International Journal of Aquatic Biology

Quantitative evaluation of metabolism and body mass in yolk-sac larvae of Japanese whiting, Sillago japonica

Dong In Kim — 2025-08-14

Understanding the early developmental physiology of marine fish larvae is crucial for elucidating their ecological adaptability and survival strategies. This study investigates the metabolic changes in Japanese whiting (Sillago japonica) yolk-sac larvae over the first four days post-hatching. Larvae were incubated under controlled laboratory conditions, and daily measurements of oxygen consumption rate (QO?), wet and dry body mass, and water content were conducted using in vitro pooled samples. The results reveal a gradual increase in absolute oxygen consumption and body mass, accompanied by a consistent wet-to-dry mass ratio, except for a transient increase on the third day. Although individual measurements were not feasible due to the minute size of the larvae, the internal consistency of pooled data supports the observed physiological trends. These findings offer novel insights into the physiological trajectories of Japanese whiting Yolk-sac larvae and provide a foundational dataset for future research on yolk-sac larval energetics and environmental sensitivity in coastal marine fishes.

Study of mTOR/PTEN gene expression in gastric cancer cell line treated with ethanolic extract of Tetraselmis suecia microalgae

Atena Ehsanbakhsh — 2025-08-14

The second leading cause of death worldwide is cancer, and the fourth most prevalent cancer is stomach cancer. Natural seafood products include a variety of biologically active compounds with medicinal properties that may be useful in cancer therapy. This study aimed to assess the growth-inhibitory impact of the ethanolic extract of Tetraselmis suecica algae on the expression of mTOR/PTEN genes using the MTT assay in the cell line. The optimal IC50 dosage of this extract was 1000 and 750 ?g/mL at 48 and 72 hours, respectively. Tetraselmis suecica extract dramatically lowered the survival rate of gastric cancer cells, increased the apoptotic PTEN gene expression, and decreased the mTOR gene expression in the cell line. The extract of T. suecica, as shown in the current study, is potentially useful in the treatment of stomach cancer.

Population dynamics of three Epinephelus groupers in the Sulawesi Sea, Indonesia

Dewi Shinta Achmad — 2025-08-21

Groupers of the genus Epinephelus play important roles in coastal ecosystems and small-scale fisheries. Market demand has driven intensive exploitation, threatening stock status and coastal community livelihoods if these valuable fisheries are poorly managed. This research on grouper population dynamics in Kwandang Bay, on the Sulawesi Sea coast of Gorontalo Province, Sulawesi, Indonesia, focused on three Epinephelus species: E. fasciatus, E. faveatus, and E. ongus. The mean length at first maturity (Lm₅₀) was estimated using the Spearman-Karber formula, and population dynamics parameters were estimated through Response Surface Analysis using the ELEFAN I suite in FISAT II. Catches of all three species were dominated by juveniles with total length TL < Lm₅₀. The respective asymptotic lengths (TL?) for E. fasciatus, E. faveatus, and E. ongus were 47.52, 53.50, and 52 cm, with von Bertalanffy growth coefficient K values of 0.49. 0.54 and 0.53, respectively. Natural and fishing mortality estimates were 1.01/year^-1 and 1.23/year^-1 for E. fasciatus, 1.05/year^-1 and 2.00/year^-1 for E. faveatus, and 1.04/year^-1 and 2.44/year^-1 for E. ongus. The Beverton and Holt yield per recruit analysis indicates overexploitation with respective exploitation rates (E) of 0.55/year^-1, 0.66/year^-1, and 0.70/year^-1, all exceeding E_max = 0.37/year^-1. Recommendations include setting minimum legal size limits (above 25 cm for E. fasciatus and E. faveatus, 26 cm for E. ongus), as well as reductions in fishing effort of 31% for E. fasciatus, 42% for E. faveatus, and 46% for E. ongus.

Hematological and histological overview of captive-bred female doublespotted queenfish Scomberoides lysan (Forsskål, 1775)

Witchaya Tongtako — 2025-08-21

Health monitoring and assessment are required to support the improvement of maintenance efficiency of captive fish, but such information is lacking for the doublespotted queenfish Scomberoides lysan (Forsskål, 1775), a new candidate species for aquaculture in Thailand. The present study aimed to examine the morphological characteristics of erythrocytes and histopathological alterations in S. lysan females for the development of a health monitoring system. Female fish were randomly collected from a pond culture (n = 6, which was 34.5±0.9 cm in total length). Blood slides for hematological observations were prepared using the Wright-Giemsa stain method, while histological observations were made of tissues from the gills, kidneys, livers, and gonads. Blood smear test results showed that oval, mature erythrocytes were the most abundant cell type. Some erythrocytes exhibited nuclear morphological abnormalities, including kidney-shaped, polymorphic, and/or notched nuclei. The prevalence of such nuclei was only approximately 2%. The secondary lamellae of the gills displayed disorganization and aneurysms. Liver tissues displayed vacuolar degeneration of hepatocytes and blood congestion. Kidney tissues displayed tubular disorganization and renal degeneration. Melanomacrophage centers were present in large numbers in both liver and kidney tissues. Our analyses confirmed that the highest histological alteration index (HAI) calculated for liver tissue was a moderate alteration. The observations of S. lysan in captivity elucidated the cellular structure of this fish; the health of this fish might be reduced in captivity.

Production, remediation, health management, and economic returns of pond-based multi-trophic aquaculture giant tiger shrimp (Penaeus monodon) in varying feeding rates

Elgen M. Arriesgado — 2025-08-25

An analysis and understanding of the proof of concept of Integrated Multi-Trophic Aquaculture (IMTA) technology, with varying feeding rates, in the context of disease and environmental management for better production of pond-based semi-intensive Penaeus monodon aquaculture, is evaluated in this study. The grow-out culture experiment was conducted for four months (120 days), utilizing eighteen units of 250 m² ponds to hold the experimental trials. Six treatment combinations in triplicate were employed, comprising P. monodon as the main cultured species, with Chanos chanos and Oreochromis niloticus as the co-cultured species. The nutrient extractive species consisted of macroalgae Ulva fasciata and Gracilaria verrucosa, and mussel Perna viridis, at 2.5 and 5% feeding rates. The growth and survival of shrimp and finfish showed no significant difference among all treatments. Water quality levels among the treatments remained within optimal ranges. Shrimp reared within the shrimp-tilapia system and subjected to a 5% feeding rate manifested infection with White Spot Syndrome Virus (WSSV). Net revenue between the two feeding rates was consistently better (129.72-167.69 USD) at 2.5% feeding rates across all treatments. Overall, the shrimp-tilapia and IMTA systems demonstrated superior management and production performances compared to the shrimp polyculture system in terms of shrimp and fish production, plankton diversity, nutrient levels, and disease management. A 2.5% feeding rate is deemed appropriate for a shrimp-milkfish-Gracilaria-green mussel IMTA system.

Production performance of cladoceran Moina micrura fed Pleurotus florida mushroom byproducts

Jay Bayron Lemosnero — 2025-08-25

Cladoceran Moina micrura is an important live food organism in aquaculture. It provides essential nutrients such as proteins, lipids, and amino acids for fish and crustacean larvae. The composition of their diet primarily influences their growth and reproduction. The spent mushroom substrate (SMS), mushroom stalk waste (MSW), and mushroom fruiting body (MFB) have the potential to serve as an alternative food source due to their nutrient content. However, their efficiency in supporting M. micrura production remains unclear. Therefore, this study aimed to evaluate the effects of Pleurotus florida mushroom byproducts on the life history and population dynamics of M. micrura. A controlled experiment was conducted using different diets provided at 1000, 500, and 250 mg/L concentrations. The positive control was provided with baker’s yeast, while the negative control was provided with tap water without feed. Selected life history variables were measured to assess the production performance. The results showed that M. micrura fed 1000, 500, and 250 mg/L of SMS, as well as 500 mg/L of MSW and MFB, exhibited better production and longevity. The findings suggest that SMS and MSW have the potential to be alternative food sources in M. micrura production. Moreover, the high cost of MFB makes it less practical for large-scale use.

Carrying capacity of 4 ppt saline water on the production performance and water quality profile of Nile tilapia (Oreochromis niloticus) at different densities

Kukuh Nirmala — 2025-08-25

Increased density in fish farming can reduce the space for fish movement. The increase in density should be followed by considering the carrying capacity, which includes using an iso-osmotic environment, in this case, 4 ppt salinity. The purpose of this study is to analyze the use of 4 ppt salinity at different densities on production performance, water quality, physiological responses, and cost analysis in Nile tilapia. The experimental method was performed using Nile tilapia measuring 4.53±0.04 cm and an average weight of 1.45±0.03 g in each different density treatment, namely the control treatment of 1000 fish m^-3, A 1250 fish m^-3, B 1500 fish m^-3, and C 1750 fish m^-3, given a salinity 4 ppt with research parameters, including production performance parameters, water quality, and stress response. The results showed that the use of 4 ppt salinity in Nile tilapia can support the success of treatment C with a density of 1750 fish m^-3, with water quality that is still in the optimal range for Nile tilapia and a survival rate of 95.6% with an average length of 6.6 cm, so that treatment C has the highest profit of IDR 51,500.00.

Green synthesis of silver nanoparticles using Ascophyllum nodosum

Sara Muonas — 2025-08-25

Nanotechnology has emerged as a sustainable alternative for producing functional nanomaterials with unique properties. This study aims to develop and optimize a green synthesis protocol for producing silver nanoparticles using the brown algae Ascophyllum nodosum and to characterize their structural properties. Algal samples of A. nodosum were collected from their natural coastal habitat, thoroughly washed with distilled water to remove debris, air-dried under ambient conditions, mechanically ground into a fine powder, and subjected to aqueous extraction to obtain bioactive compounds essential for the synthesis of silver nanoparticles. Characterisation confirmed successful synthesis: UV-Vis spectroscopy showed a surface-plasmon-resonance peak at 420 nm; AFM and FESEM revealed spherical particles 10–30 nm; EDS indicated ? 85 % elemental silver with uniform distribution; FTIR identified O–H (3280 cm?¹), C = O (1635 cm?¹) and N–H (1540 cm?¹) groups capping the nanoparticle surface. GC-MS profiling of the algal extract detected more than fifty reducing/stabilising molecules, including fatty acids and phenolics. Antioxidant activity (DPPH assay) increases dose-dependently from 60.15% at 0.12 mg mL?¹ to 72.99% at 1 mg mL?¹, highlighting enhanced radical scavenging at higher nanoparticle concentrations. These findings demonstrate the efficiency of A. nodosum as a sustainable bio-factory for producing monodisperse, bio-capped silver nanoparticles with significant antioxidant capacity and broad prospects for medical, cosmetic, and industrial applications.

Molecular study of Neoechinorhynchus iraqensis parasite collected from some freshwater fish species in the southern region aquatic ecosystems of Iraq

Afrarh Litef Gaber — 2025-08-25

The present study was conducted to examine the intestines of three freshwater fish species of Planiliza abu, Aspius vorax, and Silurus triostegus, collected from Thi-Qar Governorate, Iraq, for Neoechinorhynchus iraqensis parasitic infection. The large subunit 28S ribosomal DNA was used to identify this spiny-headed worm species. The results of the current study recorded ten isolates of N. iraqensis in Iraq. All the isolates were recorded in the International Gen Bank.

Seasonal shifts in diet composition, stomach fullness, and trophic position of Synodontis serratus in Lake Nasser, Egypt

Khaled Y. AbouelFadl — 2025-08-25

Analysis of Synodontis serratus' feeding habits is crucial to understanding its ecological role in Lake Nasser, Egypt. This study examined seasonal variation in stomach fullness in relation to diet composition and trophic level for S. serratus throughout the year, using 361 specimens collected from March 2023 to February 2024. The results from stomach content analysis indicated that S. serratus employed an omnivorous, opportunistic feeding strategy, characterized by significant consumption of benthic and pelagic organisms, including aquatic insects, diatoms, crustaceans, nematodes, mollusks, and protozoan zooplankton. There were also seasonal changes; the importance of zooplankton decreased during the summer, while both diet diversity and feeding activity diminished in winter. Stomach fullness reached its minimal levels during late winter and early spring before peaking after summer. The trophic level analysis showed that S. serratus mainly operates as a secondary consumer (mean trophic level 3.11), with peak values in March among smaller individuals. This is counterintuitive, given expectations regarding ontogenetic diet shifts and maturity, which would lead to increased resource-use efficiency due to body-size-scaled metabolic demand relative to food resource availability. These results underscore the adaptive dietary strategies exhibited by S. serratus and their prominent functional contribution to the food web, indicating that S. serratus is a key species for ecosystem resilience. This necessitates further exploration to guide fisheries management intervention strategies planned for Lake Nasser.

Ecological study of microscopic protozoa in Abbasiya Canal, Iraq

Feryal Ameen — 2025-08-25

Microscopic protozoa are water-based organisms. They pose significant concerns for human health, as serious diseases have been linked globally. This study aimed to identify and document the microscopic protozoa taxa of the Abbaseya watercourse and record some abiotic factors of their habitats and the watercourse's pollution level. Three sites along the Abbaseya watercourse were selected for collecting microscopic protozoa using a net with 55 ?m mesh openings. The abiotic factors assessed included total dissolved solids (TDS), electrical conductivity (EC), water flow, turbidity, pH, chloride ion concentration, and magnesium ion concentration. In total, 23 protozoan species of the classes Ciliata and Sarcodina were recorded. The diversity indices used were Jaccard’s similarity index and the Shannon-Weiner index. The highest Jaccard’s similarity index value, 0.79, was observed between April and May. The protozoan taxa identified in the Abbaseya watercourse are classified primarily into two classes: Ciliata and Sarcodina, with Ciliata having significantly higher taxa. A thorough assessment of protozoan species is vital for evaluating water quality, as it offers valuable insights into the ecological health of aquatic environments.

Diagnosis and antibiotic resistance of some Aeromonas species isolated from Planiliza abu at Al-Diwaniya River, Iraq

Mohanad O. Al-Jubouri — 2025-08-25

This study aimed to investigate the presence of Aeromonas species and their antibiotic resistance isolated from Planiliza abu collected from Al-Diwaniya River, Iraq. A total of 100 P. abu were examined to determine the presence of A. hydrophila from April 2021 to March 2022. The bacteria were isolated and identified using the VITEK2 system. Vital tests determined the species Aeromonas sobria, A. hydrophila, and A. veronii. Antibiotic sensitivity testing with 16 antibiotics using a VITEK2 system. The results showed these bacteria are sensitive to Levofloxacin and Ciprofloxacin.