To clarify and deepen my understanding of the Fish, I pondered the following comparisons with similar and/or opposing cards. Maybe my comparisons will inspire you to make your own!
Much / Little
Fish: Abundance, accumulation. Lots, enough of. Too many/much.
Mice: Scarcity; loss. Few, less of. Not enough.
Wealth
Fish: Financial wealth, finances in general. Accumulation, or profit, for their own sake. To work on getting more money/goods.
Bear: Ownership, property. To accumulate wealth as provision for harder times. To look well after things we already have.
