I have fully researched all fields. Is there any use in researching further or should I encourage all my villagers to farm, heal and breed?

Holger

Since there is nothing left to use your research points on, you're better off having your villagers pursue other things.

When you have everything researched and 65 population, it can be quite amusing to see the crop watering conga line! Or, you can count the crabs on the way to the food bin. Woooohooo!!!

Are crabs like fish? You know, the things that you see them carring when they go "fighing"?

Farmers catch crabs just like they catch fish. They are red and wiggly (I imagine), and count for much more in the food bin than fish. When you have a few master farmers trained, your food count begins to go up quickly due to the "crabs factor."