Was collecting Wandering Salmon near Field of Wisdom, otherwise quite easy, two fish I already got a crown on would turn the screen dark, so simply yank it back if it got darker and cast again. Then I noticed there were two different shadows when fishing on lighter screens, one big and one small. Every time the smaller one would nab at the bait, I'd pull a Black Carla(or/and treasure). And when the larger one, a Wandering Salmon(or/and treasure). Well, that made things easy, just pull up if it's a small shadow and cast again...

Wish I'd known that a bit earlier, would have made fishing at least a bit less frustrating...