The number of fish which can be called venomous is quite large. Those listed here are intended as examples of the group. While they are different in appearance and belong to a few different groups, they have in common the fact that they have one or more venomous spines. These are usually (but not always) along their back. In most cases the greatest danger is not just the venom, but the fragments of spine that can be left in the wound, and the fact that there is often significant mechanical, as well as toxic, injury.