Is the yellow toad sold in the fish shop really called toad?

Yes, the little yellow toad in the fish shop is a toad.

Little yellow toad, usually called toad, is an amphibian belonging to Ranunculaceae. Toad is a common creature, with typical frog characteristics, flat body, short and wide head, short limbs and covered with mucus. They usually live near the water or in humid environment and feed on insects, small invertebrates and plants. The name toad is the common name of this animal. Little yellow toad is a kind of toad. It may belong to some kind of toad.