Journal of Fisheries Science and Technology
Scientific Journal of Nha Trang University
Combined effects of temperature and food on growth, survival rate and oxygen consumption capacity of dog conch (Strombus canarium Linnaeus, 1758) at the veliger larvae stage
This study was carried out to determine the combined effects of different temperature and different microalgae on the growth, survival rate and oxygen consumption capacity of dog conch at the veliger larval stage in Khanh Hoa province from April to October, 2025. The experiments were designed to evaluate the impact of two factors: three levels of temperature (30oC, 32oC, 34oC) and microalgae (Isochrysis galbana, Chaetoceros muelleri, Nannochloropsis oculata) in bocals of 10 liter with five replications and initial larval density of 2 individual/mL. The results showed that there were significant combined effects of temperature with the microalgae on the growth and survival rate of dog conch (p<0.05). The growth rate (average and specific growth rate of 30.7 ± 0.6 mm/day and 5.5 ± 0.1 %/day, respectively) and survival rate (86.1 ± 2.5 %) of dog conch larval was the highest at the treatment of lowest temperature of 30oC combined with microalgae of C. muelleri as food treatment. The oxygen consumption capacity of dog conch larvae had the highest value of 184.2 ± 2.9 (mgO2/g.h) in the high temperature treatment of 34oC combined with C. muelleri as food treatment. It is recommended that the veliger larval stage of S. canarium will be nursed within the temperature of 30°C and C. muelleri as food to maximize larval performance of growth and survival rate. DOI: https://doi.org/10.53818/jfst.01.2026.637
Application of chitosan microencapsulation to enhance astaxanthin stability in a protein-carotenoid preparation
Carotenoids, particularly astaxanthin, found in protein-carotenoid preparations derived from whiteleg shrimp heads are highly susceptible to environmental factors such as light, oxygen, and temperature, leading to a rapid degradation of biological activity and color stability. Therefore, this study aimed to apply chitosan for the microencapsulation of this preparation using the ionic gelation method. The results indicated that a 2.5% chitosan concentration, used as the wall material in a 3% sodium tripolyphosphate (TPP) cross-linking solution, was the most suitable condition for the microencapsulation process. Under these conditions, the obtained microcapsules exhibited a uniform spherical shape, achieving a bead formation yield of 73.7%, an astaxanthin encapsulation efficiency of 77.3%, and a mechanical strength of 98.5% (after 48 hours). The microcapsules significantly enhanced astaxanthin stability compared to the control sample, particularly demonstrating effective protection in an aqueous environment at room temperature when stored in opaque packaging (HDPE). This study suggests a promising approach for adding value to protein-carotenoid preparations derived from shrimp by-products, with potential applications in the food and aquaculture feed industries. DOI: https://doi.org/10.53818/jfst.01.2026.614
Reshaping intensive tilapia sludge management: Integrating treatment technologies, resource recovery, and brackish water adaptations
The intensification of Nile tilapia (Oreochromis niloticus) farming is creating severe pressure from solid waste, threatening the sustainability of aquaculture ecosystems in key regions such as the Mekong Delta. To address this challenge, this paper aims to synthesize and analyze current sludge treatment methods, thereby proposing integrated management strategies based on circular economy principles. Through a critical review of data from relevant studies (2006–2025), the paper clarifies mass flows, technological efficiencies, and associated risks, contributing a comprehensive framework for sludge management adapted to both freshwater and brackish ecological conditions. The results indicate three strategic pillars. First, regarding biosafety, the sludge management regime determines resource quality; current data suggest that short-term periodic sludge removal (e.g., weekly) is an important factor in limiting heavy metal accumulation (Cd, Pb, Cr, Cu). Second, a distinct technological trade-off exists: anaerobic digestion combined with co-digestion is optimal for energy recovery (biogas), whereas aerobic processes are superior for phosphorus and nitrate mineralization in hydroponic systems. Third, for saline-intruded coastal areas, UASB technology shows potential as an alternative to stabilization ponds due to its ability to overcome salinity inhibition. Finally, the paper proposes an integrated management framework that directs the transformation of waste sludge into high-value fertilizer and energy. DOI: https://doi.org/10.53818/jfst.01.2026.636
Assessement of environmental quality in coastal cage aquaculture areas using ecological group-based biological indicators
Marine aquaculture, particularly cage culture, along Vietnam’s coastal areas, has been rapidly developing but is facing significant pressure from pollution originating from industry, tourism, domestic waste, and the farming activities themselves. Benthic fauna are recognized as suitable bioindicators of environmental quality. Globally, numerous biotic indices based on benthic community composition have been developed and successfully applied, such as the BOPA, BENTIX and AMBI, which classifies benthic species into five ecological groups according to their tolerance to organic enrichment and pollution, reflecting environmental conditions ranging from “very good” to “extremely polluted”. Studies conducted in Europe, the Mediterranean, and the Black Sea have demonstrated that the AMBI index is highly effective in assessing the degree of impact from cage culture activities on benthic environments. In Vietnam, however, environmental monitoring programs still rely mainly on physicochemical parameters, while biological indices have been applied only to a limited extent. Biological indicators, particularly AMBI, are promising tools that provide more comprehensive and sensitive assessments of environmental conditions than traditional chemical and physical methods. Therefore, it is essential to integrate biotic indices such as AMBI into regular monitoring programs and to establish a biological observation network for key aquaculture areas. This will enable early detection of pollution, promote sustainable aquaculture management, and protect Vietnam’s coastal marine ecosystems. DOI: https://doi.org/10.53818/jfst.01.2026.609
Overview of the role of zooplankton in aquaculture
Zooplankton are a group of animals that live in the aquatic environment in a floating state, diverse and useful. Zooplankton are not only an important link in most food chains and webs but also contribute to maintaining water clarity, providing dissolved nitrogen (N) and phosphorus (P) nutrients, and supporting stable phytoplankton growth in aquatic environments. Zooplankton are the first live food source for most crustacean, mollusk, and fish larvae because they are prey of various sizes suitable for mouth size, are easy to catch due to slow movement, are easy to digest and absorb because of their thin body shells, and meet the nutritional needs of young animals due to their high nutritional content. In aquaculture, the use of zooplankton as the first feed for larvae has contributed to the successful seed production of many economically valuable fish, crustaceans, and mollusks. Many groups of zooplankton (rotifers, branchiopods, copepods, artemia) are studied for biomass culture or for collecting resting eggs to feed aquatic animal larvae. Zooplankton are also being studied for use as a biological control method to manage the development of phytoplankton, regulate water clarity, and provide natural food for aquaculture species, aiming for environmentally friendly and sustainable aquaculture. Keywords: Zooplankton, aquaculture, live food, role DOI: https://doi.org/10.53818/jfst.01.2026.586
Screening of actinobacteria strains for chitinase from mangrove forests in Khanh Hoa province and investigation of culture conditions for enzyme production
Chitinase, a polysaccharide-hydrolyzing enzyme, serves as a crucial tool for caharacterizing the properties and biological functions of chitin oligosaccharides. Recently, chitinases derived from actinobacteria have received research interest due to their high activity and stability. In this study, 45 actinobacteria strains isolated from mangrove forests in Khanh Hoa Province, Vietnam, were screened for their ability to produce chitinase. The results showed that 41 strains (91.1%) exhibited enzymatic activity, with strain A41 demonstrating the highest chitin-degrading capacity, forming a hydrolysis zone of 21.50 ± 0.55 mm. Molecular identification based on 16S rRNA gene sequencing confirmed that strain A41 belongs to Streptomyces thermocarboxydus, showing 99.93% sequence similarity compared with the 16S rDNA gene database on GenBank. Optimization of culture conditions revealed that chitinase production by strain A41 reached a maximum activity of 3.39 ± 0.01 U/mL after 5 days of incubation in SCB medium supplemented with 1% sucrose and 0.5% malt extract. These findings highlight Streptomyces thermocarboxydus A41 as a promising actinobacterial strain for chitinase production with potential applications in medicine, agriculture, and environmental biotechnology. DOI: https://doi.org/10.53818/jfst.01.2026.611
Study on hydrolyzing yellowfin tuna (Thunnus albacares) fins using bromelain
This study demonstrates that the hydrolysis of yellowfin tuna fins using bromelain enzyme is an effective green technology solution for processing seafood by-products. The solution not only improves protein recovery efficiency but also contributes to addressing the problem of by-products in the tuna processing industry in a sustainable and environmentally friendly manner. Enzymatic treatment at temperature of 55 °C, with an enzyme to substrate ratio of 0.75 wt% for 4 hours, is the suitable hydrolysis condition for efficiently converting tuna fin protein into a nutrient-rich hydrolysate. The resulting hydrolysate is not bitter, has a protein content of approximately 76 g/L, and a calcium content of 774 mg/L. Furthermore, the product contains significant amounts of essential amino acids such as leucine, lysine, threonine, and valine, contributing to the enhancement of the product's biological value. The result demonstrates the broad application potential of tuna fin hydrolysate in the development of nutrient-rich food products, while also opening up avenues for efficient and sustainable exploitation of seafood by-products in the future. DOI: https://doi.org/10.53818/jfst.01.2026.634
Biological characteristics and effects of microalgal diets on growth and reproduction of the copepod Apocyclops royi (Lindberg, 1940)
Apocyclops royi is an important Copepoda species widely utilized as live feed in marine fish larval rearing at commercial hatcheries. This study was conducted with two experiments to elucidate key biological characteristics of A. royi under laboratory conditions. In the first experiment, A. royi was cultured in glass containers (1 L) at an initial density of 50 females per container to monitor development, life cycle, reproduction, and longevity. In the second experiment, A. royi was cultured with three microalgal feeding regimes: Isochrysis galbana, Chaetoceros muelleri, and a mixture of I. galbana + C. muelleri (1:1 ratio) at an initial density of 500 nauplii per container to evaluate culture performance. Each treatment was replicated five times over 33 and 10 days, respectively. Parameters assessed included size at each developmental stage, reproductive lifespan, longevity. Results showed that A. royi developed well under experimental conditions, with nauplii measuring approximately 101 µm initially reaching adult size (485–586 µm in length) after 8 days. Mean lifespan was approximately 32 days. Lifetime fecundity reached 251.7 ± 31.65 eggs per female. Microalgal feeding trials revealed no significant differences in basic biological parameters, including survival rate, eggs per female, nauplii per female, hatching rate, and adult body size among treatments, indicating that A. royi can efficiently utilize the tested microalgae. These findings provide insights into the biological characteristics of A. royi, which are crucial for developing and optimizing mass culture protocols for live feed production in marine fish larval rearing, thereby enhancing hatchery production efficiency. DOI: https://doi.org/10.53818/jfst.01.2026.633
Seasonal changes in hepatosomatic index during reproductive cycle of golden trevally (Gnathanodon speciosus)
Golden trevally (Gnathanodon speciosus) is a marine species of high economic value with strong potential for commercial aquaculture. The relationship between the hepatosomatic index (HSI) and the reproductive cycle was investigated in broodstock with average body weight and total length of 900 ± 200 g and 40 ± 5 cm, respectively. The HSI varied monthly in both females and males. In females, HSI ranged from 1.15 ± 0.25% to 1.69 ± 0.26%, while in males it ranged from 1.06 ± 0.15% to 1.59 ± 0.26%. In females, HSI differed noticeably among ovarian developmental stages, peaking at stage III (vitellogenic stage) 1.7 ± 0.5%. Conversely, in males, HSI showed little variation and no statistically significant differences (P > 0.05) among testicular developmental stages. These results indicate that the liver plays an important role in vitellogenesisin females, whereas HSI is not a useful indicator for estimating testicular developmental stages in males. DOI: https://doi.org/10.53818/jfst.01.2026.632
Current status of technical–financial conditions and the potential application of artificial intelligent of things (AIoT) device in super-intensive whiteleg shrimp farming in Ca Mau province
In recent years, shrimp farming systems have become increasingly intensive and modernized, requiring the adoption of advanced technologies, particularly solutions based on Artificial Intelligence of Things (AIoT). This study interviewed with 50 super-intensive whiteleg shrimp farmers in Ca Mau Province. Descriptive statistics and multivariate regression analysis were employed to evaluate the technical and financial indicators of the farming models. The stocking density was relatively high, reaching up to 201 individuals per m², resulting in a productivity of 32 tons per hectare per crop. This farming model requires a high level of investment and yields correspondingly high profits, with average investment costs and net returns of 887.07 million VND and 509.75 million VND per hectare per crop, respectively. Commonly used AIoT-related devices include automatic feeders, surveillance cameras, and remote control systems. The proportion of farmers using the Internet to support shrimp farming activities was 37.5%. Regression results show that the use of AIoT devices and technologies has a significant effect on shrimp farming profitability. However, fewer than 50% of the surveyed households expressed readiness to adopt AIoT technologies due to high investment costs, concerns about data accuracy, and incompatibility with their current farming scale. Therefore, the proposed solutions focus on awareness-raising, technology demonstration, and financial support to promote AIoT adoption in super-intensive whiteleg shrimp farming. DOI: https://doi.org/10.53818/jfst.01.2026.631
Effects of culture systems on cellular biological characteristics, population growth, and biochemical composition of the marine diatom Chaetoceros muelleri for larviculture of the black tiger shrimp Penaeus monodon Fabricius, 1798
This study evaluated the effects of different culture systems on the biological characteristics, population growth, and biochemical composition of the marine diatom Chaetoceros muelleri, and assessed its effectiveness as a live feed for larvae of the black tiger shrimp Penaeus monodon. The results showed that culture scale did not significantly affect diaton cell size, but was strongly associated with population growth, vertical distribution, and the accumulation of lipids and fatty acids, particularly EPA and ARA. In terms of the overall balance among evaluated parameters, the 20-L carboy culture system showed comparatively higher efficiency. In shrimp larviculture, microalgal feeding rations significantly influenced larval survival and growth, with treatment NT-2.4, corresponding to feeding rations of 300 and 200 ×10³ cells/ind/day during the Zoea and Mysis stages, respectively, producing the best performance from Zoea to PL1, although remaining lower than the control treatment. Overall, the findings confirm the high potential of C. muelleri as an important live feed source for black tiger shrimp hatchery production in Vietnam. DOI: https://doi.org/10.53818/jfst.01.2026.628
Evaluation of the usage of the MAQ22 360-degree scanning sonic on offshore purse sein fleet vessels in Gia Lai province
To evaluate the use of the MAQ22 360-degree horizontal sonar in offshore purse seine fishing in Gia Lai, a survey was conducted on 15 purse seine vessels equipped with the MAQ22. The results showed that vessels using the MAQ22 360-degree horizontal sonar achieved approximately 40.5% higher fishing efficiency compared to vessels without the sonar, and notably, the vessels never incurred losses since installation. However, fishermen still face limitations in operating the equipment, failing to fully utilize its features, thus not achieving the desired results. Therefore, understanding the current state of use, evaluating its effectiveness, and proposing solutions to improve the efficiency of the MAQ22 360-degree sonar is a pressing and timely issue. DOI: https://doi.org/10.53818/jfst.01.2026.627
Evaluation of the hydrolysis efficiency of shortfin scad (Decapterus russelli) using alcalase for the production of soluble protein hydrolysate rich in amino acids
The research has been conducted on the hydrolysis process of Indian scad (Decapterus russelli) protein using Alcalase enzyme under natural pH conditions and a water/material ratio of 1/1. The results show that in order to achieve optimal efficiency, it is necessary to use an enzyme-substrate ratio of 93.48 AU/kg protein, to maintain a temperature of 60ºC for 6 hours. Following this process, the highest hydrolysis degree achieved was 73.01%, with a nitrogen recovery efficiency of 75.30% and a total volatile basic nitrogen of 0.8 g/l in the obtained hydrolysate solution. The final product contains 13.45 g/l of amino acid nitrogen and 0.59 mg/100 g of histamine, demonstrating a significant utilisation for diverse applications across various fields. DOI: https://doi.org/10.53818/jfst.01.2026.626
Effects of black soldier fly (Hermetia illucens) larvae meal as a fish meal replacement on growth, digestive enzymes, metabolic enzymes, and oxidative status of juvenile red drum (Sciaenops ocellatus)
Cá hồng Mỹ (Sciaenops ocellatus) is a marine fish species of high economic value, widely cultured in many countries and increasingly developed in Vietnam due to its rapid growth rate, good flesh quality, and stable market demand. However, feed costs—particularly the heavy reliance on fish meal—remain a major challenge to the sustainability of red drum aquaculture. Black soldier fly (Hermetia illucens) larvae meal (BSFL) has been recognized as a promising alternative protein source, offering high nutritional value while being environmentally friendly. This study evaluated the effects of partially replacing fish meal protein with BSF larvae meal on growth performance, feed utilization efficiency, digestive enzyme activity, metabolic enzymes, and oxidative status of juvenile red drum (Sciaenops ocellatus, 3–5 cm). The experiment was conducted for 56 days with five dietary treatments (AT0, AT2, AT7, AT12, and AT17), corresponding to 0, 2, 7, 12, and 17% replacement of fish meal protein by BSF larvae meal, with three replicate tanks per treatment. The results showed no significant differences in growth parameters (body length, body weight, SGRL, SGR) or survival rate among treatments (p > 0.05), indicating good tolerance of BSF larvae meal by the fish. Feed conversion ratio (FCR) was significantly improved in AT17 (p < 0.05). Digestive amylase activity was not affected by BSF inclusion, whereas protease and lipase activities increased at BSF levels of 2–12% and declined at AT17. Serum metabolic enzymes (ALT, AST, and ALP) remained stable in AT0–AT12 but increased in AT17. In addition, fish fed AT7–AT12 diets exhibited lower malondialdehyde (MDA) levels and higher antioxidant enzyme activities (SOD, CAT, GPx), indicating improved control of oxidative stress. Overall, a BSF larvae meal replacement level of 7–12% is considered appropriate and safe for juvenile red drum. DOI: https://doi.org/10.53818/jfst.01.2026.625
Refrigerated preservation of cobia (Rachycentron canadum) fillets using kombucha-chitosan solution
Cobia (Rachycentron canadum) is an oily fish species that is highly perishable during cold storage. To extend the shelf life of fish fillets without compromising quality, the use of natural preservatives with antioxidant and antimicrobial properties has received considerable attention. Kombucha (Kb), a fermented tea product, and Chitosan (CS), derived from the chitinous shells of shrimp, are both natural substances with demonstrated antioxidant and antimicrobial capabilities.A comparative experiment was conducted to examine the characteristics of CS, Kb, and Kb - CS solutions. The results showed that the Kb - CS solution exhibited superior antioxidant activity and enhanced capability against E. coli and S. aureus compared to the individual Kb or CS solutions.Cobia fillets were subjected to dipping in Kb - CS 1.0%, CS 1.0%, Kb solutions, and a control sample (C), and subsequently stored under refrigeration for 10 days. The results indicated that the fillets coated with Kb - CS 1.0% demonstrated the highest water-holding capacity and elasticity, and the lowest peroxide value (PV) among the tested samples. Furthermore, the total viable count (TVC) was reduced by more than 3.0log(CFU/mL) compared to the control.An investigation was then conducted to assess the effect of varying CS concentrations (CS 0.5%, CS 1.0%, CS 1.5%, CS 2.0%) within the Kb - CS coating solution on fish quality after 0, 3, 6, 9, 12, and 15 days of storage. The parameters measured included the elasticity and water-holding capacity of the fish fillets, the total viable count and Coliforms density, and the sensory evaluation of fish freshness.The findings revealed that cobia fillets dipped in the Kb - CS 1.5% solution maintained muscle elasticity and water-holding capa4444city, while the PV remained virtually unchanged during 12 days of storage. The total viable count increased by only 1.0log(CFU/g) compared to the initial count after 15 days of storage. Quality Index Method (QIM) sensory evaluation also confirmed that the Kb-CS 1.5% -coated fish exhibited the slowest rate of freshness deterioration compared to the other tested samples. DOI: https://doi.org/10.53818/jfst.01.2026.621
Assessment of fishing effort and catch performance in the drift gillnet fishery for mackerel and tuna in Ho Chi Minh city
The study employed interview surveys and fishing logbook records from 30 drift gillnet vessels targeting mackerel and tuna operating in Ho Chi Minh City (formerly Bà Rịa – Vũng Tàu) during the period from July 2023 to June 2024. Based on the collected dataset, descriptive statistical methods were applied to determine key indicators for assessing the fishing performance, thereby supporting sustainable fisheries management. The results showed that the fishing effort (E) of the drift gillnet fleet ranged from 191.8 to 509.7 vessel-days, with an average of 14.8 vessel-days per vessel per month. Catch per unit effort (CPUE) varied between 399.6 and 502.8 kg/10,000 m², averaging 447.9 kg/10,000 m². Both effort and CPUE exhibited clear seasonal variability. The linear regression model between CPUE and fishing effort was determined as CPUE = 1.65E + 208.76 (R² = 0.06), indicating a positive but weak relationship. An incremental increase of 1 vessel-day resulted in only a 1.65 kg/10,000 m² increase in CPUE, suggesting that fishing effort is not the primary driver of catch rates. Instead, CPUE appears more strongly influenced by seasonal dynamics, fishing grounds, tuna school behavior, and operational techniques. Monthly catch estimates ranged from 379.7 to 478.4 tons, peaking between October 2023 and March 2024, highlighting pronounced seasonality. Overall, the findings reveal that the tuna gillnet fishery operates under a seasonal-driven pattern in which fluctuations in resource availability exert stronger effects on fishing performance than variations in effort. DOI: https://doi.org/10.53818/jfst.01.2026.616
Quality of organic composting from organic waste
Composting was used 2 main sources of organic waste: dry leaves and vegetable waste which were collected in Nha Trang university campus. The ratio of vegetable waste to dry leaves in the compost was 1:0.52. Furthermore, the compost included 10kg Song Gianh organic fertilizer and 1kg Trichoderma fungi. It spent 2 months for the mixture of materials to decay in 200L rotary drum composter. This process made the product, which has no smell, was used as organic fertilizer for greenery in Nha Trang campus. Temperature and moisture of the compost were followed every day by the sensor. pH and total organic Cacbon were analyzed in the laboratory. pH of the compost was around 7.90-8.35 which was suitable for growth of organisms. Moisture still remained at 35%. The quality of composting was analyzed based on the Vietnam Circular 09/2019/TT-BNNPTNT. In addition, tests of the quality composting was done on Basella alba L. seeds and Ruellia brittoniana branches. The tests gave good results of plant physiology in which the ratio of composting to soil was 1:1. DOI https://doi.org/10.53818/jfst.04.2020.304
Effect of different feed on growth and survival rate of goonch catfish (Bagarius rutilus) of 70-500g stage in cage culture at the lower Lo River - Phu Tho Province
This study aimed to evaluate the effects of different feed on the growth and survival rate of goonch catfish (Bagarius rutilus) of 70-500g stage in cage culture at the lower Lo River - Phu Tho. The experimental goonch catfish with initial length of 22.0-23.5cm/individual and weight of 70-72.5g/individual were raised in cages placed on the river, each cage with a volume of 9.0m3. The experiment was arranged with 3 treatments on different feed. Treatment 1 (NT1): Using industrial submersible pellet-feed; Treatment 2 (NT2): Using 100% trash fish and treatment 3 (NT3): Using 70% trash fish and 30% fresh worms, each treatment was triplicated. After 5 months of experimental period, the results showed that goonch catfish obtained the highest growth and survival rate in NT3, followe by NT2 and the lowest in NT1 (p <0.05). In NT3, harvested fish had mean weight of 542.7g/individual, 29.7cm/individual in length and 81.9% survival rate, while in NT1 that were 456.4g/individual and 59.7% survival rate. From the experimental results, it can be concluded that combination of trash fish and earthworms or trash fish are suitable feed for goonch catfish culture, whilst industrial feed used in this study is not suitable. DOI https://doi.org/10.53818/jfst.04.2020.303
Effects of the use probiotics to efficiency of cultured white legshrimp (Litopenaeus vannamei Boone, 1931) in ponds on the sand by coastal water
The study has used probiotics in water environment management of intensive whiteleg shrimp ponds with canvas in coastal water at the high-tech aquatic seed production area of Dac Loc Aqua. Co., Ltd. (hamlet 4, Xuan Hai commune, Song Cau town). Two experiments were conducted with different the used mode of probiotic: ponds using daily use of probiotics, 0.5 -1.0 g / m3 of water (equivalent to 2-4 kg / pond 4,800 m3 of water); ponds using probiotics periodically: The first month of farming, 7 days / times, the dose of 2.0 g / m3 of water; 2nd farming month, 5 days / times, dose 3.0 g / m3 of water; 3rd farming month, 3 days / times, dose 5.0 g / m3 of water. Probiotics have contained the main microoganisms strains: Bacteia Nitrosomonas sp., Nitrobacter sp. and the fungi Saccharomyces sp. Analysis of shrimp samples and ponds water showed that, in ponds using probiotics periodically, Vibrio density in shrimp (from 9,0 × 101 to 3,9 × 102CFU/g) and water samples (from 5,0 × 101 to 8,2 × 102CFU/ml) was lower, environmental parameters such as clarity, pH, DO, NH3 and NO2- were stable and is within the permitted level compared to ponds using daily use of probiotics. After 75-80 days, the yield of whiteleg shrimp harvested in ponds using probiotics periodically were 1.3 times higher than in ponds using daily use of probiotics; the feed conversion ratio (FCR) and the havervested whiteleg shrimp size (individual per kilogram) were also respectively lager (FCR=1.29 comparated to FCR=1.41; havervested whiteleg shrimp size = 64.3 inds./kg comparated to 81.5 inds./kg). The number of probiotics used in ponds using probiotics periodically are only 65.6% of the amount of inoculants used in ponds using daily use of probiotics. That has shown that the recurring probiotics use is more effective than daily use. DOI https://doi.org/10.53818/jfst.04.2020.302
Ảnh hưởng của chitosan lên sự sinh trưởng của lan Mokara nuôi cấy mô
Mokara orchid is a tropical species and easy to plant due to its vitality and endurance. The flowers are colorful and long-lasting. Thus, mokara has been intensively planted and propagated by both traditional and tissue culture methods. However, despite the rapid multiplication, the micropropagated mokara shoot and plantlets grow very slowly. In this report, chitosans extracted from shimp shell and squid pen with 3 molecular weight ranges (Mw <10, 30-50 and 80-100 kDa, coded as Mw10, Mw30 and Mw80; respectively) and 3 deacetylation degrees (72-75, 82-85 and 92-95%, coded as D70, D80 and D90; respectively) were added to the tissue culture medium to examine the ability to promote the tissue growth. As the result, chitosan originated from shrimp shell with Mw30 and D80 was more suitable for the purpose of enhancing shoot development. Applying this type of chitosan with the concentration of 20 ppm was the best for shoot multiplication and elongation. Thus, chitosan could be used as an elicitor for mokara in vitro growth. DOI https://doi.org/10.53818/jfst.04.2020.301
Optimization of ultrasound-assisted extraction conditions for phenolics with antioxidant capacity from red alga Gracilaria salicornia
This study aimed to optimize ultrasound-assisted extraction (UAE) conditions of the red seaweed Gracilaria salicornia (G. salicornia) for total phenolic content (TPC) with antioxidant power using response surface methodology (RSM) based on a Box-Behnken design. The effects of various extraction conditions on TPC and antioxidant activities of G. salicornia were investigated including extraction temperature, extraction time and material to solvent ratio with water selected as the extraction solvent. The results indicated that extraction time and material to solvent ratio signifi cantly affected TPC of G. salicornia (p < 0.05). Of these, extraction time had a positive effect on TPC, while material to solvent ratio had a negative effect. Additionally, the optimum ultrasoundassisted extraction conditions were found to be extraction temperature of 60 °C, extraction time of 40 min and material to solvent of 3/100 (g/ml). Under these conditions, the experimental yield of total phenolic compounds and ferric reducing antioxidant power were 93.95 ± 3.05 (mg GAE/100g) and 54.76 ± 0.89 (mg TE/100g), respectively. DOI https://doi.org/10.53818/jfst.04.2020.300
Study on ovarian biology of the golden trevally (Gnathanodon speciosus)
The present study was focused on ovarian biology of the golden trevally. The female broodstock with body weigth and total length were 800±200 g and 40±5 cm, respectively. Fish were kept in seacage and daily fed with trashfish at 3-5% body weight. Ovaries were monthly collected for biological parameters. The results indicated that the GSI increased from June to September. Maturation of female fish increased from May to September. Female golden trevally are multiple spawners. There were different stages of germcell development in the ovary at the same time. The biochemical composition changed based on the stages of ovarian maturation. Protein and lipid contents in mature ovary were found higher than that in immature ovary. Absolute fecundity was 121,174 ± 66.842 eggs/female, while relative fecundity was 107,607 ± 49.916 eggs/kg female. DOI https://doi.org/10.53818/jfst.04.2020.299
Effects of time after hormonal stimulation on biochemical features of seminal plasma in waigieu seaperch Psammoperca waigiensis
The objective of the present study was to assess the effects of time after stimulation with domperidone (DOM), luteinizing hormone releasing hormone analog (LHRHa) and human chorionic gonadotropin (HCG) on biochemical features of seminal plasma in Waigieu seaperch Psammoperca waigiensis over period 72h post injection. Male broodfishes were injected pectoral fin corner with either 0.9% saline solution (control) or a single dose of DOM (20 mg/kg body weight (BW)) or LHRHa (20, 50, or 80 μg/kg BW) or HCG (500, 1000, or 1500 IU/kg BW). Milt samples were collected before hormone induction (0 h) to assess original milt properties condition, and at 24 h, 48 h, and 72 h post injection (p.i.) to examine the effects of hormone treatments on aspects of spermiation. Results showed that the treatment with saline solution or DOM or LHRHa did not significantly alter seminal plasma biochemical properties. DOI https://doi.org/10.53818/jfst.04.2020.298
Study on production of fish cakes oreochromis sp withoutfood additives
Many people like fish cakes. However most fish cakes were added food additives to increase toughness, gel strength, which had negative affectstconsumers. This study aimed to createthe natural gel-strength fish cakes products that safe for consumers. The study has surveyed fish Oreochromis sp production grind mix meat fish, survey time, temperature grind mix meat fish, time kneading affect toughness, gel strength fish cake. The result grind 4 minutes at a temperature 10 ± 1ºC, then kneading mix grind meat fish 6 minutes for best result, gel strength of fish cake 310.84 ± 0.66 (g.cm). DOI https://doi.org/10.53818/jfst.04.2020.297
Effects of dietary chitin supplementation on the resistance of white leg shrimp (Litopenaeid vannamei) to Vibrio parahaemolyticus
Evaluation of the protective of dietary chitin supplementation to Vibrio parahaemolyticus in white leg shrimp Litopenaeus vannamei was performed with 6 treatments. Shrimp (mean weight 1.74 ± 0.22g) were fed diets supplemented with chitin at concentrations of 0%, 0.1%, 1%, 2%, 4% and 8% in triplicate for 2 weeks. Shrimp in all treatments were challenged by adding V. parahaemolyticus at the dose of 104,54cfu/mL directly to the culture tank. The experimental results showed that the cumulative mortality of the white leg shrimp in the treatment fed with 1% and 2% chitin supplement were 25% lower (P = 0.002) than the cumulative mortality of shrimp in the control treatment. There was no difference in cumulative mortality of white shrimp in the remaining treatments compared with control treatment (P>0.05). DOI https://doi.org/10.53818/jfst.04.2020.296
Environmental situation and disease at the on-sand farming shrimp area in Thach Ha, Cam Xuyen and Nghi Xuan, Ha Tinh
The study was conducted to assess the status of some physical, hydrological factors in shrimp ponds and some shrimp diseases on-sand farming area in 3 districts of Thach Ha, Nghi Xuan and Cam Xuyen, Ha Tinh. The results showed that the factors in the water including temperature, salinity and total suspended solids had the appropriate value for raising L. vannamei. Besides, most of the factors in water like DO, pH, some nutritious salts and oxygen consumedwere also within the safe range for farmed shrimp, except for high H2S content fluctuating in the range 0.25-0.43mg/L. For shrimp disease, the study focused on white spot syndrome virus (WSSV), acute hepatopancreatic necrosis disease (AHPND) and bacterial spores, (EHP) and results showed that: EHP occurred most common in white-leg shrimp cultured in Nghi Xuan, Thach Ha and Cam Xuyen in three months studied from August to October, followed by AHPND disease which appeared in September to October. WSSV disease only appeared in September in Nghi Xuan with a low infection rate (5.5%). DOI https://doi.org/10.53818/jfst.04.2020.295
Evaluate the quality of the polycheate from wild and farm sources on maturation white leg shrimp Litopenaeus vannamei (Boone, 1931) broodstock
The study was evaluate the quality of the polycheate from farm and wild source on maturation white leg shrimp broodstock. Results suggest that worms from farmed aquaculture, high nutritional composition and unsaturated fatty acid content used marine shrimp broodstock maturation. The female white leg shrimps fed worms from farmed aquaculture showed absolute fecundity 2% higher (28.34 × 104 compared to 27.79 × 104), actual fecundity higher 2% (16.67 × 104 so với 15.93 × 104), fertization rate higher 1.5% (85.87% so với 84.53%) and hatching rate higher 2% (88.94% so với 87.22%) compared to broodstock fed worms from wild. Metamorphorsis rate form Nauplii to Zoea 1 was higher (p<0.05). Sperm quality of male white leg shrimps showed better as they were fed worms from farmed aquaculture. DOI https://doi.org/10.53818/jfst.04.2020.294
Effects of salinity and food on growth, survival rate of mangrove snail (Nerita balteata Reeve, 1855) at the veliger larvae stage
Mangrove snail N. balteata is a potential aquaculture species with high nutritional and economic value. Although the artificial seeds production of this species have been successful but still having problems as low survival rate in the process by veliger larvae are transformed into spat larvae. Experiments were conducted to determine the effects of salinity and food on growth rate and survival rate of this snail in the stage of veliger larvae in Quang Ninh provice. The results showed that the optimal salinity for growth of veliger larvae was 25 ppt, that resulted in a absoluted growth rate of 8.99 ± 0.4 μm/day and survival rate of 54.11 ± 2.37%. The diet of algae combined with commercial feed was most suitable for the growth of mangrove snail at the veliger larvae stage with absoluted growth rate and the survival rate reached 10.35 ± 0.51 μm/day and 58.50 ± 3.04 %, respectively. These results could contribute technical knowledge of rearing veliger larvae of N. balteata with optimal salinity of 25 ppt and diet of algae combined commercial feed. DOI https://doi.org/10.53818/jfst.04.2020.293
Effects of Ulva reticulata seaweed extract on the growth of water spinach (Ipomoea aquatic)
Seaweeds have been used in many applications including organic fertilizers. The aim of our research was to evaluate the method to extract Ulva reticulata and the effect of those extracts on the growth (germination rate, shoot length, root length) and productivity of water spinach (Ipomoea aquatica). The results showed that the optimal conditions to get extracts were 121ºC/1atm for 20 minutes at pH3 and pH11. There was no difference between seaweed-extract-added treatments and tap-water control in germination rate and root length. On the other hand, the shoot length was highest when the plants were sprayed with 0.5 % of pH11-extracted liquid (34.80 ± 4.69 cm) that was significantly different from other treatments. The highest productivity was achieved in seaweed solutions extracted in pH7 and pH11 (average over 100 g/pot), which were much higher than other controls including tap water (52.3 ± 30.2 g/pot) and commercial liquid seaweed fertilizer controls (65.7 ± 9.7 g/pot). DOI https://doi.org/10.53818/jfst.04.2020.292
Effects of saltwater intrusion and extreme weather on striped catfish (Pangasius hypopthalmus) nursing –growing in Soc Trang
Saltwater intrusion and extreme weather caused many impacts on striped catfish nursing – growing in Soc Trang. Study was carried out by the survey method using the interview tool based on semi-structured questionnaire on 97 subjects that were individual nursing-fattening households, fish farms managers of companies and key-informants in Soc Trang. Most of subjects were aware of the effects of saltwater intrusion and extreme weather to this activity and considered it was rather difficult to overcome saltwater intrusion. In addition, the largest proportion in all groups showed that there were abnormalities – weather and climate extremes occurred to some extent and saltwater intrusion was the most concerned problem. In the future, saltwater intrusion would still be the highest concern for striped catfish farming activity in all groups. However, temperature fluctuations over time, weather abnormality,... would be more concerned by key-informants but would not lead to much worry by the group of direct production. Nursing – growing techniques changing for striped catfish would be considered by 3 groups as the most important adaptation measure to cope with climate change and saline intrusion. DOI https://doi.org/10.53818/jfst.04.2020.291