No man is an island. Advice and guidelines that don't take context into consideration are useful mostly as some kind of utopian ideal. The various agencies should be working together on things like this. And they sometimes do where their goals overlap. The dietary guidelines are actually an example of that since they're jointly issued by the USDA and HHS.

If the PH in our oceans became so unbalanced they could no longer support any kind of commercial fishing and it became a delicacy would they continue to push a certain percentage of fish as part of our diet? Considering the distortion lobbies create with respect to the balance of democratic power it would surprising if there weren't a certain amount of undue influence.