My point? Quite clear I thought. Chicken waste is chicken poop, cow waste I cow poop, fish waste is fish poop. There is no sewage in them, unless you have something that shows sewage is present in fish poop?What is your point? Anytime a large number of individuals are living together, whether it be human city, or a net pen of of 100,000 fish, their collective waste is harmful to the immediate environment. Sewage is the wastewater from human settlements, and includes anything sent down the toilet or sink. The main toxic component is human waste, but there is paper and a host of other substances that can be included. The waste from a fish farm is technically not sewage, but it is also primarily waste products from an animal (and uneaten food waste). The toxicity of the fish waste is not a function of its composition, but rather its concentration. At low concentrations, waste products can be beneficial as fertilizers for plant species, but as the concentration increases they can cause overgrowth of plant matter, and are directly toxic to living organisms in higher concentrations.
Stop calling it something that it isn't. Unless you can show a sewage component?