(comment contains mild gameplay spoilers)
Thanks for your comment - I consciously considered whether I should make the player's "fatigue" a visible statistic to the player. You can actually tell how tired your character is by the speed at which the bar fills up when you're reeling in. (Slower speeds = your character is more tired)
However, I do understand why it might be frustrating because there is a fair bit of randomness to the fishing mechanic; you can be fairly well rested and still get super unlucky with the fish. Although, I knew this when I was balancing the difficulty, and the game is designed to make you fail to meet everyone's needs, but will still let you survive. I wanted players to feel like there were going to lose - it adds stress and guilt.