Spareful Hand is a skill which lets you 'store' up to 3 moochable fish at a time during a fishing session. If you put away your rod with stored fish (called Swimbait), then they go away and you'll have to get them again.

You can store moochable fish if it is large-sized, that is - it's the 'large size' quality when the fish is caught. You can greatly increase and/or guarantee a large-sized fish with skills like Patience, Patience II, and Prize Catch.

It's useful for when you need to catch a fish that's off a certain mooch, or if you're going for Big Fish, you can prepare mooched fish ahead of time, if needed.