Aquaculture is probably the fastest-growing animal production sector in the Asia Pacific region. Aquaculture is predicted to continue increasing production by optimizing and intensifying existing aquaculture practices, increasing the number and type of farms, and exploring other environments. High levels of nutrients in effluent discharge to channels, rivers, or lakes may cause eutrophication and affect fisheries adversely, but in other cases, depending on dilution rates, effluents may be a beneficial addition of nutrients which boost natural productivity including fisheries. The important fish farming waste components are nutrients (dissolved and particulate) resulting from the metabolism of fish food (including natural food in the case of filter feeders such as mussels and clams), uneaten food, pseudofeces (in the case of filter feeders), escapees of farmed fish affecting the genetics of wild fisheries species, and residues of disease or parasite treatment chemicals. The environmental impact can be lessened by improved location of farms, improved farm management, or by physical and or biological treatment of the effluent. China is the leading country in aquaculture production and Vietnam and the Philippines are in the top 10. Aquaculture continues to grow in China and Vietnam but is presently declining in the Philippines because of reduction in seaweed production.