[Wil]

Caviar comes from fish, most often sturgeon. Gabbits are more amphibeons than fish. Their eggs are more like frogspawn than fish eggs.

EDIT: I suggested that, as far as any source of info could tell me, caviar is fertilised. The answer to why caviar does not hatch is not so much because they are unfertilised (which is the case), but because they are not actually fully mature.

But, I'm thinking the whole deal with Gabbiar is that it make a completely unsubtle jab at the caviar industry's effects of fish stocks, and not meant to provide so much information of Gabbit development cycles.