What is the ethical value of using a model organism, such as zebrafish for doing marine research on pathogens?

the organism can prevent diseases from being transmitted from one species to another, thereby reducing fish mortality.

the organism is immune to all diseases, so the effectiveness of new treatments can be studied over long periods of time.

the organism produces chemicals that can be extracted for use as antibiotics, so they are economically important.

the organism shares its physiology with humans, so testing of new drugs can be done without hurting people.