Fisheries and Aquatic Sciences

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.

Sabah tuz Zohora, Shahida Arfine Shimul, Saifuddin Rana, Antar Sarkar, Sui Naing Aye Marma Milky, Khing Khing U Marma, Kaji Mohammad Sirajum Monir, Farhan Azim, Tapos Kumar Chakraborty and Sk. Ahmad Al Nahid. J Ecol Environ 2024;48:. https://doi.org/10.5141/jee.24.016

The distribution of fish larvae in estuaries is crucial for comprehending the functioning of these ecosystems and their role as nursery grounds for marine fish species. Data regarding larval fish assemblages in the coastal waters of Bangladesh are currently scarce. This study examines the spatial and seasonal dynamics of larval fish communities in these waters using a two-year sampling effort with a bongo net. This study investigates the diversity, abundance, and distribution of larval fishes at four sites (Bakkhali River Estuary, Moheshkhalipara, Naf River Estuary, and Rezu Khal Estuary) on the southeastern coast of Bangladesh. A total of 10,387 fish larvae representing 25 families were identified. Clupeidae (42.9%), Engraulidae (35.5%), Ambassidae (10.1%), Myctophidae (2.1%), and Gobiidae (1.9%) were the five most dominant families based on the larval catch composition. Marked seasonal differences in the larval fish abundance were observed. However, these differences were not observed when comparing the four sampled sites. Additionally, the correlation between environmental variables and the larval abundance indicated that salinity negatively influences (p < 0.001) the larval fish abundance. This is the first comprehensive investigation of larval fish assemblages in the coastal waters of Bangladesh. The findings of this study enhance our understanding of the nursery habitat requirements for the early development stages of both migratory and resident species in subtropical coastal waters, providing valuable information for potential applications in management and conservation efforts.

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 pCO_2. 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.