The analytical experiment was executed to present detailed reports on the concentration of heavy metals (nickel, iron, zinc, manganese, chromium, lead, and cadmium) in farmed shrimp, Penaeus monodon and its concomitant human health risks upon consumption. A total of 147 farms from six sub-districts of Khulna were selected for sample collection and concentration of heavy metals were determined by Atomic Absorption Spectrometry (AAS) method, following electro-thermal heater digestion. Ni and Cr were found considerably below the detectable limit (BDL) in four sub-districts, while Cr found in shrimps from Rupsa and Paikgacha were far higher than the maximum recommended limit defined by FAO and WHO. The average concentrations of Fe and Mn in all sub-districts crossed the recommendations, whereas average concentrations of Zn, Ni, Cd, and Pb were within the recommendations. Regardless of sampling site, target hazard quotients (THQ) of more than 1 contributed by Fe confirmed higher level of hazard index (HI), indicating potential human health risk. Fortunately, no heavy metal or their additive effect found to offer lifetime potency of carcinogenesis upon consumption of these shrimps. Therefore, probabilistic non-carcinogenic human health risk from Fe contamination necessitates stringent monitoring and controlling of this metal from different sources to farms.

The use of nanotechnology in food production systems is being investigated globally, though there is limited research on its effect on fish nutrition. Therefore, this study aimed to identify the effects of silica nanoparticles (NPs) on the nutrition and physiology of tilapia, Oreochromis niloticus. Four isonitrogenous diets (300 g/kg crude protein) with NPs (0, 1, 2, and 3 mg/kg diet) were fed to fish (6.52 ± 0.20 g) in a recirculatory aquaculture system for 56 days. Throughout the study period, the effects of silica NP on survival rate, blood cell count, hemoglobin (Hb) level, condition factor (CF), and final product composition (except lipid content) were insignificant. However, growth performance and feed efficiency increased with an increasing level of silica NP, up to 2 mg/kg, and then decreased. This increase was due to the highest apparent protein digestibility and dry matter digestibility when fish were fed silica NP at 2 mg/kg. However, fish at the early stage showed better performance in all dietary groups than in later. Blood glucose (BG) content and histology of the kidney revealed that fish were stressed when a 3 mg/kg silica NP was used and they adapted through excessive excretion via expanded glomeruli. Though no significant effect on villi length was observed, silica NP increased the surface area widening the villi of the gut along with the number of goblet cells in the intestine significantly, when supplemented at a level of 2 mg/kg. The bioaccumulation of silica shows that incorporating silica NP in the fish feed will not compromise human health safety upon consumption. Although silica NP at 1 mg/kg and 3 mg/kg yielded some improvements to growth and final product quality, a 2 mg/kg silica NP generated the best results in all measured parameters.

The study was carried out to obtain information on the present status and trend of finfish diversity of the Old Brahmaputra river, Bangladesh. Samples were collected directly from a professional fishing boat caught by different nets, traps and hooks from January 2019 to December 2019. Together with 4 exotic species, a total of 49 species under 6 families were recorded. Though a biodiversity index of 3.65854 and a dominance index of 0.030929 represent the richness of ichthyo-diversity within the river, Synbranchiformes and Tetraodontiformes were not reported throughout the study period. Linear regression analysis showed a positive correlation between water height of the river and monthly abundance of the species found. Catch composition of catfishes and snakeheads slumped while barbs showed triumph over previous findings. A majority of fish recorded were within the least concern category according to IUCN (2015) but portions also belonged to critically endangered, endangered, and vulnerable categories as well. Therefore, conservation measures must be infixed in the Old Brahmaputra river to hold the fish diversity in a sustainable state.

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.

The efficacy and suitability of dietary whole wheat flour supplementation was evaluated on the growth performance and survival of rohu (Labeo rohita). The study was conducted in 12 experimental aquaria at the Wet Laboratory, Department of Aquaculture, Bangladesh Agricultural University, Mymensingh. A total of 180 fingerlings of mean initial weight of 1.744±00 g were stocked at the same stocking density (268 fingerlings/m3). Four different treatments (T1, T2, T3 and T4) each with three replications were performed having different level of whole wheat flour such as 0% whole wheat flour (T1), 5% whole wheat flour (T2), 10% whole wheat flour (T3) and 15% whole wheat flour (T4). Feeds were supplied at 5% body weight twice daily in the morning at 9.00 am and in the afternoon at 5.00 pm throughout the study period. The rations were adjusted every week when new weights of the fish for various experimental aquariums were determined. At the end of the 63 days study period, the growth performance parameters such as mean final weight (g), weight gain (g), percent weight gain (%), specific growth rate (%/day) and the best feed utilization in terms of food conversion ratio were found highest at treatment 4 where fishes were fed with inclusion of 15% whole wheat flour and lowest was found at treatment 1 (fed with inclusion of 0% whole wheat flour). Water quality parameters were within the acceptable range and survival rate was found 100% in all treatment. Therefore, it can be concluded that treatment 4 (highest growth performance and survival rate of L. rohita with supplementation of 15% whole wheat flour containing diet) can be chosen by fish farmers for commercial culture of this species. Res. Agric., Livest. Fish.6(2): 345-352, August 2019