Given the most fish you could possibly catch from fish spawns is around 60/ hour given the cast > strike time being around double that of open water ocean fishing, at around 1 min, it's hard to see how you would get close to that figure.

60 yellow quality fish even at an Imperial Trader flat bonus of 250% at a value of say 55K is 3.3M.

You get no relics in spawns to boost income, or Coel (unless from Coelacanth spawn single cast). The fish seals will boost it up a fair amount.

Then you haven't factored in sailing time out to spawns; travel time between spawns; RNG of actually finding spawns in the areas being sailed; travel time to the Trader.

Not sure why you would even Trade to Valencia given it is not as high a distance bonus as Ancado or Arehaza?

Then you have the CP investment to link all the way round there is a factor.

Fishing for longer periods you then have to factor in Condition lose which limits time fishing not to lose income to lower condition.

If you provide more details of location, distance bonus etc. to amke a proper judgement.