Horses for courses, JR : merchants need means to earn coin so pirates can raid them : if we impoverish the traders, who will there be to plunder? Fishing fleets can still be lit up and hit : to an extent, it makes the pirates task easier as they will tend to all be in the same port for fast, multiple hits.
I support fishing also as a lower-risk means for newer players to accumulate coin which they can then invest in 'normal' trade fleets and take their first steps into building significant battle fleets : we tend to forget, as we older players tend have more officers than we ever really need, that new players struggle to recruit their first ten merchants to gain auto-stop, never mind the admirals and captains they require, along with ship-build costs.
Will some big, well-established players benefit from fishing? Of course, but lets not allow any desire to limit them throw the babies out with the bathwater.