I regularly watch Masaru take apart all kinds of wild caught fish and they're almost all litered with parasites. I wonder if that's normal or the result of some stressor.
Fish farming is especially bad for diseases and parasites. The densities of fish farms are truly insane leading to high rates of disease, waste accumulation, very high fish mortality rates, etc.
personally i think fish farming is cost effective, from a protein mass/farming cost ratio standpoint. If big fish benefits the same subsidies as big red meat does, fish farming would be more sustainable and a farmer could use a less denser farm to minimize disease risk, also it would enable him to buy more medicine to fight parasites while maintaining a healthy margin