So my counter to this is the button seems unfinished. It looks as if the original intent was not to have the player be required to open their inventory then right click select apply to switch bait. The issue here is if this was the intent then why was the bait still included in your inventory.
Clearly they can add separate space for these items and this is not an isolated issue to fishing but to all gathering professions. I prefer to have a little more faith in Square then some of the other posters and pray it is not a game to gouge players for money to add more bag space.
If their intent is to fix professions to be more fun and user friendly then this is a core issue with all gathering professions currently. Even something as simple as what WoW did with a separate bag that holds only crafting items helped a huge amount.
