Cork bobber is definitely best here, because it means the fish won't escape so quickly while not in the green bar. You can't create the same effect any other way.
But, on top of your trap bobber, you can replicate a similar effect to a cork bobber (ie make the bar a decent amount larger) with a +3 fishing buff from fish stew. It's a ridiculously easy recipe to cook, because you can simply grow the tomatoes, while all the fish ingredients (crayfish, mussel, periwinkle) are caught with crab pots. Those are easily purchased from Willy and can be spammed on the river and the beach to catch what you need. Plus if you set up to do even as little as 30 pots per day, you'll rake in an extra 150 fishing xp power day, which will help you level up faster too.
Two fish stew should be enough to last a whole day; they're easier to make than dish of the sea and they last a lot longer too. Get the recipe by getting Willy up to seven hearts quickly, easiest way is to spam him twice a week with gold star pumpkins