DIRECT AXES FORMATION OF Kappaphycus alvarezii USING BROWN SEAWEED LIQUID EXTRACTS FROM Ascophyllum nodosum AND Laminaria digitata USING TISSUE CULTURE TECHNIQUES

Antoniette Lorain Dimaano1*, Iris Ann G. Borlongan1, Franck Hennequart2, Alan Critchley3, Anicia Hurtado4

1Institute of Aquaculture, College of Fisheries and Ocean Sciences, University of the Philippines Visayas, 5023 Miagao, Iloilo, Philippines

2Algaia R&D Center 91 rue, Edouard Branly 5000 Laint-Lo France

3Verschuren Centre for Sustainability in Energy and Environment, Cape Breton, Canada 4Integrated Services for the Development of Aquaculture and Fisheries (ISDA) Inc., McArthur Highway Tabuc Suba, Jaro, 5000 Iloilo, Philippines

*Corresponding author: azdimaano@up.edu.ph

Kappaphycus alvarezii is one commercially valuable, cultivated seaweed in Southeast Asia. However, intensive farming of such species through repeated vegetative propagation and monocropping has resulted in low genetic diversity and loss of strain vigor, hence its increased susceptibility to disease and epiphyte infestations. As one solution, biostimulants from various seaweed extracts have been utilized to promote vigorous growth and alleviate abiotic and biotic stress. The present study determined the efficacy of commercial liquid extracts from the brown seaweeds Ascophyllum nodosum (ANE) and Laminaria digitata (LDE) on the direct axes formation and survival of K. alvarezii using tissue culture techniques. Apical sections of K. alvarezii (2–3 mm in length, 1 section:10 mL) were cultured at different concentrations of ANE and LDE (0.01, 0.1, 1.0, 3.0, 5.0 mL 1.8L-1 UV-filtered seawater, n = 3 per treatment), and negative control (UV-filtered seawater), respectively. Sampling and renewal of culture medium were done every 7 days for the entire 45-day culture period. Results showed that between the two seaweed liquid extracts, LDE provided better overall performance to K. alvarezii in tissue culture. The use of 1 mL LDE 1.8 L-1 is recommended in tissue culture of K. alvarezii, given the highest percent direct axes formation (26.9 ± 10.2%, mean ± SEM), and relatively high percent survival (51.7 ± 3.7%) and shoot length (0.7 ± 0.1 mm) after the 45- day culture. However, such interpretation should be taken cautiously as the effects on direct axes formation, survival, and length were different. Further experiments for K. alvarezii are necessary in order to confirm the optimum concentration of ANE or LDE that can be applied as tissue culture medium for the seaweed.

Keywords: Kappaphycus alvarezii, Eucheuma denticulatum, Ascophyllum nodosum, Laminaria digitata, micropropagation, biostimulant

EFFECT OF PHOTOPERIOD ON GROWTH, SURVIVAL, FCR AND RESISTANCE TO STRESSES OF JUVENILE GIANT TREVALLY (Caranx ignobilis)

Dang Thi Bich Tram¹ , Hoang Thi Thanh¹ , Ngo Van Manh¹*

Institute of Aquaculture, Nha Trang University, No 2 Nguyen Dinh Chieu Street, Nha Trang City, Viet Nam

*Corresponding author: manhnv@ntu.edu.vn

The experiment was conducted to investigate the effects of photoperiod (12L:12D; 18L:6D; 24L:0D and natural daylight - Control) on growth, survival, feed conversion ratio (FCR) and resistance to temperature and salinity changes of juvenile giant trevally (Caranx ignobilis). Juvenile (mean length 26.0 ± 1.33 mm and weight 0.26 g/fish) were randomly distributed into 12 fiberglass tanks (70 L/tank) in triplicates with 140 fish per tank. Fish was fed a commercial diet (NRD 5/8, G8, INVE, Thailand) until apparent satiation four times daily for four weeks. Results showed that growth rate of giant trevally were significantly higher in control and 12L:12D treatments than other groups. Fish cultured at 12L:12D; 18L:6D and 24L:0D photoperiods had significantly higher survival rate than those in control group, while FCR was lower in 12L:12D and 18L:6D groups than those in 24L:0D and control treatments. The photoperiods did not affect the mortality of juveniles after challenge test against temperature and salinity changes. Thus, the photoperiod (12L:12D) can be performed to improve growth performance and FCR of giant trevally during juvenile rearing.

Key words: Caranx ignobilis, photoperiod, giant trevally, growth, survival, FCR

EFFECTS OF ARTEMIA AND TILAPIA DENSITY ON THE ABILITY TO TREAT ORGANIC MATTER IN WASTEWATER FROM WHITE LEG SHRIMPS     (Litopenaeus vannamei) FARMING

Hong T B Truong^1* vs Huy Đ Nguyen¹

¹Cam Ranh Centre for Tropical Marine Research and Aquaculture, Institute of Aquaculture, Nha Trang University, No 2 Nguyen Dinh Chieu Street, Nha Trang City, Viet Nam

^* Corresponding author: hongttb@ntu.edu.vn

White leg shrimp (Litopenaeus vannamei) farming effluent contains pollutants that include high levels of total suspended solid (TSS), chemical oxygen demand (COD) and growth promoting substances. This study investigated on ability of Artemia and Tilapia (Oreochrois niloticus) to treat organic matter in wastewater shrimp farming. The analytical results of input factors showed that total suspended solid (TSS) in bottom of wastewater from shrimp farming was higher than those of values given in QCVN 11: 2008/BTNMT 1.4 times. Both Artemia and Tilapia had the ability to rapidly reduce organic matter content in wastewater of shrimp farming. After the experiment, the biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), total suspended solid (TSS) met effluent standards in 44/2010/TT-BNNPTNT and QCVN 11: 2008/BTNMT in all of the investigated plots. In surface of wastewater from shrimp farming, TSS, BOD₅, COD and total Coliforms were lowest 6.2 ± 1.1 mg.l^-1, 3.9 ± 0.5 mg.l^-1, 8.6 ± 1.4 mg.l^-1, 1.7.10² (MPN/100ml) in the treatment of 300 Artemia individuals.l^-1 , respectively. In bottom of wastewater from shrimp farming, TSS, BOD₅, COD and total Coliforms were lowest 21.4 ± 5.1 mg.l^-1, 8.5 ± 1.5 mg.l^-1, 11.6 ± 3.6 mg.l^-1, 28 (MPN/100ml) in the treatment of 16 Tilapia individuals.m^-3, respectively.

Keywords: Artemia, Shrimp farming, Suspended solid, Tilapia, Wastewater.

EFFECTS OF DIFFERENT LIGHT INTENSITIES ON THE GROWTH AND SURVIVAL RATE OF BLACK APPLE SNAIL (Pila polita)

Tran Van Kha¹, Tran Nguyen Duy Khoa¹ & Ngo Thi Thu Thao¹

¹ College of Aquculture & Fisheries, Cantho University, Campus II, 3/2 street, Cantho City, Vietnam

Corresponding author: thuthao@ctu.edu.vn 

This study was conducted to evaluate the effects of light intensities on growth and survival rate of black apple snail, Pila polita. The experiment includes 6 treatments and 3 replicates in each treatment as follow: 1) Normal light condition (without net cover, NL); 2) 1 white cylindrical LED bulb (1D); 3) 2 white cylindrical LED bulb (2D); 4) 3 white cylindrical LED bulb (3D); 5) 4 white cylindrical LED bulb (4D) and 6) Shade (OD). The light used in the experiment has an intensity 50W. The newly hatched snails with initial weight and shell height of (0.07 g and 6.38 mm). The plastic container tank volume was 60 L (size 45×43×51 cm, water column of 35 cm), distance from light bulb to water level 30 cm and with the density of 100 ind./plastic container. Different light intensities are arranged to illuminate with 12/24 time (12 h ligh: 12 h dark), all lights are turned on at 6am and turned off at 18pm daily. After 35 days of nursing, snails in 2D yielded significantly higher specific growth rates in length (2.35±0.05%/day) and weight (6.44±0.76%/day) compared to normal light condition, 1D and shade condition. Survival rate was highest in 2D (72.33±7.23%) and lowest in normal light condition (22.7±1.15%) and it was significant difference among treatments (p<0.05). The results of this study showed that the growth rate and survival rate were highest when reared juvenile black apple snails with 2 LED bulbs.

Keywords: Black apple snail, Growth, Light intensity, Pila polita, Survival

EFFECTS OF SUBSTRATE ON THE GROWTH AND SURVIVAL RATE OF MUD CLAM (GELOINA COAXANS)

Nha Le Quang ^1*, Thao Ngo Thi Thu ² and Kien Ly Thi Hoang ³

¹ College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Viet Nam

²Ph.D Program in Aquaculture Course 2017-2021, College of Aquaculture and Fisheries, Can Tho University

³ Master Program in Aquaculture Course 26, College of Aquaculture and Fisheries, Can Tho University

^* Corresponding author: thuthao@ctu.edu.vn

This study evaluated the effects of substrates on growth and survival rate of mud clam (Geloina coaxans) in the tank. The experiment consisted of four treatments and each treatment was repeated 3 times with substrates as follow: 1) 100% mud (B); 2) Combines 50% of mud and 50% sand (BC); 3) 100% sand (C); 4) Without substrates (KD). Clams with initial shell length (32,67±1,40 mm) and weight (8,31±0,93 g), were arranged with a density of 20 clam tank (size 40 ×60 sm, 100L volume, with up-welling aeration). Mud clam were fed daily with algae (Chlorella sp. and Chaetoceros sp. with 1:1 ratio). After 90 days of culture, the survival rate of treatment KD was highest (98,33%), the lowest was in treatment BC (88,33%), however, there was not significant different among treatments (p>0.05). Clams in the mud substrate (treatment B) obtainedthe highest growth, weight and length at SGR_L = 0,026±0,003 (%/day), SGR_W = 0,086±0,009 (%/day).

Keywords: Geloina coaxans, growth, mud clam, survival rate, substrate.

EFFICACY OF HETEROTROPHIC NITRIFYING BACTERIUM TO REDUCE TOTAL AMMONIA NITROGEN IN RECIRCULATING AQUACULTURE SYSTEMS OF TILAPIA (OREOCHROMIS SP.)

Aveananta Bayuesaruka¹, Evy Sholehah Afnur¹, Indah Istiqomah¹*, Bambang Triyatmo^1, Alim Isnansetyo¹, Rustadi¹

¹Faculty of Agriculture, Gadjah Mada University, Sleman, D.I. Yogyakarta, Indonesia

^*Corresponding author: indah_ist@ugm.ac.id

Recirculating aquaculture systems (RAS) rely on a nitrification process to convert ammonia to nitrate. The biofilter in the RAS system is the major part of ammonia waste decomposition. Inoculation of nitrifying bacteria can speed up biofilter tasks.The purpose of this study was to test the heterotophic nitrifying bacterium Klebsiella sp. A2 in support biofilter of recirculation aquaculture system of  tilapia to reduce ammonia concentration in the water. Nine aquariums were set up with a recirculation system with fish density 120 fish/m³. Bioballs was used as biofilter matrix in a volume of 0.2 m³. Fish were reared in the RAS system for 2 weeks, then tested with three treatments, namely the application of nitrifying bacterium at 10⁶ cells/ml media, ¹⁰⁵ cells/ml media, and without nitrifying bacteria (control). Water quality was observed on the 3rd day after nitrifying bacteria inoculation. Fish survival and growth were observed at two weeks post-inoculation. The results showed that the water temperature, dissolved oxygen content and pH were not significantly different between treatments. The application of the nitrifying bacteria Klebsiella sp. A2 has an effect on reducing the ammonia content in the tilapia (Oreochromis sp.)rearing medium. There was no difference in the effect of nitrifying bacteria dose on the anomia reduction in tilapia cultivation media and fish growth.

Keywords: oral, probiotics, water, catfish, mibrobiome

EXTRACTS FROM BROWN SEAWEED Sargassum:  ITS EFFECT IN PROMOTING GROWTH OF Kappaphycus striatus (SOLIERIACEAE, RHODOPHYTA) IN MICROPROPAGATION

Robert Christian F. Patani^1,*, Iris Ann G. Borlongan¹, Vince Matthew S. Bolido¹, Reymark C. Busalla¹

¹Institute of Aquaculture, College of Fisheries and Ocean Sciences, University of the Philippines Visayas, Miag-ao 5023, Iloilo, Philippines

*Corresponding author: rfpatani@up.edu.ph

The micropropagation of Kappaphycus spp. using organic culture media such as brown seaweed extracts are continually investigated to respond to the scarcity of healthy seaweed propagules for farming. Commercial extracts of temperate brown seaweeds as organic culture media have shown promising results, yet their utilization in the Philippines would entail cost primarily because of importation. Conversely, there are also tropical brown seaweeds such as Sargassum used as liquid fertilizer for land crops. However, their utilization in the micropropagation of Kappaphycus is yet to be explored. The present study developed extracts from Sargassum spp. using two different extraction techniques: hot extraction (HE) and alkaline-treated extraction (ATE), and investigated their potential as biostimulants on the micropropagation of K. striatus. The study was divided into two parts: (1) the development and characterization of HE and ATE extracts, and (2) the determination of the effects of these extracts on the direct shoot formation and survival of K. striatus. The second part involved a 45-day culture of K. striatus sections (2–3 mm long) in Sargassum extract-seawater solution at different concentrations [0.01, 0.1, 1.0, 2.0, and 3.0 mL L^-1]. ATE revealed a higher content of macro- and micronutrients than HE. Kappaphycus striatus responded differently (p < 0.05) at varying concentrations of ATE and HE, where lower concentrations (0.01–0.1 mL L^-1) of ATE resulted in the highest percentage of direct shoot formation (12.5–27.1%), longest length (0.6–0.7 mm) at the end of the 45-day culture period, and yet the lowest percent survival (76.3–77.5%). While further investigations are necessary to confirm the optimal concentrations of ATE applicable for mass production of seaweed propagules, the present study provided encouraging results in the efficacy of Sargassum extracts as an organic medium in the micropropagation of a highly-valuable seaweed species in the country.

Keywords: Kappaphycus striatus, Sargassum extract, micropropagation, alkaline-treated extraction (ATE), hot extraction (HE)

Harvesting of Marine Crabs (Scylla paramamosain) in Earthen Pond Culture Systems

Saweit Chaimongkol^1*, Sarinya Makkaew, Supat Khongpuang¹

¹Department of Agricultural and Fishery Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus 181 Charoenpradit Rd., Muang, Pattani Thailand

^*Corresponding author: saweit.c@psu.ac.th

Study on harvesting of marine crabs (Scylla paramamosain) in pond culture was done at the culture site of the Faculty of Science and Technology Prince of Songkla University Pattani Campus. To obtain the suitable harvesting strategy, 3 main trapping schemes including 1) different fishing gears (rectangular and rounded collapsible traps), 2) different baits (fresh fish and squid) and 3) different times of day (4 am., 10 am, 4 pm. and 10 pm.), were conducted. Some water parameters were included. Study results found that average catch of rectangular collapsible trap (0.58±0.56) is not significant different from the other (0.36±0.53). Average catch from using fresh fish bait (0.24±0.428) is similar to the other (0.18±0.443). The significantly highest yields (p<0.05) were found at 10 am (0.38±0.56 piece/trap) and 4 pm (0.41±0.56 piece/trap), follow by the yield of 10 pm (0.26±0.48) and 4 am (0.07±0.26). Water parameters during a study period comprising salinity, water temperature, alkalinity and DO were considered suitable for crab culture. In summary, both types of collapsible traps are suitable fishing gears for harvesting crab by using fresh fish bait. Trapping should be done at 10 am. and 4 pm.   

Keywords:  Marine crab, Collapsible traps, Bait type, Marine crab culture

ISOLATION, IDENTIFICATION, AND POTENTIAL PROBIOTIC CHARACTERIZATION OF LACTIC ACID BACTERIA ISOLATED FROM INTESTINAL TRACTS OF MARINE FISH

Rohaya Salah, Supinya Thapthong, Pochanart Kanjan*

Department of Agricultural and Fishery Science, Faculty of Science and Technology, Prince of Songkla University, Pattani 94000, Thailand

^*Corresponding author: pochanart.k@psu.ac.th  

This study involved isolation of lactic acid bacteria (LAB) from intestinal tracts of marine fish and characterization of their physiological and probiotic properties based  on antibacterial activity against pathogenic bacteria, salt tolerance, and antibiotic susceptibility. A total of 38 presumptive LAB colonies that appeared as Gram-positive and catalase- negative were collected. Only 5 isolates designated LAB 1, LAB 3, LAB 11, LAB 29 and LAB 37 exhibited an excellent inhibitory zone diameter against aquatic pathogenic bacteria when evaluated by agar spot test. Lactic acid bacterial isolates with antibacterial activity showed strong salt tolerance which survival rates more than 90% and presented no significant concerns with regards to antibiotic resistance. Among these, isolate LAB 29 showing the highest antibacterial activity against all pathogenic bacteria was identified as Lactobacillus plantarum based on 16S rRNA sequence analysis. This research suggests that selected LAB could be used as a food/feed supplement to reduce pathogenic bacteria in food or aquatic animal.

Keywords: Lactic acid bacteria; marine fish; pathogenic bacteria; probiotic

SALINITY STRESS TOLERANCE OF Eucheuma denticulatum FROM TISSUE CULTURE USING ACADIAN MARINE PLANT EXTRACT POWDER (AMPEP)

Hazel Coleen Gaya^1*, Iris Ann Borlongan¹

¹Institute of Aquaculture, College of Fisheries and Ocean Sciences, University of the Philippines Visayas, 5023 Miagao, Iloilo, Philippines

*Corresponding author: hggaya@up.edu.ph  

Climate change negatively affects the ocean and everything in it including the economically important carrageenophytes, causing salinity fluctuations that have adverse effects on seaweed farming. Seaweed production in the Philippines continues to decline, mainly due to loss of strain vigor and increased incidences of pests and diseases brought about by repeated vegetative propagation from a limited genetic stock. The use of Acadian Marine Plant Extract Powder (AMPEP) in in vitro tissue culture of seaweeds has been revealed as an effective biostimulant for mass production of seedlings, further providing levels of protection against biotic and abiotic stresses. The present study aimed to determine the response of Eucheuma denticulatum produced from tissue culture using AMPEP to salinity variations. Micropropagules of E. denticulatum (90-day post-tissue culture) were further cultured for 45 days in UV-filtered natural seawater at different salinities (15, 20, 25, 30, 35, 40, and 45 PSU), with renewal of respective seawater treatments every 7 days. Percent survival of E. denticulatum micropropagules at 20–45 PSU showed no significant difference with relatively high values (96.25 ± 2.39% at 20 PSU to 100 ± 0.00% at 45 PSU, mean ± SEM). Micropropagules at 15 PSU showed signs of thallus whitening as early as Day 28, and eventually disintegrated. Specific growth rates of E. denticulatum at 20 (1.37 ± 0.07% day^-1) and 25 PSU (1.52 ± 0.09% day^-1) were comparable to those exposed to natural seawater salinities (1.58 ± 0.04% day^-1 at 30 PSU and  1.38 ± 0.05% day^-1 at 35 PSU); whereas values significantly decreased at hypersaline conditions (1.12 ± 0.11% day^-1 at 40 PSU and  0.52 ± 0.07% day^-1 at 45 PSU). High chlorophyll-a content was observed on micropropagules in hypersaline conditions (0.007–0.011 mg mL^-1). These results suggest that while E. denticulatum from tissue culture using AMPEP had a wide range of salinity tolerance from 20 to 45 PSU, its growth was reduced with increased chlorophyll-a content in hypersaline conditions.

Keywords: Salinity tolerance, Eucheuma denticulatum, tissue culture, AMPEP, biostimulant

SEED PRODUCTION AND GROWTH-OUT CULTURE OF GOLDEN TREVALLY (Gnathanodon speciosus) IN KHANH HOA PROVINCE, VIET NAM

Ngo Van Manh*, Hoang Thi Thanh, Pham Duc Hung, Le Minh Hoang

Institute of Aquaculture, Nha Trang University, No 2 Nguyen Dinh Chieu Street, Nha Trang City, Viet Nam

*Corresponding author: manhnv@ntu.edu.vn

This study was conducted to develop protocols for seed production and grow-out culture of golden trevally, an important commercially marine finfish species for mariculture in Vietnam for three consecutive years since 2020. Broodstock (weight 1.4 – 3.5 kg) were cultured in floating-cage located in Nha Phu lagoon, Khanh Hoa, Vietnam and fed fresh trash fish, squid and shrimp once daily. Matured broodstock were induced spawning with single dose of LHRH-A (40 µg/kg) + HCG (1000 IU/kg) female in the early morning. Fish started spawning 32 – 35 hours after hormone injection. Mean spawned eggs, fertilization and hatching rate were 123,000 – 358,000 eggs/kg female, 57 – 92% and 83 - 96%, respectively. Larvae were reared in cement tanks with standard protocols for marine finfish hatchery. Survival rate from hatching larvae to fingerling (4 - 6cm) was 4.2 – 27.8%. Growth-out culture, fingerlings (mean weight 1.7 g) were cultured at sea cage at stocking density of 80 - 90 fish/m³ and reduced to 12 – 15 fish/m³ at harvesting. Fish was fed commercial pellets (44-46% protein) to apparent satiation at 2 - 3 times daily. After 15 months, the survival rate, harvested weight, productivity and feed conversion ratio were 76%, 670g, 7.4 kg/m³ and 3.17, respectively. 

Key words: Gnathanodon speciosus, golden trevally, seed production, grow-out, cage culture

THE EFFECT OF PHOTOPERIOUS ON GROWTH, SURVIVAL AND COEFFI-CIENT VARIATION OF EELS (MONOPTERUS ALBUS) LARVAE

Huynh Minh Hieu ¹, Pham Thi Anh ¹

¹Nha Trang University, No 02 Nguyen Dinh Chieu, Nha Trang city, Khanh Hoa province, Viet Nam

Corresponding author: hieu.hm.61ntts@ntu.edu.vn 

Studying the effect of the lighting cycle on growth, survival, and coefficient variation of field eels (Monopterus albus) was carried out with 4 photoperiods: (12L:12D; 8L:20D; 4L:20D and 0L:24D-light: dark cycle). The initial average weight and length of eels in the experiment were 5.9 gram and 17.0 cm, respectively.Field eels were fed twice daily. Each treatment was run triplicates at stocking density of 50 eels/tank. The experiment was carried out for 8 weeks. As a result, light cycle clearly affected on the growth, survival and coefficient variation (P<0.05). The highest growth rate was obtained at 8L:12D treatment with the final weight and length of 21.61± 0.11 g, and 25.44± 0.51 cm, respectively. The survival rate of each group was over 90% and the coefficient variation was the best in 8L:20D treatment (0,45 ± 0.02).

Keywords: Photoperiods, Field eels, Growth performance, Survival rate, Coefficient variation

UPTAKE OF NITROGEN AND PHOSPHORUS IN SOME Green and RED seaweed Under laboratory condition

Rapeeporn Ruangchuay*^1,2, Nontawit Anurit¹, Nuttapong Bovornruangroj¹

¹Department of Agricultural and Fishery Science, Faculty of Science and Technology, Prince of Songkla University, Pattani 94000, Thailand.

² Discipline of Excellence (DoE) in Sustainable Aquaculture, Prince of Songkla University, Songkhla 90110 Thailand

^*Corresponding author: rapeeporn.r@psu.ac.th

The study of the nitrogen and phosphorus uptake in algae for water treatment was done to fulfill data for benefiting in marine aquaculture. The experiment was performed in 12-L of glass container: 20 cm in diameter and 35 cm high with filled of 30 ppt seawater enriched with nutrients. Three species of green algae namely, Chaetomorpha crassa, Ulva rigida and Caulerpa sertularioides and one the red alga, Gracilaria fisheri were used with initial density of 5 g·L^-1. The experiment was set under 45 µmol·photon·m^-2·s^-1 of fluorescent light for 10 days of culture period. The nutrient absorption was checked every 2 days and the algae were weighed in final day. The results found that C. crassa. was the best to absorb ammonia-nitrogen, nitrate-nitrogen, nitrite-nitrogen and phosphate-phophorous. The efficiency adsorptions of C. crassa to those nutrients were 100.0, 98.5, 100.0 and 27.0 %, respectively at day 2. The growth of C. crassa showed the lowest among of the green algae and provided the specific growth rate of 17.4±5.4 %·day^-1. For the study for the optimum density of C. crassa to nutrient adsorption at three levels: 1, 5 and 10 g L^-1 in the same conditions. The results found that on the seaweed density of 10 g·L^-1 show the best. Therefore, the green seaweed, Chaetomorpha crassa was the suitable to apply for nutrient absorption efficacy.

Keywords: Chaetomorpha crassa, water treatment, nutrient uptake, nutrient absorption

UTILIZATION OF MICROALGAE, Chlorella sp. UMT LF2 FOR BIOREMEDIATION OF Litopenaeus vannamei CULTURE SYSTEM AND HARVESTING USING BIO-FLOCCULANT, Aspergillus niger

Nurfarahana Mohd Nasir^a,b, Ahmad Jusoh^b, Nor Azman Kasan^*c, Amyra Suryatie Kamaruzzan^c, Wan Azlina Wan Abdul Karim Ghani*^a, Setyo Budi Kurniawan^d, Fathurrahman Lananan^e

^a Sustainable Process Engineering Research Centre (SPERC), Department of Chemical and Environmental Engineering, Universiti Putra Malaysia, Serdang, Selangor 43400, Malaysia

^b Faculty of Ocean Engineering Technology and Informatics, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia

^c Higher Institution Centre of Excellence (HiCoE), Institute of Tropical Aquaculture and Fisheries (AKUATROP), Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia

^d Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

^e East Coast Environmental Research Institute, Universiti Sultan Zainal Abidin, Gong Badak Campus, 21030 Kuala Nerus, Terengganu

*Corresponding author: norazman@umt.edu.my, wanazlina@upm.edu.my

Microalgae are well known as autotrophic microorganisms in aquaculture wastewater treatment, however their role in the aquaculture system is rarely explored. The purpose of this study is to evaluate the influence of adding microalgae, Chlorella sp. UMT LF2, on the functionality for bioremediation and growth performance of whiteleg shrimp, Litopenaeus vannamei in the nursery phase reared in a control culture system. Secondly, the response surface methodology (RSM) was used to investigate further on the optimal condition for the harvesting process of excess microalgae biomass using bio-flocculant from the filamentous fungus, Aspergillus niger. The experimental set-up with Chlorella sp. additions were compared to the control group without the microalgae addition based on the water quality, microalgae biomass and shrimp growth performance. Water samples were collected and underwent in-situ and ex-situ involving nine physicochemical parameters. The results showed that introducing microalgae with zero water exchange as treatment tanks reduced the NH₃, NO₂^- and PO₄^3- during the intermediate until the two days before the 30-day culture period’s end. Microalgae also enhanced shrimp survival and growth performance significantly 89% as compared to the control, 68%. Furthermore, the culture with the addition of microalgae were maintained pH stability and enhanced dissolved oxygen during daytime in the culture water. Therefore, this finding confirmed that Chlorella sp. UMT LF2 addition is promising in improving rearing environment and nursery performance for L. vannamei in culture system. However, further research is required to demonstrate the harvesting by-product from the culture system and the potential applications.

Keywords: Microalgae; Aquaculture System; Nutrient Removal; Bioremediation; Bio-harvesting, Response Surface Methodology

Phung Bay*, Nguyen Van Minh, Ngo Anh Tuan, Tran Thi Hien

EFFECT OF STOCKING DENSITIES ON GROWTH AND SURVIVAL RATE OF GIANT CLAM LARVAE (Tridacna squamosa Lamarck, 1819)

Phung Bay¹, Nguyen Van Minh²*, Ngo Anh Tuan², Tran Thi Hien¹

¹ Research Institute for Aquaculture No3, Vietnam

² Institute of Aquaculture, Nha Trang University, Nha Trang, Vietnam

*Corresponding author: minhnguyen@ntu.edu.vn

In order to improve techniques for production of giant clam, Tridacna squamosa, in the hatchery, the present experiment aimed to evaluate the effects of stocking density on growth and survival rate of the clam at veliger stage. The larvae (2 days post hatched, DPH) were reared in the conical fiberglass tanks at densities of 3, 5, 7 and 9 larvae mL^-1 (so-called D3, D5, D7 and D9, respectively) for a period of 7 days. Each density was randomly assigned to triplicate tanks. The larvae were fed  a combination of Isochrysis galbana and Chaetoceros muelleri (density of 5,000 cells/ml each type of algae), twice a day. Extracted zooxanthelle was seeded into the larvae in the afternoon at 4DPH.

The results showed that there were significant differences in shell mean length, specific growth rate and survival rate of the larvae amongst rearing densities (P< 0.05). Of which, the larvae at D3 gained the highest shell length, specific growth rate and survival rate. Meanwhile, the larvae D9 had the lowest shell length, specific growth rate and survival rate. Better results were found for survival and growth in the densities of 3 and 5 larvae ml^-1. However, in order to improve productivity of the larvae clam for massive seed production, a stocking density of 5 larvae mL^-1 is recommended.

Keywords: Tridacna squamosa, stocking density, live algae.

EXPERIMENTING AND DEVELOPING AN ENVIRONMENTAL FRIENDLY OYSTER (Crassostrea rivularis) FARMING

Ton That Chat*¹, Nguyen Duy Quynh Tram¹, Vo Duc Nghia¹, Nguyen Thi Thanh Thuy¹

¹Hue University of Agriculture and Forestry

102 Phung Hung Street, Hue City, Thua Thien Hue Province, Viet Nam

^*Corresponding author: tonthatchat@huaf.edu.vn 

Oysters are a favorite food with potential health benefits and are considered as “functional foods”. Today, in the world, the number of oysters is declining rapidly due to the threatened habitat. About 85% of the oyster's coral habitat has disappeared. In Vietnam, there are many different methods of oyster farming but the method of rearing oysters with tires is recently more popular because of its convenience. However, the local government does not encourage the development of this method because tires worsen the landscape and the environment further and the diners do not prefer raw oysters on tires to that on natural substrates. This study used oyster shell wire to raise oysters and this is considered as an alternative method to reduce the excessive use of tires in oyster farming in the study area. Advantages and disadvantages of raising oysters with old tires: With tire farming, farmers use substrates (tires) for oyster larvae to cling to, live and develop for life in a fixed position; This is a simple farming method, low investment costs, easy harvesting; But leaves bad consequences for the environment and landscape. Solution proposed by the research team: Guide farmers to make oyster shell wire. Make use of locally available oyster shells as a substrate to raise oysters.

Overdevelopment without planning hinders navigation, negatively affects the environment. The quality indicators of water and oyster meat obtained from the treatments were within the allowable range of QCVN-MT:2015/BTNMT and a number of food safety standards. Oyster shell wire has not shown an advantage in terms of economic efficiency compared to old tires. However, the transition from growing oysters with tires to raising oysters with oyster shells currently being encouraged to apply in order to minimize negative impacts on the landscape and environment as well as address the sensory needs of users.

Keywords: Oyster, pollutants, envinronmently, friendly