Journal of Fisheries Science and Technology, Nha Trang University

Assessment of the current status of exploitation and preservation of diamondback squid (Thysanoteuthis rhombus) in Vietnam

2025-06-13T08:52:01+00:00

The research results determined that the total number of vessels unintentionally capture diamondback squid in the three fisheries: stick held falling net, purpleback squid hand line and ocean tuna hand line is 3,697; Basic parameters of fishing gear are as follows: main line length from 120 - 160m, branch line length from 5 - 6m, number of hooks from 1 - 2 hooks/branch, each branch line is equipped with 01 blue or seven-color wireless LED light; fishing grounds often encounter diamondback squid from 10 - 18 degrees North latitude and from 110 - 118 degrees East longitude, especially the area around Hoang Sa and Truong Sa archipelagos; diamondback squid fishing season achieves high productivity from February to July of the solar calendar, in which the time with the highest productivity is from March to May; fishing productivity of stick held falling net, ocean tuna hand line and purpleback squid hand line is 2.5 kg/day/vessel, 2.3 kg/day/vessel and 1.9 kg/day/vessel respectively; revenue from diamondback squid of purpleback squid hand line is about 30.24 million VND/ship/year, ocean tuna hand line is about 15.15 million VND/ship/year and stick held falling net is 12.61 million VND/ship/year; diamondback squid after being brought onto the ship is usually processed by removing the internal organs (for squid >1 kg/ squid) or leaving the squid whole (for squid <1 kg/ squid) then put in a sealed plastic bag or dried and preserved with ice; diamondback squid is consumed domestically and initially exported to China (through unofficial channels) and Korea.

Keywords: Diamondback squid, stick held falling net, purpleback squid handline, tuna handline, fishing, preservation

Effect of nutritional powder and marshmallow on the quality of nut candy supplemented with seaweed

2025-06-19T07:51:58+00:00

The objective of this study is to develop a nutritious nut candy product and to create a new product with high nutritional value and sensory quality. The research was conducted to evaluate the effects of the proportion of nutritional powder and marshmallow on the quality of nut candy supplemented with seaweed. The investigated factors included sensory quality, hardness, cutting force, and reducing sugar content, with varying proportions of nutritional powder (6%, 8%, 10%, 12%, 14%) and marshmallow (10%, 15%, 20%, 25%, 30%). The results indicated statistically significant differences in sensory quality, hardness, cutting force, and reducing sugar content (p<0.05). The optimal proportions were found to be 8% nutritional powder and 25% marshmallow, yielding a product with good sensory quality, moderate hardness, uniform structure, and stable cutting force (40.4N – 41.1N). The product meets nutritional standards and has potential for further commercialisation.

Keywords: hardness, cutting edge, nutrient powder, Marshmallow, seaweed-supplemented candy nuts.

Optimization of protein hydrolysis conditions from whiteleg shrimp heads Litopenaeus vannemei) using alcalase

2025-06-30T02:11:29+00:00

Protein hydrolysates obtained from aquatic animals generally contain high levels of small peptides, amino acids, and bioactive compounds, which have many applications in the food industry. The objective of this study was to optimise the hydrolysis conditions for alcalase (enzyme concentration, temperature, and hydrolysis time) to obtain protein hydrolysate from whiteleg shrimp heads using a Box–Behnken experimental design of response surface methodology (RSM). Two regression equations were established to evaluate the effects of alcalase concentration, temperature, and hydrolysis time on the degree of hydrolysis (DH) and soluble protein (SP) content in the protein hydrolysate. Both regression equations were found to be suitable, with a confidence level greater than 99%. An alcalase concentration of 0.77% (w/w), a temperature of 54.4 °C and a hydrolysis time of 7.1 h were found to be the optimum coditions to achieve the maximum DH of 40.98% and a SP content of 50.67 mg/mL.

Keywords: protein hydrolysates, enzyme alcalase, hydrolysis conditions, optimisation.

Status of shrimp larvae and juvenile resources in several offshore seamounts located in The Southeast Region of Vietnam

2025-06-09T07:43:37+00:00

The study was conducted to assess the status species composition, abudance and distribution of larvae and juveniles of shrimp species in several several offshore seamounts in the Southeast region of Vietnam, providing a scientific basis to support the development of appropriate fishing strategies. Data used for analysis and assessment were collected from two surveys: one during the Northeast monsoon season of 2023 and the other during the Southwest monsoon season of 2024, using 24 fixed sampling stations across three seamounts (S13, S14 and S15). The results showed that 53 taxons were identified belonging to 20 families, including 5 economically significant shrimp families (mantis shrimp, two families of caridean shrimp and two families of penaeid shrimp). In the Northeast monsoon season, these families accounted for a higher proportion (53%) compared to the Southwest moonsoon season (40%). The average density of shrimp larvae and juveniles in the offshore seamount areas of the Southeast region was 546±12 individuals/1000m³ of seawater. Specifically, the density in the Northeast monsoon season reached 659±15 individuals/1000m³, which was much higher than the density at 433±8 individuals/1000m³ during the Southwest monsoon. The highest density of shrimp larvae and juveniles was in the seamount S15 compared to the others (p<0.05). This area is one of the transitional and recruitment zones linking the offshore and coastal areas of the Southeast region of Vietnam.

Keywords: larval-juvenile shrimps, species composition, the Southeast region of Vietnam, seamounts of Vietnam

Molecular and biochemical identification of Phototobacterium damselae isolated from diseased golden pompano in Khánh Hòa

2025-06-06T01:01:15+00:00

Hemorrhagic septicemia and skin ulcers in golden pompano (Trachinotus spp.) are common syndromes that significantly impact aquaculture productivity. This study aimed to isolate and identify bacteria suspected to be the causative agents in cage-cultured pompano exhibiting hemorrhagic septicemia and sporadic mortality in Khanh Hoa. Gram-negative, short rod-shaped bacteria were observed and isolated from the internal organs of diseased fish. A total of six bacterial strains with similar colony morphology were obtained on Nutrient Agar, TCBS, and Hicrome™ Vibrio agar. Biochemical characterization using the API 20E system showed that all isolates had identical profiles of P. damselae subsp. damselae. Species-specific PCR amplification of the ureC gene produced ~448 bp products in all isolates, matching the positive control using DNA from P. damselae. The results confirm that all bacterial isolates from diseased pompano are P. damselae subsp. damselae. These findings provide a basis for further studies on the virulence and pathogenicity of this bacterium in golden pompano in Việt Nam.

Keywords: Photobacterium damselae, golden pompano, pathogenic bacteria, sea-cage farming, Khánh Hoà

Impact of probiotic supplementation on gut microbiota, metabolic pathways, and antibiotic resistance genes in whiteleg shrimp (Litopenaeus vannamei) using shotgun metagenomics

2025-06-13T01:36:52+00:00

This study utilized shotgun metagenomics to evaluate the impact of supplementing a probiotic mixture (Lactobacillus acidophilus and Bacillus subtilis) on the gut microbiota of Pacific white shrimp (Litopenaeus vannamei). The 84-day experiment involved two treatments, a control group and a probiotic-supplemented group. Results revealed significant changes in the shrimp gut microbiota. Regarding species composition, probiotic supplementation notably reduced the abundance of Vibrio – a key pathogen in shrimp aquaculture. Functional metagenomic analysis indicated that probiotics promoted the activity of various beneficial metabolic pathways, including the biosynthesis of fatty acids, lipids, and amino acids, while also enhancing the degradation of aromatic compounds, thereby suggesting improved nutrient utilization and detoxification. Concerning antibiotic resistance genes (ARGs), a diverse array was found, with multidrug, tetracycline, and aminoglycoside resistance genes being predominant. However, statistical analysis showed no significant difference in the overall ARG composition between the two treatments, which could be attributed to insufficient dosage or duration, or the inherent stability and strong horizontal gene transfer potential of these genes in the aquaculture environment. These findings reinforce the role of probiotics in improving shrimp health and provide valuable insights into the ARG reservoir in aquaculture.

Keywords: metabolic pathway, gut microbiota, antibiotic resistance genes, shotgun metagenomics, Pacific whiteleg shrimp

Research on determining the appropriate ratio of fish meat, gelatin and starch for the producing of smoked croaker sausage

2025-06-11T01:39:46+00:00

Ben Tre is a province with a fairly developed fishing industry with a total number of 3,882 registered fishing vessels. According to the survey results of Nguyen Thu Hong - Nha Trang Institute of Oceanography in 2018, the total fish output in Ben Tre was about 92,258 tons, of which the output of croaker was about 1,115 tons [3]. According to the preliminary investigation of the research team from import and export sources, the total output of Ben Tre's fishing is about 270,000 tons/year, of which trash fish is about: 120,000 tons/year and croaker output is about 5,000 tons/year. Despite croaker having white flesh and a high yield, studies on its processed products remain scarce and have not been adequately prioritised.Therefore, Ben Tre province has allowed Associate Professor, Dr. Vu Ngoc Boi to carry out the Ben Tre provincial level project "Research on processing technology of some products from croaker in Ben Tre province" aiming to develop value-added products to boost production, enhance the value added of exploited products, thereby helping fishermen in maintaining their livelihood at sea. From the project budget, we conducted "Research on processing smoked croaker sausage".Within the scope of this article, we publish only the research focused on determining the appropriate ratio of croaker meat, gelatin ratio and starch ratio for producing smoked croaker sausage from croaker raw material exploited in Ben Tre. Our research results showed that the croaker fish exploited in Ben Tre had a high protein content of up to 17.33% and the ratio of fish meat to total weight was up to 50.68%. The analysis results also showed that the raw material of croaker fish exploited in Ben Tre had heavy metal index lower than the level prescribed by the current regulations of the Vietnam Ministry of Health and the fish fully met the standards for use as raw material for food processing. The research results determined that appropriate ratio of pork butt/crockery fish meat/pork butt fat was 25/60/15; The appropriate ratio of gelatin and starch was 2% and 1%, respectively, compared to the raw materials of crockery fish meat, pork butt and pork butt fat. The smoked croaker sausage produced using the researched formula exhibited grade A elasticity, a gel strength of 1326.36g.cm and a total sensory score of 19.04 points.

Keywords: crockery fish meat, elasticity, gel strength, smoked croaker sausage.

Research on steaming duration, temperature and smoking time for the processing of smoked croaker sausage

2025-06-12T03:57:21+00:00

Ben Tre province is known for developed fishing industry. According to the data from import and export sources, the total output of Ben Tre's fishing is about 270,000 tons/year, of which trash fish is about: 120,000 tons/year and croaker output is about 5,000 tons/year. Although croaker has a large output, people and researchers have not paid much attention to researching and processing croaker into refined products.Therefore, "Research on processing technology of some products from croaker in Ben Tre province" was carried out with the goal of processing croaker into added products to expand output, increase the value of exploited products, thereby helping fishermen staying at sea. "Research on processing smoked croaker sausage" was conducted. Following previous articles and within the scope of this article, we only publish the research part to determine some technological factors in the processing of smoked croaker sausage from croaker exploited in Ben Tre: steaming duration, temperature and smoking duration. Our research results have determined some suitable parameters for the production process of smoked croaker sausage: the suitable duration for steaming to create croaker sausage at 80⁰C is 20 minutes; the suitable temperature for smoking to create smoked croaker sausage is 80⁰C and the suitable smoking duration is 1 hour.

Keywords: steaming duration, smoking temperature, smoking duration, smoked croaker sausage.

Effects of feeding frequency on juvenile malabar snapper (Lutjanus malabaricus Bloch & Schneider, 1801)

2025-06-26T02:17:17+00:00

The study aimed to determine the effects of feeding frequency on growth, feed conversion ratio (FCR), protein conversion ratio (PER) and survival rate of juvenile malabar snapper. Malabar snapper (initial weight of 0.18 ± 0.01 g; initial length 1.93 ± 0.10 cm) were reared in 500 liter-cylindrical composite tanks (Ø=0.8 m) at the density of 0.75 fish per liter. The fish were fed to satiation with 4 feeding frequencies, including 2, 3, 5 and 7 times per day (corresponding to F2, F3, F5, F7) using a commercial diet containing 55.0% protein, 9.0% lipid (NRD, INVE, Thailand) for 35 days. Each treatment was run with 4 replication tanks. The results showed that feeding frequency affected growth, FCR, PER and survival rate in juvenile malabar snapper. The fish in treatments F3 and F5 gained higher growth in length and weight than those from treatments F2 and F7, of which the fish in treatment F2 showed the lowest growth rate (P<0.05). There was no significant difference in coefficient of variance of length and weight, condition factor (K), viscerosomatic index (VSI) and hepatosomatic index (HSI) amongs the fish from different feeding frequencies(P>0.05). Meanwhile, FCR of the fish in F7 was higher than those from other treatments (P<0.05). Survival rate (SR) of the fish in F5 was higher than those in the F2 and F7 (P<0.05), while SR of the fish in F3 treatment did not significantly differ from other treatments. The above results indicated that feeding frequency of 3-5 times per day is suitable for growth, survival rate and feed conversion efficiency of juvenile malabar snapper.

Key words: Lutjanus malabaricus, malabar snapper, feeding frequency, growth performance, survival rate.

Effects of DHA content in live food enrichment on growth and survival rate of malabar red snapper (Lutjanus malabaricus Bloch & Schneider, 1801)

2025-06-27T10:03:18+00:00

This study was conducted to evaluate the effects of different DHA enrichment levels (50, 100, 150, 200, and 250 ppm) in live feeds on the growth and survival of red snapper larvae. Newly hatched red snapper larvae were reared in 500-Ler composite tanks at a density of 30 larvae per Ler. The larvae were fed DHA-enriched live feeds (A1 DHA Selco), consisting of small-type luân trùngs (Brachionus plicatilis) from 2 to 17 days after hatching, and from day 14 onward, a combination of luân trùngs and Artemia metanauplii until 28 days of age. The experiment was carried out in triplicate over a 28-day period. The results showed that DHA enrichment levels significantly affected the growth and survival of red snapper larvae (P < 0.05). Within the range of 50-200 mg/L DHA added to live food, a higher enrichment concentration would result in a higher growth rate and survival rate of the larvae. A DHA level of 200 ppm was determined to be optimal for enriching live feeds for red snapper larvae

Key words: Red snapper, DHA enrichment, Growth, Survival rate, Larvae

Effects of initial feed and DHA protein selco enrichment levels in rotifers on the growth and survival rate of giant trevally (Caranx ignobilis, Forsskål 1775) larval

2025-06-25T01:04:31+00:00

This study was conducted to evaluate the effects of different types of initial feed and various levels of DHA supplementation for rotifers (Brachionus plicatilis) on the growth, survival rate of giant trevally (Caranx ignobilis, Forsskål 1775) larvae. The experimental period lasted from the onset of exogenous feeding until the larvae transitioned to Artemia, at which point the experiment ended. In Experiment 1, three-day-old larvae were fed with three different diets: fertilized oyster eggs, rotifers, and a combination of rotifers and fertilized oyster eggs. Experiment 2 was carried out using five different DHA enrichment levels for rotifers and one control treatment: 70 mg/L, 150 mg/L, 225 mg/L, 300 mg/L, and 375 mg/L and 0 mg/L (control treatment), with each treatment replicated three times. The results showed that in Experiment 1, larvae fed with rotifers exhibited greater length growth compared to those fed oyster eggs or the combination of oyster eggs and rotifers. Larvae fed with oyster eggs alone had the lowest survival rate among the treatments. The results of Experiment 2 showed that DHA enrichment supplementation significantly affected the growth rate, survival rate, and biomass of giant trevally larvae (P<0.05), with the 300 mg/L enrichment level identified as optimal. Increasing the supplementation level to 375 mg/L did not improve survival and even led to reduced rearing performance, comparable to the control treatment (0 mg/L). Based on this study, it can be concluded that giant trevally larvae should be fed DHA-enriched rotifers at a level of 300 mg/L during the initial exogenous feeding stage to achieve optimal growth rate, survival, and biomass

Keywords: Giant trevally, rotifer enrichment, fertilized oyster eggs, larvae, live foods.

Optimization study of sciaenidae fish drying by infrared radiation combined with indirect solar drying

2025-08-01T07:31:50+00:00

This paper presents an experimental study aimed at optimizing the drying parameters for Sciaenidae fish using a combined infrared radiation and indirect solar drying (IR–ISD) system. The Taguchi orthogonal array design method combined with response surface methodology (RSM) was employed to investigate the effects of four key factors (drying temperature, air velocity, infrared distance and infrared power) on three output responses (drying time, specific energy consumption and moisture reabsorption ratio). The results indicated that the regression models exhibited a high degree of fit with the experimental data. The optimal drying parameters were determined as follows: drying temperature of 59.5°C, air velocity of 2.11 m/s, infrared distance of 0.26 m, and infrared power of 1980 W. Under these conditions, the corresponding output responses were: drying time of 6,93 hours, specific energy consumption of 9.84 kWh/kg_H2O, and moisture reabsorption ratio of 1.6 g_VLA/g_VLK. The system's thermal operating conditions under the optimal mode were as follows: the average water temperature entering and leaving the calorifer was 40.5°C and 35°C, respectively; the air temperature entering and leaving the calorifer was 31.1°C and 35.1°C, respectively. These findings highlight the potential of the IR–ISD system in enhancing the drying efficiency of fish products while promoting the sustainable utilization of renewable energy sources.

Keywords: Sciaenidae fillet, infrared drying, solar energy, infrared–indirect solar drying, optimization, RSM, Taguchi.

Developing a scale model of Cam Ranh port for training in logistics and seaport engineering

2025-08-08T07:56:24+00:00

This paper presents the process of designing, manufacturing, and operating a scale model that simulates the operation of Cam Ranh port, serving as a training and research tool in the field of logistics and seaport operations. The model was developed to visualize operational processes such as ship dispatching, container loading and unloading, and wharf equipment control, thereby improving the quality of practical teaching. The scale model features an automatic control system that utilizes Arduino microcontrollers, sensors, and electromechanical modules to simulate port operation functions in a realistic environment. The implementation results demonstrate that the model is highly interactive, meets the requirements of technical simulation, has low manufacturing costs, and offers flexible expansion capabilities, making it suitable for application in technical, logistics, and maritime training facilities.

Keywords: scale model, seaport simulation, Cam Ranh port, automatic control, Arduino, port logistics.

Preparation of Chitosan/SiO2/Anthocyanin films for quality indicator of fresh shrimp during storage

2025-08-25T10:00:54+00:00

In this study, a pH-responsive color indicator film of chitosan/nano-SiO₂ contained anthocyanin (ACN). Chitosan and nano-SiO₂ were recovered from shrimp shells and rice husks, respectively; anthocyanin was extracted from dragon fruit shells. Among the obtained samples, the composite film with a CTS/SiO₂/ACN ratio of 10:1.5:8 had the best physical and mechanical properties with an average thickness of 0.22 ± 0.08 mm, tensile strength of 0.59 ± 0.03 MPa and swelling of ~320% after 10 minutes. The obtained film contained a pH-responsive color indicator and was used to monitor the quality changes of fresh shrimp stored for 30 h at room temperature. The results showed that the resulting indicator film had good sensitivity, indicating a promising direction for product application in identifying the quality of fresh shrimp during storage.

Keywords: Chitosan, nano-SiO₂, Anthocyanin, indicative film, fresh shrimp storage

Technical characteristics and economic efficiency of oyster (Crassostrea belcheri) farming in Ben Tre, Bac Lieu and Ca Mau provinces

2025-08-18T01:43:56+00:00

The results of the survey were conducted among oyster farmers in Bac Lieu, Ca Mau and Ben Tre provinces to collect information on farming techniques and economic efficiency of the oyster farming model. Oyster farmers in Ben Tre use cement roofing sheets to collect seeds and raise them on the fixed frame until harvest, while farmers in Bac Lieu-Ca Mau bought wild seeds originally collected from the mangrove forest and raise them on the floating rafts. Oyster culture period in Bac Lieu, Ca Mau and Ben Tre areas was 12.10 ± 0.45 and 17.04 ± 1.26 months, respectively. The survival rate was 83.25 ± 10.55% and 69.6 ± 14.6%, the average yield of one crop was 498.13 ± 74.92 kg/10 m² of floating raft and 358.72 ± 135.98 kg/10 m² of fixed frame. The profit after one crop in Bac Lieu and Ca Mau area was 3.047 ± 1.426 million VND/10 m² and in Ben Tre was 4.274 ± 2.244 million VND/10 m², the corresponding profit ratio was 52.8 ± 27.0% and 138.2 ± 61.0%. Factors such as culture period, survival rate, productivity, total cost, profit and profit margin between models showed significant differences (P < 0.05). The survey results also showed major difficulties arising from farming practices such as lack of investment and technical knowledge… and recommendations to develop oyster farming in the Mekong Delta provinces in a sustainable direction.

Keywords: farming techniques, financial efficiency, Mekong Delta, oysters,

The effect of temporal and environmental conditions on cpue of squid (Loligo sp.) Caught by the stick-held falling net fishery in the Gulf of Tonkin

2025-09-03T09:51:51+00:00

This study investigates the effect of temporal (year, month) and environmental conditions (lunar phase, sea surface temperature) on the catch per unit effort (CPUE) of squid (Loligo sp.) catched by stick-held falling net fisheries in the Gulf of Tonkin. Data were collected from vessel NA91678TS during the period 2018–2023, including fishing time, catch, species and environmental parameters (sea surface temperature) at the fishing areas. A Generalized Additive Model (GAM) was employed to characterize the nonlinear relationships between CPUE and the predictor variables. The results revealed that Moon phase exerted the strongest effect on CPUE, followed by year and month, indicating significant temporal and seasonal patterns in squid catchability. Sea surface temperature did not show statistically significant influence, although a potential nonlinear trend was observed. The s stick-held falling net caught the highest yield in September, October and during periods near the new Moon, reflecting the seasonal nature of the fishery and the strong positive phototactic behavior of squid. The study contributes to the understanding of critical factors affecting the catch rates of valuable species, which helps to determine the optimal fishing process of the stick-held falling net fisheries and facilitate sustainable development in fisheries production and management.

Keywords: CPUE, Moon phase, sea surface temperature, squid (Loligo sp.), the stick-held falling net fishery.

Effects of substrates and food on the growth, settlment and survival rates of winged pearl oyster (Pteria penguin Roding, 1798) at the spat stage

2025-08-12T09:28:26+00:00

To determine the best substrates and the best food for winged pearl oyster (Pteria penguin Roding, 1798) larvae, contributing to the improvement of the rearing process, two experiments were conducted in 100- liter composite tanks. The feeding density of algae was from 15,000 cells/ml to 30,000 cells/ml. Each experiment had four treatments, replicated four times and lengthened in 20 days. Experiment 1 consisted of four mixed algae feed treatments: TA1 (Nannochloropsis oculata and Isochrysis galbana at a ratio of 1:1), TA2 (N. oculata and Chaetoceros gracilis at a ratio of 1:1), TA3 (I. galbana and C. gracilis at a ratio of 1:1), TA4 (N. oculata, I. galbana and C. gracilis at a ratio of 1:1:1). The initial density of pediveliger larvae was 3 larvae/ ml. The result showed that the larval averaged growth, settlement rate and survival rate of TA4 treatment were highest, corresponding to 1210 µm/ individual, 48.7% and 28.7% respectively. Experiment 2 has 4 different types of substrates: VB 1 (Orchid nets), VB 2 (Plastic sheets), VB 3 (Dead corals) and VB 4 (Ropes). Larvae were fed like TA4 twice a day. The result showed that the larval averaged growth, settlement rate and survival rate of VB 1 (Orchid nets) treatment obtained the best performance corresponding to 1128.4 µm/individual, 48.6% and 28.6% , respectively.

Key words: Spat stage, winged pearl oyster, substrates

Current status of equipment on offshore purse seine vessels in the Southeastern Region of Vietnam

2025-09-03T04:21:38+00:00

This study evaluates the current status of offshore purse seine fleets in the Southeastern region through a survey of vessel specifications, machinery, fishing gear, and onboard equipment. Findings indicate that the fleet generally meets size and engine power requirements and is equipped with basic navigation devices such as GPS, fish finders, and lighting systems. However, modernization is still limited: lighting systems are energy-intensive, net haulers and purse line winches are mostly semi-mechanized or manual, fish aggregating devices lack satellite integration, and the use of advanced navigation equipment remains low. These limitations reduce operational efficiency, increase costs, and lower productivity. The results provide a practical database on offshore purse seine fleets, supporting policy formulation and sustainable fisheries development.

Keywords: Purse seine; Offshore fishing; Fishing equipment; Fleet modernization.