I think Seaspiracies argument is that current "sustainable fishing" efforts are not actually sustainable and are designed to appear to solve the problem while a

I think Seaspiracies argument is that current "sustainable fishing" efforts are not actually sustainable and are designed to appear to solve the problem while avoiding regulations that would actually enforce sustainable fishing (and hence massively disrupt the industry.) If that is their argument, the push to stop eating fish would be justified only in the current environment where there is no ecologically sustainable source. Maybe I being too generous, but "fishing can never be sustainable" appears to be blatantly false so I feel we have to look for the "strongest plausible interpretation".