t took me awhile to figure this out. There are "pools" near the pond and the docks. The one with white bubbles are fish, click on them and select "Fish" the green ones are the leeches, click and select "Collect Leeches."
This is what the pools look like. To the left you can see the "white" (blue?) fishing pool and the green leech pool. You don't need a pole or anything, just click and go. Hope that helps.