International Journal of Aquatic Biology

Ecological responses of pen shell, Atrina lischkeana, and ark shell, Scapharca kagoshimensis, to sediment characteristics in a temperate tidal flat

Tatsuya Yurimoto — 2025-12-25

To investigate the ecological responses of pen shells and ark shells to sediment characteristics in a temperate tidal flat in Japan, field surveys were conducted during spring low tides. Bivalve distributions were recorded, and sediment samples were collected from 32 sites. Regression analyses were performed to examine the relationships between bivalve density and sediment parameters, including mean grain size (Md?), mud layer thickness, moisture content, mud content, and loss on ignition (LOI) at 600°C and 800°C. Pen shells showed significant negative correlations with Md?, mud layer thickness, moisture content, mud content, and LOI at 600°C, but a positive correlation with LOI at 800°C. In contrast, ark shells were positively correlated only with Md? and mud content, with no significant associations with other parameters. These patterns were further supported by correlation matrix analysis and principal component analysis. Overall, the results suggest that pen shells exhibit selective habitat preferences, favoring sandy sediments with low mud content and high coarse shell material. In contrast, ark shells demonstrate broader ecological tolerance to sediment variation, resulting in a wider distribution.

Growth patterns, sex maturation stages, and fatty acid profiling of hatchery-cultured male short-finned eel (Anguilla Bicolor) in relation to the reproduction index under different hormonal treatments

Hanis Binti Abd Mohmin — 2025-12-25

This study investigated the effects of different hormonal treatments on growth performance, maturation, and fatty acid composition in hatchery-cultured male short-finned eel (Anguilla bicolor). A total of 12 individuals were subjected to four treatments — control (no hormone), Human Chorionic Gonadotropin (HCG), pituitary gland extract (PG), and Ovaprim (OVP) — over 100 days. Growth patterns were assessed through morphometric measurements and allometric analysis, while reproductive development was evaluated using gonadosomatic index (GSI), hepatosomatic index (HSI), histological characteristics, and steroid hormone profiling (11-ketotestosterone and estradiol). Fatty acid composition was determined using gas chromatography (GC). The HCG treatment significantly enhanced gonadal development (GSI = 4.36±0.21, P<0.001) and elevated 11-KT levels, promoting advanced spermatogenesis, as further evidenced by histological analysis. However, the HCG-injected eel showed lower body weight gain and a weaker length-weight correlation, indicating a shift in energy allocation toward reproduction. Meanwhile, the OVP-injected eel exhibited balanced growth with strong weight-length relationships (R² = 0.94) and the highest monounsaturated fatty acid (MUFA) levels. PG-injected eel, however, demonstrated moderate effects on reproductive and growth indices. Fatty acid profiling revealed that HCG increased polyunsaturated fatty acids (PUFA), particularly docosahexaenoic acid (DHA), which corresponded with higher spermatozoa abundance. These results show that HCG can effectively induce sexual maturation in male short-finned eels, although it may reduce somatic growth. The varied responses to hormone treatments suggest the potential for enhancing breeding strategies in eel aquaculture through more precise hormonal management.

Preliminary investigation on the tail regeneration of the juvenile marine polychaete, Perinereis wilsoni

Mercedes Maceren-Pates — 2025-12-25

In Perinereis wilsoni, gonad formation is thought to depend on germ cells supplied by the tail-end segment (pygidium). In this study, we investigated the regenerative capacity of germ cells in the pygidium following posterior amputation, using vasa as a putative germ cell marker. At 3 days post-amputation (dpa), pw-vasa-positive cells were scattered around the amputated area of the posterior segment, with some located near germ cell clusters in the distal parapodial region of the adjacent unamputated segment. By 4 dpa, pw-vasa expression was observed in the segment addition zone. At 7 dpa, pw-vasa was detected in germ cell clusters within the regenerating pygidium, and by 10 dpa, expression was evident in both the pygidium and the distal parapodia of the regenerated segment. These findings suggest that the re-emergence of germ cells in the pygidium may be supported by germ cell supply from the parapodia of the neighboring unamputated segment.

Biological traits of striped dwarf catfish, Mystus vittatus (Bloch, 1794) (Bagridae) in the Old Brahmaputra River, Northeastern Bangladesh: Implications for sustainable fisheries management

Imran Bin Younos — 2025-12-25

The present study investigates the population dynamics and biological traits of Mystus vittatus in the Old Brahmaputra River. A total of 515 specimens were collected between January and December 2024, excluding the breeding season (March to May), using gill nets. Standard biometric methods were applied to analyze length–frequency distributions, length–weight (LWR), and length–length (LLR) relationships. Three condition factors (allometric (KA), Fulton’s (KF), and relative (KR)), form factor (a?.?), and relative weight (WR) were also assessed. The growth pattern was negatively allometric (b-value = 2.56). KA = 0.0287±0.004, KF = 1.2286±0.263, and KR = 1.0241±0.142 indicated healthy physiological status and adequate food availability. A strong linear relationship was found between total length and standard length. The form factor (a?.? = 0.0068) reflected a streamlined body shape suited to flowing waters. WR ranged from 71.25 to 142.15, indicating favorable growth conditions with some seasonal variation. These biometric insights provide valuable baseline data for assessing population health and growth dynamics of M. vittatus. Given ongoing habitat pressures and reduced river flow, species-specific management and conservation measures are urgently needed to ensure the sustainability of fisheries in the Old Brahmaputra River.

GC-MS profiling and antioxidant activity of ethanol extracts from tissue-cultured Kappaphycus alvarezii and their effect on Nile Tilapia (Oreochromis niloticus) growth performance and hematological parameters

Salnida Yuniarti Lumbessy — 2025-12-25

This study aimed to identify the bioactive compounds present in Kappaphycus alvarezii ethanol extracts using various solvent ratios, through GC-MS analysis and antioxidant activity assays. The ultimate goal is to provide critical insights supporting the application of K. alvarezii extract as a feed additive in the diet of Nile tilapia (Oreochromis niloticus). The research was conducted in two experimental phases. Phase 1 involved the preparation of ethanol extracts using three different solvent ratios: 1:3 (A), 1:4 (B), and 1:5 (C). Each extract was analyzed using Gas Chromatography-Mass Spectrometry (GC-MS) to profile the chemical constituents, followed by evaluation of their antioxidant activity. Phase 2 assessed the application of these ethanol extracts in commercial fish feed over a 40-day rearing period. Four dietary treatments were tested: commercial feed only (P1), and commercial feed supplemented with K. alvarezii extract at ratios of 1:3 (P2), 1:4 (P3), and 1:5 (P4). A Completely Randomized Design (CRD) with three replicates per treatment was employed, resulting in a total of 12 experimental units. Growth performance and survival rate of Nile tilapia were evaluated. GC-MS profiling revealed that the ethanol extracts were dominated by palmitic acid (hexadecanoic acid), a compound known for its antioxidant potential. The extract with a 1:3 solvent ratio exhibited the strongest antioxidant activity, with an IC?? value of 34.66 ppm. Application of this extract in fish feed significantly influenced growth and survival performance. The 1:3 treatment yielded the best results, enhancing absolute weight gain (4.51±0.47 g), specific growth rate (1±0.07%/day), and achieving a 100% survival rate. Additionally, this treatment improved the fish’s health status, as indicated by elevated erythrocyte counts (306,000 cells µL?¹) and hematocrit levels (25.7%).

Reproductive biological characteristics of the polychaete Dendronereis chipolini distributed in the Mekong Delta, Vietnam

Yen Thi Tran — 2025-12-25

The reproductive biology of the polychaete Dendronereis chipolini, collected from extensive shrimp ponds in coastal areas of the Mekong Delta, was investigated to provide baseline data for future efforts to artificially reproduce the species. Live specimens were examined to determine sex differentiation, fecundity, gonadal development, and patterns of embryonic and larval development. Sex was primarily distinguished by body coloration: mature males exhibited a bright milky-green hue, whereas mature females displayed a dark moss green coloration. Absolute fecundity averaged 185,773±76,352 eggs per female, while relative fecundity was 209,520±31,414 eggs per gram of female body weight. Histological analysis revealed four distinct stages of oocyte development, characterized by increasing egg diameters ranging from 40-80 µm (Stage I) to 100-120 µm (Stage IV). Embryonic development, from fertilization to hatching, was completed within 7 hours and 30 minutes at a temperature range of 28-30°C. Larval development progressed through three stages: Trochophore, Metatrochophore, and Nectochaete, with the final stage exhibiting morphological features resembling those of adult worms. These findings contribute to the foundational knowledge required for developing reproductive protocols for D. chipolini in aquaculture systems.

Enhanced removal of PVC nanoplastics from water using microwave-activated palm frond biochar

Zaniab J. Kadhum — 2025-12-25

Nanoplastic polyvinyl chloride (PVC) is increasingly reported in aquatic environments, yet remains difficult to capture with conventional treatment. This study develops a low-cost sorbent from palm-frond waste by microwave activation and NaOH treatment, and further produces a magnetically retrievable variant by depositing Fe?O?. Materials prepared at 800 W for 20 min using NaOH (0.5, 2, and 4 M) were characterized by FTIR, FESEM, and XRD, then evaluated in batch tests across initial PVC concentrations of 0.2-1.0 ppm, sorbent doses of 0.1-1.0 g L?¹, and contact times up to 30 min. The biochar achieved complete removal at 0.2 ppm and 99% at 1.0 ppm within 30 min, with performance increasing with dose and contact time. At 0.6 ppm, removal rose from 89 to 97% as contact time approached 30 min. Spectroscopic and microscopic analyses indicate that oxygenated surface groups and hierarchical porosity underpin hydrophobic and electrostatic interactions with PVC, while magnetization enables rapid post-treatment separation without compromising the active surface. By valorizing agricultural waste into an efficient, retrievable sorbent, this work offers a practical, energy-lean pathway for nanoplastic remediation.

Species confirmation of freshwater prawns in Ternate Island, Indonesia, through DNA barcoding: Not Macrobrachium rosenbergii

Muhammad Nur Findra — 2025-12-25

Freshwater prawns of the genus Macrobrachium are widely distributed across tropical and subtropical regions. On Ternate Island, the local community refers to native freshwater prawns as “udang galah”, a name typically associated with Macrobrachium rosenbergii. This study aimed to accurately identify freshwater prawn species on Ternate Island using DNA barcoding. Prawn samples were collected from two different locations on Ternate Island: Togafo River, which has a steep gradient and flows directly into the sea without being affected by tidal salinity, and the river in Fitu Village, which consists of isolated pools with no connection to marine waters. Tissue samples were taken and preserved in 96% alcohol for molecular analysis. DNA barcoding results confirmed that the identified species is Macrobrachium lar, with genetic similarity ranging from 99.50% to 99.83% to reference data in GenBank. The presence of M. lar in isolated freshwater habitats raises questions about its dispersal patterns and life cycle, as this species is amphidromous and typically requires brackish water for larval development. These findings suggest the possibility of local adaptation or alternative dispersal mechanisms that warrant further investigation. Additionally, this study highlights the effectiveness of DNA barcoding for species identification, particularly for Macrobrachium species with high morphological variation or classified as cryptic.

Effect of water pollution in Sevastopol bays (Black Sea) on histopathological and oxidative stress biomarkers of black scorpionfish Scorpaena porcus

Irina Ivanovna Rudneva — 2025-12-25

In two of the bays, Streletskaya Bay and Balaklavskaya Bay (Sevastopol, Black Sea), historically affected by various kinds of anthropogenic activity, we assessed environmental pollution using liver, gonads, and gill histopathological indicators and antioxidant biomarkers in black scorpionfish Scorpaena porcus L. The results show several differences in histological alterations across the liver, gills, and gonads, as well as in blood antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and glutathione reductase) among fish from the study areas. Gonads of all females examined from both bays showed atresia of vitellogenic oocytes. Histological analysis of the fish gills has demonstrated hyperplasia of the respiratory lamellae, which could significantly decrease the interlamellar length. In both areas, the most prominent histological changes observed in liver tissue were lipid alterations in hepatocytes. In several females, degeneration of the hepatic parenchyma was also found. These findings indicate that living conditions at both sites were suboptimal for the examined species, with soluble toxicants potentially contributing to the observed tissue alterations. Analyses of histological alterations in the tissues tested and of antioxidant enzyme activities, such as peroxidase and superoxide dismutase, in fish blood may reflect varying levels of pollution across bays, with higher levels in Streletskaya Bay than in Balaklavskaya Bay. The biomarkers examined could be used in future monitoring of water quality in the Sevastopol bays.

Bioactive properties of cuttlefish, Sepia pharaonis, ink extracted with different solvents

Patcharee Kaeoprakan — 2025-12-25

Cuttlefish ink, a multifunctional marine byproduct, has attracted increasing interest due to its bioactive properties and potential applications in the food, pharmaceutical, and other industries. This study investigated the antimicrobial activity, physicochemical characteristics, and biochemical composition of Sepia pharaonis ink extracted using various solvents. The well diffusion method revealed that isopropanol-extracted (IPA) ink exhibited the highest antibacterial activity (27±0.41?mm), while distilled water showed the lowest activity. Biochemical groups in ink and ink extract were identified by FTIR spectroscopy. The ink powder showed strong absorbance peaks followed by IPA, ethanol, and methanol, respectively. Different peaks of absorbance of ink powder and ink extracted with different solvents, indicating the presence of varying absorbance value peaks of phenolic, alcohol, and amine groups. Among the solvents, IPA exhibited absorbance peaks close to those of the ink powder. The FTIR transmittance was found to be significantly lower in the ink powder (76.2±0.04%) and in the ink extracted with IPA (83.81±0.03%). Proximate analysis indicated that ink powder contained higher levels of lipid (0.21%), ash (16.27±0.05%), and crude protein (45.99±0.72%) compared to ink extracts. The DPPH radical scavenging activity assay showed significantly higher activity in ink extracted with distilled water (66.21±0.12% at the concentrate test at 12.5 mg/mL) than with IPA (52.82±0.97% at the tested concentration of 1000 mg/mL). IPA demonstrated superior extraction efficiency, achieving an average yield of 101.31±0.51%. Regarding functional properties, the water absorption index (WAI) remained stable, while the water solubility index (WSI) increased significantly with longer mixing times, reaching a maximum value of 22.09±0.40 after 24 hours. These results demonstrate the potential of S. pharaonis ink, depending on the solvent type, to have a significant impact on the effectiveness and functionality of extraction. IPA serves as an effective solvent for ink extraction, exhibiting high absorption characteristics and a significantly larger antimicrobial zone, which indicates potent bioactivity. These findings suggest that IPA-extracted ink possesses promising potential as a natural antioxidant. Ink powder and ink extract have the potential to be implemented, and their commercial viability and safety can be evaluated in the future for biomedicine applications.