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Plastic pollution is one of the pressing issues in freshwater ecosystems that may further contribute to coastal pollution. The present study aimed to address the state of macroplastics pollution in the Surma River system, Bangladesh. Six sampling sites were allocated in the river starting from upstream to downstream, water parameters and fin fish assemblage were recorded, and plastic debris was collected from each site. Afterward, macroplastics were categorized and weighed to measure their abundance. Previous data on rainfall, water discharge, and depth were aggregated to study the trend of river depth changes. A survey was conducted to identify the possible sources of plastic pollution in the river and awareness of the pollution. The results showed that Kazir Bazar (Site 4) and Beter Bazar (Site 5), comparatively contained poor water quality, diverse macroplastics categories, and higher macroplastics abundance. The water pollution index (WPI) also ranked the above sites as extremely polluted. Similarly, biodiversity indices revealed lower diversity at Site 4 and Site 5. The river depth analysis revealed that there was no remarkable tendency to change the depth. To conclude, the Surma River system is being polluted due to inadvertent plastic dumping. Contemporary awareness is highly required, and proper policies should be implemented to minimize the detrimental effects of macroplastics.

The rise of microplastics (MPs) as a significant environmental contaminant has raised concerns about their potential presence in aquatic ecosystems and food webs. The current study aimed to evaluate the properties and frequency of MPs in Bangladeshi commercial fish feed, a vital aquaculture sector component. Twenty‐one commercial fish feed samples representing three distinct grades (starter, nursery, and grower) and seven commercial formulations were tested. Standard digestion, density separation, and filtering techniques were used to extract MPs. The findings demonstrated that all the samples had extensive MPs contamination, with an average concentration of 9.23–14.27 MPs per gram of feed. Grower feeds have the lowest frequency of MPs, while starter feeds show highest MP abundance. The most abundant forms were fibers (45.44%), followed by fragments (36.30%) and microbeads (18.26%). The most frequently occurring colors were black (33.30%), transparent (27.37%), and blue (13.63%). The most dominant group of MPs was <300 µm (52.36%). Polystyrene (PS) and ethylene–vinyl acetate (EVA) were found to be the predominant polymers, making up 32.12% and 23.85% of the total MPs, respectively, based on Attenuated Total Reflection Fourier Transform Infrared Spectroscopy. Nitrile butadiene rubber (NBR) indicated low hazard, while low‐density polyethylene (LDPE) medium, polymethyl methacrylate (PMMA), polycarbonate (PC), and acrylonitrile butadiene styrene (ABS) indicated very high hazard. In addition, fish feed samples remained at low risk as specified by the Pollution Load Index (PLI). Given the possible dangers to fish health, human consumption, and environmental sustainability, this study emphasizes the urgent need for mitigation techniques to minimize MP contamination in aquafeeds.

Lead (Pb) is one of the toxins responsible for the deterioration of ecological health in aquatic environments. The present study investigated the effects of Pb(NO3)2 toxicity on growth, blood cell morphology, and the histopathology of gills, liver, and intestine of juvenile Nile tilapia, Oreochromis niloticus. A 30-day long aquarium trial was conducted by assigning three treatment groups T1 5.20 mg L−1, T2 10.40 mg L−1, and T3 20.80 mg L−1, and a control 0 mg L−1 following the 96 h LC50 of 51.96 mg L−1 from acute toxicity test. Overall growth performance significantly declined in all the Pb(NO3)2 treated groups and the highest mortality was recorded in T3. Behavioural abnormalities were intense in all the treatment groups compared to the control. Hepatosomatic index (HSI) values were reported as higher in treatment groups. Reduced nucleus diameter and nuclei size in erythrocytes were reported for T2 and T3 groups. Dose-dependent histological alterations were visible in the gills, liver, and intestine of all the Pb(NO3)2 treated groups. The width of the intestinal villi was highly extended in T3 showing signs of severe histological alterations. In conclusion, Pb toxicity causes a negative effect on growth performance, erythrocyte morphology, and affected the vital organs histomorphology of juvenile O. niloticus.

A 90‐day long indoor aquarium trial was conducted to assess the consequence of temperature on the growth, blood chemistry and histology of gill, intestine and liver tissues of Ompok bimaculatus juveniles. Homogeneous juveniles were randomly stocked into four different treatments of 20, 35 30 and 25℃ (room temperature as control), and these replications were marked as T20, T30, T35 and T25, respectively. Juvenile fish were fed with commercial diets at 5% body weight three consecutive times a day. Fish in T30 showed significantly higher growth performances and a higher percentage of specific growth rate (SGR%) in comparison to the control group in T25 (p < 0.05). However, no significant (p > 0.05) changes in SGR% were reported between T30 and T35 groups. Haematological analyses showed significant (p < 0.05) decreases in haemoglobin (Hb) and white blood cell (WBC) in T20 and T35 compared to control T25. Significantly higher Hb and WBC were observed in T30 among treatments. No significant changes (p > 0.05) in red blood cells (RBC) were observed between T25 and T30, while T20 and T35 showed significantly lower RBC. Histological analyses revealed that the liver and gill tissues were well‐shaped in T30 compared to distinctive pathology in other treatments. Again, the apparent formation of intestinal villi height was highest observed in T30 in comparison to other groups. It is concluded that the highest growth performance and physiological development of butter catfish would be obtained at 30℃ rearing temperatures. A 90‐day aquarium trial was conducted to evaluate the effect of temperature on the growth, blood chemistry and histology of vital organs in juvenile Ompok bimaculatus. Fish reared at 30℃ showed significantly higher growth performances, specific growth rate and haemoglobin and white blood cell counts in comparison to the control group at 25℃. Fish at 30℃ also revealed well‐structured histology in all studied vital organs. It is concluded that the highest growth performance and physiological development of butter catfish would be obtained at 30℃ rearing temperature.

Pb is one of the most extensively used harmful heavy metals in Bangladesh, and its occurrence in waters affects aquatic organisms significantly. The tropical pearl mussel, Lamellidens marginalis, was exposed to different concentrations (T1 21.93 mgL−1, T2 43.86 mgL−1, and T3 87.72 mgL−1) of Pb(NO3)2 and was evaluated against a control C 0 mgL−1 of Pb(NO3)2, followed by a 96 h acute toxicity test. The LC50 value was recorded as 219.32 mgL−1. The physicochemical parameters were documented regularly for each treatment unit. The values of % SGR, shell weight, soft tissue wet weight, and weight gain remained statistically higher for the control group in comparison with the treatment. No mortality was noted for control units, while a gradually decreased survival rate was recorded for the different treatment groups. Fulton’s condition factor was recorded as highest in the control and lowest in the T3 unit, while the condition indices did not vary between the control and treatment groups. The hemocyte was accounted as maximum in the control and T1, while minimum in T2 and T3. The serum lysosomal parameters also followed a similar pattern, and a significantly low level of lysosomal membrane stability, and serum lysosome activity was noted for T3 and T2 units in comparison to the control group. The histology of the gill, kidney, and muscle was well structured in the control group, while distinct pathologies were observed in the gill, kidney, and muscle tissue of different treatment groups. The quantitative comparison revealed that the intensity of pathological alteration increased as the dosage of Pb increased. The current study, therefore, indicated that intrusion of Pb(NO3)2 in the living medium significantly alters growth performance and hemocyte counts, and chronic toxicity induces histomorphological abnormalities in vital organs.

The apple snail Pila globosa is a widely distributed mollusc in tropical freshwater ecosystems, where it plays a crucial ecological role. This study examined the morphometric features, condition indices, and reproductive traits of P. globosa to gain insights into its population structure in the Ratargul Freshwater Swamp Forest, Bangladesh. Water quality parameters were recorded, and various morphometric measurements were analysed, including their correlations and seasonal variations. The mean values for shell length, shell weight, shell width, spiral length, base length, aperture length, aperture width, and soft tissue wet weight were 4.64 ± 0.97 cm, 38.29 ± 15.27 g, 3.56 ± 0.74 cm, 2.32 ± 0.51 cm, 3.33 ± 0.74 cm, 3.46 ± 0.64 cm, 2.01 ± 0.45 cm, and 18.05 ± 11.39 g, respectively. Linear regression analyses revealed strong correlations among length–length and length–weight parameters, indicating consistent growth patterns. Monthly frequency distributions showed distinct variations in shell size and form. The sex ratio was 1:1.23 (male–female), not significantly different from parity. Histological analysis during the rainy season revealed reproductive activity, including mature ova, previtellogenic and vitellogenic oocytes, and spermatogonia and spermatids. These findings enhance understanding of the species’ biology and its interaction with environmental conditions, offering valuable data for the conservation and management of freshwater mollusc populations in wetland ecosystems.

and tidal rivers of Bangladesh and India. In the present study, the reproductive biology of A. gagora was assessed in Meghna River system at Kushiara River. Length-weight relationship was found strongly correlated for male (r2 = 0.98), female (r2 = 0.97) and combined sex (r2 = 0.81), respectively. Chi-square tests revealed no significant difference between sex ratios round the year and not deviated from the expected value of 1:1 (%2 = 5.57) and the critical chi-square value calculated was 143.25. The fecundity found to be ranged from 43333.12±829.83 to 53948.81±1743.28 in April to August. The relationship of fecundity with ovary weight (r2 = 0.79), ovary length (r2 = 0.88), total length (r2 = 0.85) and total weight (r2 = 0.68) were found positively correlated. Monthly study of gonadosomatic index (GSI) revealed that the breeding season for this fish species may be between July to August with a single peak spawning month in August. Size at sexual maturity was estimated as 30.01 cm total length. Fulton's condition factor (K) value varied in both males and females and indicates that the overall health condition of both the male and female were excellent. Breeding season was found significantly correlated with rainfall, but not with other biological, meteorological, and hydrological parameters. Ovarian development of A. gagora was assessed macroscopically and three broad gonad developmental stages were identified. Maturity was specified based on the presence of green egg in the peritoneal cavity. These findings should benefit and improve the sustainable management and conservation of this species both in Bangladesh and its bordering countries.

Microplastics (MPs) are significant environmental pollutants that have rapidly garnered public attention due to their widespread presence and harmful effects on ecosystems and human health. While MP pollution in the coastal regions has been widely reported, their potential impacts on public health are still not fully understood. The current study examined MP contamination in nine commercially important fish and shellfish species collected from the coastal waters of Bangladesh, specifically from the Bay of Bengal. MP abundances (fiber, fragment, and microbeads) were evaluated in the gastrointestinal tract (GIT) and gills of fish and in the whole body of shellfish. Fibers were the most prevalent MP types found across the samples. In the case of gills, the highest abundance of MPs was found in Bombay duck, while the lowest was in pomfret. For GIT samples, hilsa showed the highest MP concentration, whereas the lowest was observed in bombay duck. Moreover, the highest level was observed in crabs, while the lowest was in squid ( p < 0.05), likely because crabs are benthic feeders exposed to sediment‐bound MPs, whereas squids are pelagic predators with lower exposure and more selective diets. Attenuated total reflectance Fourier transform infrared research revealed that the major polymer types were polymethyl methacrylate (43.33%), ethylene vinyl acetate (23.33%), nitrile butadiene rubber (1.67%), polypropylene (5%), polycarbonate (3.33%), acrylonitrile butadiene styrene (6.67%), nylon (5%), high‐density polyethylene (1.67%), polyvinyl chloride (6.67%), and polyurethane (3.33%). MP contamination in fish and shellfish was assessed using contamination factor and pollution load index values, both below 10, indicating low to moderate pollution levels. The polymer hazard index further categorized the identified polymer types into risk levels ranging from low to very high, highlighting potential ecological and health concerns. These results underscore the urgent need for effective environmental management and continuous monitoring to mitigate MP‐related risks.

Long-whiskered catfish Sperata aor is a freshwater catfish known for its supreme flesh quality and fast growth, whose captive-reared broodstock denotes a difficult challenge for aquaculture. The reproductive dysfunctions in long-whiskered catfish raised in tank conditions were observed by comparing tissue biochemical composition and ovarian histology of wild female broodstock. Sixty (60) female broodstocks were used in the current study, consisting of 30 reared at sandy-muddy soil tank bottoms in captive conditions and 30 wild individuals collected from the haor basin during the breeding season. The fish reproductive state was investigated using the biometric and reproductive parameters, biochemical composition and levels of amino acids in the different tissues, and histological analysis of ovarian development. Results revealed that the biometrical parameters of wild and captive female broodstocks exhibited no remarkable difference (p > 0.05). Nevertheless, the wild fish had remarkably higher (p < 0.05) GSI (8.73%), oocyte weight (0.45 mg/egg), and ripeness (27.08%) in comparison with captive-reared broodstock. The total length and body weight, body weight and ovary weight, ovipositor diameter and ovary weight, and GSI and HSI displayed a positive relationship with R 2  = 1, R 2  = 1, R 2  = 0.993, and R 2  = 0.973, respectively, for wild broodstock, while R 2  = 0.994, R 2  = 0.806, R 2  = 0.804, and R 2  = 0.896, respectively, for captive broodstock. Additionally, the proximate composition in oocytes and liver tissues in both broodstocks did not differ significantly (p > 0.05). However, two essential amino acids (EAA), i.e., lysine and phenylalanine, and two non-essential amino acids, i.e., glutamic acid and glycine, were highly significant differences (p < 0.05) in the oocytes and liver of wild broodstock compared to the captive-reared broodstock. On the other hand, the EAA, e.g., isoleucine, threonine, leucine, and arginine, were highly dominated in both wild and captive female brood oocytes and liver. The ovarian histological slides from each fish group showed three oocytes developmental stages that indicated the asynchronous-reproductive ovarian oocytes of this fish. This study may be useful to fully understand the factors affecting the spawning and reproduction of S. aor broodstock, crucial for management in captive conditions as well as conservation and protection for sustainable aquaculture management of S. aor .

To clarify the phylogenetic relatedness of rotaviruses causing gastroenteritis in children and adults, an epidemiologic investigation was conducted in Mymensingh, Bangladesh, during the period between July 2004 and June 2006. A total of 2,540 stool specimens from diarrheal patients from three hospitals were analyzed. Overall, rotavirus-positive rates in children and adults were 26.4 and 10.1%, respectively. Among the 155 rotavirus specimens examined genetically from both children and adults, the most frequent G genotype was G2 (detection rate: 54.0 and 47.6%, respectively), followed by G1 (21.2 and 26.2%, respectively), and G9 (15.9 and 9.5%, respectively). G12 was also detected in five specimens (3.2% in total; four children and one adult). Sequence identities of VP7 genes of G2 rotaviruses from children and adults were higher than 97.8%, while these Bangladeshi G2 viruses showed generally lower identities to G2 rotaviruses reported elsewhere in the world, except for some strains reported in African countries. Similarly, extremely high sequence identities between children and adults were observed for VP7 genes of G1, G9 and G12 rotaviruses, and also for the VP4 genes of P[4], P[6], and P[8] viruses. Rotaviruses from children and adults detected in this study were included in a single cluster in phylogenetic dendrograms of VP7 or VP4 genes of individual G/P types. Rotaviruses with two emerging types, G9 and G12, had VP7 genes that were phylogenetically close to those of individual G-types recently reported in Bangladesh and India and were included in the globally spreading lineages of these G-types. These findings suggested that genetically identical rotaviruses, including those with the emerging types G9 and G12, were circulating among children and adults in city and rural areas of Bangladesh.