So I wanted to play this game with my 7yo and my 4yo, as it looked like a game my kids would really enjoy. However, the "wishes" part of the game was going to be a bit too complex (at least for my 4yo), so I came up with the following variant.
There are only 2 actions: Take a fish card, sell a fish.
You cannot use a card for it's wish.
When selling a fish to a market that has one or more buyers on it, move the biggest buyer to the next market space (clockwise).
They really enjoyed the game with the simplified rules and had a lot of interesting decisions to make without being too complicated.
They kept trying to not only sell where the buyers were, but also to collect the fish in the next markets to allow for the buyers moving around. Worked really well and they asked to play again right away!
If you have little kids and thought the normal game might be too complex, give this a try