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Two field trials were conducted in Northern Thailand from 2018 to 2020 to determine the best manual harvesting method for maximizing seed yield and seed quality of two Urochloa ruziziensis cultivars, cv. OKI-1 and cv. Br-203. Four manual seed harvesting methods were implicated in a randomized complete block design with four replicates. The four methods were as follows: knocking seeds from seedheads into a nylon net receptacle and collecting them once every day (T1); knocking seeds from seedheads into a nylon net receptacle and collecting them once every three days (T2); allowing ripe seeds to fall into a nylon net sheet that was stretched as a receptacle beneath the seedheads and collecting seeds once every five days (T3); and covering the tied seedheads with a nylon net bag and collecting seeds once every five days (T4). The highest pure seed yield was obtained from T3 in cv. Br-203 (333.11 kg/ha), as well as the highest trend in cv. OKI-1 (534.67 kg/ha). T3 produced 22–46% and 11–27% more pure germinated seed yields than the other methods in cv. Br-203 and cv. OKI-1, respectively. As a result, T3 was recommended for higher seed yield, convenient seed harvest, and reduced manual seed harvest time. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the seasonal and spatial variations in water quality parameters and determine the main contamination sources in the Shari-Goyain River, Bangladesh. Therefore, surface water was sampled monthly from six sampling sites, where six water quality parameters were evaluated. Data were analyzed by applying the Canadian Council of Ministers of the Environment (CCME) water quality index (WQI) and multivariate statistical methods. The results reveals that most of the examined water quality parameters crossed the acceptable range, and significant variations were observed spatiotemporally (p < 0.05). Based on the CCME WQI value, the water quality of the river is classified as poor to marginal with a score range between 33.40 and 51.30. This range of values demonstrates that the river's water quality is far from desirable for aquatic life and that it is being impacted and deteriorated by external drivers. Principal component analysis (PCA) retained two principal components (Factors 1 and 2), explaining about 79.17% of the total variance in the studied parameters and identified acidic pollution sources. Cluster analysis also reveals relative differences in water quality throughout sites and seasons, which supported the CCME WQI and PCA. Finally, Kruskal-Wallis one-way analysis of variance by ranks has identified coal mine drainage (CMD) as the main pollutant source for the Shari-Goyain River. In order to mitigate the CMD impact on land and water, different nature-based solutions are proposed, particularly passive mine water treatment approaches through constructed wetlands that could also mitigate the transboundary waters problem. [ABSTRACT FROM AUTHOR]

This study evaluated the status of the well-being of wild Nandus nandus in the Kawadighi Haor through morphometric and gastrointestinal indices and local people's perceptions. Basic macroscopic morphology of the gastrointestinal tract (GIT), the viscera somatic index (VSI), the hepatosomatic index (HSI), the condition factor (K), length–weight relationships, and gut histology were analyzed from the regular commercial catch. The GIT morphology includes a tube-like esophagus, a tapering stomach, a tubular intestinal region, and a rectum, all of which have clinically normal shapes and conditions. VSI and HSI values fluctuate throughout the year, indicating the periodic variation of food content and availability in the ecosystem. The condition factor (K) was generally stable, with minor deviations in December. The mucosa, submucosa, muscularis, and serosa were identified from the stomach of N. nandus and showed normal histological characteristics. There were numerous proliferated villi in the tunica mucosa, but no histopathological abnormalities were found in the gut. These findings suggest that the current population of N. nandus in the Haor is in a favorable condition. However, local people reported some potential threats that might be a concern for the long-term survival of this species. The results of the present study will be useful for effective and sustainable stock management of the N. nandus fishery in the Kawadighi Haor and other floodplain ecosystems. [ABSTRACT FROM AUTHOR]

The Halda River and Haor basins are considered unique breeding habitats for carps in Bangladesh. The purpose of the study was to evaluate the natural spawning environment of carp species, with an emphasis on the hydrological conditions of the Halda River, the Surma River, and Tanguar Haor. This study, which covers the years 2021 and 2022, considered two spawning seasons. The results revealed that temperature, total dissolved solids (TDS), salinity, turbidity, conductivity, and pH were significantly different in the Halda River to the Surma River and Tanguar Haor. However, sudden rainfall and upstream runoff in 2021 were deemed as major factors causing an increment in TDS and electrical conductivity. The water pollution index was excellent in the Surma River and Tanguar Haor, and good in the Halda River. The study reported moderately reduced IMC fry production in 2021 because of inconsistent turbidity, high conductivity, and increased salinity which interrupted the ideal spawning habitat. However, in 2022, the spawning environment was favorable in the Halda River, while the Surma River and Tanguar Haor were considered to be comparatively favorable in both years. Differences were also found in the climatic and meteorological conditions, which revealed uneven rainfall, higher temperatures, decreasing water discharge, and low water levels. The meteorological data also revealed that the overall rainfall showed a decreasing trend for all sites in the last 20 years causing an interrupted water discharge. It was discovered that the amount of carp spawn obtained in the Halda River was greater than that obtained in the Surma River and Tanguar Haor. In terms of hydrological conditions and spawning performance, the Surma River and Tanguar Haor were reported to have significant differences, which may be due to their geographical location. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Two field trials were conducted in Thailand to determine an appropriate closing cut date (CCD) and rate of nitrogen application (N-rate) to maximize seed yield and seed quality of the two novel cultivars (cv.) of Urochloa spp. (Synonym Brachiaria spp.), cv. 'OKI-1' (an open-pollinated tetraploid Urochloa ruziziensis (R. Germ. and C.M. Evrard) Crins originated from cv. 'Miyaokikoku-ichigou') and cv. 'Br-203' (U. ruziziensis cv. 'Miyaokikoku-ichigou' × U. hybrid cv. 'Mulato'). The following treatments were evaluated in this study: four CCDs (uncut, 15 June, 1 July, and 15 July) and four N-rates (0, 50, 100, and 150 kg/ha). The cv. 'OKI-1' showed somewhat differences in tiller number/m2 (TN), fertile tiller percentage (FTP), inflorescence number/tiller (IN/T) and spikelet number/raceme (SN/R) with the CCD, while the cv. 'Br-203' showed only in SN/R. However, TN and SN/R were highest for 15 June, and FTP and IN/T were highest for 1 July in cv. 'OKI-1'. The cv. 'OKI-1' showed the highest total seed yield (TSY), pure seed yield (PSY), and pure germinated seed yield (PGSY) for 1 July, followed by 15 June, and the cv. 'Br-203' showed the highest TSY, PSY, and PGSY for 15 July, followed by 1 July. Nitrogen (N) fertilization showed a negative effect on TSY for both the cultivars due to the higher N content in the soil. Withholding N fertilizer, a CCD in late-June to early-July and early-July to mid-July is recommended for cv. 'OKI-1' and cv. 'Br-203', respectively. [ABSTRACT FROM AUTHOR]