If you have an Android, I recommend checking out the Crosspedia app. It has a critterperdia that can be sorted by
- Everything
- What's not donated
- What's available in the current season
- and What's available at that very minute.
When sorted by everything, you can click on an image of the critter you wish to learn about. You can see the time it spawns, the size, and the price.
It was great help when I completed the museum a second time for my second island.