The list of animals that use tools, an ability once thought to be the sole province of human beings, is steadily expanding. First great apes, then other primates, mammals, birds, and now fish have been found manipulating their environments for specific purposes. Here, Giacomo Bernardi of the University of California Santa Cruz documents an example of a fish using an anvil.
The orange-dotted tuskfish (Choerodon anchorago) shown in the video is a member of a very large family of marine fishes known as wrasse. The fish first collects a specimen by fanning sand away from it and then searches for a suitable rock on which to smash it. As you can see in the clip, this takes quite a bit of searching and several attempts. Although it's usually a mistake to anthropomorphize animals, this fish certainly looks like it has a clear intent.
Interestingly, three other species of wrasse have been observed (but not documented) engaging in the same behavior. Because the family of wrasse is so large and diverse, these four species are not closely related to one another evolutionarily. This suggests that all wrasse may be capable of using anvils in this manner, or even that other types of fish are as well.