Md Aklakur, Subham Bakli, Parmanand Prabhakar and Ashutosh D Deo

The use of aqua feed in semi-intensive and intensive culture practices has raised several issues, like high organic load and altered nutrients in the culture environment, effluent to the natural aquatic ecosystem, the prevalence of diseases, and altered water quality parameters eutrophication, etc. and finally leading undesired heavy algal bloom. Later, the system triggers a chain of issues such as reduced dissolved oxygen level, diurnal fluctuation of fundamental water quality parameters, and stress to the culture animals. The situation aggravates when such blooms are caused or dominated by cyanotoxin-rich blue-green algae and have a harmful impact on fish physiology. The sub-lethal levels of cyanotoxins may reduce growth and alter feed performance efficiency. Therefore, the cumulative impact of reduced dissolved oxygen, altered fundamental water quality parameters, and presence of cyanotoxins even at the sublethal level may result in poor feed performance. The cyanobacterial blooms can look like foam, scum, or mats in culture ponds and may float on the surface or near dyke of the water's surface. According to their toxicological targets, cyanotoxins are classified as hepatotoxins (microcystins, nodularins, cylindrospermopsin), neurotoxins (anatoxin-a, saxitoxins), dermatotoxin (irritants), cytotoxins (aplysiatoxin, Lyngbyatoxin-a), and endotoxins (irritants) (lipopolysaccharides). The implementation of effective mitigation strategies such as chemical, biological, and farmer's awareness approaches may be the most realistic; however, the nutritional measure to overcome the aquaculture incidence of cyanobacterial bloom and associated lethal and sub-lethal impact in aquaculture needs special attention in relation on the impact on growth and feed efficiency.

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