How did the disappearance of the sea otters affect the coastal marine ecosystem?

Rotenone is an insecticide that is toxic

The fish shown above is a tarpon. it is a fast-swimming and powerful open-water fish. its closest relatives, oddly, are burrow-dwelling conger eels that stay on the bottom. both eels and tarpon developed from snake-like larvae that float in the plankton during the first stages of life. once they mature, tarpon and eels are not found near one another in the ocean. the tarpon and the eel illustrate all of the following except

Which would be the most useful source of evidence to support mcneill's contention?