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Petrtyl M.,Czech University of Life Sciences | Bohlen J.,Academy of Sciences of the Czech Republic | Kalous L.,Czech University of Life Sciences | The Bui A.,Research Institute For Aquaculture No 1 | Chaloupkova P.,Czech University of Life Sciences
Folia Zoologica | Year: 2011

During the last decades, agriculture activities in the mountainous northern provinces of Vietnam intensified drastically, and today rice fields occupy the complete valleys of local streams and rivers. Upstream of the fields, many dams were built mainly for irrigation purposes; sometimes stopping the flow through the lower courses of the creek completely. Illegal fishing with electro-fishing gears is a common way to improve food supply for local villagers. Larger rivers are impacted by non-selective fishing, gravel mining and pollution. These factors represent threats to the local fish communities, which typically include one or several species of loaches. With usage of electro-fishing gear and hand net we surveyed 16 localities of the river basins of the River Ky Cung and the River Bang Giang. Both rivers belong to the drainage area of the River Pearl in the provinces Lang Son and Cao Bang in Northern Vietnam. We focused on getting maximum number of fish species with special attention to loaches at each locality. Ten species of loaches were found; at least two of them represent undescribed species. The main conclusion is that the ichthyofauna of Northern Vietnam still holds a hidden diversity, but at the same time is under strong anthropogenic pressure, so that parts of the diversity may be lost soon.

Cuong D.B.,Hanoi University of Science and Technology | Dung V.K.,Hanoi University | Hien N.T.T.,Research Institute For Aquaculture No 1 | Thu D.T.,Hanoi University of Science and Technology
Journal of Aquaculture Research and Development | Year: 2013

β-Mannooligosaccharides, produced by partial enzymatic hydrolysis of copra pulp residues using recombinant A. niger β-mannanase, were evaluated for its potential use as a prebiotic feed supplement for L. vannamei culture. Results observed in a 30-day feeding trial showed that dietary supplementation of copra-derived MOS, with doses varying from 4 to 10 g kg-1 of dried feed, increased the number of intestinal Lactobacilli and Bifdobacteria in shrimps fed copra-MOS supplemented diets increased approximately from 150-300%. The number of intestinal presumptive Vibrio, Coliforms, Clostridia and Salmonella reduced to 39.6-54.1%, 56.9-65.9%, 71.8-86.1% and 100-100%, respectively. In addition, copra-MOS supplement in the feed led to an enhancement of the weight gain, specifc growth rate, feed conversion ratio and feed intake of shrimps (P<0.05). After a 7-day challenging test with Vibrio harveyi pathogen (~106 CFU mL-1) by immersion, the cumulative mortality of the shrimps fed with the diet supplemented 10 g kg-1 copra-MOS was 3.5%, that obviously decreased compared to the control shrimps (29.5% mortality). Taking advantage of its intestinal microfora modulation towards increasing probiotic-like bacteria and Vibriosis resistance, this cheap oligosaccharide will be valuable in various aquatic animal farming. © 2013 Cuong DB, et al.

Nguyen H.Q.,Norwegian University of Science and Technology | Reinertsen H.,Norwegian University of Science and Technology | Rustad T.,Norwegian University of Science and Technology | Tran T.M.,Research Institute For Aquaculture No 1 | Kjorsvik E.,Norwegian University of Science and Technology
Aquaculture Research | Year: 2012

Twenty egg batches spawned naturally from 17 different females over two spawning seasons were used to evaluate the egg quality of cobia Rachycentron canadum. A reduction in egg size was observed towards the end of the spawning season for both years. The proportion of floating eggs demonstrated a positive linear relationship with both yolk-sac larval survival (r 2=0.91, P<0.05) and batch larval production (r 2=0.80, P<0.01). Viable egg batches (i.e. fertilization success >50%) were of higher batch fecundity, had larger eggs and a higher proportion of floating eggs than non-viable batches (i.e. 0% fertilization success). Also, biochemical analyses revealed that these viable eggs had significantly higher protein and amino acid contents. A multiple regression model based on the proportion of floating eggs, batch fecundity and fertilization success provided the most accurate predictions of batch larval production (r 2=0.95, P<0.001). Similarly, using the egg content of arginine/glycine and methionine significantly increased the correlation coefficient in the multiple regression model predicting larval deformity (r 2=0.92, P=0.002). This study reveals that accurate determination of egg quality in cobia can be improved using a combination of several variables rather than a single variable. © 2011 Blackwell Publishing Ltd.

Ninh N.H.,Research Institute For Aquaculture No 1 | Thoa N.P.,University of The Sunshine Coast | Knibb W.,University of The Sunshine Coast | Nguyen N.H.,University of The Sunshine Coast
Aquaculture | Year: 2014

The main aim of this paper was to report genetic parameters and selection response from a synthetic population of Nile tilapia selected for improved growth performance in brackish water systems in Vietnam. The synthetic base population was formed in 2007 from the best performing individuals for growth produced from a complete diallel cross involving three strains of Nile tilapia, namely GIFT (Genetically Improved Farmed Tilapia), Taiwan and NOVIT4 (GIFT-derived) strains. Selection was practised for increased harvest weight in brackish water (15-20ppt) over four generations from 2008 to 2011. A total of 12,006 individuals had performance data records. They were offspring of 341 sires and 450 dams (averaging 3000 offspring and 70 sires and 90 dams in each generation). Mixed models fitted to the data included the fixed effects of generation, sex, their two way interaction and a linear covariate of age within sex and generation. The random terms in the model were sire within generation and dam within sire and generation. The estimates of heritability for body traits and survival were moderate to high (0.27 to 0.53). Genetic correlations between harvest weight and body length were high and positive (0.97), whereas those between body traits and survival were low and not significantly different from zero. Genetic gain per generation was measured as estimated breeding values and expressed in actual units (original scale of measurement) and genetic standard deviation unit (σG). The improvement achieved for harvest weight ranged from 1.1 to 1.6 σG after four generations of selection (one year per generation). Selection for increased harvest weight was however accompanied by a non-significant decrease in survival by -0.24%-units or -0.16σG. The large genetic variation in both harvest weight and survival, however, suggests that there is a scope for simultaneous improvement of both traits in this population of Nile tilapia. It is concluded that our selective breeding programme has succeeded in developing a productive strain of Nile tilapia under brackish water systems, but the future work should include survival rate in the recording system, selection index and breeding objective. © 2014 Elsevier B.V.

Nguyen H.Q.,Norwegian University of Science and Technology | Tran T.M.,Research Institute For Aquaculture No 1 | Reinertsen H.,Norwegian University of Science and Technology | Kjorsvik E.,Norwegian University of Science and Technology
Journal of the World Aquaculture Society | Year: 2010

Broodstocks of cobia, Rachycentron canadum, were fed raw fish (RF) or three formulated diets of similar proximate composition but different n-3 highly unsaturated fatty acid (HUFA) levels: 0.94% (D1), 1.31% (D2), or 1.72% (D3) of the dry weight (dw). Egg fatty acid composition was significantly different between dietary groups and reflected that of the diets. The total n-3 HUFA and especially docosahexaenoic acid contents in eggs of groups fed formulated diets were significantly lower than in group fed RF, whereas the egg content of arachidonic acid (ARA) in groups fed Diets D2 and D3 were significantly higher than in groups fed Diets D1 and RF (P <0.05). Although no significant differences in spawning quality were found among dietary groups (P >0.05), a tendency of better spawning performance was observed in the group fed RF (1.86% n-3 HUFA of dw). A tendency of lower fertilization success was associated with groups that had higher egg content of ARA (D2 and D3). Results of this study suggest that cobia broodstock requirements of dietary n-3 HUFA should be higher than 1.86% dw and that high dietary levels of ARA (0.42-0.60% dw) may affect cobia fertilization success negatively. © by the World Aquaculture Society 2010.

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