No abstract

Earlier research has mostly focused on the impacts of stocking density on fish growth, yield, and survival rate; however, knowledge of the effects of stocking larger-sized fish, particularly Nile Tilapia, is lacking. This type of research is critically important for increasing food security, achieving sustainable goals, and facing the challenges of climate change in the near future. Therefore, we investigated the effects of initial stocking body sizes of Nile Tilapia (Oreochromis niloticus) on water quality, growth performance, and economic yield in tropical riverine cages for 120 days in two culture cycles. Nile Tilapia of three different body sizes (34.06 ± 0.22 g, 10.98 ± 0.09 g, and 5.47 ± 0.04 for the first cycle and 33.85 ± 0.01 g, 11.07 ± 0.05 g, and 5.38 ± 0.06 g for the second cycle, indicated as T1, T2, and T3) were stocked in the culture treatments where unique stocking density and feed rations were maintained. The results revealed that water quality parameters did not differ significantly (p > 0.5) and were within a suitable range for Nile Tilapia culture. Treatments with larger-sized fish demonstrated a higher growth performance. The stocking fish size of 34.14–34.71 g was found to be the best among the three treatments regarding growth performance and economic return. As a result, except for T1 and T2 at a rural site and T1 at a semi-urban site, all of the treatments had negative allometry (b < 3.0), indicating that larger-sized fish and the rural site of the river are more suitable for cage culture. The rural site was found to be more suitable, possibly due to less variation of water parameters, more natural foods, and less pollution. The cages with larger-sized fish stocked had a higher net present value (NPV); internal rate of return (IRR); benefit–cost ratio (BCR); and rate on return (ROI), indicating that cage culture with larger-sized fish stocked is economically viable in the riverine system. Therefore, stocking the larger-sized fish (T1) and rural site are more suitable for cage culture.

Bangladesh, one of the top fish producers in the world, has rapidly been expanding its annual fish production. However, the COVID-19 pandemic and related preventative measures have had a substantial impact on the nation’s fishing sector. In this study, a survey was performed in the Brahmanbaria subdistrict of Bangladesh to assess the impact of COVID-19 and the subsequent efforts made by the Department of Fisheries (DoF), Bangladesh, to mitigate the negative impact on the culture and capture fisheries. The socioeconomic profile of fishery stakeholders for the years 2019, 2020, and 2021 was used to assess the impact of the COVID-19 pandemic situation on fish farming, fish hatcheries, fish nurseries, the fish feed industry, and the dry fish industry. Data analysis showed that the COVID-19 pandemic had a negative impact on the income of fishery stakeholders and their livelihoods. The income of fish farmers decreased by 47.49% in 2020 as compared to the base year of 2019 but increased by 129.34% in 2021, showing the effects of COVID-19 and mitigation efforts. Transport and movement restrictions adversely affected the culture fisheries while favouring capture fisheries with an increased annual catch. To counter or reduce most of those issues, the DoF, Bangladesh, took necessary steps, such as constructing a virtual control room and engaging the fishermen in some unique activities. Fishermen and other stakeholders benefitted because of farm visits, online training, improved interdepartmental coordination, monitoring of fish-selling marketing channels, activation of the FIAC (Farmer’s Information and Advice Centre), and women’s engagement through the provision of subsidies and loans. The DoF constructed fish sanctuaries and implemented law enforcement in 2020 and 2021 to safeguard the habitat for small indigenous species (SIS). These actions might have improved the stakeholders’ income and the post-pandemic scenario by increasing fish productivity. However, further study is recommended on the effective mitigation measures for drawing a clear conclusion.