That could get a little hairy in some spots.
I suggest you consider making some triggers and stuff based on the ratio between the hunters and fish. Say, the fish could only build a number of buildings equal to some number times the number of hunters divided by the number of fish. That way, the more hunters you have and the least fish, the more buildings you get to build. Of course, you'd have to choose a very decent number of towers in some spots, because a full house will halve that number of buildings that can be built (and that would make it too easy for hunters) while having two hunters versus six fish would actually reduce the number _less_, as the ratio would be 1/3 instead of 1/2. So, you'd want to try to find a good number that could be incremented.
In fact, you may even consider making some abilities more potent when there are more fishies around and less hunters. There are many possibilities to that kind of balancing.