UW-Madison Center for Limnology:
“The story in Trout Lake played out in three acts. From 1981, when data collection began, to 2006, the Trout Lake ecosystem was humming along in a state scientists often refer to as “equilibrium” with its food web dominated by three main characters.
Tiny, free-floating crustaceans called zooplankton formed the base of the food web and ate large quantities of algae, which helped keep the water clear. A small, silvery species of prey, or “forage,” fish called cisco ate the zooplankton. And lake trout, the large, apex predator that gave the lake its name, ate the cisco.
During this “first act,” cisco dominated the food web. They were the more numerous of the two fish species, which is the common arrangement in predator/prey dynamics, and their high numbers kept zooplankton populations in check.”
