This study was designed to elucidate the effects of arsenic (As) on the morpho-behavior, growth development and molecular mechanisms of a commercially important fish, rohu carp, Labeo rohita, in Bangladesh. Fish fry with an average weight of 387.5 ± 169.25 mg and an average length of 3.35 ± 0.37 cm were collected from a local hatchery in Mymensingh, Bangladesh and acclimatized for a week in the Department of Fisheries, University of Dhaka before starting the exposure with arsenic. Fishes were exposed for a period of 14 days with three treatments of NaAsO₂, namely treatment 1(T1)—2.5 mg/L; treatment 2 (T2)—15 mg/L; and treatment 3 (T3)—30 mg/L, along with a control (C)—0.0 mg/L, with three replicates. These concentrations were determined based on the LC₅₀ value for 96 h measured for this experiment. This study revealed remarkable morphological abnormalities and deformities in arsenic-exposed rohu carp. In fish exposed to 30 mg/L, caudal fin erosion was a frequent deformity. There was no significant difference in RNA:DNA ratio among the treatments. The overall weight of fish was decreased as the concentration of arsenic was increased. The T3 fish had a statistically significant negative weight gain (−0.05 ± 0.07 g), but the other treatments (T1 and T2) and control fish had no significant weight gain. Different types of histopathological changes were observed in the gills and intestines of arsenic-treated fish. Necrosis and severe damages were found in the secondary lamellae of gills at the highest arsenic concentration (30 mg/L). Epithelial lifting, irregular shape and damages in the gill raker were also observed in the primary lamellae of the gills for the same treatment. In this study, the expression of heat shock protein (HSP 60) and metallothionein (MT) genes was assessed by qPCR, and these genes were upregulated in different treatments compared to controls. The findings of the present study suggest that arsenic pollution significantly changes the morphology, behavior, growth, development, histopathology and molecular mechanisms of this economically important fish, rohu carp, in Bangladesh.

Complete mitochondrial DNA genome annotation of an ecologically and commercially important fish species Cirrhinus cirrhosus was executed with next-generation sequencing (NGS) for nucleotide and phylogenetic analyses. The findings of this study showed that the Cirrhinus cirrhosus mitochondrial genome contained 16,593 bp, including 13 protein-coding genes, 2 ribosomal RNA genes, 22 tRNA genes, and a D-loop region. The overall base composition was 32% adenine, 25% thiamine, 16% guanine, and 27% cytosine. This mitochondrial DNA exhibits an AT biasness, with 56% AT content in its genome. Significant fluctuations were identified in the AT and GC skew values of the ND6 gene, indicating that the selection and mutation forces acting on this gene might be different from those acting on other genes. The Ka/Ks ratios of most protein-coding genes were less than 1, indicating very strong natural selection pressure. Phylogenetic analysis of Cirrhinus cirrhosus with Cirrhinus mrigala and Bangana tungting suggested a closer evolutionary relationship among these species, which might have shared a more recent common ancestor. It has been also found that the genera Labeo and Cirrhinus are not monophyletic.

Transcriptome differences between wild and hatchery‐reared Gibelion catla collected from Halda (HL) and Padma River (PD) as wild and a hatchery (HR) population in Bangladesh were identified in this study. A total of 6780 differentially expressed genes (DEGs) in HL compared to HR indicated significant variations in gene expression consistent with habitat‐ambitious transcriptional divergence. Gene ontology and KEGG pathway revealed that HL was characterized by enhanced growth and energy‐related processes, including ribosome pathways, ATP biosynthesis, cell cycle regulation, and oxidative phosphorylation compared to HR and PD. Conversely, PD showed enrichment in the nucleotide, cofactor and carbohydrate metabolism pathways, suggesting higher metabolic efficiency under natural environmental conditions. In contrast to wild populations, HR was enriched by endocrine, immune and stress‐related pathways, including ATPase regulatory molecular function and pathogen‐associated signalling, suggesting elevated physiological stress in the hatchery environment. Overall, wild populations showed enhanced metabolic efficiency and growth, while the hatchery population displayed reduced metabolic performance and heightened stress responses. These findings showed habitat fragmentation influenced the growth, metabolism and stress response in both wild and hatchery population, where the different environmental factors shape the population's genetics and different biological pathways, which made the wild population unique and more suitable for improving breeding programs, boosting aquaculture productivity and ensuring the aquaculture sustainability of this important fish species in Bangladesh.

Biscuits are widely consumed and serve as an effective vehicle for nutritional fortification due to their convenience, acceptability, and extended shelf life. This study is aimed at evaluating the nutritional, bioactive, microbiological, and sensory properties of biscuits formulated with tilapia ( Oreochromis niloticus ) fish powder (TFP) and jackfruit ( Artocarpus heterophyllus ) seed flour (JSF). Four formulations were prepared: control (C1), 5% TFP (T1), 10% JSF (T2), and a composite formulation (T3) containing T1 and T2. The incorporation of TFP and JSF resulted in increased protein, lipid, mineral, and dietary fiber contents compared with the C1 formulation. The amino acid profile indicated improved levels of both essential and nonessential amino acids in fortified samples. JSF‐enriched biscuits exhibited higher total phenolic content and antioxidant activity, whereas microbiological analysis indicated acceptable safety levels during storage. Sensory evaluation suggested that the T3 was the most preferred in terms of overall acceptability. This study represents a preliminary investigation based on a limited number of independent experimental trials. Due to the exploratory nature of the work and absence of biological replication, the findings should be interpreted as indicative rather than conclusive. Further studies incorporating independent experimental replication are required to validate these results.

Morphological and genetic diversity of three wild zebrafish populations in Bangladesh (Rangpur, Netrokona, and Cumilla) were elucidated using DNA barcoding and Random Amplified Polymorphic DNA (RAPD). Morphometric variation was minimal therefore, RAPD profiling and DNA barcoding were also used. Total 236 bands, including 29 polymorphic bands and 2 unique bands in RAPD showed 14.09% polymorphism indicating a low genetic diversity among them. Genetic distances were ranged from 0.0048 to 0.1031, with the highest genetic distance between Rangpur and Netrokona populations. DNA barcoding showed 99% similarity to Danio rerio from the GenBank, and multiple sequence alignment confirmed high genetic similarity (99.41) among these populations. Phylogenetic analysis showed these three zebrafish populations were grouped into distinct clusters, supporting the presence of genetic structure across populations. These information provides an essential reference data for the conservation, management, and potential selective breeding of zebrafish. The findings of this research also emphasize the efficacy of DNA barcoding and RAPD as complementary methods in the study of population genetics.