STUDY ON USING TREATED WASTEWATER FROM SNAKEHEAD FISHPONDS TO CULTURE SRPIRULINA PLATENSIS

Pham Kim Long¹, Duong Hoang Oanh¹

¹Tra Vinh University, No 126 Nguyen Thien Thanh Street, Tra Vinh City, Tra Vinh Province, Viet Nam

^*Corresponding author: kimlong_phm@tvu.edu.vn

This study performed the creation of a new nutrient solution from wastewater treatment of snakehead fishponds and added some nutritional components to grow algea Spirulina platensis. The result of the new nutrient environment is the combination of nutrients available in the treated wastewater of snakehead fishponds comprising K, PO₄, Na, SO₄, Mg, Cl, Ca and the addition of some nutritional components including EDTA, NaNO₃, FeSO₄.7H₂O and NaHCO₃ towards the similarity of Zarrouk. The optimal content of nutritional components including EDTA, NaNO₃, FeSO₄.7H₂O and NaHCO₃ is 0.012 g/L, 0.375 g/L, 0.0015 g/L, and 2.52g/L, respectively. The content of these additional components accounted for ~15% of their concentrations in the Zarrouk. Research using new nutritional environment and Zarrouk to grow Spirulina platensis with 2 treatments: Control treatment (using Zarrouk standard) and experimental treatment (using new nutrient environment), each experiment was repeated 3 times. The experimental results showed that the cultural algae in the 2 treatments together reached the highest density at the day 14^th with statistically significant difference (P<0.05), specifically the control treatment reached the density of 71,720±4,098 cells/mL with the algae biomass of 11.63±0.91 g/L, while the experimental treatment reached the density of 87,160±1,698 cells/mL with the algae biomass of 12.29±0.44 g/L. Concluding the advantages of this new nutrient environment is completely feasible both in terms of economy and solving environmental pollution problems of wastewater from snakehead fishponds. This saves the cost of spirulina nutrient environment when culturing up to 85% compared to Zarrouk.

Keywords: additional component, nutrient environment, snakehead fish, spirulina platensis, wastewater, Zarrouk,

APPETITE CONTROL, FEED INTAKE AND GROWTH IN CLOWNFISH Amphiprion ocellaris EXPOSED TO HIGH TEMPERATURE AND LIMITED FEED AVAILABILITY

Linh P. Pham^{1,2 *}, Minh V. Nguyen¹, Ann-Elise Olderbakk Jordal², and Ivar Rønnestad²

¹ Institute of Aquaculture, Nha Trang University, Nha Trang, Vietnam

² Department of Biological Sciences, University of Bergen, Bergen, Norway

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

Episodes of elevated temperature, combined with lower feed availability, are among the predicted scenarios of climate change and represents a challenge for coral reef fish. We mimicked two scenarios to explore the short- and long-term response of clownfish (Amphiprion ocellaris) with regards to feed intake, growth, metabolic rate; and expression of selected neuropeptide genes controling appetite (pomca&b; agrp1&2; and one mc4r-like). In the short term (acute) experiment, fasted fish were exposed to elevated temperature (from 28°C (control) to 32°C) within 24 hours then given a single meal to satiation. In the long term experiment, the exposure period was 8 weeks and fish were offered one meal compared to three meals per day in control treatment. We found that feed intake was increased when fish were long-term exposed to elevated temperature but decreased in short-term exposure. High temperature induced stronger asymmetrical growth of fish population (tank) in long-term and faster gut transit in short-term trial. Average growth rate of fish was lower due to limited feed availability in long-term. The routine metabolic rate was higher and postprandial metabolic rate was lower at shortly elevated temperature. These results show clownfish, given sufficient time, can acclimate to high temperature and low feeding but they will be stressed in the acute thermal change. At 32°C, in long term acclimated fish, low pomca was linked to higher feed intake and, in short term, the postprandial expression of pomca correlated with faster gut transit. Expression of agrp1 was affected by the interaction between long-term elevated temperature and low feed availability and associated with higher feed intake. Agrp2 responded to time related to meal, but the effects was significant only after acute exposure to 32°C. mc4r-like also corresponded to a faster gut transition at 32°C and inversely correlates with fish body weight. pomcb seemed to act anorexigenic in fish after feeding when acutely exposed to 32°C. All together, these results suggest that low feed availability and a temperature of 32°C mainly stimulate anorexigenic pathways in short-term exposure and both orexigenic and anorexigenic ones in long-term exposure in clownfish.

Keywords: Clownfish; Temperature; Food Availability; Food Intake; Appetite; Gene Expression

“STRANGE SLIMY MATERIAL” CAUSED ACUTE DEATH IN TROPICAL MARINE BROODSTOCKS

Mai Dang^1,, Hai Thanh T. Nguyen^2*, Van Manh Ngo², Tran Duc Dien³, Tran Ngoc Thang², Nguyen Thi Phương Thao⁴, Binh Thuy Dang², Ha Thanh Dong⁵

¹Institute for Veterinary Research and Development of Central Vietnam, Nha Trang, Khanh Hoa, Vietnam

² Nha Trang University, No 2 Nguyen Dinh Chieu Street, Nha Trang City, Khanh Hoa, Viet Nam

³ Institute of Aquaculture, Nha Trang University, Nha Trang, Khanh Hoa, Vietnam

³ Coastal Branch, Vietnam – Russia Tropical Center, Nha Trang, Khanh Hoa, Vietnam

⁴ South Research Sub-Institute for Marine Fisheries, Research Institute for Marine Fisheries, Vung Tau, Vietnam

⁵ AARM/FAB, School of Environment, Resources and Development, Asian Institute of Technology, Pathum Thani, Thailand

Corespondence: thanhnth@ntu.edu.vn

In February 2022, unusual acute mortalities were observed in snubnose pompano (Trachinotus blochii) and permit (T. falcatus) broodstock held in sea cages in Nha Phu lagoon, Khanh Hoa, Vietnam. The investigation was conducted three weeks after the mortality event to determine the potential cause. Initial examination of the field suggested that the sea anemones may be the culprit, causing the acute death of the pompano. We conducted experiments on the effects of these sea anemones on local marine fish, including pompano and red drum, and successfully proved that sea anemones (Bunodeopsis sp.) caused the acute death of pompano broodstock and somehow affected the health of red drum and barramundi broodstock in Nha Phu lagoon, Khanh Hoa, Vietnam. This is the first report of acute death in marine cultured fish, which is most likely associated with the deadly toxin(s) produced by the sea anemones Bunodeopsis sp. The lethal impact of this sea anemone on several marine fish species suggests that farmers in areas where this sea anemone is naturally distributed should improve their awareness and routinely inspect for its presence. This study underlines the critical need for further research to prevent and mitigate the harmful effects of this sea anemone on marine cultured fish.

Keywords: Broodstock; Mortality; Permit; Red drum; Snubnose pompano.

THE MUSCLE ORGANIZATION OF EPISESARMA SINGAPORENSE, AS AN IMPORTANT SEARMA CRAB FROM THAILAND

Phimolnard Chomchuen¹*, Pornthep Wirachwong¹, Supparat Kong-Oh¹, Wannee Jiraungkoorskul², Gen Kaneko³, Sinlapachai Senarat¹, Supapong Imsonpang⁴, Atsuo lida⁵, Chanyut Sudtongkong¹

¹Department of Marine Science and Environment, Faculty of Science and Fisheries Technology, Rajamangala University of Technology Srivijaya, Trang, Thailand Agriculture

²Department of Anatomy, Faculty of Medical Science, Naresuan University, 65000 Thailand

³College of Natural and Applied Science, University of Houston-Victoria, Victoria, Texas, USA

⁴Division of Health and Applied Sciences, Faculty of Science, Prince of Songkla Univerity, Songkhla 90110, Thailand

⁵Department of Animal Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan

*Corresponding author: phimolnard41.pc@gmail.com

The muscle structure has been investigated in many crabs in relation to their growth and development; however, such information has not been covered in E. singaporense. In this study, we investigated the muscle histology of E. singaporense using the morphometric analysis between different areas (Area 1: abdomen, Area 2: Cheliped and Area 3: working leg). Thirty muscle fibers from each area were measured. It was clear that the organization of E. singaporense skeleton was tightly packed, showing the striated muscle in longitudinal sections. Within the muscle, the muscle fibers contained several myofilaments. Multiple peripherally located nuclei were visible in the muscle fiber, and the muscle fiber ran through the entire length of the actual muscle. According to the morphometric data, all muscular areas were differed. Our results suggested that the Area 1 of E. singaporense skeleton would be where the highest muscle mass growth takes place and is suitable for crab meat consumption.

Keywords: Histology, Muscular organization, Searma crab, Thailand

SCREENING THE QUALITY OF FEED INGREDIENTS FOR Pangasius nasutus THROUGH In Vitro DIGESTIBILITY STUDY

Lidya¹, Hon Jung Liew¹, Abol-Munafi Ambok Bolong¹, Sharifah Rahmah^1,2*

¹Institute of Tropical Aquaculture and Fisheries, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Malaysia

²Faculty of Fisheries and Food Science, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia

*Corresponding author: sharifah.rahmah@umt.edu.my

Searching for alternative feed ingredients is necessary to reduce the dependency on fishmeal due to its unsustainable supply and high cost. The ability of the protein and carbohydrate in the feed ingredients to be digested by the fish determines its quality and can be preliminarily predicted prior to feed formulation. This study evaluates the in vitro protein and carbohydrate digestibilities of selected feed ingredients of Pangasius nasutus. Fish were anaesthetized and dissected to obtain the intestines. The intestines were homogenized and centrifuged, and the supernatant was kept at -20℃ as crude enzymes for in vitro digestibility analysis. The results showed that the apparent protein digestibility (APD) was highest for Danish fishmeal and local fishmeal (LFM), followed by the poultry by-product meal and black solder fly larvae meal (BSFLM). The lowest APD was observed for fish bone meal (FBM), wheat flour (WF), soybean meal (SBM) and wheat gluten meal (WGM). For apparent carbohydrate digestibility (ACD), the highest result was shown for wheat flour, followed by BSFLM and LFM. Wheat gluten meal, DFM, SBM, FBM and PBP had the lowest ACD compared to WF but were not significantly different from BSF and LFM. In conclusion, P. nasutus had different ability to digest different ingredients and it could be a practical and rapid method to screen for potential feed ingredients prior to feed formulation and feeding trial. Nevertheless, the in vitro data should be validated through the in vivo study.

Keywords: In vitro Protein Digestibility, In vitro Carbohydrate Digestibility, Feed Ingredients, Fishmeal Replacement

EFFECT OF LYSINE LEVELS ON GROWTH AND SURVIVAL RATE OF RABBITFISH (Siganus guttatus) Bloch, 1787

Binh Mac Nhu^1*, Dan Van Truong¹, Thuy Thanh Nguyen Thi¹,Ngo Thi Huong Giang¹, Tran Nguyen Ngoc¹,  Augusto E. Serrano.Jr²

¹Hue University of Agriculture and Forestry, No 102 Phung Hung Street, Hue City, Thua Thien Hue Province, Viet Nam; ²University of the Philippines Visayas

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

The study aimed to determine the optimum dietary lysine level of the orange-spotted rabbitfish Siganus guttatus Bloch, 1787 (average body weight range of 5.2 to 7.6 g×fish-1). The feeding trial was conducted for 8 weeks employing six experimental diets which were isonitrogenous, isocaloric, and isolipidic (35% crude protein (CP), 18.3 MJ×kg-1 of gross energy, and 5% lipid). The lysine content ranged from 1.22 g to 2.12 g lysine ×kg-1 dry diet (35 to 70 g×kg-1 CP). Results showed that percent weight gain (PWG), and specific growth rate (SGR) peaked at a lysine level of about 55 g×kg-1 CP equivalent to 1.93 g×kg dry diet-1). Feed efficiencies i.e., protein efficiency ratio and food conversion ratio values as well as survival were not affected by the dietary treatments. Lysine requirement level for juvenile rabbitfish was estimated using both broken-line and quadratic regression analyses of PWG and SGR against dietary lysine levels to be between 15.9 and 18.3 g×kg-1 diet (=45.3 and 52.3 g×kg-1 CP).

Keywords: amino acid, rabbitfish, growth, survival, feed