproduction. Both prostrate or upright branches can develop into fronds. But using initial seed segments with the length about 10-20 cm is the best. The initial stocking rate is 100 g/m2 suitable for commercial aquaculture. The growth rate can get the best value on muddy sand bottom of culture tank, reaching 2.59%/day. The optimum salinity is 33‰. This seaweed can grow very good in rather large light intensity ranging from 50 to 250 mol.s-1.m-2. In strong light intensity (500 mol.s-1.m2), productivity is low. When the temperature increases to 340C, the photosynthesis intensity decreases. The seaweed grows well in pond with the growth rate of 2.99%/day (in experiment with the initial stocking rate of 100 g/m2).

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SOME RESULTS ON ARTIFICIAL BREEDING OF TOPSHELL TROCHUS NILOTICUS (LINNE, 1767)
 
Do Huu Hoang, Hua Thai Tuyen, Hoang Duc Lu
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Trochus (Trochus niloticus Linne, 1767) is a mollusc species, commonly found  in the coral reef in Indo – Pacific regions. Overexploitation activities for economical purpose resulted in the rapid natural resource degradation of this species. One of effective trends to recover natural resource of Trochus is artificial breeding and releasing larvae as well as juveniles to the nature. Artificial breeding practice of Trochus at Institute of Oceanography in Nha Trang showed that: two methods of induced spawning by temperature shock and UV stimulation result in effective spawning of the Trochus. Juveniles were obtained in three of eleven times of artificial breeding with the average survival rate of 0.42%, in one batch, F1 had been bred successfully with the survival rate of juvenile of 0.77%. The results are the basic for improving the artificial breeding process of the Trochus in Vietnam, and opening up a solution for recoving Trochus resource in Vietnam.
 
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PROCESS OF EMBRYO DEVELOPMENT AND THE LARVAE METAMORPHOSIS OF TOPSHELL-TROCHUS NILOTICUS LINNE, 1767
 
Hoang Duc Lu, Vo Si Tuan, Do Huu Hoang, Hua Thai Tuyen
Institute of Oceanography (Nha Trang)
 
ABSTRACT: The shape of Topshell eggs is spherical with the diameter of 218,33 ± 22,092 µm, covering by a mucus layer thickness of  516,66 ± 36,187 µm. At water temperature of 27.5 - 310C and salinity of 33‰ the segment happened 50 minutes after fertilizing. The segment ended after 8 hours. After about 12 hours 30 minutes the trochophore were hatched and veligers occurred after 36-40 hours. After 48-50 hours the larvae sinked to the bottom of the tanks. After 60 hours the metamorphosis ended.

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SOME BIOLOGICAL CHARACTERISTICS OF RED-LIP CONCH (STROMBUS LUHUANUS LINNAEUS, 1758) IN KHANH HOA SEAWATERS
 
Huynh Minh Sang, Do Huu Hoang
Institute of Oceanography (Nha Trang)
 
ABSTRACT: The study was carried out from February to December in 2005. The studied results showed that catching size ranged from 26 – 72 mm, concentrating in the size group of 42 – 48 mm; Von Betalanffy coefficients were: L∞= 75.6 mm, K = 0.51/year and to = 0 year; Length – weight relationship of male and female was not different, specifically: W♀ = 0,0005 x L♀2,6903 , W♂ = 0,0004 x L♂2,7323. The results on reproductive characteristics showed that spawning season of the conch in Khanh Hoa was from April to September, mostly from April to July; Mean absolute fecundity was 251,080 ± 89,843 eggs/ind.; the highest was 441,000 and the lowest was 166,000 eggs/ind. Mean relative fecundity was 8,353 ± 2,869 eggs/gram of body weight. Male : Female ratio was 27:1. Length at sexual maturity was 41.02 mm. Sand, organic debrit and propotozoe were the highest components in the gut of the conch. The above results are the basic for artificial breeding of this species.

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RESULTS ON EXPERIMENTAL CULTURE OF RED-LIP CONCH
(STROMBUS LUHUANUS LINNAEUS, 1758)
IN NHA TRANG - KHANH HOA - VIETNAM
 
Huynh Minh Sang, Ha Le Thi Loc, Nguyen Thi Kim Bich,
Ho Thi Hoa, Nguyen Thi Thanh Thuy
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Experiment on two size groups (36.10  2.54 (s.d.)  mm and 55.24  3.88 (s.d.) mm) of Red-lip conch fed with bran and seaweed (Sagassum spp.) was performed from April to August in 2005. Survival rate of cultured conches was more than 96% after 105 days of culture. For the conches with small size, growth and survival rate of the conches fed with bran was higher than the conches fed with seaweed. For the conches with large size,  there was no significant difference in growth and survival between the two diet used. The results are basis for broodstock culture and commercial culture of this species.

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SOME RESULTS OF REPRODUCTION OF FRESHWATER SNAILS – CIPANGOPALUDINA LETHOIDES (BENSON, 1857)
IN CHO LACH DISTRICT, BEN TRE PROVINCE
 
Nguyen Van Luc, Huynh Minh Sang
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Based on data of 12 surveys of freshwater snail resource in the riverine bottom at Vinh Binh village, Cho Lach district, Ben Tre province in 2004 – 2005, this paper presents some results on reproductive characteristics of freshwater snail such as: The spawning season, fecundity, size of the smallest individuals in spawning season, spawning way, etc.
 
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GROWTH OF SHORT-NECKED CLAM PAPHIA UNDULATA (BORN, 1778)
IN THE COASTAL WATERS OF BINHTHUAN PROVINCE
 
Hua Thai Tuyen, Vo Si Tuan, Nguyen Thi Kim Bich
Institute of Oceanography (Nha Trang)
 
ABSTRACT: The Short-necked clam Paphia undulata is an important bivalve resource in the coastal waters of Binh Thuan province (South Vietnam). It’s production was around 25,000 – 40,000 tons/year in the period of 2002 – 2004. Total of 3,612 specimens of Short-necked clam were collected from August 2002 to May 2005 for the study on growth of the population. The values of condition coefficient show the best favorable months for clam growth are between August – December (during and after upwelling period). The calculation by the different methods provided the values of infinity height (Hï‚¥), ranking between 48.34 mm – 53.89 mm, and growth coefficient (K), ranking from 0.89 to 1.126.
 
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SPAT COLLECTION AND DEVELOPMENT OF CULTURING THE OYSTER (CRASSOSTREA LUGUBRIS) IN NHA PHU LAGOON, KHANH HOA PROVINCE
 
Cao Van Nguyen, Nguyen Tac An
Institute of Oceanography (Nha Trang)
 
ABSTRACT: The study on spat collection and development of culturing the oyster (Crassostrea lugubris) was carried out at Nha Phu lagoon from 2003 to 2005. Results showed that: the best  times to collect the spat are:
 -The first season was from 25/3 to the end of June.
-The second season was from the beginning of September to the end of October.
Spat collecting flat must be near the stock oyster flat. Spat collection cultch is very diversified, such as bivalve shells, the branch of mangrove vegetation, automobile tire pieces, split bamboo, polyethylene sheet, polyethylene net, cement tupes, stones, rock pieces. The types of spat collection may be in the suspended water or at the hard bottom.
Three different culture models have been developed at Nha Phu lagoon such as: Stake culture, tray culture and bottom culture. The growth and the survival rate of these three culture types  showed that:
- Stake culture: the average growth rate of 9  0.5 mm/month shell length, the weight of 9.6  0.3g/month, the survival rate is 100%.
- Tray culture: the average growth rate of 8.4  0.5 mm/month shell length, the weight of 8.2  0.5g, the survival rate of 97%.
- Bottom culture: the average growth rate of 7.6  0.6mm/month shell length, the weight of 7.4  0.6g/month, the survival rate of 82%.

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THE STATUS OF CULTURING EDIBLE OYSTER - CRASSOSTREA LUGUBRIS
(SOWERBY, 1871) IN LANG CO LAGOON - THUA THIEN HUE
 
Ha Le Thi Loc, Nguyen Thi Kim Bich
Institute of Oceanography (Nha Trang)
 
ABSTRACT: The studied results from 2 survey trips in the rainy and dry seasons from Thua Thien Hue to Binh Thuan in 2001 showed that edible oyster Crassostrea lugubris had been cultured at Lang Co lagoon with many different styles as: cultured on the cement block stakes connecting as trellis, cultured in the small cage hanging on the trellis, wooden stakes, rubber tires and stones. Bottom substrate is mud or muddy sand. Salinity fluctuated from 4-5‰ in the rainy season and 27 - 30‰ in the dry season. The depth of culture area depended on the culturing styles, ranged from 1m to 4m. The seed was collected from the nature. The culture duration should be estimated since the substrata were installed until harvest about 10 months. The culture area at Lang Co lagoon was 129,749m2. Yield of cultured edible oyster in 2001 at Lang Co lagoon was 170,935kg.

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MICROBIAL SEAFOOD SAFETY ASSESSMENT ON OYSTER
(CRASOSSTREA LUGUBRIS) CULTURED IN NHA PHU LAGOON
 
Le Lan Huong, Le Hoai Huong, Vo Hai Thi
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Food safety is becoming social serious problem day by day. Food poisoning has been caused with higher frequency and that request the warning of updating information about food safety. During 14 months of observing and checking the gut and tissue of oyster (Crasosstrea lugubris) cultured in Nha Phu lagoon, it is shown that oyster was always threatened by pathogenic bacteria. Members of Coliform, Vibrio groups and Escherichia coli as well Staphylococcus aureus have frequently presented in oyster body with high density. It is necessary to have reasonable monitoring and checking in order to prevent danger of disease for human community.

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BIOLOGICAL CHARACTERISTICS OF THE REPRODUCTION OF
GREEN MUSSEL Perna viridis (Linnaeus, 1758) IN AREA OF LOBSTER CULTURE IN XUAN TU, VAN NINH, KHANH HOA
 
Bui Quang Nghi
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Collection and analysis of 330 individuals of Green Mussel (Perna viridis) from May 2003 to March 2004 showed that: Sex ratio was 1 male/0.84 female. The size of first maturity was 50 mm in length. The first spawning period was in September, but mainly in November and December.

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DESCRIPTION OF THE ADDITIONAL SPECIES OF ECHINODERMS TO THE INVERTEBRATE FAUNA IN VIETNAMESE WATERS
(CONTINUED)
 
Dao Tan Ho
Institute of Oceanography (Nha Trang)
 
ABSTRACT: This is the second paper described the species of Echinoderm that were the first time found in Vietnamese waters and added for the species composition list of marine Invertebrate in Vietnam (The first one was printed in  “Journal of Marine Science and Technology”, Supplement Issue 4 (5), 2005: 139-149).
This paper  introduces continuously 08 species of Brittle-Stars (class Ophiuroidea) as follows: Ophiothrix (Keystonea) propinqua, Ophiothrix (Ophiothrix) plana, Ophiothrix (Ophiothrix) trilineata, Ophiomusium scalare, Ophiomusium simplex, Ophioconis permixta, Ophiopsammus yoldii and Ophiozonella subtilis.

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MORPHOLOGY AND EXPLOITATION OF SILVERSTRIPED ROUND HERRING-Spratelloides gracilis (TEM. & SCHL., 1846)
IN THE SEAWATERS OF NHA TRANG – KHANH HOA
 
Vo Van Quang, Ho Ba Dinh, Le Thi Thu Thao,
Nguyen Phi Uy Vu, Tran Thi Hong Hoa
Institute of Oceanography (Nha Trang)
 
ABSTRACT: This paper presents the studied results on morphology and exploitation of Silverstriped round herring in Nha Trang seawaters. These results show that this is pelagic small fish, exploited by anchovy seine net all year round with high yield. This paper also presents different characteristics between Silverstriped round herring  and anchovy (genera: Stolephorus and Encrasicholina).
Key words: Silverstriped round herring, morphologic characteristics, yield.

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IMPROVING THE PROCESS OF PRODUCING SEAHORSE FRY
(Hippocampus kuda) IN THE SEAWATERS OF KHANH HOA
 
1.Truong Si Ky, Hoang Duc Lu,
2. Ngo Dang Nghia, Dang Thuy Binh, Bui Van Khanh
1. Institute of Oceanography (Nha Trang)
2. University of Fisheries in Nha Trang

ABSTRACT: Producing seahorse fry was carried out  at Institute of Oceanography in Nha Trang from 7 June  2006 to 6 July 2006. Fry fish, with density of 1 individual  per liter, was reared in the aquarium (150 liters) in recirculation system with biofilter. The water was changed 300% - 500% per day.
The results show that seahorse grows  fast: length of fry fish in the tank No. 1 is largest - L (mm) - 27.50 mm and fry fish in the tank No. 3  has the lowest growth rate (L - 25.70 mm). There is no significant difference in juvenile with growth rate between tanks (P>0.001). Survival rate is high and ranges from 64 – 76%. Discussion of experimental results is  described in detail in the paper.
 
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TRIAL FOR CAGE CULTURE OF BLACK SEAHORSES (Hippocampus kuda) BLEEKER IN NHA TRANG BAY- KHANH HOA
 
Ho Thi Hoa
Institute of Oceanography (Nha Trang)
 
ABSTRACT:  Black seahorses (H. kuda) were cultured in cages at Nha Trang bay from  November 2005 to March 2006. An experiment for survival and growth of seahorse juveniles was carried out with different ages: 45, 60  and 75 days.        
The daily length growth of 75-days seahorses was the lowest (0.61 mm/day), while that of 60-days seahorse was 0.62 mm/day. The highest rate was found in 45-days seahorses with 0.64 mm/day.
Survival rate of seahorses after 2 months was 60.3% for 45-days seahorses, 77.5% for 60-days seahorses and 89,4% for 75 days seahorses.

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EFFECT OF CATHARANTHUS ROSEUS (L.) G. DON EXTRACT DIET ON PLASMA PHOSPHATASE ACTIVITIES AND DISEASE RESISTANCE TO AEROMONAS HYDROPHILA IN ROHU (Labeo rohita Ham.) FINGERLINGS
 
Nguyen Thi Thanh Thuy
Institute of Oceanography (Nha Trang)
 
ABSTRACT: Rohu fingerlings (Labeo rohita Ham.) were fed on plant Catharanthus roseus (L.) G. Don extract diet with varying doses of 10, 20 and 30 ml/100g feed, corresponding to treated groups, namely T1, T2 and T3. After three weeks, blood was collected from all groups for testing of plasma alkaline phosphatase (ALP) and acid phosphatase (ACP). Then, all groups were immunized with 1% formalin-killed Aeromonas hydrophila. After two weeks of immunization, all groups were challenged with live A. hydrophila. The results indicated that plasma ALP activity significantly decreased (P<0.05) in C. roseus extract treated fish. After immunization and infection these enzyme activities considerably fluctuated. There was no significant difference (P>0.05) in disease resistance against A. hydrophila infection between the control and T1 (10 ml/100 g feed) and T2 (20 ml/100 g feed) groups. In contrast, the disease resistance against A. hydrophila infection in T3 (30 ml/100 g feed) group decreased clearly.
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Written By: Administrator Account
Date Posted: 11/12/2007
Number of Views: 12458

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