The present study investigated the seasonal variations of physicochemical and sediment parameters in the Manakudy Estuary, a critical tropical estuarine ecosystem in India. Key water quality variables encompassing basic physicochemical properties, oxygen dynamics, inorganic carbon, major ions, primary productivity, and nutrient regimes were analysed, as these collectively regulate estuarine biogeochemical processes and biological functioning. These parameters are essential as they collectively influence the chemical and biological environment of the estuary. Seasonal samples were collected from three selected sites across the estuary over a one-year period from March 2024 to February 2025, covering four seasons with triplicate sampling at each site. Descriptive statistics i.e., mean ± standard error (SE) were calculated based on replicate samples at each site and season to evaluate spatial and temporal variability. Two-way ANOVA revealed significant effects of season and site on several physicochemical and soil parameters (p<0.001), indicating pronounced spatio-temporal heterogeneity in the ecological conditions of the Manakudy Estuary. Such variability reflects shifts in nutrient availability, oxygen balance, and productivity patterns, providing clear insights into the ecological condition and ecosystem health of the Manakudy Estuary and its vulnerability to environmental stressors.

Despite its aquaculture potential, Asian seabass (Lates calcarifer) has not yet been adopted for cage culture in Bangladesh. This pilot study aimed to assess the feasibility of cage culture of this species in coastal rivers of Bangladesh. A total of six cages (18 m3 each) were installed in a coastal river and each was stocked with 50 fish (7.70 ± 0.18 g). Three feeding treatments were applied: 100% live feed (live and/or trashed juvenile tilapia) (T1); 50% live feed with 50% formulated feed (T2); and 100% formulated feed (T3). The experimental fish were reared for 12 weeks and fed at 8% of their body weight during the initial 3 weeks and at 6% during the later weeks. Fish refused formulated feed. Survival in T3 (64%) was significantly lower compared to that in T1 (88%) or T2 (82%) but did not differ between T1 and T2. Mean specific growth rates (SGR) were 1.66, 1.12, and 0.90 % d–1; daily growth rates (DGR) were 2.20, 0.74, and 0.44 g, and weight gain (WG) values were 182.50, 61.10, and 36.50 g in T1, T2, and T3, respectively. SGR values significantly differed among the treatments. DGR and WG values in T1 were significantly higher than that in T2 or T3 but did not differ between T2 and T3. Results indicate that cage culture of Asian seabass in Bangladesh requires live and/or trash fish as feed, or else advances in domestication and artificial feed development.

Pesticides, an integral part of agricultural practices, contaminate aquatic bodies through surface runoff and leaching and threaten non-target organisms like fish. Synthetic pyrethroids, a widely used insecticide group have been shown to have detrimental effects on fish. Pethia conchonius, a non-target fish from river Teesta was used as a model organism to evaluate the detrimental effects of pyrethroid insecticide, cypermethrin on fish. The comet and micronucleus assays revealed cypermethrin-induced severe nuclear DNA damage showing three-fold decrease in % head DNA with a concomitant 70-fold increase in % tail DNA, and up to 21 times increase in MN frequency for SLC III at 96 hr exposure. The SOD, CAT, and GPx assays in gills and their mRNA expression analysis indicated down regulation of these anti-oxidant enzymes in a concentration and time-dependent response, with the lowest decrease being 4.2, 2.2, and 1.8-folds respectively for each of the enzymes at 96 hr of cypermethrin treatment in comparison to the control (p > 0.05). Subsequently, elevated levels of MDA in the gills of cypermethrin-treated P. conchonius further indicated increased oxidative stress and lipid peroxidation. Elevated oxidative stress and ROS levels can cause DNA damage and disrupt normal cell functioning, biochemical pathways, and cell cycle. The results indicated that cypermethrin is highly genotoxic and induces oxidative stress in the fish, supporting its hazardous effect on non-target organisms in aquatic ecosystems.

The trade of freshwater shellfish is growing but has received insufficient attention from researchers. In this study, we examined various aspects of shellfish harvesting (catch amount and composition, socio-economic profiles of shellfish collectors, distribution channels and perceptions of major stakeholder groups) over a six-month period (October 2023 to March 2024) in the largest wetland of Bangladesh, the Chalan Beel. The daily shellfish catch was higher during the low-water period (October – December; 10.7 ± 3.3 kg person–1) than during the dry period (January – March; 0.6 ± 0.2 kg person–1) (t-test: t = –32.4, p < 0.001). Catch composition varied significantly across groups (ANOVA: F = 10823, p < 0.001). Freshwater snails (primarily Pila globosa) contributed the most (70.1%) to the total catch, followed by mussels (primarily Lamellidens marginalis; 19.7%) and crab (Cancer pagurus; 10.2%). Three key actor groups involved in shellfish distribution were crab collectors, traders and consumers. Most collectors (65%), traders (54%) and consumers (89%) disagreed that shellfish are an important component of the aquatic environment. All traders and 96% of collectors agreed that shellfish collection and trade are profitable, whereas all consumers maintained a neutral standpoint. All consumers agreed that shellfish are good food, while the majority of collectors (93%) and traders (93%) remained neutral. Additionally, all consumers and most collectors (67%) and traders (73%) supported harvesting shellfish from other aquatic ecosystems. The results of this study are expected to be useful in formulating appropriate policies for wetland and resource management.

Shellfish are important components of aquatic ecosystems, including freshwater wetlands. In this study, we examined shellfish species diversity and their utilisation by humans in the largest wetland of Bangladesh, the Chalan Beel. Through systematic, standardised field surveys, we recorded 19 shellfish species, including 14 molluscs and five arthropods. The global conservation status of the recorded species was retrieved from the IUCN Red List database, and all were classified as Least Concern. Among the 19 recorded species, the majority—11 species—are used for human consumption, followed by use as animal feed (e.g. for fish, shrimp and poultry) (eight species), as fish bait (eight species), in traditional medicine (eight species), as ornamental species in aquariums (two species) and in freshwater pearl culture (one species). Six threats to shellfish populations have been identified: (i) harvesting for commercial trade, (ii) use of illegal fishing gear, (iii) construction of irrigation canals, (iv) destructive ‘katha’ fishing methods, (v) changes in land use and (vi) duck farming in the wetland. The findings of this study will serve as baseline data for future research. To ensure a sustainable supply of shellfish for human consumption and animal feed, we recommend focusing on shellfish aquaculture rather than harvesting from the wild. This approach may be particularly beneficial for mollusc populations. We also advocate for the formulation of conservation regulations for shellfishes in the country.

In India, diversification in shrimp culture area is required due to climate changes, fluctuation in resources, and its marginal profit. Near Threatened pabda (Ompok bimaculatus) may be an alternative aquaculture species which can fulfil all the demands for the shrimp farmers. In this study, healthy, disease-free, 12-month reared brood fishes were collected and stocked in eight tanks (8×4×2 feet) sex wise (130 pairs) with shower facilities. Synthetic hormone was used to induce both male and female fishes at 0.3 and 0.6 ml (T1); 0.5 and 0.7 ml (T2) and 0.7 and 0.8 ml (T3) kg-1 body weight (bw) respectively, having 3 replicates for each treatment. Ovulation period (7 to 11 hours), relative fecundity (105.20±39.93 eggs g–1 bw of female), fertilization rates (67.37±20.73 to 75.88±24.84%), hatching rates (62.57±18.46 to 79.67±26.68%) and survival rates (55.01±14.93 to 65.62±19.91%) were observed. Among treatments, T2 exhibited better breeding performance but no significant differences with other treatments were observed. Important water quality parameters like temperature (28.27±1.68°C), pH (7.10±0.44), dissolved oxygen (4.25±0.37 mg L–1), hardness (210.96±9.31 mg L–1) and alkalinity (202.78±8.00 mg L–1) were also recorded during this experiment. After 48 hours of hatching, hatchlings were reared in aerated tanks for another four days with close observation and fries were harvested 24 days of rearing. From the present experiment, T2 exhibited best effective dose for successful induced breeding of pabda.

The Northeast India has several natural water resources that support a variety of aquatic fauna. However, many parts of the region have remained unexplored for ichthyofauna. Research on the diversity of fishes in large water bodies has received significant attention from many researchers in the region. In contrast, studies on small stream rivers are very scant. Therefore, the present study aims to record the diversity of fish fauna in the small stream Diring River of Baksa District, Assam. In this survey, 27 species of fishes were recorded from five study sites. The dominant family was Cyprinidae, comprising 48% of the total fish species. The conservation status of the majority of species was Least Concern (88.8%) followed by Near Threatened (3.7%) and Vulnerable (3.7%). However, conservation status of 3.7% of the fish species was not evaluated by IUCN. The Shannon diversity index ranged from 1.5 to 2.6, the evenness index from 0.84 to 0.98, and the richness index from 1.1 to 2.6, indicating a good status of ichthyofaunal resources in the study sites. Since there were no existing records on the fish diversity of the Diring River, this maiden study might serve as baseline information for further research.

This research presents primary evidence regarding the occurrence of Atherina boyeri in Kılıçkaya Dam lake. A total of 345 specimens were obtained from local fishermen during May to June 2023. The sampled fish displayed a length range between 50.30 and 94.24 mm and weight between 0.76 and 4.30 g. The study established the length-weight relationship (LWR) based on total length (TL) as W = 0.00002285 L2.7018 for females, W = 0.00003297 L2.6033 for males and W = 0.00002501 L2.6746 for the pooled individuals. The exponential value b of TL-W ratio was determined as 2.6746, indicating negative allometric growth in the species. The average condition factor (CF) was computed as 0.641 ± 0.067. This investigation not only provides initial and valuable insights into the presence of A. boyeri in Kılıçkaya Dam lake but also enhances the understanding of the diversity of aquatic ecosystem. The findings of this study offer practical guidance to local fishery management authorities and decision-makers aiding in the implementation of suitable fishery management strategies to ensure the sustainability of fishery resources.

Eleven fish species, namely Heniochus singularius Smith & Radcliffe, 1911; Entomacrodus vermiculatus (Valenciennes, 1836); Pomacentrus similis Allen, 1991; Myripristis berndti Jordan & Evermann, 1903; Myripristis seychellensis Cuvier, 1829; Sargocentron cornutum (Bleeker, 1854); Thalassoma lunare (Linnaeus, 1758); Pardachirus pavoninus (Lacepède, 1802); Paraplotosus albilabris (Valenciennes, 1840); Canthigaster papua (Bleeker, 1848), have been documented for the first time in Andhra Pradesh state of India associated with artificial reef and rocky shoreline habitats. Additionally, E. thalassinus has been recorded for the first time in India from this study. The study provides detailed descriptions of the diagnostic characteristics and distribution of these ten species. These findings highlight the richness of fish fauna along the Andhra Pradesh coastline of India.

The stock assessment of the threadfin beam, Nemipterus japonicus, collected from the Tha-Bawt-Seik of the Andaman Sea in Myanmar were analysed from January to December 2018. The purpose of this study is to evaluate the condition of the N. japonicus population. For all 1866 specimens, the asymptotic length (L∞), growth rate (K) and growth performance index (Ǿ) were 22.05 cm, 1.4 year–1 and 2.833 respectively. There were 4.89 year–1, 2.47 year–1 and 2.41 year–1 for the total mortality rate (Z), natural mortality rate (M) and fishing mortality rate (Z) respectively. The maximum exploitation rate (Emax) was 0.703, while the exploitation rate (Ecurrent) was 0.49. There were two main recruitment pulses in the pattern of continual recruitment. When the dry season began, threadfin beams became one of the principal species in Tha-Bawt-Seik. The outcomes of the study showed that while the N. japonicus stock is currently safe; there are signs of growth overfishing and any rise in the existing pace of exploitation is likely to exacerbate this issue.