The Food Web
The Damsel fish in this foodweb is located under the zooplankton marked as a Plankton Invertebrate Feeder. From the food web you can see that the damsel fish eats the zooplankton but gets eaten by the sharks and the barracuda. they don't get eaten by the wrass or butterfly fish because they are marked as coral feeders so they eat the coral that the damsel fish try to protect. If the Damsel fish were to die out then there would be algae and zoo plankton and there would also be less coral because the damsel fish protect the coral from other fish and so there is no one to protect the coral anymore. The Barracuda and sharks wouldn't eventually die out because they have so many other different kinds of prey so it wouldn't affect them that much.