I don't think that strength is the problem here. Rather, E is the opposite of what the author would believe, although the wording is convoluted.
To put it simply, the author believes that the pollution caused by intensive farming could put more pressure on wild fish stocks through untreated waste and habitat destruction.
E. "Such pollution is, however harmful, unlikely to prevent fish farming from eventually relieving the pressure on wild fishery stocks."
Quite the opposite! The author would say that pollution is likely to prevent the relief to wild stocks.