Journal of Fisheries and Environment

Fish Antioxidant Enzyme Activity as Protein-Level Biomarkers of Ecological Stress in Tropical Eutrophic Wetlands: A Review

Fri, 01 Aug 2025 00:00:00 +0700

Eutrophication-related stressors, including low dissolved oxygen, nutrient enrichment, and harmful algal blooms, negatively affect the health and function of organisms, populations, and ecosystems, resulting in ecological stress. Aquatic life struggles to withstand such irregular and abrupt disruption to ecosystem homeostasis, leading to alteration in ecosystem metabolism(e.g., simplified food webs and shortened food chains), reduced nutrient uptake and utilization efficiency, hyperphosphorylation-induced cellular damage, and increased pathogen virulence. As a first line of defense against eutrophication stress, fish release antioxidant enzymes (AOEs) such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), peroxidase (POD), acetylcholinesterase (AChE), and others from various body organs. These enzymes react with reactive oxygen species (ROS) produced during stress and convert them into less harmful compounds. Most studies indicate that SOD is the primary enzyme secreted in response to ammonia and nitrate toxicity in eutrophic water bodies. The liver is the main organ responsible for AOE release followed by the gills and brain. Maximum AOE activity is typically observed at 48–96 h of exposure to ammonia, nitrate, or microcystin contamination. Thus, species-specific AOE release mechanisms can reflect the nature and intensity of stressor impact and may serve as biomarkers of ecological stress in tropical eutrophic wetlands. These eco-remediation tools can help mitigate the effects of eutrophication and promote healthier aquatic environments for species to thrive and develop.

Integrative Taxonomy of Riverine Cyprinids (Genera Henicorhynchus and Labiobarbus) in the Mekong Delta: Morphological and DNA Barcoding Approaches

Fri, 01 Aug 2025 00:00:00 +0700

Riverine cyprinids, known as "ca linh" in Viet Nam play a vital role in the economic and ecological systems of the Mekong Delta, particularly during the flooding season. These fish include four species from two genera: Labiobarbus (L. leptocheilus and L. siamensis) and Henicorhynchus (H. entmema and H. siamensis). Identifying species within each genus is challenging for non-ichthyologists due to their similar external appearance, particularly at early developmental stages. This study aimed to combine morphological and DNA-based approaches to comprehensively analyze morphological variations and DNA barcoding of riverine cyprinids in the Mekong Delta, Viet Nam. Fish samples were collected along the Mekong River during the flooding seasons. Initially, morphological classification was performed, including the measurement of meristic and morphometric parameters. The results revealed additional morphometric differences between congeneric species. Subsequently, the cytochrome c oxidase subunit I (COI) gene of each species was sequenced. The Kimura 2-parameter (K2P) genetic distances between the two species within each genus, Labiobarbus and Henicorhynchus, were 0.0878±0.0135 and 0.1005±0.123, respectively. Meanwhile, intraspecific genetic distances ranged from 0 to 0.0046. The findings emphasize the importance of integrating traditional morphological taxonomy with molecular methods to overcome challenges in fish species identification.

Field-Based Assessment of Aluminum Industry Effluent: Hematological and Biochemical Responses of Nile Tilapia, Oreochromis niloticus

Fri, 01 Aug 2025 00:00:00 +0700

The presence of unacceptable levels of heavy metals from untreated effluents and other contaminants can destabilize ecosystems, leading to physiological changes in aquatic organisms. To investigate this concern, water samples and Nile tilapia (Oreochromis niloticus) were collected from three locations along the Mbaa River to assess heavy metal concentrations in the water and the physiological profiles of the fish. The sampling sites, designated as Site A, B and C, were spaced 50 m apart. Site A was located upper stream; Site B was situated at the point source of an aluminium industry and represented the midstream area, while Site C was down-stream. A fish farm at the Federal University of Technology, Owerri, served as the control site. A significant difference (p<0.05) was observed in the concentrations of lead, zinc, cadmium, copper, and iron in water samples from Site B compared to the other sites and the control. Morphological indices of the fish showed no significant difference in body weight, liver weight, or fork length across all stations. However, compared to the control, fish from Site B exhibited a decrease in red blood cell (RBC) count and packed cell volume (PCV), along with a significant increase (p<0.05) in white blood cell (WBC) count. Serum levels of alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase did not show significant variation among fish from different sites. The findings of this study contribute to environmental monitoring and conservation efforts, highlighting the need for proper treatment of industrial effluents prior to discharge into aquatic environments in order to mitigate their impact on fish populations.

Food and Feeding Habits of Three Ecologically Important Fish Species in Lake Hawassa, Ethiopia

Teshome Belay, Elias Dadebo, Girma Tilahun, Degsera Aemro — Fri, 01 Aug 2025 00:00:00 +0700

Understanding the feeding behavior of fish species is crucial for evaluating ecosystem health, trophic relationships, and resource availability in aquatic environments. This study investigated the feeding habits of three fish species in Lake Hawassa, Ethiopia, during two rainy and two dry months in 2024: the straightfine barb [Enteromius paludinosus (Peters, 1852)], the stone-lapping minnow [Garra quadrimaculata (Rüppell, 1835)], and the black lampeye [Aplocheilichthys antinorii (Vinciguerra, 1883)]. A total of 1,795 specimens were collected using beach seines and hand nets. Gut content analysis was conducted using frequency of occurrence, volumetric contribution, and index of preponderance methods. A high degree of dietary overlap (C>60%) was observed across size classes in all species, with some exceptions. Seasonal variation in prey availability was reflected in the frequency and volume of consumed items. E. paludinosus consumed seven main prey categories, including phytoplankton, detritus, macrophytes, zooplankton, fish eggs, and nematodes. G. quadrimaculata ingested all these items, while A. antinorii consumed all except nematodes. Phytoplankton dominated the diet of all three species, with the highest frequency of occurrence (87.17%, 63.18%, and 84.10%), volumetric contribution (84.24%, 46.38%, and 59.88%), and index of preponderance (85.94%, 47.71%, and 63.16%) for E. paludinosus, G. quadrimaculata, and A. antinorii, respectively. Seasonal variations in diet composition were significant, while intraspecific dietary overlap remained consistently high (C>60%) across size classes. The results indicate that all three species exhibit omnivorous feeding habits.

Seasonal Fluxes of Dissolved Nutrients and Suspended Solids at the Tha Chin River Mouth, Thailand (2023–2024)

Fri, 01 Aug 2025 00:00:00 +0700

Eutrophication in the inner Gulf of Thailand is strongly influenced by nutrient discharges from multiple river systems, with the Tha Chin River being one of the major sources. This study assessed concentrations and land–sea fluxes of dissolved nutrients and total suspended solids (TSS) at the river mouth from 2022 to 2023 across wet, dry, and transitional seasons of the Tha Chin River. Sampling was conducted every 25 h over full tidal cycles. Dissolved oxygen levels remained critically low throughout the period, ranging from 0.66 to 2.87 mg·L⁻¹. TSS peaked in the transitional season (497.41±347.44 mg·L⁻¹) and was lowest during the wet season (38.64±43.93 mg·L⁻¹). Ammonia (612.91–1,291.49 µg N·L⁻¹) and DIP (165.34–265.42 µg P·L⁻¹) reached hypertrophic levels, with nitrogen identified as the limiting nutrient based on the Redfield ratio. Water fluxes peaked in the wet season (61.26×10⁶ m³·d⁻¹), over five times higher than in the dry season. The Tha Chin River delivered substantial nutrient loads: ammonia fluxes were 38.42 t N·d⁻¹ (wet), 20.20 t N·d⁻¹ (dry), and 36.70 t N·d⁻¹ (transitional). DIP fluxes were 10.43, 4.04, and 4.78 t P·d⁻¹, respectively. TSS flux was highest during the transitional season (4,749.77 t·d⁻¹) and lowest in the dry season (1,571.86 t·d⁻¹). Normalized to watershed area, the Tha Chin River yielded higher net DIN and DIP loads than other major Thai rivers. These findings underscore the river’s key role in eutrophication and red tide formation in the inner Gulf, emphasizing the urgent need for effective watershed and nutrient management to mitigate coastal ecosystem degradation.

Monsoonal Effects and Hydro–Biogeochemical Characteristics in Maritime Cargo Areas of Siracha Bay, Eastern Upper Gulf of Thailand

Saranya Rakseree, Prasarn Intacharoen, Vichaya Gunboa, Anukul Buranapratheprat — Fri, 01 Aug 2025 00:00:00 +0700

Nutrient dynamics play a crucial role in regulating seawater quality and maintaining ecological balance in coastal environments. While moderate nutrient inputs support productivity, excessive loading, often linked to human activities, can lead to eutrophication and oxygen depletion. This study investigated seasonal variations in marine water quality in the cargo area off Sriracha and Sichang Island, Chonburi Province, Thailand, using water samples collected from 16 locations during the dry season (March 2020) and rainy season (August 2020). Results showed elevated concentrations of ammonia (50.77±8.28 µg N·L⁻¹), nitrite (21.40±13.19 µg N·L⁻¹), nitrate (10.82±3.32 µg N·L⁻¹), and particulate organic matter (0.08±0.05%) in near-bottom waters at the loading site during the rainy season. In contrast, total nitrogen (82.98±15.29 µg N·L⁻¹) and total phosphorus (24.16±2.49 µg P·L⁻¹) were elevated during the dry season. These patterns indicate that loading activities contribute to organic matter accumulation in sediments, which subsequently release inorganic nutrients into the water column. High nutrient concentrations and low dissolved oxygen during the rainy season were associated with water column stratification. Most parameters met seawater standards, except for orthophosphate in near-bottom water during the rainy season. Further research is needed to determine the degradation rate of tapioca starch, identify associated byproducts, and evaluate its contribution to hypoxia. A systematic investigation will help clarify its long-term environmental impact and support improved water quality management in maritime cargo areas.

Preliminary Study on Bradycardia in Scylla serrata (Forskål, 1775) in Response to Pure Tone Stimuli

Meng-Li Tsai, Ming-Ta Chiang, Ping-Jung Chu, Tsen-Chien Chen — Fri, 01 Aug 2025 00:00:00 +0700

There are growing concerns about the effects of human-generated sounds on aquatic animals. Mud crabs of the genus Scylla, which are economically important species, are typically farmed along coastal areas that are potentially threatened by man-made noise. We observed the heart rate of mud crabs Scylla serrata (Forskål, 1775) exposed to pure tones lasting 1 s (short-duration) and 30 s (long-duration). Crabs were exposed to both short- and long-duration sounds at eight frequencies (ranging from 100 Hz to 2,200 Hz). Our results revealed the following: (1) the initial sound elicited bradycardia across all experimental conditions; (2) both playing sound and the cessation of the sound elicited bradycardia in many long-duration sound tests; and (3) bradycardia disappeared following repeated exposures to sound; however (4) bradycardia was sustained in nearly all short-duration exposures at frequencies ≤1,000 Hz. We suspect that the crabs may have been more stressed than expected, as we observed sustained bradycardia frequently following short-duration exposures to lower acoustic frequencies and twice in long-duration exposure tests. The growth and health of reared crabs may be negatively impacted, which could subsequently affect the production.

First Record of the Pathogenic Protist Labyrinthula sp. Infecting the Seagrass Enhalus acoroides (L.f.) Royle

Fri, 01 Aug 2025 00:00:00 +0700

Labyrinthula is a globally distributed pathogen known to cause wasting disease and large-scale die-offs in various seagrass species. However, infection in Enhalus acoroides has not been previously documented. In this study, the marine slime mold Labyrinthula sp., was isolated from a lesion leaf of Enhalus acoroides collected at Pa Khlok Beach, Phuket, Thailand in February 2024. Leaf sections with lesions or suspected affected areas were cut and placed on serum seawater agar for cultivation and examination. The isolate was subsequently inoculated onto axenic E. acoroides plantlets to assess pathogenicity. Within 24–48 hours of incubation, spindle-shaped cells of Labyrinthula sp. formed dense colonies embedded in ectoplasmic networks emerging from leaf edges. By the third week, brown lesions appeared on inoculated plantlets, expanding into band-like patterns by the fourth week. These symptoms confirm the ability of the isolated Labyrinthula sp. to induce lesions and contribute to wasting disease in E. acoroides. However, despite its pathogenic potential, there is not yet conclusive evidence linking this organism to the broader seagrass die-off observed in this region. This study presents the first report of Labyrinthula sp. infecting the seagrass, E. acoroides, and the first documented case of seagrass infection by Labyrinthula in Southeast Asia.

First Record of the Diamondback Squid Thysanoteuthis rhombus Troschel, 1857 (Cephalopoda: Thysanoteuthidae) in the East Malaysian Coastal Waters

Fri, 01 Aug 2025 00:00:00 +0700

This study documents the first confirmed record of the diamondback squid, Thysanoteuthis rhombus Troschel, 1857, along the east coast of Peninsular Malaysia. Two individuals, a subadult male and a female, were collected from a local fish market in Terengganu. Although T. rhombus is typically associated with warm tropical and subtropical offshore waters, its occurrence in Malaysian coastal waters had not been previously reported. Morphological identification was conducted and further validated through molecular analysis using mitochondrial cytochrome c oxidase subunit I (COI) gene sequencing. Phylogenetic comparisons revealed that the specimens clustered within the same clade as populations from the Pacific region, including Japan, the Philippines, and Vietnam. This finding significantly extends the known distribution range of T. rhombus and contributes new data to the cephalopod biodiversity of Malaysian waters. The presence of this oceanic squid species in local fish markets suggests possible changes in distribution patterns, which may be influenced by oceanographic or climatic factors. Given the ecological role and potential fishery value of T. rhombus, continued monitoring and further studies are warranted to assess its population status, habitat preferences, and implications for local fisheries. This record provides a valuable baseline for future taxonomic, ecological, and conservation research in the Southeast Asian marine region.

Spatiotemporal Patterns of Eggs of Bartail Flathead, Platycephalus indicus in Coastal Southern Yellow Sea

Sanny Tri Utami, Zhenjiang Ye, Wenchao Zhang, Yixiao Zhang — Fri, 01 Aug 2025 00:00:00 +0700

The distribution of fish spawning grounds is a key factor influencing larval transport, growth, mortality, and early recruitment success. Understanding the spatiotemporal patterns of fish egg distribution provides a scientific foundation for comprehending population fluctuations. This study investigated the spawning patterns and environmental impacts on the egg distribution of Platycephalus indicus in the Southern Yellow Sea (SYS). Data were collected from 27 ichthyoplankton survey cruises conducted during the spawning season from 2013 to 2018 in the coastal waters of the Southern Yellow Sea waters. A two-stage Generalized Additive Model (GAM) was used to analyze the spatiotemporal distribution patterns of eggs and their non-linear relationships with environmental factors, including sea surface temperature (SST), salinity (SSS), water depth, longitude, and latitude. Results indicated that spawning mainly occurred from April to July, peaking in May. GAM analysis identified SST, longitude, latitude, and water depth as significant predictors of egg presence, explaining 34.5% of the variance (AIC = 835.22). For egg abundance, SST, SSS, water depth, longitude, latitude, and offshore distance were key predictors, accounting for 55% of the variance (AIC = 778.73). SST was the most influential variable for both presence and abundance, showing a positive correlation with SST below 17 °C and a negative correlation above this threshold. Optimal egg abundance occurred between 15 °C and 19 °C. High egg concentrations were found in nearshore waters. These findings emphasize the importance of monitoring SST and protecting nearshore spawning grounds to support the conservation and management of P. indicus in the Southern Yellow Sea.

Ichthyofaunal Diversity and Limnological Characteristics of the Kakodonga River Flowing in Golaghat District Assam, India

Mitali Chetia; Himadri Kalita, Saibal Sengupta — Fri, 01 Aug 2025 00:00:00 +0700

The present study investigates the ichthyofaunal diversity and distribution patterns in relation to various limnological parameters across five sites along the Kakodonga River in the Golaghat district of Assam, India. A total of 46 fish species, 36 genera, 21 families, and 9 orders were recorded. The family Cyprinidae exhibited the highest species richness (eight species), followed by Danionidae (five species) and Sisoridae (four species). Total suspended solids (TSS) and conductivity (Con) had a significant positive influence on the spatial fish abundance, while dissolved oxygen (DO) and water temperature (Tem) significantly affected temporal variations in fish abundance. Canonical Correspondence Analysis (CCA) based on site-wise data, revealed that TSS and conductivity were the primary environmental variables shaping the spatial distribution of fish species, collectively explaining 79.11% of the total variance across the first two ordination axes. Site- specific fish assemblages were identified through Bray-Curtis analysis. The Shannon-Weiner diversity index (H), Pielou’s evenness index (J), Simpson’s diversity index (1 ̶ λ), and taxonomic distinctness (Δ*) did not exhibit significant seasonal variation (p≥0.05). However, Margalef’s richness index (d) and abundance per sampling event showed significant seasonal differences. Site-wise comparisons revealed significant differences in all diversity indices except for Pielou’s evenness index, which remained consistent across sites. These findings provide essential baseline data for fish assemblages and their environmental drivers that can support future monitoring and conservation of the Kakodonga River ecosystem.

Sustainability of Small-Scale Capture Fisheries to Climate Change in Pangpang Bay, Banyuwangi Regency, Indonesia

Ervina Wahyu Setyaningrum, Abu Bakar Sambah, Dewa Gede Raka Wiadnya — Fri, 01 Aug 2025 00:00:00 +0700

Pangpang Bay, located in Banyuwangi Regency, is characterized by its mangrove forests, which are utilized for various purposes, including capture fisheries, Pacific white shrimp farming, and mangrove conservation. Among these uses, small-scale fisheries represent the most significant potential in capture fisheries; however, their sustainability may be affected by climate change. This study aims to assess the sustainability of small-scale fisheries in Pangpang Bay. To achieve this, the Rapfish methodology was employed to analyze the vulnerability of these fisheries to both small-scale and coastal factors. This research employed a descriptive method using a quantitative approach. The parameters assessed included newly introduced dimensions, specifically, coastal vulnerability and capture fisheries vulnerability, alongside other dimensions derived from the Rapfish technique. The data analysis method used was the Rapid Appraisal for Fisheries (Rapfish) sustainability analysis. The results indicated that the sustainability status of small-scale capture fisheries in Pangpang Bay, Banyuwangi, with an MDS (Multidimensional Scaling) value of 47.25, was classified as less sustainable. Conversely, dimensions with MDS values exceeding 50 are considered moderately sustainable, particularly in the domains of coastal vulnerability, resources, and technology. It is recommended that policymakers address the challenges posed by climate change, through measures such as mitigating its adverse impacts, enhancing the capacity of small-scale fishers, integrating efforts among relevant stakeholders, and strengthening regulation and law enforcement.

Impact of Spray Drying Encapsulation on Metabolite Profile and Quality of Fish Oil Products

Fri, 01 Aug 2025 00:00:00 +0700

Encapsulation is one of the techniques to preserve fish oil compounds from deterioration and degeneration caused by oxidation. In the encapsulation process, the matrix wall protects fish oil substances, particularly when using the spray-drying method. This mechanism can induce changes in metabolite profiles while maintaining the quality of fish oil. In this study, metabolite changes were analyzed using high-performance liquid chromatography coupled with high-resolution mass spectrometry (HPLC-HRMS), alongside measurements of free fatty acids, acid values, and scanning electron microscope (SEM). The results showed distinct clusters between encapsulated and raw fish oil, with 75 metabolites identified, of which 35 were considered variables important in projection (VIP) metabolites. Statistical analysis revealed significant changes in 63 metabolites. Principal component analysis (PCA) clearly distinguished raw from encapsulated fish oil across a broad range, while the heatmap showed that most metabolites significantly differed among the treatment groups. PLS-DA identified 35 VIP metabolites, of which (1S,4S)-4-hydroxy-3-oxocyclohexanecarboxylic acid showed the highest VIP score. The VIP metabolites included 15 types of lipid derivatives, two amino acid derivatives, two carboxylic acid derivatives, two carbohydrate derivatives, two phenolic compounds, two aromatic compounds, and several minor substances. Additional findings showed a significant (p<0.05) decline in both free fatty acid and acid value levels for encapsulated fish oil, along with the formation of spherical encapsulated powder particles. The combination of HPLC-HRMS-based metabolomics with encapsulation analysis remains underexplored, and this study provides valuable insights into the encapsulation process for fish oil products.

Repeated Spawning Performance of Female Giant Freshwater Prawn (Macrobrachium rosenbergii de Man) in a Recirculating Water System

Fri, 01 Aug 2025 00:00:00 +0700

Repeated spawning of female giant freshwater prawn (Macrobrachium rosenbergii de Man) is a promising strategy to enhance broodstock utilization and seed production efficiency. However, concerns persist regarding its potential impacts on reproductive performance and larval quality. This study evaluated the effects of repeated spawning in individually reared females maintained in floating perforated boxes under a single-pair mating system, with in vivo egg incubation over a 180-day period. Only 33.33% of the initial broodstock completed three spawning cycles. Although the realized larval yield (number of hatching larvae per female) remained stable across spawnings, the relative larval yield (number of larvae per gram of female body weight) significantly declined (p<0.05), despite consistently high hatching rates (88.40–89.89%). The spawning interval increased with each successive spawning (35.42–42.33 days). While post-larval weight remained unaffected (p≥0.05), post-larval quality deteriorated with repeated spawning, as evidenced by reduced survival rates, prolonged larval development duration, and decreased stress resistance (shorter time to 50% mortality after acute freshwater exposure), despite comparable weight per 100 post-larvae across spawning events. These findings highlight the trade-offs between maximizing broodstock use and maintaining seed quality, emphasizing the need for improved broodstock management strategies in repeated spawning systems.

Enhancing Common Carp (Cyprinus carpio) Health Aspects and Performance with Garden Cress (Lepidium sativum) Seed Powder

Fri, 01 Aug 2025 00:00:00 +0700

This study aimed to evaluate the effects of garden cress (Lepidium sativum) seed powder on the growth and physiological activity of common carp (Cyprinus carpio). Fish were fed diets containing 0 (control), 5, 10, or 15 g·kg⁻¹ seed powder. Cress seed inclusion significantly influenced growth performance (p<0.05), with the 15 g·kg⁻¹ group showing higher feed efficiency ratio (FER) and protein efficiency ratio (PER) than other treatments. The 5% g·kg⁻¹ group showed significant increases in hemoglobin (HGB), hematocrit (HCT), platelet count, mean corpuscular volume (MCV), and white blood cell (WBC) count. Elevated alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activities, granulocyte levels, and creatine kinase (CK) activity were observed in the 10 and 15 g·kg⁻¹ groups. Conversely, lymphocyte, glucose, and monocyte levels were reduced in the 15 g·kg⁻¹ group. Other biological indices, including condition factor (K), hepato-somatic index, splenosomatic index, kidney somatic index, gill somatic index, intestine weight index, red blood cell (RBC) count, cholesterol, triglycerides, albumin (ALB), and total proteins (TP), exhibited minimal variation. The findings suggest that 15 g·kg⁻¹ dietary cress seed powder is optimal for enhancing the performance of common carp.