EQUITABILITY AND TROPHIC LEVELS IN AN EOCENE FISH POPULATION

A collection of fossil fish from Fossil Lake, Wyoming (Eocene) was compared with samples from three modern natural lakes and an artificial fish pond. All fish were divided into predators or planktivores. The predators all had higher equitabilities than did the planktivores from the same locality. This suggests that the predators are resource limited (food) and that if migration to and from the lakes is not excessive, the equitability of the predatory forms will eventually stabilize at a higher level than that of the planktivorous forms. The paleontological sample follows this pattern, probably from the same causative factors.