Microalga Chlorella vulgaris was cultured in different concentrations of normal molasses medium (NMM0.5 g/l, NMM1.0 g/l, and NMM1.5 g/l) to evaluate growth performance of the sugar mill byproduct as a low cost culture media and Bold basal medium (BBM) as control. Maximum growth of Chlorella vulgaris was found in NMM 1.0 g/l on 8th day of the culture followed by BBM, NMM 0.5 g/l and NMM 1.5 g/l. Similar findings were also observed in determining chlorophyll a content and optical density of C. vulgaris. Maximum cell growths 191.88 (Χ 105)/mL, chlorophyll a content 10.60 (mg/l) and optical density 2.15 were recorded in NMM1.0 g/l. Maximum SGR of cell was determined 0.56 (mg/day) grown in NMM1.0 g/l followed by 0.52, 0.52 and 0.48 (mg/day) in BBM, NMM0.5 g/l and NMM1.5 g/l, respectively. Chlorophyll a content and total biomass of Chlorella vulgaris followed the similar trend. Protein (46.49%) and lipid (14.18%) of C. vulgaris was detected significantly higher (P<0.01) in NMM1.0 g/l than that grown in BBM and other concentrations of NMM. The growth performance of the investigating molasses medium (NMM1.0 g/l) indicates that the molasses may be a good low cost culture medium ingredient source for C. vulgaris or any other microalga species.

Objective: The levels of five heavy metals—zinc (Zn), lead (Pb), chromium (Cr), cadmium (Cd) and arsenic (As)—in soil, water, feed and fish were investigated in this study at different culture phases (early, nursery, grower and harvest) of Oreochromis niloticus (tilapia). Unlike previous studies that focused on one or two sources, this research provides a comprehensive assessment across all major inputs during the entire production cycle, offering new insight into potential contamination pathways.Results: Heavy metal accumulation varied across sources and stages. Cr and As in sediment, and Cr in feed at the early stage, exceeded the permissible boundaries set by the Food and Agriculture Organization (FAO) and the World Health Organization (WHO). As the culture progressed, sediment showed increasing levels of Pb, Cr and As, all surpassing safe thresholds during the nursery to harvest phases. Feed also retained elevated Cr concentrations throughout. In contrast, water samples showed minimal contamination, and heavy metal levels in fish stayed within acceptable bounds for human consumption, although Zn and Cr gradually increased toward harvest. These findings suggest that sediment and feed are the primary sources of heavy metal accumulation, with water contributing minimally.Conclusion: The results indicate that tilapia raised in contaminated environments may not pose an immediate risk to consumers, but long‐term exposure through sediment and feed can lead to gradual metal build‐up. Therefore, routine monitoring of feed quality and sediment conditions is critical for safe aquaculture practices. These findings offer valuable guidance for hatchery operators and fish farmers, emphasising the need for preventive strategies to ensure the sustainable and safe production of tilapia.

Objectives: The prevalence and impact of the branchiuran copepod parasite Argulus japonicus on the snakehead fish Channa punctata were investigated in the southwestern region of Bangladesh.Methods: Parasitic infestation was examined to determine parasitological indexes including prevalence (%), mean intensity (MI), abundance (A), and index of infestation (IOI). Haematological parameters were also determined, along with morphological identification, clinical signs, and size grading of A. japonicus. In addition, histological alterations in the liver, kidneys, gills, and skin of C. punctata were examined.Results: Among 140 C. punctata individuals, 85 were found to be infested with a total of 245 A. japonicus parasites. Most of the parasites were located on the gill surfaces, around the eyes, and on the external parts of the body. The main physical features of A. japonicus were identified and documented during the observations. The haematological parameters showed variation across different experimental sites, and several clinical signs of infestation were observed. Four treatment methods for the elimination of A. japonicus were tested. Heat treatment (T₃) was found to be the most effective method of the four.Conclusion: This study highlights the serious health problems caused by A. japonicus infestation in C. punctata in southwestern Bangladesh.

Background: The presence of Klebsiella pneumoniae and heavy metals in tilapia ( Oreochromis niloticus ) has significant public health concerns. Objectives: This study was aimed at detecting antibiotic resistance genes in K. pneumoniae and determine the heavy metal contamination in tilapia. Methods: In total, 250 tilapias were aseptically collected from Khulna, Bangladesh, from 12 October to 12 November 2023. K. pneumoniae were isolated using real‐time PCR targeting 16S‐23S ITS , IntI, bla _CTX‐M , bla _TEM and bla _SHV genes. Disc diffusion assay and bivariate analysis were performed for investigating the antibiogram, with multivariable linear regression analysis for the potential predictors of multidrug resistance (MDR). Heavy metals were measured by atomic absorption spectrometry. Results: The overall prevalence of Klebsiella spp. was 35.6% (89/250). Out of 30 Klebsiella spp., 24 were positive for K. pneumoniae , which were highly resistant to tetracycline, ampicillin and ceftazidime. Bivariate analysis showed significant correlations between the antibiotics. MDR isolates were 70.83% (17/24), and the multiple antibiotic resistance index ranged from 0.08 to 0.7. Misuse or overuse of antibiotics was the potential predictor of MDR. Among 24 K. pneumoniae , 11 were positive for IntI , 15 for bla _CTX‐M , 8 for bla _TEM and 13 for bla _SHV . The concentrations of Cd and Zn were highest in Chitrali Bazar, Cr and Fe in Gallamary Bazar and Pb in Dumuria. For Fe, target hazard quotient values revealed a higher level of hazard index, where target cancer risk values exceeded the recommended value (<10 ⁻⁴ ). Conclusions: The prevalence of K. pneumoniae and heavy metals in tilapia in this study should be a matter of concern to public health risk management.

The present study aims to assess the levels of selected heavy metals—zinc (Zn), chromium (Cr), cadmium (Cd), lead (Pb), and arsenic (As)—in commercial fish feeds obtained from 17 different feed companies in Khulna district, Bangladesh. The collected feed samples were analyzed at the Interdisciplinary Institute for Food Security (IIFS) Laboratory using Graphite Furnace Atomic Absorption Spectrometry (GFAAS) to determine the concentrations of the targeted heavy metals. The results showed that zinc concentrations varied among the feeds, ranging from 52.73 ppm in Aman Feed Grower to 95.20 ppm in Mega Grower Feed. All values were below the maximum permissible limit of 100 ppm set by the WHO and FAO. In contrast, chromium concentrations were of greater concern. The highest level was found in Agroho Grower Feed (6.33 ppm), while the lowest was in Lily Starter Feed (0.43 ppm). Chromium was not detected in Mega Grower Feed. Cadmium, lead, and arsenic were not detected in any of the samples, indicating a relatively low risk from these toxic metals in the feeds tested. Zinc levels in the tested feeds are within safe limits; however, chromium concentrations substantially exceed international safety standards, highlighting the need for continuous monitoring to ensure fish and public health safety.

This research was carried out to evaluate the effect of copra meal (Coconut oilcake) as a partial replacement of soybean meal on the growth and survival rate of the Nile tilapia (Oreochromis niloticus) fingerlings. Four treatments (T1, T2, T3, and T4) were designed, each with three replicates. Copra meal was used to replace soybean meal at different inclusion levels: 0% in T1 (control), 25% replacement in T2 (7.5% copra meal in the diet), 30% replacement in T3 (9.0% copra meal in the diet), and 35% replacement in T4 (10.5% copra meal in the diet). Water quality parameters were within the acceptable range during the study period. Final weight (g), weight gain (g), percent weight gain (%), feed conversion ratio (FCR), specific growth rate (%/day), protein efficiency ratio (PER) and daily growth co-efficient (DGC) varied from 14.11 to 18.92g, 12.47 to 17.28g, 760.36 to 1053.35%, 1.34 to 1.89, 4.3 to 4.89, 2.69 to 1.88 and 0.25 to 0.35, respectively. According to the results of the current study, 35% replacing of copra meal/kg (10.5% used in diet) in place of soybean meal resulted in the best growth performance and survival rate of tilapia.