That's disappointing but this is good enough for most maps at least.
Actually I had a non -fishing related question... I noticed that Giants added onions to all maps with the DLC installed, am I right in thinking there must be a way to add custom crops to a map without editing the map files now?
I play Judith Plains (DJ unedited version) and it was made long before Onions were added to game but onions are on the crop calendar and PDA map. I found it interesting, not sure how feasible it would be but it seems the door was opened for adding new crops to any map using scripting and injecting the prefabs.