Heavy metal (As, Cr, and Pb) contamination and associated human health risks in two commercial fish species in Bangladesh.

Contamination of fish with metals is a worldwide consumer safety concern. In this study, three metals such as arsenic (As), chromium (Cr), and lead (Pb) were measured in two commonly consumed fish species Oreochromis niloticus (Tilapia) and Pangasianodon hypophthalmus (Pangasius) that are commercially farmed. The concentration of the metals studied was found within the permissible limits. The concentrations of As, Cr, and Pb in tilapia fluctuated, ranging from not detected (ND) to 0.114 mg/kg, ND to 0.009 mg/kg, and ND to 0.085 mg/kg, respectively. For Pangasius, the concentrations were in the range of 0.014 to 0.118 mg/kg for As, ND to 0.02 mg/kg for Cr, and ND to 0.047 mg/kg for Pb. Hierarchical clustering revealed that As was possibly taken up by leachate and groundwater, while Cr and Pb were from contaminated feed. The results of the calculations for estimated daily intake, target hazard quotient, hazard index, and carcinogenic risk made it clear that consumption of the fish studied does not have a significant adverse effect on consumer health. In conclusion, the contamination levels of farmed tilapia and Pangasius sold in the study area are within acceptable limits, but regular monitoring is required to ensure safe production.

Acidification scenario of Cox's Bazar coast of the Bay of Bengal, Bangladesh and its influence on fish larvae abundance.

Ocean acidification is caused mainly by atmospheric carbon dioxide stored in the ocean. Ocean acidification is considered a major threat to aquatic life, and how it influences the abundance of marine fish larvae is still unclear. This research was designed to measure the current ocean acidification scenario of the Cox's Bazar coast of the Bay of Bengal, Bangladesh, and its probable influence on the abundance of fish larvae. Three research stations were selected: Bakkhali river estuary, Naf river estuary, and Rezu Khal. Monthly sampling was done, and larvae sample was collected from the surface water column (depth: 0.5 m) using a bongo net. Water parameters such as temperature, salinity, total alkalinity, and pH were determined using laboratory protocol. The seacarb package of the R programming language was used to determine ocean acidification factors. The Bakkhali river estuary showed the highest partial carbon dioxide (143.99 ± 102.27 µatm) and the lowest pH (8.27 ± 0.21). A total of 19 larvae families were identified, and the highest larval count was found in Rezu Khal (390 larvae/1000 m3), while the lowest was found in the Bakkhali river (3 larvae/1000 m3). Clupeidae, Myctophidae, and Engraulidae comprised more than 50% of the identified larvae. Blenniidae, Carangidae, Clupeidae, Engraulidae, and Gobiidae were found in all three seasons. Most of the larvae families showed the highest mean abundance under less pCO2. A negative correlation was observed between larvae and acidification factors such as pCO2, HCO3-, and dissolved inorganic carbon (DIC). The study revealed that acidification parameters of the Cox's Bazar coast were not in an acute state for the aquatic organisms' survival, but fish larvae abundance could be declined with raises in the partial carbon dioxide. The results of this study may aid in developing a management plan for conserving Bangladesh's marine and coastal fish.

Enhancement of body coloration of sword-tail fish (Xiphophorus helleri): Plant-derived bio-resources could be converted into a potential dietary carotenoid supplement.

The effects of natural plant-derived carotenoid sources on body coloration and growth performance of Sword-Tail Fish (Xiphophorus helleri) were investigated using four different dietary treatments; Commercial Feed (CF), China Rose Flower (CRF), Marigold Flower (MFF), and Carrot (CAF). CF was used as the control treatment without a natural source of carotenoids. The sources were mixed with feed (15 g/100 g) during the diet preparation. Fish were fed with four treatments twice a day for eight weeks, and then sampling was done weekly. A total of 96 fish were used for the experiment, and the mean initial weights were 3.314 g. MFF-treated fishes showed better growth performance in terms of mean weight, length and Specific Growth Rate (SGR), and carotenoid gain than the other treatments. The lowest Food Conversion Ratio (FCR) was also observed in the MFF-treated fish. The study suggested that marigold flower mixed feed could increase the body coloration and boost the growth performance of sword-tail fish and may be manufactured.