Journal of Fisheries and Environment

Leaching and Fluorescence Characteristics of Dissolved Organic Matter Released from Common Consumer Plastics

Marut Suksomjit — 2025-12-31

Plastic pollution poses increasing risks to wildlife, human health, and aquatic ecosystems, acting as a source and vector of dissolved compounds. This study investigated the leaching and fluorescence characteristics of dissolved organic matter (DOM) from three common consumer plastics: polypropylene (PP), low-density polyethylene (LDPE), and polyethylene terephthalate (PET). Plastics were incubated under simulated light or dark conditions for 21 days, and dissolved organic carbon (DOC) and fluorescent DOM (FDOM) were measured to quantify leaching amounts and characterize DOM quality. Our results showed that PP released the highest DOC concentrations, while LDPE and PET showed much lower levels. By day 21, average DOC leaching from PP, LDPE, and PET was 10.50, 1.62 and 0.53 mg C·m^-2 of plastic surface, respectively. Corresponding leaching rates were 4.02, 0.56 and <0.10 mg C·m^-2·d^-1. In contrast to differences in DOC quantity, the FDOM of all plastics exhibited similar spectral features, with a major tryptophan-like peak at 295–305 nm excitation and 335–340 nm emission, and a minor peak at 235–254 nm excitation and 335–340 nm emission. These fluorescence signals suggest that plastic-derived DOM is bio-labile and potentially influenced by additives. Overall, the results confirm that common consumer plastics are a reactive source of DOM that may alter carbon cycling and microbial processes in aquatic environments. We suggest that both plastic type and additives likely affect DOM leaching behavior, with implications for understanding the broader ecological impacts of plastic pollution.

Evaluation of Spray-Dried Porcine Plasma for Growth Performance, Production Yield, Immune Responses, and Total Vibrio Counts in Pond-Reared Giant Tiger Prawn (Penaeus monodon)

Nithit Anakthanakit — 2025-12-31

Spray-dried porcine plasma (SDP) is a protein-rich feed ingredient derived from animal blood with potential health benefits. This study evaluated the effects of dietary SDP on growth, survival, and immune responses in pond-reared giant tiger prawn (Penaeus monodon). Six earthen ponds in a commercial farming system in Prachuap Khiri Khan Province, Thailand, were stocked with postlarvae at a density of 750,000 shrimp·ha^-1 (75 shrimp·m^-2). Three ponds received a standard commercial diet (Control group), while the other three ponds were fed a pelleted diet containing 4.5% SDP (SDP group) for 30 days (days 30–60 post-stocking), after which all ponds were fed a standard diet until harvest. The inclusion of SDP improved feed conversion ratio (FCR) compared with the control group. Shrimp fed the SDP diet showed significant (p<0.05) increases in immune parameters and reduced total Vibrio counts in both the hepatopancreas and intestine. Unexpectedly, an outbreak of acute hepatopancreatic necrosis disease (AHPND) occurred on day 80, affecting all control ponds and one SDP pond, while the other two SDP ponds remained AHPND-negative. This suggested a potential protective effect of SDP. Although the AHPND outbreak limited conclusive assessment of growth and production, the observed improvement in FCR, immunity, and in Vibrio reduction indicates that dietary SDP may enhance shrimp health under farm conditions.

Assessment of Eutrophication in Middle-Lower Chao Phraya River (2020–2022)

Nattapong Satja — 2025-12-31

This study investigated eutrophication in the Chao Phraya River from 2020 to 2022, focusing on ten monitoring stations between Ayutthaya and Samut Prakan. Distinct seasonal dynamics associated with the monsoon were observed. During the wet season (May–November), agricultural and urban runoff elevated BOD, suspended solids, and nutrient concentrations. In contrast, during the dry season (December–April), reduced freshwater discharge intensified salinity intrusion. Hypoxic conditions, with dissolved oxygen (DO) frequently dropping below 2 mg·L⁻¹ near the river mouth. Nutrient enrichment–particularly dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP)–was strongly associated with phytoplankton blooms, especially near the salinity front where chlorophyll-a concentrations peaked. Nutrient levels increased downstream, driven by untreated discharges from urban, agricultural, and industrial sources. Wastewater nitrification increased nitrate levels, while nitrate overall comprised 41.36% of the total DIN. Peaks in phosphate and total dissolved phosphorus (TDP) followed agricultural runoff, notably in November 2020. Principal component analysis (PCA) revealed clear spatial distinction between middle and lower river stations, with the lower section characterized by elevated nitrogen, phosphorus, and chlorophyll-a concentrations. The AARL-PC Score (a trophic state index) supported these findings, showing consistently high trophic scores in downstream stations indicative of eutrophic conditions, particularly during June and July 2020. Overall, the results indicate a worsening ecological condition compared to historical records and highlight the urgent need for integrated pollution control and sustainable river basin management to protect this tropical urban river.

Dietary Resin Acids Oil Enhances Immunity, Stress Response, and Intestinal Integrity in Juvenile Red Tilapia (Oreochromis niloticus x Oreochromis mossambicus) Challenged with Aeromonas hydrophila

Chonnikarn Piyavorasakul — 2025-12-31

The effects of dietary resin acid oil (RAO; Progres®, AB Vista, UK) on intestinal integrity, stress response, and immunity of red tilapia (Oreochromis niloticus x Oreochromis mossambicus) were evaluated during an Aeromonas hydrophila immersion challenge. The experiment followed a completely randomized design (CRD) with three treatments and three replicates. A total of 90 red tilapia (14.65–15.07 g) were randomly distributed into nine aquaria and fed diets containing RAO at 0 ppm (control), 350 ppm (R350), and 700 ppm (R700) three times daily for two weeks. Dietary RAO supplementation significantly reduced serum cortisol and markedly increased hemoglobin concentrations compared to the control (p<0.05). Hemoglobin levels in the control, R350, and R700 groups were 3.92±0.10, 4.29±0.02, and 4.38±0.10 g·dL^-1, respectively. Corresponding cortisol levels were 131.90±27.90, 64.74±3.99, and 63.55±8.66 μg·mL⁻¹, with RAO groups showing values less than half that of the control (p<0.05). Intestinal Aeromonas counts were significantly lower in R700 group (6.06±0.43 CFU·mL^-1) than in the control (7.20±0.09 CFU·mL^-1) and the R350 groups (7.02±0.14 CFU·mL^-1) (p<0.05). Histological analysis revealed that the RAO-fed fish exhibited longer intestinal villi and reduced tissue degeneration in both the intestine and liver under pathogen stress. These findings demonstrate that dietary RAO at 350–700 ppm improves the stress response and protects intestinal and hepatic tissues of red tilapia. Therefore, RAO shows promise as a natural alternative for disease management in aquaculture.

Sex-Associated Microsatellite Marker for Neomale Identification and Histological Analysis of Gonadal Maturation in Ompok bimaculatus

Kedsirin Ruttajorn — 2025-12-31

This study aimed to develop sex-associated microsatellite markers for identifying neomales in Ompok bimaculatus and to characterize their gonadal structures histologically. Newly hatched larvae were treated with 17α-methyltestosterone (MT), and MT-treated fish were sampled up to 180 days post-hatching. Gonadal tissues were examined histologically, and caudal fins from ten males, ten females, and ten MT-treated individuals were used for DNA extraction. MT-treated fish showed smaller, translucent testes with markedly reduced spermatozoa density. A novel sex-associated microsatellite marker was identified, characterized by a dinucleotide (CA)n repeat: (CA)₁₉ in males and (CA)₁₅ in females and neomales, indicating sex linkage. These findings support the molecular identification of neomales and provide a foundation for developing reliable markers for sex determination and controlled breeding in O. bimaculatus.

Photosynthetic Efficiency and Survival of Tissue-Cultured Eucheuma denticulatum Microplantlets under Varying Transport Conditions

Jose Leo Fortellano — 2025-12-31

The cultivation of eucheumatoids (Eucheuma and Kappaphycus) is increasingly threatened by pests, diseases, climate change, and biosecurity concerns, leading to declining yields. Tissue culture offers a more resilient propagation approach; however, the success of outplanting depends on minimizing stress and mortality during the transfer of cultivars. This study evaluated the effects of different transport treatments on the photosystem II (PSII) photochemical efficiency and survival of tissue-cultured Eucheuma denticulatum microplantlets. An 8-h transport simulation followed by a 7-day laboratory culture was conducted to evaluate the effectiveness of various packaging and storage conditions. After 8 h, the maximum quantum yields (Fv/Fm) of transport treatments 1 (0.53±0.08) and 2 (0.51±0.11), in which explants were placed in plastic bags containing 250 mL of seawater stored in a styrofoam box without and with ice, respectively, did not significantly differ from their initial values (0.58±0.11 and 0.54±0.08, respectively). All explants in these treatments remained viable after 7 days. In contrast, treatments 3 (0.33±0.11) and 4 (0.44±0.09), where explants were wrapped in moistened muslin cloths and stored in a styrofoam box without and with ice, respectively, showed significantly lower Fv/Fm values compared with their initial states (0.64±0.09 and 0.63±0.11, respectively), with treatment 3 resulting in complete die-off (0.01±0.06) after 7 days. These findings suggest that transporting microplantlets in seawater-filled plastic bags, especially with ice insulation, is the most effective method for maintaining photochemical efficiency and viability during transport.

Automated Flow-Rate Control in Intelligent Recirculating Aquaculture Systems (i-RAS) to Improve Water Quality, Energy Use, and Hybrid Catfish Growth

Dome Adoonsook — 2025-12-31

This study evaluated an automated flow-rate control system for hybrid catfish (Clarias macrocephalus × C. gariepinus) in a recirculating aquaculture system (RAS). The experiment employed a completely randomized design with four treatments, each replicated three times: an ammonia-sensor-driven variable flow (5–15 m³·h^-¹) and three fixed flow rates: low (0.5×), medium (1.0×), and high (1.5× tank volume·h^-1). Fish were stocked in circular tanks with a capacity of 3,500 L (3.0 m in diameter and 0.5 m in depth) at a stocking density of 100 fish·m⁻², with an initial average weight of 13–15 g·fish^-1. Fish were fed commercial pellets (≥30% protein) to apparent satiation twice daily and cultured for 16 weeks under continuous aeration and real-time monitoring of NH₃-N, dissolved oxygen (DO), temperature, and pH. After 16 weeks, the automated and high-flow treatments achieved the highest final weights (308.95±1.43 and 304.99±3.27 g) and survival rates (90.90±0.46 and 90.86±0.29%), which were significantly greater than those in the medium- and low-flow treatments (p<0.05). The automated system produced the lowest FCR (1.48±0.01; p<0.05) and maintained water quality (TAN, NH₃-N, NO₂^--N) comparable to the high-flow treatment, with TAN reduced by approximately 54% compared with the low-flow treatment (p<0.05). Energy consumption was reduced by approximately 25% compared with that of a constant high recirculation rate. These findings demonstrate that real-time, sensor-driven flow regulation can enhance fish growth, maintain water quality, and reduce energy demand, thereby improving the sustainability of RAS operations.

Seasonal Fluxes of Dissolved Inorganic Nutrients and Suspended Solids at the Mouth of the Prasae River, Eastern Thailand

Anukul Buranapratheprat — 2025-12-31

This study investigates the seasonal fluxes of freshwater, suspended solids, and dissolved inorganic nutrients (ammonia, nitrite, nitrate, phosphate, and silicate) at the Prasae River mouth in eastern Thailand. Water sampling and flux measurements were conducted over eight time points between 2016 and 2017, covering both dry and wet seasons. Water quality and suspended solids showed pronounced seasonal and vertical variations driven by monsoon rainfall and tides, with strong stratification in October 2016 and September 2017. Ammonia spiked to >600 µg N·L^-1 in June 2016 and ~280 µg N·L^-1 in September 2017, while nitrite (~10 µg N·L^-1) and nitrate (~350 µg N·L^-1) peaked in October 2016, reflecting rapid terrestrial input. Phosphate reached ~100 µg P·L^-1 during peak runoff, and silicate remained high (>1,000 µg Si·L^-1), peaking near 3,000 µg Si·L^-1. Suspended solids were low at the surface (<40 mg·L^-1) but elevated near the bottom, indicating sediment resuspension. River fluxes showed strong monsoonal influence, with peak wet-season exports of nitrate (>2,200 kg N·d^-1), phosphate (~480 kg P·d^-1), and silicate (~10,000 kg Si·d^-1); ammonia and nitrite fluxes were more variable. During the wet season, nutrient exports were mainly discharge-driven, whereas internal processes were more influential in the dry season. TSS fluxes were episodic, indicating alternation between source and temporary sink. Compared with the Rayong, Trat, and Chanthaburi Rivers, the Prasae River shows elevated inorganic nutrient levels.